Human cytomegalovirus immunity and immune evasion

Virus Research 157 (2011) 151–160

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Review

Human cytomegalovirus immunity and immune evasion Sarah E. Jackson, Gavin M. Mason, Mark R. Wills ∗ Department of Medicine, University of Cambridge, Level 5, Addenbrookes Hospital, Hills Rd, Cambridge CB2 0QQ, UK

a r t i c l e

i n f o

Article history: Received 26 August 2010 Received in revised form 27 October 2010 Accepted 28 October 2010 Available online 5 November 2010 Keywords: Cytomegalovirus Immunology Immune evasion

a b s t r a c t Human cytomegalovirus (HCMV) infection induces both innate immune responses including Natural Killer cells as well as adaptive humoral and cell mediated (CD4+ helper, CD8+ cytotoxic and ␥␦ T cell) responses which lead to the resolution of acute primary infection. Despite such a robust primary immune response, HCMV is still able to establish latency. Long term memory T cell responses are maintained at high frequency and are thought to prevent clinical disease following periodic reactivation of the virus. As such, a balance is established between the immune response and viral reactivation. Loss of this balance in the immunocompromised host can lead to unchecked viral replication following reactivation of latent virus, with consequent disease and mortality. HCMV encodes multiple immune evasion mechanisms that target both the innate and acquired immune system. This article describes the current understanding of Natural killer cell, antibody and T cell mediated immune responses and the mechanisms that the virus utilizes to subvert these responses. © 2010 Elsevier B.V. All rights reserved.

Contents 1. 2. 3.

4. 5.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Innate immunity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Natural Killer (NK) cells and immune evasion mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Humoral immunity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. CD8+ T cell responses and MHC Class I downregulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. CD4+ T cell responses and MHC Class II downregulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gamma delta T cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction The immune response to human cytomegalovirus (HCMV) has been intensively studied over the last 40 years and still remains the focus of attention for numerous research groups. The virus elicits a very broad spectrum of immune responses starting with innate mechanisms, including, inflammatory cytokines from viruscell binding, natural killer cell induction which subsequently drives adaptive immunity, including antibody production and the generation of CD4+ and CD8+ T cell responses. However, the virus is also a paradigm for pathogen mediated immune evasion, expressing multiple genes that interfere with multiple innate and adaptive immune responses. Therefore, it is somewhat of a paradox that

∗ Corresponding author. Tel.: +44 1223 336862; fax: +44 1223 336846. E-mail address: [email protected] (M.R. Wills). 0168-1702/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.virusres.2010.10.031

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HCMV is usually an asymptomatic infection which generates a strong immune response controlling viral replication but, if the immune system is suppressed, this leads to unchecked viral replication and ultimately morbidity and mortality. However, it is also evident that the primary immune response is unable to prevent the virus establishing latency and furthermore the subsequent long term immune response is unable to clear the virus, which, consequently, remains with the host for life. This paper presents a general overview of the immune response to HCMV and the mechanisms the virus uses to modulate the immune response. The review is primarily concerned with the human immune response to cytomegalovirus but draws on the results from various animal models of cytomegalovirus infection in order to try to understand the impact of immunity and evasion on pathogenesis of the virus. Cytomegaloviruses are highly species specific such that HCMV does not infect mice, rats or guinea pigs. However all these small

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animals have species specific cytomegaloviruses that are infectious and pathogenic and have been used as models of cytomegalovirus infection. The use of murine cytomegalovirus (MCMV) infection of inbred mice has been extensively utilized as a model system to help to further understand HCMV infections, including aspects of immune responses, latency and immunopathology (Polic et al., 1998a,b; Reddehase, 2002; Reddehase et al., 2002). The guinea pig model of cytomegalovirus (GPCMV), is particularly useful as the virus is able to cross the placenta and causes infection in utero, and has thus been used to understand aspects of immunity that protect the foetus in the hope of developing vaccine strategies for use in humans (Schleiss, 2006, 2008). MCMV and GPCMV do have some significant differences to HCMV with a number of genes having no homologue. Whilst chimpanzee CMV (CCMV) is very closely related to HCMV this is not a widely applicable model primate system. However, rhesus macaques and the associated rhesus CMV (RhCMV) is a much more widely available experimental system which is showing promise as a tool to study immunology and pathogenesis as well as vaccines strategies for preventing CMV infection (Powers and Fruh, 2008). 2. Innate immunity It is now recognised that activation of the innate immune system is crucial in order to drive a high quality acquired immune response. This includes the induction of primary interferons, the activation of professional antigen presenting cells and the recruitment and activation of natural killer cells which themselves promote more efficient activation of antigen presenting cells and T cells. The binding and entry of HCMV into the cell initiates a number of pathways leading to the upregulation of NFkB and interferon regulatory factor 3 (IRF3) which can ultimately lead to the production of primary interferon and inflammatory cytokines (reviewed in (Isaacson et al., 2008)). This innate cellular response to the initial stages of infection is mediated by Toll like receptor 2 (TLR2) signalling, this receptor has been shown to recognize the viral surface glycoproteins gB and gH (Boehme et al., 2006; Compton et al., 2003) 2.1. Natural Killer (NK) cells and immune evasion mechanisms NK cells are a component of the innate immune system and characterized by the lack of both CD3 T and CD19 B cell markers, and play an important role in the early control of viral infections and activity against certain tumors, they also help to drive subsequent adaptive immunity. MCMV infection of mice provides direct evidence of the importance of NK cells in cytomegalovirus immunity; suckling mice are highly sensitive to MCMV infection until NK cell responses become apparent at 3 weeks and adoptive transfer of NK cells into these mice or adult SCID mice can confer protection (reviewed in (Tay et al., 1998). Inbred mouse strains have differing resistance to MCMV (Scalzo et al., 1992), in part dependant on the cmv1 resistance locus which was subsequently characterized as an activating NK cell receptor (Ly49H) which enables receptor bearing NK cells to directly recognize the MCMV protein m157 and kill virus infected cells (Brown et al., 2001; Daniels et al., 2001; Lee et al., 2001). There is only limited evidence for the role of NK cells in immunity to HCMV infection. Patients with rare NK cell defects can have serious recurrent episodes of HCMV disease (Biron et al., 1989; Gazit et al., 2004). Recovery of NK cell activity following Bone Marrow transplantation has also been associated with survival from CMV related disease (Quinnan et al., 1982). Indirect evidence for the importance of these cells in the innate response to HCMV is suggested by the extensive mechanism that HCMV encodes to prevent NK cell activation.

NK cells are inhibited by signals delivered via inhibitory receptors interacting with class I MHC molecules on the surface of target cells. Since reduced surface Class I MHC levels on HCMV infected cells (Reddehase, 2002) would also reduce NK inhibitory signals, this could render the infected cells susceptible to NK cell cytotoxicity (Biassoni et al., 2001; Karre et al., 1986; Ravetch and Lanier, 2000). Consequently, it was hypothesized that HCMV must encode mechanisms inhibiting NK cell recognition. As predicted, we and others have observed that HCMV encodes multiple genes controlling NK cell activation and cytotoxicity by the provision of inhibitory signals and suppression of activating signals (Wilkinson et al., 2008). Two mechanisms describing HCMV-mediated inhibitory receptor signalling have been reported. Firstly, HCMV uses the host HLA-E pathway to inhibit NK cells via the CD94/NKG2 heterodimeric inhibitory receptor (Braud et al., 1998; Posch et al., 1998) by promoting cell surface HLA-E expression as the viral UL40 protein contains a nonomeric peptide which binds HLA-E promoting its cell surface expression (Tomasec et al., 2000; Ulbrecht et al., 2000). Secondly, HCMV expresses a viral homologue of cellular MHC Class I, UL18 (Beck and Barrell, 1988). UL18 is trafficked to the cell surface where it binds the inhibitory NK cell receptor, LILRB1 (LIR-1) with higher affinity than MHC Class I (Chapman et al., 1999; Cosman et al., 1997) inhibiting LILRB1+ NK cell activation (Prod’homme et al., 2007). NK cell activation can also be mediated by engagement of activating receptors with their ligands on the surface of infected cells. To date, HCMV encodes five genes which prevent activating NK cell receptor signalling. The pp65 tegument protein (UL83) dissociates CD3␨ signalling from NKp30 (Arnon et al., 2005), whilst intracellular retention of CD155 and CD112 by UL141 prevents activation of NK cells via receptors CD226 and CD96 (Prod’homme et al., 2010; Tomasec et al., 2005). The remaining viral proteins interfere with NKG2D-mediated NK cell activation. NKG2D, a major activating receptor expressed on all human NK cells (Bauer et al., 1999), is engaged by at least eight NKG2D ligands (NKG2DL) induced by HCMV infection (Eagle et al., 2006): MICA/B, ULBP1-3, RAET1E, (ULBP4), RAET1G(ULBP5) and RAET1L(ULBP6). In response, viral UL16 protein binds ULBP1, 2 and 6, as well as MICB (but not ULBP3/MICA) (Cosman et al., 2001; Eagle et al., 2009) mediating their intracellular retention to inhibit surface up-regulation (Dunn et al., 2003; Rolle et al., 2003). MICB expression is also controlled by an HCMV encoded microRNA-UL112-1—which reduces translation (Stern-Ginossar et al., 2008). Down-regulated surface expression of the closely related MICA has also been demonstrated in infected cells mediated by UL142 (Ashiru et al., 2009; Chalupny et al., 2006; Wills et al., 2005), and an, as yet, unidentified viral gene (Zou et al., 2005). UL142 a late viral gene that is inhibitory to NK cells, is a member of the UL18 gene family (Dolan et al., 2004), localises to the ER and cis-Golgi and prevents cell surface expression of MICA and ULBP3 by promoting intracellular retention in a compartment likely to be the cis-Golgi (Ashiru et al., 2009; Bennett et al., 2010; Wills et al., 2005).

3. Humoral immunity Evidence from both the mouse and guinea pig animal models suggest that antibody is important in protection from a lethal infective dose and in reducing fetal infection (Harrison et al., 1995; Rapp et al., 1992). In humans pre-existing anti-cytomegalovirus antibodies generated following primary infection prior to conception play an important role in preventing congenital infection of the foetus during pregnancy (Fowler et al., 1992) and can protect against transfusion borne infection in premature infants (Yeager et al., 1981). The role of HCMV specific antibodies to control reac-

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tivation and viral dissemination in immunosupressed patients is less clear. Evidence for the benefits of administration of HCMV specific antibody (hyperimmune globulin) to immunosuppressed transplant patients either for primary infection or reactivation has been described in renal transplants (Snydman et al., 1987), but the benefit is less clear in allogeneic stem cell transplantation patients, with some evidence that it is beneficial (Messori et al., 1994) and others suggesting no beneficial outcome (Guglielmo et al., 1994; Munoz et al., 2001). HCMV primary infection elicits antibodies specific for numerous HCMV proteins including structural tegument proteins (e.g. pp65 and pp150), envelope glycoproteins (predominantly gB and gH) as well as non structural proteins such as the Immediate Early 1 protein (IE1, UL123) (Britt, 1991; Landini and Michelson, 1988). It was initially reported that viral neutralizing activity is predominantly mediated by antibodies specific for gB and gH in in vitro assay systems (Britt et al., 1988; Urban et al., 1996). More recently it has been recognized that passage of wild-type HCMV strains leads to the mutation and deletion of numerous viral genes (Dargan et al., 2010) and of particular relevance to antibody mediated neutralization is the five member complex of gH/gL/UL128-131A which is required to mediate entry into various cell types including endothelial, epithelia and myeloid cells (Gerna et al., 2004; Hahn et al., 2004; Sinzger et al., 1999; Wang and Shenk, 2005a,b). Antibodies to conformational epitopes formed by two or more members of the complex are generated to HCMV infection and have a superior neutralizing ability when compared to gB and gH antibodies (Macagno et al., 2010) 3.1. CD8+ T cell responses and MHC Class I downregulation There is strong evidence from both the murine MCMV model and from patients undergoing bone marrow (BM) and stem cell transplantations (SCT) that HCMV specific CD8+ T cells are a crucial protective component of the immune response to this virus. Mice are protected from lethal MCMV challenge following adoptive transfer of MCMV immediate early antigen specific CD8+ T cells into animals with an ablated immune system (Reddehase et al., 1987), CD8+ T cells were able to prevent lethal infection in the absence of CD4+ T cells (Podlech et al., 2000; Reddehase et al., 1987, 1988). In murine models of BMT, removal of reconstituted CD8+ cells leads to lethal disease and reconstituted CD8+ T cells transferred to immunocompromised mice could prevent disease (Polic et al., 1998a,b). However, other lymphocyte subsets can provide functional redundancy as following CMV reactivation in B cell deficient mice it has been demonstrated that removal of the CD4+ and NK cells lead to reactivation (Polic et al., 1998a,b). In human bone marrow transplantation studies where HCMV infection can cause significant morbidity it was evident that there was a strong correlation between recovery of the CD8+ T cell population and protection from CMV disease (Avetisyan et al., 2007; Barron et al., 2009; Cwynarski et al., 2001; Tormo et al., 2010). Adoptive transfer studies of CMV specific T cells have been performed for almost two decades, patients who have received ex vivo expanded CMV specific CD8+ T cells are protected from both primary and reactivating CMV infection (Einsele et al., 2002; Peggs et al., 2003; Riddell et al., 1992; Walter et al., 1995a,b). Studies on the specificity, function and phenotype of HCMV specific CD8+ T cells have been ongoing for 30 years. The first viral proteins identified as targets of the CD8+ T cell response to HCMV was the immediate early protein (Borysiewicz et al., 1988) and the tegument protein pp65 (UL83) (McLaughlin Taylor et al., 1994). Numerous studies have since been performed utilizing increasingly sensitive methods of detection (IFN␥ secretion either by ELISPOT or intracellular flow cytometry as well as MHC Class I tetramers) have shown that most HCMV seropositive individuals have a CD8+

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T cell responses to pp65 and IE and that the magnitude of these responses is often very high (Borysiewicz et al., 1983; Kern et al., 1999a,b; Khan et al., 2002a,b; McLaughlin Taylor et al., 1994; Walter et al., 1995a,b). PBMC stimulation with HCMV infected fibroblasts identified CD8+ T cell responses to pp150 (UL32), pp28 (UL98), pp50 (UL44)), glycoproteins (gB (UL55) and gH (UL75) (Boppana and Britt, 1996). A bioinformatics approach was also used to predict CD8+ T cell epitopes derived from the published sequence of 14 HCMV encoded proteins (pp28, pp50, pp65, pp150, pp71, gH, gB, IE1, US2, US3, US11, UL16 and UL18). Numerous new HCMV T cell epitopes were predicted, many of which were verified using an ELISPOT assay measuring IFN␥ production (Elkington et al., 2003). Stimulation of PBMC using US2 to US11 deleted HCMV infected autologous fibroblasts (this virus can no longer cause MHC Class I downregulation), revealed high frequency responses to pp65 and IE1, pp150 and gB. However, T cells with many other specificities were also generated many of them were immediate early or early viral protein specific, although the ORFs were not defined (Manley et al., 2004). The most comprehensive study has determined IFN␥ responses from both CD4+ and CD8+ T cells to 213 predicted HCMV encoded open reading frames (ORFs) using 13,687 peptides and a panel of 33 seropositive donors with disparate MHC Class I types. 151 ORF’s were shown to elicit a CD4+ or CD8+ T cell response in at least one donor. Three ORF’s were recognised by more than half of the cohort, UL48, UL83 (pp65), and UL123 (IE). CD8+ T cell responses from HCMV seropsitive donors recognized a median of 8 ORFS, however responses were highly heterogeneous between individuals with some recognizing only a single ORF and as many as 39 (Sylwester et al., 2005). During latency transcription of viral genes is highly restricted a number of genes have been shown to be expressed. These include UL111.5 a viral IL-10 homologue (Cheung et al., 2009), UL138 (Goodrum et al., 2007) and UL8182AS a viral transcript found antisense to UL81-82 termed latent undefined nuclear antigen (LUNA) (Bego et al., 2005). UL138 and a truncated sequence of UL111.5 were included in the T cell proteome screen, UL138 was both a CD4 and a CD8 target in just one donor (Sylwester et al., 2005). More recently T cell responses to UL138 and LUNA were examined in detail in 22 individuals no evidence for CD4 responses was found however a CD8 response was seen exclusively in donors with HLA-B3501 and this was mapped to the same peptide in each case (Tey et al., 2010). Despite the extensive number of HCMV proteins that are targets for the CD8 T cell response the vast majority of the immunobiology of the CD8 T cell response in primary infection and long term memory has been studied using pp65 and IE specific T cells. There are a limited number of studies of CMV T cell dynamics and phenotype in humans during primary CMV infection, in part because the infection is often asymptomatic. However, CD8+ T cell function and phenotype in HCMV seronegative renal transplant patients who develop primary HCMV infection after receiving a graft from HCMV seropositive donor has been studied (van de Berg et al., 2008; van Lier et al., 2003). CD8+ T cells specific to pp65 are detected shortly after the appearance of specific antibodies in symptomatic patients. These CD8+ T cells exhibit an activated and cytolytic phenotype with high expression of ki67, granzyme B, perforin and a CD27+, CD45RO+, CCR7−, CD28− phenotype (Gamadia et al., 2003; van de Berg et al., 2008). There have been a few studies of T cell dynamics during natural primary infection (Day et al., 2007; Wills et al., 1999), and these studies have also shown a large expansion of pp65 specific CD8 T cells with the majority expressing CD45RO and a corresponding high level of ex vivo cytotoxicity against pp65 peptide pulsed target cells (Wills et al., 1999). The murine studies show that IE protein specific CD8+ T cells undergo a rapid expansion and have a diverse set of T cell receptor clones. This is then followed by a contraction phase with a decline in the fre-

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quency of CD8+ T cells and the residual memory population focuses on particular clones form the original response (Karrer et al., 2003). In agreement with this the immediate CD8+ T cell response (at least to pp65) in humans uses a diverse range of TCR clones (Day et al., 2007). The clonal repertoire of the CD8+ T cell CMV specific memory response observed during latent infection is distinct from that observed during the acute phase of CMV infection. In the murine model the expanding memory population focuses on particular clones from the original response (Karrer et al., 2003). Likewise, in human studies it has been shown that the TCR clones usage (of pp65 specific T cells) rapidly focuses onto a few or even a single V␤ segment from the initial polyclonal pool of T cells, data suggests that these are of a higher affinity than those that are not selected into the memory pool (Day et al., 2007). The total CD8 T cell response to HCMV is large, an estimation of about 10% of the peripheral CD8 memory T cells are directed against HCMV determined by screening all the HCMV ORFs in multiple individuals, this group included young to middle aged individuals but not old individuals (Sylwester et al., 2005). A large proportion of pp65 specific CD8+ memory T cells have reexpressed CD45RA (Appay et al., 2002a,b; Champagne et al., 2001; Harari et al., 2009; Khan et al., 2002a,b; Komatsu et al., 2006; Miles et al., 2007; Sauce et al., 2007; van de Berg et al., 2008; Wills et al., 1999, 2002), these populations are derived from the same clones that expressed CD45RO previously (Iancu et al., 2009; Wills et al., 1999). CD45RA re-expressing memory cells are also observed in EBV specific CD8 memory populations (Faint et al., 2001), and they are both functional and apoptosis resistant. In CMV, the CD45RA+ memory CD8 cells also retain functionality, they are still cytotoxic expressing both perforin and granzyme (Appay et al., 2002a,b; Boutboul et al., 2005; Gillespie et al., 2000; Harari et al., 2009; Khan et al., 2002a,b; Libri et al., 2008; Makedonas et al., 2010; van de Berg et al., 2008; Wills et al., 2002). In post stem cell transplant studies it has been shown that CD45RA+ memory CD8 cells are better at controlling reactivation (Luo et al., 2010; Moins-Teisserenc et al., 2008). The CD45RA+ population is also present in the HCMV memory population from a very young age (Komatsu et al., 2006; Miles et al., 2007) and expands with old age (Komatsu et al., 2006). HCMV specific CD8+ memory T cells have usually lost expression of the co-stimulatory molecule CD28 and have variable expression of CD27; they generally do not express the chemokine receptor CCR7, which is associated with homing to lymph nodes (Gamadia et al., 2003; Gillespie et al., 2000; Kern et al., 1999a,b; Khan et al., 2002a,b; Komatsu et al., 2006; Miles et al., 2007; Pita-Lopez et al., 2009; Scheinberg et al., 2009; van de Berg et al., 2008). However HCMV specific memory cells do express other chemokine receptors including CCR5 which enables migration to sites of inflammation and may be associated with the migration phenotype enabling homing to the bone marrow, where HCMV specific memory CD8+ T cell populations are found (Letsch et al., 2007; Melenhorst et al., 2009; Palendira et al., 2008). HCMV specific memory cells have been described as having an “effector memory” phenotype which includes lost expression of IL-7R␣ and expression of CD57, a marker of activation which is associated with a late differentiated phenotype (Day et al., 2007; Gillespie et al., 2000; Khan et al., 2002a,b; van Leeuwen et al., 2005). Many CMV specific memory CD8+ T cells also express inhibitory and activating Natural Killer Cell Receptors (van de Berg et al., 2008; van Stijn et al., 2008), including CD85j, CD244 (Pita-Lopez et al., 2009) and KLRG1 (Ouyang et al., 2003). Expression of inhibitory receptors on HCMV specific CD8+ memory T cell populations may explain why earlier reports of the highly differentiated phenotype of this population concluded that the cells were terminally differentiated (Champagne et al., 2001). KLRG1 signalling prevents Akt phosphorylation and a subsequent loss of proliferative capac-

ity (Henson et al., 2009) also the transcription factor BMI-1 which is important for replicative competence in CD8+ T cells via T cell receptor ligation is not expressed in KLRG1+ cells (Heffner and Fearon, 2007). A further negative control of CMV specific memory CD8 cell function is the gene Jakmip1 which is highly expressed in CD45RA+ CMV specific CD8+ T cells and negatively regulates cytotoxicity (Libri et al., 2008). There is evidence from post stem cell transplant patients that expression of inhibitory NK receptors and loss of function is only observed following ligation, in the absence of the corresponding ligands CMV specific CD8+ T cells retain functionality (van der Veken et al., 2009). In addition to expressing the cytotoxic molecules granzyme and perforin, CD8+ CMV memory T cell populations can also secrete a range of cytokines. Polyfunctional CMV specific CD8 T cells are more efficient at preventing CMV reactivation in post transplant patients than monofunctional IFN␥ only secreting CD8+ CMV specific T cells (Zhou et al., 2009). Polyfunctional CD8 cells secrete a combination of TNF␣, MIP1␤, and IFN␥ and upregulate CD107a, a marker of degranulation (Gillespie et al., 2000; Makedonas et al., 2010; Scheinberg et al., 2009; Zhou et al., 2009), they do not generally secrete high levels of IL-2, this may be because secretion of IL-2 is associated with expression of CD28 (Makedonas et al., 2010). CMV specific CD8+ memory T cells appear to compensate for the loss of the co-stimulatory molecules CD28 and CD27 by up regulating other co-stimulatory molecules, in particular 41BB, a TNFR family member, is unregulated on activated CMV specific CD8+ T cells (Wehler et al., 2008) and signalling following 41BB ligation can restore proliferative capacity in CMV specific CD28− CD8+ T cells (Waller et al., 2007). In murine models of CMV infection it is clear the CD8+ CMV specific T cell population expands over time, this phenomenon has been termed “memory inflation” (Karrer et al., 2003). The expanded CD8+ memory T cell populations retain functionality and do not require high levels of viral activity to persist and expand (Snyder et al., 2008). More recently it has been shown that in the chronically MCMV infected mouse the memory inflation of CMV specific CD8+ T cell populations, is maintained by the continuous recruitment of less differentiated CMV memory populations or naive cells generating a highly functional but short lived population of cells which increases in number with duration of chronic infection (Snyder et al., 2008). In humans it is clear in studies comparing CMV seropositive donors of different ages that the proportion of CD8+ T cells specific to HCMV proteins expands with age (Hadrup et al., 2006; Khan et al., 2002a,b; Komatsu et al., 2006; Pita-Lopez et al., 2009; Snyder et al., 2008; Vescovini et al., 2007). This expansion of pp65 and IE specific population has been equated with the memory inflation observed in MCMV infected mice, however direct comparisons are not possible due to the observational nature of the human studies. The marked expansion of pp65 and IE specific specific populations is seen usually seen in later adult life but has also been noted in younger adults, transplantation settings and in some chronic inflammatory diseases, in paediatric CMV seropositive patients, analysis has shown that the size of the CD8+ HCMV memory T cell population is reasonably constant (Komatsu et al., 2006; Miles et al., 2007). It is clear that the proportion of memory CD8+ T cells specific for HCMV is very large in older donors (greater than 70 years old) and that this expanded population exhibits signs of dysfunction compared to the HCMV memory population in younger donors. This dysfunction may be partly due to greater focusing on individual oligoclonal populations in the expanded population restricting clonality (Khan et al., 2002a,b), increased expression of killer inhibitory receptors (Northfield et al., 2005; Pita-Lopez et al., 2009) a decrease in functionally intact cells (Hadrup et al., 2006). The dysfunction of some of the CD8+ memory T cell response towards HCMV may explain why although there is no overt CMV disease in the elderly, chronic

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reactivation of HCMV can be frequently detected in elderly donors which is not observed in younger HCMV seropositive donors (Stowe et al., 2007). HCMV infection has also been implicated in causing changes within the total T cell population and contributing negatively to the immune health of older individuals. The decline in overall immune health in the elderly is termed immunosenescence and the immune risk phenotype (IRP) of which HCMV seropositivity is one parameter, has been proposed to predict an increased risk of mortality in the elderly (Wikby et al., 2002) (This is discussed in more detail in this issue by Graham Pawelec). HCMV employs a number of mechanisms to interfere with the normal cellular MHC Class I processing and presentation pathways in order to prevent CD8+ T cell recognition. HCMV viral genes US2 and US11 degrade newly synthesised MHC Class I heavy chains (Wiertz et al., 1996a,b; Jones et al., 1995). US3 retains MHC Class I peptide complexes in the endoplasmic reticulum (ER) (Jones et al., 1996). US6 blocks peptide translocation into the ER (Ahn et al., 1997). The number and diversity of these mechanisms is surprising. However, this apparent redundancy may have distinct advantages to the virus. The sequential expression of the US3 and US11 gene products which would lead to MHC Class I-peptide complex retention in the ER followed by degradation of de novo MHC Class I heavy chains may be very efficient. The combination of US2 and US11 may allow many different MHC Class I heavy chains to be redirected to the cytosol for degradation. HCMV infects a number of different cell types in vivo and it is conceivable that some of these gene products are more efficient in some cell types than others. The genes are also expressed at different times during HCMV replication, US3 is expressed at immediate early times while the other proteins are expressed from early times, expression then continues through the viral life cycle. The action of these genes may not completely protect cells from CD8+ T cell recognition dependant on the antigen specificity of the T cell. While HCMV infected cells expressing US2-11 prevent any presentation of IE antigen to human T cells, pp65 peptides were still presented (Besold et al., 2007). There is also some evidence that MHC Class I downregulation genes are not redundant as mutant viruses expressing gpUS2 and gpUS11 alone only incompletely protect HCMV infected fibroblasts from CTL recognition by both IE and pp65 specific T cells (Besold et al., 2009). 3.2. CD4+ T cell responses and MHC Class II downregulation Human CD4+ T cells include multiple subsets which can be broadly divided into helper T cells (further subdivided into those that provide help to CD8 T cells (Th1) and those that interact with B cells (Th2)), regulatory T cells (Treg) and specialist subsets such as Th17 cells that are involved in inflammation and anti parasite responses. Evidence for their protection role in cytomegalovirus immunity is supported by studies in mice infected with MCMV, which show that long term depletion of the whole CD4+ T cell compartment in vivo, was associated with persistent virus replication at specific anatomical sites (Jonjic et al., 1989). In humans it has been shown that an extended period of HCMV secretion was seen in young children with an impaired HCMV specific CD4+ T cell response (Tu et al., 2004). In renal transplant patients undergoing primary HCMV infection IFN␥producing CD4+ T cells precede the emergence of the CD8+ T cell response in patients with asymptomatic infection, whereas those patients that had a delay in HCMV specific CD4+ T cell generation developed disease (Gamadia et al., 2003). Following bone marrow transplantation, the maintenance of HCMV specific CD8+ T cell infusions was dependent on the presence of HCMV-specific CD4+ cells (Einsele et al., 2002; Walter et al., 1995a,b), suggest-

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ing that CD4+ helper T cells are essential for effective CD8+ T cell responses. Human antigen-specific CD4+ T cells have been identified by intracellular cytokine production, CD4+ T cells often respond to the same ORFs as CD8+ T cells and both pp65 and IE-specific CD4+ T cells have been detected in a very high proportion of individuals tested (Beninga et al., 1995; Davignon et al., 1995; Fuhrmann et al., 2008; Kern et al., 2002). Individual peptide epitopes have been identified in pp65, IE, gB and gH (Davignon et al., 1996; Elkington et al., 2004; Kern et al., 2002; Wills et al., 2006). An analysis of the CD4+ T cell response to the whole HCMV proteome has shown that the response is very broad, with an individual responding to a median of 12 ORFs, five ORFs (UL55, UL83 (pp65), UL86, UL99, and UL122/123 (IE)) were recognized by more than half the donors tested. It was estimated that the entire HCMV specific CD4+ T cell response in these young to middle aged donors comprised about 10% of the CD4+ T cells present in the peripheral blood (Sylwester et al., 2005). During primary infection (in a kidney transplant model), HCMV specific CD4+ T cells, can be detected 7 days after the detection of HCMV DNA in peripheral blood (Rentenaar et al., 2000). These cells produce T helper type 1 (Th1) cytokines IFN␥ and TNF␣ but not the T helper type 2 (Th2) cytokine IL-4 (van Leeuwen et al., 2006a,b). The surface phenotype of memory HCMV specific CD4+ T cells have been determined by a consensus of studies using multiparameter flow cytometry. Upon stimulation activated HCMV specific CD4+ T cells have subpopulations displaying enrichment of a CD45RO+, CD27−, CD62L−, CD11ahigh , and CCR7− phenotype (Bitmansour et al., 2002; Rentenaar et al., 2000; Sester et al., 2002). Most HCMV specific memory CD4+ T cells secrete IFN␥, some also secrete TNF␣ and IL-2 however IL-4 is secreted by very few HCMV specific CD4+ T cells (Bitmansour et al., 2002; Rentenaar et al., 2000). A subset of CD4+ T cells which lack the CD28 costimulatory receptor, (usually a rare subset in peripheral blood) are found in high frequencies in HCMV seropostive individuals. These HCMV specific CD4+ CD28− T cells are able to proliferate and secrete IFN␥, they express the cyctoxic granule components perforin and granzyme B, and can mediate MHC class II restricted cytotoxicity (van Leeuwen et al., 2004, 2006a,b). Studies of the HCMV CD4+ T cell response in young and old subjects has confirmed high frequencies of CD4+ T cells which lack CD28 expression and in addition CD27, it was also noted that in the elderly subjects these cells had a very low proliferative capacity (Fletcher et al., 2005). During primary HCMV infection these cells are detected immediately after the disappearance of DNAemia indicating that HCMV infection may trigger the formation of this particular T cell subset (van de Berg et al., 2008; van Leeuwen et al., 2004). The circulating HCMV specific CD4+ T cells of healthy carriers are oligoclonal. HCMV in vitro stimulated CD4+ T cells show restricted TcR V␤ segment useage. RT-PCR analysis of sorted HCMV specific CD4+ T cells showed that the TCR V␤ expanded populations were composed of a limited number of clonotypes dominated by 1–3 clones alongside a cohort of subdominant and minor variants. Interestingly, upon stimulation of CD4+ T cells with individual pp65 peptides, the same dominant clones were also identified (Bitmansour et al., 2002). It is unclear, however, how soon after primary infection by HCMV that the pattern of clonal focusing develops and to what extent the relative clonal dominance changes in long term virus carriers. There is also accumulating evidence suggesting that HCMV specific CD4+ T cells can act as effectors directly upon virally infected cells (Appay et al., 2002a,b; Gamadia et al., 2004; Rentenaar et al., 2000; van Leeuwen et al., 2004). Subjects with higher levels of HCMV specific CD4+ T cells that secrete IFN␥ clear the virus faster and exhibit fewer symptoms (Gamadia et al., 2003; Sester et al., 2001). Whilst T cell mediated cytotoxicity is usually associated with CD8+ T cells, a number of HCMV antigens, including pp65, IE, gB and

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gH, have been shown to induce antigen specific CD4+ T cells capable of mediating, MHC class II restricted cytotoxicity in vitro (Hopkins et al., 1996) (Elkington et al., 2004; Weekes et al., 2004). The majority of CD4+ T cells specific to gB express granzyme B directly ex vivo, which correlated with the ability for a number of gB specific CD4+ T cell clones to mediate cytotoxicity against a range of target cells (Hegde et al., 2005). Further studies focusing upon the gB specific CD4+ cytotoxic T cell response have identified an immunodominant peptide (DYSNTHSTRYV) restricted to HLA-DRB*0701 (Crompton et al., 2008). T cell receptor usage for both the TCR␣ and TCR␤ chains showed extreme conservation, reflecting what had been seen in previous studies for CD8+ T cells. The ability of a CD8+ or CD4+ T cell to produce multiple cytokines and have multiple effector functions is an essential component of a high quality T cell response for a range of microbial pathogens (Boaz et al., 2002; Darrah et al., 2007; Emu et al., 2005; Harari et al., 2005; Younes et al., 2003) In a longitudinal study of HCMV seropositive liver transplant patients, there was a significantly lower frequency of polyfuntional (IFN␥ and IL-2 secretion) HCMV specific CD4+ T cells in patients who exhibited HCMV DNAemia (Nebbia et al., 2008). A large number of HCMV encoded gene products target the MHC class I antigen presentation pathway in an attempt to avoid CD8+ T cell recognition. HCMV also evades the CD4+ T cell response by a number of methods. Disrupting IFN␥ induced, upregulation of MHC class II molecules to the cell surface by preventing the expression of Janus kinase 1 and repression of Class II transactivator mRNA. The virally encoded gene product of US2 also inhibits MHC class II presentation to CD4+ T cells by redirecting the HLA-DR␣ and HLA-DM␣ chains to the cytosol where they are degraded (Miller et al., 2001). More recently a truncated transcript to UL111A, a viral homologue of the immunomodulatory cytokine IL-10, which is expressed during latency (cmvLA IL-10) has been shown to down regulate expression of MHC class I and II molecules, inhibit proliferation of peripheral blood mononuclear cells and inhibit the production of inflammatory cytokines (Jenkins et al., 2004, 2008; Spencer et al., 2002). The same group in a further study showed that the presence of cmvLA IL-10 during latent infection of myeloid progenitor cells, suppressed both allogeneic and autologous recognition by CD4+ T cells and may represent a mechanism by which HCMV latency evades the CD4+ T cell response and aid in the maintenance of the latent state (Cheung et al., 2009). 4. Gamma delta T cells Evidence from kidney, lung and stem cell transplant recipients suggest that a subset of gamma delta (␥␦) T cells (the minor V␦2 negative subpopulation) are expanded following HCMV reactivation in these patients. Further evidence from some of these studies using in vitro cultured cells showed the ability to mediated cytotoxicity of HCMV infected target cells (Dechanet et al., 1999; Halary et al., 2005; Knight et al., 2010). The ␥␦ T cell subset does not recognize classically processed antigen presented via MHC Class I or II and currently it is not known what these cells recognise on the surface of HCMV infected cells. The role for ␥␦ T cells in the control of CMV infection is further supported in MCMV infected mice which show an increase of these cells in the salivary gland (Cavanaugh et al., 2003). Primary infection shows accumulation in liver and antibody depletion of gamma delta cells prior to infection correlates with an increase in MCMV titre (Ninomiya et al., 2000). 5. Concluding remarks The evidence reviewed in this chapter supports the view that both the innate and acquired immune system respond robustly

following primary HCMV infection. This response is protective in healthy immunocompetent individuals resulting in asymptomatic infection or only mild disease. However, despite this, HCMV is able to establish latency and the virus is never eliminated from the infected individual. Instead, there is a complex interplay between the immune system and HCMV-mediated immune evasion strategies that allow viral reactivation but prevent extensive viral replication, dissemination and clinical disease. A major challenge will be to manipulate the immune response to achieve protection of the foetus in utero upon infection of HCMV naïve mothers, or immunospressed transplant patients. The ultimate goal would be the targeting and elimination of latently infected cells in vivo. Acknowledgements SEJ and GM contributed equally to this review. References Ahn, K., Gruhler, A., Galocha, B., Jones, T.R., Wiertz, E.J., Ploegh, H.L., Peterson, P.A., Yang, Y., Fruh, K., 1997. The ER-luminal domain of the HCMV glycoprotein US6 inhibits peptide translocation by TAP. Immunity 6 (5), 613–621. Appay, V., Dunbar, P.R., Callan, M., Klenerman, P., Gillespie, G.M., Papagno, L., Ogg, G.S., King, A., Lechner, F., Spina, C.A., Little, S., Havlir, D.V., Richman, D.D., Gruener, N., Pape, G., Waters, A., Easterbrook, P., Salio, M., Cerundolo, V., McMichael, A.J., Rowland-Jones, S.L., 2002a. Memory CD8+ T cells vary in differentiation phenotype in different persistent virus infections. Nat. Med. 8 (4), 379–385. Appay, V., Zaunders, J.J., Papagno, L., Sutton, J., Jaramillo, A., Waters, A., Easterbrook, P., Grey, P., Smith, D., McMichael, A.J., Cooper, D.A., Rowland-Jones, S.L., Kelleher, A.D., 2002b. Characterization of CD4(+) CTLs ex vivo. J. Immunol. 168 (11), 5954–5958. Arnon, T.I., Achdout, H., Levi, O., Markel, G., Saleh, N., Katz, G., Gazit, R., Gonen-Gross, T., Hanna, J., Nahari, E., Porgador, A., Honigman, A., Plachter, B., Mevorach, D., Wolf, D.G., Mandelboim, O., 2005. Inhibition of the NKp30 activating receptor by pp65 of human cytomegalovirus. Nat. Immunol. 6 (5), 515–523. Ashiru, O., Bennett, N.J., Boyle, L.H., Thomas, M., Trowsdale, J., Wills, M.R., 2009. NKG2D ligand MICA is retained in the cis-Golgi apparatus by human cytomegalovirus protein UL142. J. Virol. 83 (23), 12345–12354. Avetisyan, G., Aschan, J., Hagglund, H., Ringden, O., Ljungman, P., 2007. Evaluation of intervention strategy based on CMV-specific immune responses after allogeneic SCT. Bone Marrow Transplant 40 (9), 865–869. Barron, M.A., Gao, D., Springer, K.L., Patterson, J.A., Brunvand, M.W., McSweeney, P.A., Zeng, C., Baron, A.E., Weinberg, A., 2009. Relationship of reconstituted adaptive and innate cytomegalovirus (CMV)-specific immune responses with CMV viremia in hematopoietic stem cell transplant recipients. Clin. Infect Dis. 49 (12), 1777–1783. Bauer, S., Groh, V., Wu, J., Steinle, A., Phillips, J.H., Lanier, L.L., Spies, T., 1999. Activation of NK cells and T cells by NKG2D, a receptor for stress-inducible MICA. Science 285 (5428), 727–729. Beck, S., Barrell, B.G., 1988. Human cytomegalovirus encodes a glycoprotein homologous to MHC class-I antigens. Nature 331 (6153), 269–272. Bego, M., Maciejewski, J., Khaiboullina, S., Pari, G., St Jeor, S., 2005. Characterization of an antisense transcript spanning the UL81-82 locus of human cytomegalovirus. J. Virol. 79 (17), 11022–11034. Beninga, J., Kropff, B., Mach, M., 1995. Comparative analysis of fourteen individual human cytomegalovirus proteins for helper T cell response. J. Gen. Virol. 76 (Pt. 1), 153–160. Bennett, N.J., Ashiru, O., Morgan, F.J., Pang, Y., Okecha, G., Eagle, R.A., Trowsdale, J., Sissons, J.G., Wills, M.R., 2010. Intracellular sequestration of the NKG2D ligand ULBP3 by human cytomegalovirus. J. Immunol. 185 (2), 1093–1102. Besold, K., Frankenberg, N., Pepperl-Klindworth, S., Kuball, J., Theobald, M., Hahn, G., Plachter, B., 2007. Processing and MHC class I presentation of human cytomegalovirus pp65-derived peptides persist despite gpUS2-11-mediated immune evasion. J. Gen. Virol. 88 (Pt. 5), 1429–1439. Besold, K., Wills, M., Plachter, B., 2009. Immune evasion proteins gpUS2 and gpUS11 of human cytomegalovirus incompletely protect infected cells from CD8 T cell recognition. Virology 391 (1), 5–19. Biassoni, R., Cantoni, C., Pende, D., Sivori, S., Parolini, S., Vitale, M., Bottino, C., Moretta, A., 2001. Human natural killer cell receptors and co-receptors. Immunol. Rev. 181, 203–214. Biron, C.A., Byron, K.S., Sullivan, J.L., 1989. Severe herpesvirus infections in an adolescent without natural killer cells. N. Engl. J. Med. 320 (26), 1731–1735. Bitmansour, A.D., Douek, D.C., Maino, V.C., Picker, L.J., 2002. Direct ex vivo analysis of human CD4(+) memory T cell activation requirements at the single clonotype level. J. Immunol. 169 (3), 1207–1218. Boaz, M.J., Waters, A., Murad, S., Easterbrook, P.J., Vyakarnam, A., 2002. Presence of HIV-1 Gag-specific IFN-gamma + IL-2+ and CD28 + IL-2+ CD4 T cell responses is associated with nonprogression in HIV-1 infection. J. Immunol. 169 (11), 6376–6385.

S.E. Jackson et al. / Virus Research 157 (2011) 151–160 Boehme, K.W., Guerrero, M., Compton, T., 2006. Human cytomegalovirus envelope glycoproteins B and H are necessary for TLR2 activation in permissive cells. J. Immunol. 177 (10), 7094–7102. Boppana, S.B., Britt, W.J., 1996. Recognition of human cytomegalovirus gene products by HCMV-specific cytotoxic T cells [Full text delivery]. Virology 222 (1), 293–296. Borysiewicz, L.K., Morris, S., Page, J.D., Sissons, J.G., 1983. Human cytomegalovirusspecific cytotoxic T lymphocytes: requirements for in vitro generation and specificity. Eur. J. Immunol. 13 (10), 804–809, issn: 0014-2980. Borysiewicz, L.K., Hickling, J.K., Graham, S., Sinclair, J., Cranage, M.P., Smith, G.L., Sissons, J.G., 1988. Human cytomegalovirus-specific cytotoxic T cells. Relative frequency of stage-specific CTL recognizing the 72-kD immediate early protein and glycoprotein B expressed by recombinant vaccinia viruses. J. Exp. Med. 168 (3), 919–931, issn: 0022-1007. Boutboul, F., Puthier, D., Appay, V., Pelle, O., Ait-Mohand, H., Combadiere, B., Carcelain, G., Katlama, C., Rowland-Jones, S.L., Debre, P., Nguyen, C., Autran, B., 2005. Modulation of interleukin-7 receptor expression characterizes differentiation of CD8 T cells specific for HIV, EBV and CMV. Aids 19 (17), 1981–1986. Braud, V.M., Allan, D.S., O’Callaghan, C.A., Soderstrom, K., D’Andrea, A., Ogg, G.S., Lazetic, S., Young, N.T., Bell, J.I., Phillips, J.H., Lanier, L.L., McMichael, A.J., 1998. HLA-E binds to natural killer cell receptors CD94/NKG2A B and C. Nature 391 (6669), 795–799. Britt, W.J., 1991. Recent advances in the identification of significant human cytomegalovirus-encoded proteins. Transplant. Proc. 23 (3 Suppl 3), 64–69, discussion 69. Britt, W.J., Vugler, L., Stephens, E.B., 1988. Induction of complement-dependent and -independent neutralizing antibodies by recombinant-derived human cytomegalovirus gp55-116 (gB). J. Virol. 62 (9), 3309–3318. Brown, M.G., Dokun, A.O., Heusel, J.W., Smith, H.R., Beckman, D.L., Blattenberger, E.A., Dubbelde, C.E., Stone, L.R., Scalzo, A.A., Yokoyama, W.M., 2001. Vital involvement of a natural killer cell activation receptor in resistance to viral infection. Science 292 (5518), 934–937. Cavanaugh, V.J., Deng, Y., Birkenbach, M.P., Slater, J.S., Campbell, A.E., 2003. Vigorous innate and virus-specific cytotoxic T-lymphocyte responses to murine cytomegalovirus in the submaxillary salivary gland. J. Virol. 77 (3), 1703– 1717. Chalupny, N.J., Rein-Weston, A., Dosch, S., Cosman, D., 2006. Down-regulation of the NKG2D ligand MICA by the human cytomegalovirus glycoprotein UL142. Biochem. Biophys. Res. Commun. 346 (1), 175–181. Champagne, P., Ogg, G.S., King, A.S., Knabenhans, C., Ellefsen, K., Nobile, M., Appay, V., Rizzardi, G.P., Fleury, S., Lipp, M., Forster, R., Rowland-Jones, S., Sekaly, R.P., McMichael, A.J., Pantaleo, G., 2001. Skewed maturation of memory HIV-specific CD8 T lymphocytes. Nature 410 (6824), 106–111. Chapman, T.L., Heikeman, A.P., Bjorkman, P.J., 1999. The inhibitory receptor LIR-1 uses a common binding interaction to recognize class I MHC molecules and the viral homolog UL18. Immunity 11 (5), 603–613. Cheung, A.K., Gottlieb, D.J., Plachter, B., Pepperl-Klindworth, S., Avdic, S., Cunningham, A.L., Abendroth, A., Slobedman, B., 2009. The role of the human cytomegalovirus UL111A gene in down-regulating CD4+ T-cell recognition of latently infected cells: implications for virus elimination during latency. Blood 114 (19), 4128–4137. Compton, T., Kurt-Jones, E.A., Boehme, K.W., Belko, J., Latz, E., Golenbock, D.T., Finberg, R.W., 2003. Human cytomegalovirus activates inflammatory cytokine responses via CD14 and Toll-like receptor 2. J. Virol. 77 (8), 4588–4596. Cosman, D., Fanger, N., Borges, L., Kubin, M., Chin, W., Peterson, L., Hsu, M.L., 1997. A novel immunoglobulin superfamily receptor for cellular and viral MHC class I molecules. Immunity 7 (2), 273–282. Cosman, D., Mullberg, J., Sutherland, C.L., Chin, W., Armitage, R., Fanslow, W., Kubin, M., Chalupny, N.J., 2001. ULBPs, novel MHC class I-related molecules, bind to CMV glycoprotein UL16 and stimulate NK cytotoxicity through the NKG2D receptor. Immunity 14 (2), 123–133. Crompton, L., Khan, N., Khanna, R., Nayak, L., Moss, P.A., 2008. CD4+ T cells specific for glycoprotein B from cytomegalovirus exhibit extreme conservation of T-cell receptor usage between different individuals. Blood 111 (4), 2053–2061. Cwynarski, K., Ainsworth, J., Cobbold, M., Wagner, S., Mahendra, P., Apperley, J., Goldman, J., Craddock, C., Moss, P.A., 2001. Direct visualization of cytomegalovirus-specific T-cell reconstitution after allogeneic stem cell transplantation. Blood 97 (5), 1232–1240. Daniels, K.A., Devora, G., Lai, W.C., O’Donnell, C.L., Bennett, M., Welsh, R.M., 2001. Murine cytomegalovirus is regulated by a discrete subset of natural killer cells reactive with monoclonal antibody to Ly49H. J. Exp. Med. 194 (1), 29–44. Dargan, D.J., Douglas, E., Cunningham, C., Jamieson, F., Stanton, R.J., Baluchova, K., McSharry, B.P., Tomasec, P., Emery, V.C., Percivalle, E., Sarasini, A., Gerna, G., Wilkinson, G.W., Davison, A.J., 2010. Sequential mutations associated with adaptation of human cytomegalovirus to growth in cell culture. J. Gen. Virol. 91 (Pt. 6), 1535–1546. Darrah, P.A., Patel, D.T., De Luca, P.M., Lindsay, R.W., Davey, D.F., Flynn, B.J., Hoff, S.T., Andersen, P., Reed, S.G., Morris, S.L., Roederer, M., Seder, R.A., 2007. Multifunctional TH1 cells define a correlate of vaccine-mediated protection against Leishmania major. Nat. Med. 13 (7), 843–850. Davignon, J.L., Clement, D., Alriquet, J., Michelson, S., Davrinche, C., 1995. Analysis of the proliferative T cell response to human cytomegalovirus major immediateearly protein (IE1): phenotype, frequency and variability. Scand. J. Immunol. 41 (3), 247–255. Davignon, J.L., Castanie, P., Yorke, J.A., Gautier, N., Clement, D., Davrinche, C., 1996. Anti-human cytomegalovirus activity of cytokines produced by CD4+

157

T- cell clones specifically activated by IE1 peptides in vitro. J. Virol. 70 (4), 2162–2169. Day, E.K., Carmichael, A.J., Ten Berge, I.J., Waller, E.C., Sissons, J.G., Wills, M.R., 2007. Rapid CD8+ T cell repertoire focusing and selection of high-affinity clones into memory following primary infection with a persistent human virus: human cytomegalovirus. J. Immunol. 179 (5), 3203–3213. Dechanet, J., Merville, P., Berge, F., Bone-Mane, G., Taupin, J.L., Michel, P., Joly, P., Bonneville, M., Potaux, L., Moreau, J.F., 1999. Major expansion of gammadelta T lymphocytes following cytomegalovirus infection in kidney allograft recipients. J. Infect. Dis. 179 (1), 1–8. Dolan, A., Cunningham, C., Hector, R.D., Hassan-Walker, A.F., Lee, L., Addison, C., Dargan, D.J., McGeoch, D.J., Gatherer, D., Emery, V.C., Griffiths, P.D., Sinzger, C., McSharry, B.P., Wilkinson, G.W., Davison, A.J., 2004. Genetic content of wild-type human cytomegalovirus. J. Gen. Virol. 85 (Pt. 5), 1301–1312. Dunn, C., Chalupny, N.J., Sutherland, C.L., Dosch, S., Sivakumar, P.V., Johnson, D.C., Cosman, D., 2003. Human cytomegalovirus glycoprotein UL16 causes intracellular sequestration of NKG2D ligands, protecting against natural killer cell cytotoxicity. J. Exp. Med. 197 (11), 1427–1439. Eagle, R.A., Traherne, J.A., Ashiru, O., Wills, M.R., Trowsdale, J., 2006. Regulation of NKG2D ligand gene expression. Hum. Immunol. 67 (3), 159–169. Eagle, R.A., Traherne, J.A., Hair, J.R., Jafferji, I., Trowsdale, J., 2009. ULBP6/RAET1L is an additional human NKG2D ligand. Eur. J. Immunol. 39 (11), 3207–3216. Einsele, H., Roosnek, E., Rufer, N., Sinzger, C., Riegler, S., Loffler, J., Grigoleit, U., Moris, A., Rammensee, H.G., Kanz, L., Kleihauer, A., Frank, F., Jahn, G., Hebart, H., 2002. Infusion of cytomegalovirus (CMV)-specific T cells for the treatment of CMV infection not responding to antiviral chemotherapy. Blood 99 (11), 3916–3922. Elkington, R., Walker, S., Crough, T., Menzies, M., Tellam, J., Bharadwaj, M., Khanna, R., 2003. Ex vivo profiling of CD8+-T-cell responses to human cytomegalovirus reveals broad and multispecific reactivities in healthy virus carriers. J. Virol. 77 (9), 5226–5240. Elkington, R., Shoukry, N.H., Walker, S., Crough, T., Fazou, C., Kaur, A., Walker, C.M., Khanna, R., 2004. Cross-reactive recognition of human and primate cytomegalovirus sequences by human CD4 cytotoxic T lymphocytes specific for glycoprotein B and H. Eur. J. Immunol.. Emu, B., Sinclair, E., Favre, D., Moretto, W.J., Hsue, P., Hoh, R., Martin, J.N., Nixon, D.F., McCune, J.M., Deeks, S.G., 2005. Phenotypic, functional, and kinetic parameters associated with apparent T-cell control of human immunodeficiency virus replication in individuals with and without antiretroviral treatment. J. Virol. 79 (22), 14169–14178. Faint, J.M., Annels, N.E., Curnow, S.J., Shields, P., Pilling, D., Hislop, A.D., Wu, L., Akbar, A.N., Buckley, C.D., Moss, P.A., Habu, S., 2001. Memory T cells constitute a subset of the human CD8(+)CD45RA(+) pool with distinct phenotypic and migratory characteristics. J. Immunol. 167 (1), 212–220. Fletcher, J.M., Vukmanovic-Stejic, M., Dunne, P.J., Birch, K.E., Cook, J.E., Jackson, S.E., Salmon, M., Rustin, M.H., Akbar, A.N., 2005. Cytomegalovirus-specific CD4+ T cells in healthy carriers are continuously driven to replicative exhaustion. J. Immunol. 175 (12), 8218–8225. Fowler, K.B., Stagno, S., Pass, R.F., Britt, W.J., Boll, T.J., Alford, C.A., 1992. The outcome of congenital cytomegalovirus infection in relation to maternal antibody status. N. Engl. J. Med. 326 (10), 663–667. Fuhrmann, S., Streitz, M., Reinke, P., Volk, H.D., Kern, F., 2008. T cell response to the cytomegalovirus major capsid protein (UL86) is dominated by helper cells with a large polyfunctional component and diverse epitope recognition. J. Infect. Dis. 197 (10), 1455–1458. Gamadia, L.E., Remmerswaal, E.B., Weel, J.F., Bemelman, F., van Lier, R.A., Ten Berge, I.J., 2003. Primary immune responses to human CMV: a critical role for IFNgamma-producing CD4+ T cells in protection against CMV disease. Blood 101 (7), 2686–2692. Gamadia, L.E., Rentenaar, R.J., van Lier, R.A., ten Berge, I.J., 2004. Properties of CD4(+) T cells in human cytomegalovirus infection. Hum. Immunol. 65 (5), 486–492. Gazit, R., Garty, B.Z., Monselise, Y., Hoffer, V., Finkelstein, Y., Markel, G., Katz, G., Hanna, J., Achdout, H., Gruda, R., Gonen-Gross, T., Mandelboim, O., 2004. Expression of KIR2DL1 on the entire NK cell population: a possible novel immunodeficiency syndrome. Blood 103 (5), 1965–1966. Gerna, G., Baldanti, F., Revello, M.G., 2004. Pathogenesis of human cytomegalovirus infection and cellular targets. Hum. Immunol. 65 (5), 381–386. Gillespie, G.M., Wills, M.R., Appay, V., O’Callaghan, C., Murphy, M., Smith, N., Sissons, P., Rowland-Jones, S., Bell, J.I., Moss, P.A., 2000. Functional heterogeneity and high frequencies of cytomegalovirus-specific CD8(+) T lymphocytes in healthy seropositive donors. J. Virol. 74 (17), 8140–8150. Goodrum, F., Reeves, M., Sinclair, J., High, K., Shenk, T., 2007. Human cytomegalovirus sequences expressed in latently infected individuals promote a latent infection in vitro. Blood 110 (3), 937–945. Guglielmo, B.J., Wong-Beringer, A., Linker, C.A., 1994. Immune globulin therapy in allogeneic bone marrow transplant: a critical review. Bone Marrow Transplant 13 (5), 499–510. Hadrup, S.R., Strindhall, J., Kollgaard, T., Seremet, T., Johansson, B., Pawelec, G., thor Straten, P., Wikby, A., 2006. Longitudinal studies of clonally expanded CD8 T cells reveal a repertoire shrinkage predicting mortality and an increased number of dysfunctional cytomegalovirus-specific T cells in the very elderly. J. Immunol. 176 (4), 2645–2653. Hahn, G., Revello, M.G., Patrone, M., Percivalle, E., Campanini, G., Sarasini, A., Wagner, M., Gallina, A., Milanesi, G., Koszinowski, U., Baldanti, F., Gerna, G., 2004. Human cytomegalovirus UL131-128 genes are indispensable for virus growth in endothelial cells and virus transfer to leukocytes. J. Virol. 78 (18), 10023–10033.

158

S.E. Jackson et al. / Virus Research 157 (2011) 151–160

Halary, F., Pitard, V., Dlubek, D., Krzysiek, R., de la Salle, H., Merville, P., Dromer, C., Emilie, D., Moreau, J.F., Dechanet-Merville, J., 2005. Shared reactivity of V{delta}2(neg) {gamma}{delta} T cells against cytomegalovirus-infected cells and tumor intestinal epithelial cells. J. Exp. Med. 201 (10), 1567–1578. Harari, A., Vallelian, F., Meylan, P.R., Pantaleo, G., 2005. Functional heterogeneity of memory CD4 T cell responses in different conditions of antigen exposure and persistence. J. Immunol. 174 (2), 1037–1045. Harari, A., Enders, F.B., Cellerai, C., Bart, P.A., Pantaleo, G., 2009. Distinct profiles of cytotoxic granules in memory CD8 T cells correlate with function, differentiation stage, and antigen exposure. J. Virol. 83 (7), 2862–2871. Harrison, C.J., Britt, W.J., Chapman, N.M., Mullican, J., Tracy, S., 1995. Reduced congenital cytomegalovirus (CMV) infection after maternal immunization with a guinea pig CMV glycoprotein before gestational primary CMV infection in the guinea pig model. J. Infect. Dis. 172 (5), 1212–1220. Heffner, M., Fearon, D.T., 2007. Loss of T cell receptor-induced Bmi-1 in the KLRG1(+) senescent CD8(+) T lymphocyte. Proc. Natl. Acad. Sci. U.S.A. 104 (33), 13414–13419. Hegde, N.R., Dunn, C., Lewinsohn, D.M., Jarvis, M.A., Nelson, J.A., Johnson, D.C., 2005. Endogenous human cytomegalovirus gB is presented efficiently by MHC class II molecules to CD4+ CTL. J. Exp. Med. 202 (8), 1109–1119. Henson, S.M., Franzese, O., Macaulay, R., Libri, V., Azevedo, R.I., Kiani-Alikhan, S., Plunkett, F.J., Masters, J.E., Jackson, S., Griffiths, S.J., Pircher, H.P., Soares, M.V., Akbar, A.N., 2009. KLRG1 signaling induces defective Akt (ser473) phosphorylation and proliferative dysfunction of highly differentiated CD8+ T cells. Blood 113 (26), 6619–6628. Hopkins, J.I., Fiander, A.N., Evans, A.S., Delchambre, M., Gheysen, D., Borysiewicz, L.K., 1996. Cytotoxic T cell immunity to human cytomegalovirus glycoprotein B. J. Med. Virol. 49 (2), 124–131. Iancu, E.M., Corthesy, P., Baumgaertner, P., Devevre, E., Voelter, V., Romero, P., Speiser, D.E., Rufer, N., 2009. Clonotype selection and composition of human CD8 T cells specific for persistent herpes viruses varies with differentiation but is stable over time. J. Immunol. 183 (1), 319–331. Isaacson, M.K., Juckem, L.K., Compton, T., 2008. Virus entry and innate immune activation. Curr. Top. Microbiol. Immunol. 325, 85–100. Jenkins, C., Abendroth, A., Slobedman, B., 2004. A novel viral transcript with homology to human interleukin-10 is expressed during latent human cytomegalovirus infection. J. Virol. 78 (3), 1440–1447. Jenkins, C., Garcia, W., Godwin, M.J., Spencer, J.V., Stern, J.L., Abendroth, A., Slobedman, B., 2008. Immunomodulatory properties of a viral homolog of human interleukin-10 expressed by human cytomegalovirus during the latent phase of infection. J. Virol. 82 (7), 3736–3750. Jones, T.R., Hanson, L.K., Sun, L., Slater, J.S., Stenberg, R.M., Campbell, A.E., 1995. Multiple independent loci within the human cytomegalovirus unique short region down-regulate expression of major histocompatibility complex class I heavy chains. J. Virol. 69 (8), 4830–4841. Jones, T.R., Wiertz, E., Sun, L., Fish, K.N., Nelson, J.A., Ploegh, H.L., 1996. Human cytomegalovirus US3 imparis transport and maturation of major histocompatability complex class I heavy chains. Prox. Natl. Acad. Sci. 93, 11327–11333. Jonjic, S., Mutter, W., Weiland, F., Reddehase, M.J., Koszinowski, U.H., 1989. Site-restricted persistent cytomegalovirus infection after selective long-term depletion of CD4+ T lymphocytes. J. Exp. Med. 169 (4), 1199–1212. Karre, K., Ljunggren, H.G., Piontek, G., Kiessling, R., 1986. Selective rejection of H2-deficient lymphoma variants suggests alternative immune defence strategy. Nature 319 (6055), 675–678. Karrer, U., Sierro, S., Wagner, M., Oxenius, A., Hengel, H., Koszinowski, U.H., Phillips, R.E., Klenerman, P., 2003. Memory inflation: continuous accumulation of antiviral CD8+ T cells over time. J. Immunol. 170 (4), 2022–2029. Kern, F., Khatamzas, E., Surel, I., Frommel, C., Reinke, P., Waldrop, S.L., Picker, L.J., Volk, H.D., 1999a. Distribution of human CMV-specific memory T cells among the CD8pos. subsets defined by CD57, CD27, and CD45 isoforms. Eur. J. Immunol. 29 (9), 2908–2915. Kern, F., Surel, I.P., Faulhaber, N., Frommel, C., Schneider-Mergener, J., Schonemann, C., Reinke, P., Volk, H.D., 1999b. Target structures of the CD8(+)-T-cell response to human cytomegalovirus: the 72-kilodalton major immediate-early protein revisited [In Process Citation]. J. Virol. 73 (10), 8179–8184. Kern, F., Bunde, T., Faulhaber, N., Kiecker, F., Khatamzas, E., Rudawski, I.M., Pruss, A., Gratama, J.W., Volkmer-Engert, R., Ewert, R., Reinke, P., Volk, H.D., Picker, L.J., 2002. Cytomegalovirus (CMV) phosphoprotein 65 makes a large contribution to shaping the T cell repertoire in CMV-exposed individuals. J. Infect. Dis. 185 (12), 1709–1716. Khan, N., Cobbold, M., Keenan, R., Moss, P.A., 2002a. Comparative analysis of CD8+ T cell responses against human cytomegalovirus proteins pp65 and immediate early 1 shows similarities in precursor frequency, oligoclonality, and phenotype. J. Infect. Dis. 185 (8), 1025–1034. Khan, N., Shariff, N., Cobbold, M., Bruton, R., Ainsworth, J.A., Sinclair, A.J., Nayak, L., Moss, P.A., 2002b. Cytomegalovirus seropositivity drives the CD8 T cell repertoire toward greater clonality in healthy elderly individuals. J. Immunol. 169 (4), 1984–1992. Knight, A., Madrigal, A.J., Grace, S., Sivakumaran, J., Kottaridis, P., Mackinnon, S., Travers, P.J., Lowdell, M.W., 2010. The role of Vdelta2-negative gamma-delta T cells during cytomegalovirus reactivation in recipients of allogeneic stem cell transplants. Blood. Komatsu, H., Inui, A., Sogo, T., Fujisawa, T., Nagasaka, H., Nonoyama, S., Sierro, S., Northfield, J., Lucas, M., Vargas, A., Klenerman, P., 2006. Large scale analysis of pediatric antiviral CD8+ T cell populations reveals sustained, functional and mature responses. Immun Ageing 3, 11.

Landini, M.P., Michelson, S., 1988. Human cytomegalovirus proteins. Prog. Med. Virol. 35, 152–185. Lee, S.H., Girard, S., Macina, D., Busa, M., Zafer, A., Belouchi, A., Gros, P., Vidal, S.M., 2001. Susceptibility to mouse cytomegalovirus is associated with deletion of an activating natural killer cell receptor of the C-type lectin superfamily. Nat. Genet. 28 (1), 42–45. Letsch, A., Knoedler, M., Na, I.K., Kern, F., Asemissen, A.M., Keilholz, U., Loesch, M., Thiel, E., Volk, H.D., Scheibenbogen, C., 2007. CMV-specific central memory T cells reside in bone marrow. Eur. J. Immunol. 37 (11), 3063–3068. Libri, V., Schulte, D., van Stijn, A., Ragimbeau, J., Rogge, L., Pellegrini, S., 2008. Jakmip1 is expressed upon T cell differentiation and has an inhibitory function in cytotoxic T lymphocytes. J. Immunol. 181 (9), 5847–5856. Luo, X.H., Huang, X.J., Liu, K.Y., Xu, L.P., Liu, D.H., 2010. Protective immunity transferred by infusion of cytomegalovirus-specific CD8(+) T cells within donor grafts: its associations with cytomegalovirus reactivation following unmanipulated allogeneic hematopoietic stem cell transplantation. Biol. Blood Marrow Transplant 16 (7), 994–1004. Macagno, A., Bernasconi, N.L., Vanzetta, F., Dander, E., Sarasini, A., Revello, M.G., Gerna, G., Sallusto, F., Lanzavecchia, A., 2010. Isolation of human monoclonal antibodies that potently neutralize human cytomegalovirus infection by targeting different epitopes on the gH/gL/UL128-131A complex. J. Virol. 84 (2), 1005–1013. Makedonas, G., Hutnick, N., Haney, D., Amick, A.C., Gardner, J., Cosma, G., Hersperger, A.R., Dolfi, D., Wherry, E.J., Ferrari, G., Betts, M.R., 2010. Perforin and IL-2 upregulation define qualitative differences among highly functional virus-specific human CD8 T cells. PLoS Pathog. 6 (3), e1000798. Manley, T.J., Luy, L., Jones, T., Boeckh, M., Mutimer, H., Riddell, S.R., 2004. Immune evasion proteins of human cytomegalovirus do not prevent a diverse CD8+ cytotoxic T-cell response in natural infection. Blood 104 (4), 1075–1082. McLaughlin Taylor, E., Pande, H., Forman, S.J., Tanamachi, B., Li, C.R., Zaia, J.A., Greenberg, P.D., Riddell, S.R., 1994. Identification of the major late human cytomegalovirus matrix protein pp65 as a target antigen for CD8+ virus-specific cytotoxic T lymphocytes. J. Med. Virol. 43 (1), 103–110, issn: 0146-6615. Melenhorst, J.J., Scheinberg, P., Chattopadhyay, P.K., Gostick, E., Ladell, K., Roederer, M., Hensel, N.F., Douek, D.C., Barrett, A.J., Price, D.A., 2009. High avidity myeloid leukemia-associated antigen-specific CD8+ T cells preferentially reside in the bone marrow. Blood 113 (10), 2238–2244. Messori, A., Rampazzo, R., Scroccaro, G., Martini, N., 1994. Efficacy of hyperimmune anti-cytomegalovirus immunoglobulins for the prevention of cytomegalovirus infection in recipients of allogeneic bone marrow transplantation: a metaanalysis. Bone Marrow Transplant 13 (2), 163–167. Miles, D.J., van der Sande, M., Jeffries, D., Kaye, S., Ismaili, J., Ojuola, O., Sanneh, M., Touray, E.S., Waight, P., Rowland-Jones, S., Whittle, H., Marchant, A., 2007. Cytomegalovirus infection in Gambian infants leads to profound CD8 T-cell differentiation. J. Virol. 81 (11), 5766–5776. Miller, D.M., Cebulla, C.M., Rahill, B.M., Sedmak, D.D., 2001. Cytomegalovirus and transcriptional down-regulation of major histocompatibility complex class II expression. Semin. Immunol. 13 (1), 11–18. Moins-Teisserenc, H., Busson, M., Scieux, C., Bajzik, V., Cayuela, J.M., Clave, E., de Latour, R.P., Agbalika, F., Ribaud, P., Robin, M., Rocha, V., Gluckman, E., Charron, D., Socie, G., Toubert, A., 2008. Patterns of cytomegalovirus reactivation are associated with distinct evolutive profiles of immune reconstitution after allogeneic hematopoietic stem cell transplantation. J. Infect. Dis. 198 (6), 818–826. Munoz, I., Gutierrez, A., Gimeno, C., Farga, A., Alberola, J., Solano, C., Prosper, F., Garcia-Conde, J., Navarro, D., 2001. Lack of association between the kinetics of human cytomegalovirus (HCMV) glycoprotein B (gB)-specific and neutralizing serum antibodies and development or recovery from HCMV active infection in patients undergoing allogeneic stem cell transplant. J. Med. Virol. 65 (1), 77–84. Nebbia, G., Mattes, F.M., Smith, C., Hainsworth, E., Kopycinski, J., Burroughs, A., Griffiths, P.D., Klenerman, P., Emery, V.C., 2008. Polyfunctional cytomegalovirusspecific CD4+ and pp65 CD8+ T cells protect against high-level replication after liver transplantation. Am. J. Transplant 8 (12), 2590–2599. Ninomiya, T., Takimoto, H., Matsuzaki, G., Hamano, S., Yoshida, H., Yoshikai, Y., Kimura, G., Nomoto, K., 2000. Vgamma1+ gammadelta T cells play protective roles at an early phase of murine cytomegalovirus infection through production of interferon-gamma. Immunology 99 (2), 187–194. Northfield, J., Lucas, M., Jones, H., Young, N.T., Klenerman, P., 2005. Does memory improve with age? CD85j (ILT-2/LIR-1) expression on CD8 T cells correlates with ‘memory inflation’ in human cytomegalovirus infection. Immunol. Cell Biol. 83 (2), 182–188. Ouyang, Q., Wagner, W.M., Voehringer, D., Wikby, A., Klatt, T., Walter, S., Muller, C.A., Pircher, H., Pawelec, G., 2003. Age-associated accumulation of CMV-specific CD8+ T cells expressing the inhibitory killer cell lectin-like receptor G1 (KLRG1). Exp. Gerontol. 38 (8), 911–920. Palendira, U., Chinn, R., Raza, W., Piper, K., Pratt, G., Machado, L., Bell, A., Khan, N., Hislop, A.D., Steyn, R., Rickinson, A.B., Buckley, C.D., Moss, P., 2008. Selective accumulation of virus-specific CD8+ T cells with unique homing phenotype within the human bone marrow. Blood 112 (8), 3293–3302. Peggs, K.S., Verfuerth, S., Pizzey, A., Khan, N., Guiver, M., Moss, P.A., Mackinnon, S., 2003. Adoptive cellular therapy for early cytomegalovirus infection after allogeneic stem-cell transplantation with virus-specific T-cell lines. Lancet 362 (9393), 1375–1377. Pita-Lopez, M.L., Gayoso, I., DelaRosa, O., Casado, J.G., Alonso, C., Munoz-Gomariz, E., Tarazona, R., Solana, R., 2009. Effect of ageing on CMV-specific CD8 T cells from CMV seropositive healthy donors. Immun. Ageing 6, 11.

S.E. Jackson et al. / Virus Research 157 (2011) 151–160 Podlech, J., Holtappels, R., Pahl-Seibert, M.F., Steffens, H.P., Reddehase, M.J., 2000. Murine model of interstitial cytomegalovirus pneumonia in syngeneic bone marrow transplantation: persistence of protective pulmonary CD8-T-cell infiltrates after clearance of acute infection. J. Virol. 74 (16), 7496–7507. Polic, B., Hengel, H., Krmpotic, A., Trgovcich, J., Pavic, I., Luccaronin, P., Jonjic, S., Koszinowski, U.H., 1998a. Hierarchical and redundant lymphocyte subset control precludes cytomegalovirus replication during latent infection. J. Exp. Med. 188 (6), 1047–1054. Polic, B., Hengel, H., Krmpotic, A., Trgovcich, J., Pavic, I., Lucin, P., Jonjic, S., Koszinowski, U.H., 1998b. Hierarchical and redundant lymphocyte subset control precludes cytomegalovirus replication during latent infection. J. Exp. Med. 188 (6), 1047–1054. Posch, P.E., Borrego, F., Brooks, A.G., Coligan, J.E., 1998. HLA-E is the ligand for the natural killer cell CD94/NKG2 receptors. J. Biomed. Sci. 5 (5), 321–331. Powers, C., Fruh, K., 2008. Rhesus CMV: an emerging animal model for human CMV. Med. Microbiol. Immunol. 197 (2), 109–115. Prod’homme, V., Griffin, C., Aicheler, R.J., Wang, E.C., McSharry, B.P., Rickards, C.R., Stanton, R.J., Borysiewicz, L.K., Lopez-Botet, M., Wilkinson, G.W., Tomasec, P., 2007. The human cytomegalovirus MHC class I homolog UL18 inhibits LIR-1+ but activates LIR-1-NK cells. J. Immunol. 178 (7), 4473–4481. Prod’homme, V., Sugrue, D.M., Stanton, R.J., Nomoto, A., Davies, J., Rickards, C.R., Cochrane, D., Moore, M., Wilkinson, G.W., Tomasec, P., 2010. Human cytomegalovirus UL141 promotes efficient downregulation of the natural killer cell activating ligand CD112. J. Gen. Virol.. Quinnan Jr., G.V., Kirmani, N., Rook, A.H., Manischewitz, J.F., Jackson, L., Moreschi, G., Santos, G.W., Saral, R., Burns, W.H., 1982. Cytotoxic t cells in cytomegalovirus infection: HLA-restricted T-lymphocyte and non-T-lymphocyte cytotoxic responses correlate with recovery from cytomegalovirus infection in bonemarrow-transplant recipients. N. Engl. J. Med. 307 (1), 7–13. Rapp, M., Messerle, M., Buhler, B., Tannheimer, M., Keil, G.M., Koszinowski, U.H., 1992. Identification of the murine cytomegalovirus glycoprotein B gene and its expression by recombinant vaccinia virus. J. Virol. 66 (7), 4399–4406. Ravetch, J.V., Lanier, L.L., 2000. Immune inhibitory receptors. Science 290 (5489), 84–89. Reddehase, M.J., 2002. Antigens and immunoevasins: opponents in cytomegalovirus immune surveillance. Nat. Rev. Immunol. 2 (11), 831–844. Reddehase, M.J., Mutter, W., Munch, K., Buhring, H.J., Koszinowski, U.H., 1987. CD8positive T lymphocytes specific for murine cytomegalovirus immediate-early antigens mediate protective immunity. J. Virol. 61 (10), 3102–3108. Reddehase, M.J., Jonjic, S., Weiland, F., Mutter, W., Koszinowski, U.H., 1988. Adoptive immunotherapy of murine cytomegalo-virus adrenalitis in the immunocompromised host—Cd4-helper-independent antiviral function of Cd8-positive memory lymphocytes-T derived from latently infected donors. J. Virol. 62 (3), 1061–1065. Reddehase, M.J., Podlech, J., Grzimek, N.K., 2002. Mouse models of cytomegalovirus latency: overview. J. Clin. Virol. 25 (Suppl 2), S23–36. Rentenaar, R.J., Gamadia, L.E., van DerHoek, N., van Diepen, F.N., Boom, R., Weel, J.F., Wertheim-van Dillen, P.M., van Lier, R.A., ten Berge, I.J., 2000. Development of virus-specific CD4(+) T cells during primary cytomegalovirus infection. J. Clin. Invest. 105 (4), 541–548. Riddell, S.R., Watanabe, K.S., Goodrich, J.M., Li, C.R., Agha, M.E., Greenberg, P.D., 1992. Restoration of viral immunity in immunodeficient humans by the adoptive transfer of T cell clones. Science 257 (5067), 238–241 [see comments] issn: 0036-8075. Rolle, A., Mousavi-Jazi, M., Eriksson, M., Odeberg, J., Soderberg-Naucler, C., Cosman, D., Karre, K., Cerboni, C., 2003. Effects of human cytomegalovirus infection on ligands for the activating NKG2D receptor of NK cells: up-regulation of UL16binding protein (ULBP)1 and ULBP2 is counteracted by the viral UL16 protein. J. Immunol. 171 (2), 902–908. Sauce, D., Larsen, M., Leese, A.M., Millar, D., Khan, N., Hislop, A.D., Rickinson, A.B., 2007. IL-7R alpha versus CCR7 and CD45 as markers of virus-specific CD8+ T cell differentiation: contrasting pictures in blood and tonsillar lymphoid tissue. J. Infect. Dis. 195 (2), 268–278. Scalzo, A.A., Fitzgerald, N.A., Wallace, C.R., Gibbons, A.E., Smart, Y.C., Burton, R.C., Shellam, G.R., 1992. The effect of the Cmv-1 resistance gene, which is linked to the natural killer cell gene complex, is mediated by natural killer cells. J. Immunol. 149 (2), 581–589. Scheinberg, P., Melenhorst, J.J., Brenchley, J.M., Hill, B.J., Hensel, N.F., Chattopadhyay, P.K., Roederer, M., Picker, L.J., Price, D.A., Barrett, A.J., Douek, D.C., 2009. The transfer of adaptive immunity to CMV during hematopoietic stem cell transplantation is dependent on the specificity and phenotype of CMV-specific T cells in the donor. Blood 114 (24), 5071–5080. Schleiss, M.R., 2006. Nonprimate models of congenital cytomegalovirus (CMV) infection: gaining insight into pathogenesis and prevention of disease in newborns. Ilar J. 47 (1), 65–72. Schleiss, M.R., 2008. Comparison of vaccine strategies against congenital CMV infection in the guinea pig model. J. Clin. Virol. 41 (3), 224–230. Sester, M., Sester, U., Gartner, B., Heine, G., Girndt, M., Mueller-Lantzsch, N., Meyerhans, A., Kohler, H., 2001. Levels of virus-specific CD4 T cells correlate with cytomegalovirus control and predict virus-induced disease after renal transplantation. Transplantation 71 (9), 1287–1294. Sester, M., Sester, U., Gartner, B., Kubuschok, B., Girndt, M., Meyerhans, A., Kohler, H., 2002. Sustained high frequencies of specific CD4 T cells restricted to a single persistent virus. J. Virol. 76 (8), 3748–3755. Sinzger, C., Schmidt, K., Knapp, J., Kahl, M., Beck, R., Waldman, J., Hebart, H., Einsele, H., Jahn, G., 1999. Modification of human cytomegalovirus tropism through

159

propagation in vitro is associated with changes in the viral genome. J. Gen. Virol. 80 (Pt. 11), 2867–2877. Snyder, C.M., Cho, K.S., Bonnett, E.L., van Dommelen, S., Shellam, G.R., Hill, A.B., 2008. Memory inflation during chronic viral infection is maintained by continuous production of short-lived, functional T cells. Immunity 29 (4), 650–659. Snydman, D.R., Werner, B.G., Heinze-Lacey, B., Berardi, V.P., Tilney, N.L., Kirkman, R.L., Milford, E.L., Cho, S.I., Bush Jr., H.L., Levey, A.S., et al., 1987. Use of cytomegalovirus immune globulin to prevent cytomegalovirus disease in renaltransplant recipients. N. Engl. J. Med. 317 (17), 1049–1054. Spencer, J.V., Lockridge, K.M., Barry, P.A., Lin, G., Tsang, M., Penfold, M.E., Schall, T.J., 2002. Potent immunosuppressive activities of cytomegalovirus-encoded interleukin-10. J. Virol. 76 (3), 1285–1292. Stern-Ginossar, N., Gur, C., Biton, M., Horwitz, E., Elboim, M., Stanietsky, N., Mandelboim, M., Mandelboim, O., 2008. Human microRNAs regulate stress-induced immune responses mediated by the receptor NKG2D. Nat. Immunol. 9 (9), 1065–1073. Stowe, R.P., Kozlova, E.V., Yetman, D.L., Walling, D.M., Goodwin, J.S., Glaser, R., 2007. Chronic herpesvirus reactivation occurs in aging. Exp. Gerontol. 42 (6), 563– 570. Sylwester, A.W., Mitchell, B.L., Edgar, J.B., Taormina, C., Pelte, C., Ruchti, F., Sleath, P.R., Grabstein, K.H., Hosken, N.A., Kern, F., Nelson, J.A., Picker, L.J., 2005. Broadly targeted human cytomegalovirus-specific CD4+ and CD8+ T cells dominate the memory compartments of exposed subjects. J. Exp. Med. 202 (5), 673–685. Tay, C.H., Szomolanyi-Tsuda, E., Welsh, R.M., 1998. Control of infections by NK cells. Curr. Top. Microbiol. Immunol. 230, 193–220. Tey, S.K., Goodrum, F., Khanna, R., 2010. CD8+ T-cell recognition of human cytomegalovirus latency-associated determinant pUL138. J. Gen. Virol. 91 (Pt. 8), 2040–2048. Tomasec, P., Braud, V.M., Rickards, C., Powell, M.B., McSharry, B.P., Gadola, S., Cerundolo, V., Borysiewicz, L.K., McMichael, A.J., Wilkinson, G.W., 2000. Surface expression of HLA-E, an inhibitor of natural killer cells, enhanced by human cytomegalovirus gpUL40. Science 287 (5455), 1031. Tomasec, P., Wang, E.C., Davison, A.J., Vojtesek, B., Armstrong, M., Griffin, C., McSharry, B.P., Morris, R.J., Llewellyn-Lacey, S., Rickards, C., Nomoto, A., Sinzger, C., Wilkinson, G.W., 2005. Downregulation of natural killer cell-activating ligand CD155 by human cytomegalovirus UL141. Nat. Immunol. 6 (2), 181– 188. Tormo, N., Solano, C., Benet, I., Clari, M.A., Nieto, J., de la Camara, R., Lopez, J., LopezAldeguer, N., Hernandez-Boluda, J.C., Remigia, M.J., Garcia-Noblejas, A., Gimeno, C., Navarro, D., 2010. Lack of prompt expansion of cytomegalovirus pp65 and IE-1-specific IFNgamma CD8+ and CD4+ T cells is associated with rising levels of pp65 antigenemia and DNAemia during pre-emptive therapy in allogeneic hematopoietic stem cell transplant recipients. Bone Marrow Transplant 45 (3), 543–549. Tu, W., Chen, S., Sharp, M., Dekker, C., Manganello, A.M., Tongson, E.C., Maecker, H.T., Holmes, T.H., Wang, Z., Kemble, G., Adler, S., Arvin, A., Lewis, D.B., 2004. Persistent and selective deficiency of CD4+ T cell immunity to cytomegalovirus in immunocompetent young children. J. Immunol. 172 (5), 3260–3267. Ulbrecht, M., Martinozzi, S., Grzeschik, M., Hengel, H., Ellwart, J.W., Pla, M., Weiss, E.H., 2000. Cutting edge: the human cytomegalovirus UL40 gene product contains a ligand for HLA-E and prevents NK cell-mediated lysis. J. Immunol. 164 (10), 5019–5022. Urban, M., Klein, M., Britt, W.J., Hassfurther, E., Mach, M., 1996. Glycoprotein H of human cytomegalovirus is a major antigen for the neutralizing humoral immune response. J. Gen. Virol. 77 (Pt. 7), 1537–1547. van de Berg, P.J., van Stijn, A., Ten Berge, I.J., van Lier, R.A., 2008. A fingerprint left by cytomegalovirus infection in the human T cell compartment. J. Clin. Virol. 41 (3), 213–217. van der Veken, L.T., Campelo, M.D., van der Hoorn, M.A., Hagedoorn, R.S., van Egmond, H.M., van Bergen, J., Willemze, R., Falkenburg, J.H., Heemskerk, M.H., 2009. Functional analysis of killer Ig-like receptor-expressing cytomegalovirusspecific CD8+ T cells. J. Immunol. 182 (1), 92–101. van Leeuwen, E.M., Remmerswaal, E.B., Vossen, M.T., Rowshani, A.T., Wertheim-van Dillen, P.M., van Lier, R.A., ten Berge, I.J., 2004. Emergence of a CD4+ CD28− granzyme B+, cytomegalovirus-specific T cell subset after recovery of primary cytomegalovirus infection. J. Immunol. 173 (3), 1834–1841. van Leeuwen, E.M., de Bree, G.J., Remmerswaal, E.B., Yong, S.L., Tesselaar, K., ten Berge, I.J., van Lier, R.A., 2005. IL-7 receptor alpha chain expression distinguishes functional subsets of virus-specific human CD8+ T cells. Blood 106 (6), 2091–2098. van Leeuwen, E.M., Remmerswaal, E.B., Heemskerk, M.H., ten Berge, I.J., van Lier, R.A., 2006a. Strong selection of virus-specific cytotoxic CD4+ T-cell clones during primary human cytomegalovirus infection. Blood 108 (9), 3121–3127. van Leeuwen, E.M., Remmerswaal, E.B., Heemskerk, M.H., Ten Berge, I.J., van Lier, R.A., 2006b. Strong selection of virus-specific cytotoxic CD4+ T cell clones during primary human cytomegalovirus infection. Blood. van Lier, R.A., ten Berge, I.J., Gamadia, L.E., 2003. Human CD8(+) T-cell differentiation in response to viruses. Nat. Rev. Immunol. 3 (12), 931–939. van Stijn, A., Rowshani, A.T., Yong, S.L., Baas, F., Roosnek, E., ten Berge, I.J., van Lier, R.A., 2008. Human cytomegalovirus infection induces a rapid and sustained change in the expression of NK cell receptors on CD8+ T cells. J. Immunol. 180 (7), 4550–4560. Vescovini, R., Biasini, C., Fagnoni, F.F., Telera, A.R., Zanlari, L., Pedrazzoni, M., Bucci, L., Monti, D., Medici, M.C., Chezzi, C., Franceschi, C., Sansoni, P., 2007. Massive load of functional effector CD4+ and CD8+ T cells against cytomegalovirus in very old subjects. J. Immunol. 179 (6), 4283–4291.

160

S.E. Jackson et al. / Virus Research 157 (2011) 151–160

Waller, E.C., McKinney, N., Hicks, R., Carmichael, A.J., Sissons, J.G., Wills, M.R., 2007. Differential co-stimulation through CD137 (4-1BB) restores proliferation of human virus-specific “effector memory” (CD28-CD45RAhi) CD8+ T Cells. Blood. Walter, E.A., Greenberg, P.D., Gilbert, M.J., Finch, R.J., Watanabe, K.S., Thomas, E.D., Riddell, S.R., 1995a. Reconstitution of cellular immunity against cytomegalovirus in recipients of allogeneic bone marrow by transfer of T-cell clones from the donor. N. Engl. J. Med. 333 (16), 1038–1044. Walter, E.A., Greenberg, P.D., Gilbert, M.J., Finch, R.J., Watanabe, K.S., Thomas, E.D., Riddell, S.R., 1995b. Reconstitution of cellular immunity against cytomegalovirus in recipients of allogeneic bone marrow by transfer of T-cell clones from the donor [see comments]. N. Engl. J. Med. 333 (16), 1038–1044, issn: 0028-4793. Wang, D., Shenk, T., 2005a. Human cytomegalovirus UL131 open reading frame is required for epithelial cell tropism. J. Virol. 79 (16), 10330–10338. Wang, D., Shenk, T., 2005b. Human cytomegalovirus virion protein complex required for epithelial and endothelial cell tropism. Proc. Natl. Acad. Sci. U.S.A. 102 (50), 18153–18158. Weekes, M.P., Wills, M.R., Sissons, J.G., Carmichael, A.J., 2004. Long-Term Stable Expanded Human CD4+ T Cell Clones Specific for Human Cytomegalovirus Are Distributed in Both CD45RAhigh and CD45ROhigh Populations. J. Immunol. 173 (9), 5843–5851. Wehler, T.C., Karg, M., Distler, E., Konur, A., Nonn, M., Meyer, R.G., Huber, C., Hartwig, U.F., Herr, W., 2008. Rapid identification and sorting of viable virus-reactive CD4(+) and CD8(+) T cells based on antigen-triggered CD137 expression. J. Immunol. Methods 339 (1), 23–37. Wiertz, E.J., Jones, T.R., Sun, L., Bogyo, M., Geuze, H.J., Ploegh, H.L., 1996a. The human cytomegalovirus US11 gene product dislocates MHC class I heavy chains from the endoplasmic reticulum to the cytosol. Cell 84 (5), 769–779. Wiertz, E.J., Tortorella, D., Bogyo, M., Yu, J., Mothes, W., Jones, T.R., Rapoport, T.A., Ploegh, H.L., 1996b. Sec61-mediated transfer of a membrane protein from the endoplasmic reticulum to the proteasome for destruction [see comments]. Nature 384 (6608), 432–438. Wikby, A., Johansson, B., Olsson, J., Lofgren, S., Nilsson, B.O., Ferguson, F., 2002. Expansions of peripheral blood CD8 T-lymphocyte subpopulations and an association with cytomegalovirus seropositivity in the elderly: the Swedish NONA immune study. Exp. Gerontol. 37 (2–3), 445–453.

Wilkinson, G.W., Tomasec, P., Stanton, R.J., Armstrong, M., Prod’homme, V., Aicheler, R., McSharry, B.P., Rickards, C.R., Cochrane, D., Llewellyn-Lacey, S., Wang, E.C., Griffin, C.A., Davison, A.J., 2008. Modulation of natural killer cells by human cytomegalovirus. J. Clin. Virol. 41 (3), 206–212. Wills, M.R., Carmichael, A.J., Weekes, M.P., Mynard, K., Okecha, G., Hicks, R., Sissons, J.G., 1999. Human virus-specific CD8+ CTL clones revert from CD45ROhigh to CD45RAhigh in vivo: CD45RAhighCD8+ T cells comprise both naive and memory cells. J. Immunol. 162 (12), 7080–7087. Wills, M.R., Okecha, G., Weekes, M.P., Gandhi, M.K., Sissons, P.J., Carmichael, A.J., 2002. Identification of naive or antigen-experienced human CD8(+) T cells by expression of costimulation and chemokine receptors: analysis of the human cytomegalovirus-specific CD8(+) T cell response. J. Immunol. 168 (11), 5455–5464. Wills, M.R., Ashiru, O., Reeves, M.B., Okecha, G., Trowsdale, J., Tomasec, P., Wilkinson, G.W., Sinclair, J., Sissons, J.G., 2005. Human cytomegalovirus encodes an MHC class I-like molecule (UL142) that functions to inhibit NK cell lysis. J. Immunol. 175 (11), 7457–7465. Wills, M.R., Carmichael, A.J., Sissons, J.G.P., 2006. Adaptive Cellular Immunity to Human Cytomegalovirus. In: Reddehase, M.J. (Ed.), Cytomegaloviruses Molecular Biology and Immunology,. Caister Academic Press, pp. 341– 365. Yeager, A.S., Grumet, F.C., Hafleigh, E.B., Arvin, A.M., Bradley, J.S., Prober, C.G., 1981. Prevention of transfusion-acquired cytomegalovirus infections in newborn infants. J. Pediatr. 98 (2), 281–287. Younes, S.A., Yassine-Diab, B., Dumont, A.R., Boulassel, M.R., Grossman, Z., Routy, J.P., Sekaly, R.P., 2003. HIV-1 viremia prevents the establishment of interleukin 2-producing HIV-specific memory CD4+ T cells endowed with proliferative capacity. J. Exp. Med. 198 (12), 1909–1922. Zhou, W., Longmate, J., Lacey, S.F., Palmer, J.M., Gallez-Hawkins, G., Thao, L., Spielberger, R., Nakamura, R., Forman, S.J., Zaia, J.A., Diamond, D.J., 2009. Impact of donor CMV status on viral infection and reconstitution of multifunction CMV-specific T cells in CMV-positive transplant recipients. Blood 113 (25), 6465–6476. Zou, Y., Bresnahan, W., Taylor, R.T., Stastny, P., 2005. Effect of human cytomegalovirus on expression of MHC class I-related chains A. J. Immunol. 174 (5), 3098–3104.