Renal manifestations of hepatitis C virus infection

Kidney International, Vol. 46 (1994), pp. 1255—1263

PERSPECTIVES IN CLINICAL NEPHROLOGY

Renal manifestations of hepatitis C virus infection The existence of viral hepatitis has been known for centuries. In the 5th century B.C. Hippocrates noted epidemics of a jaundice-

open reading frame that encodes a 3010 amino acid polyprotein

that undergoes proteolytic processing to form structural and like illness. These were particularly common during various nonstructural viral proteins (Fig. 1). At the 5' end is a highly military campaigns, and likely represents one of the earliest conserved untranslated region, followed by the nucleocapsid reports of "infectious hepatitis" due to hepatitis A virus, an illness domain which encodes the core antigen (c22-3), a region coding passed by fecal-oral route as a consequence of poor sanitation. for at least two envelope glycoprotein antigens (El and E2INS1), The observation in the late 1800's that hepatitis could develop and a region encoding at least four nonstructural gene products after smallpox vaccination with human lymph [1] and in the 1940's (NS2-NS5). The functions of the nonstructural proteins are not that hepatitis could be passed by transfusion to volunteers [2] led completely elucidated, but it is believed that NS2 codes for a to the realization that there was a second type of hepatitis (that is, protease, NS3 likely encodes helicase (involved in unraveling the "serum" hepatitis) spread by contaminated blood products. Fol- RNA genome for replication), NS4 codes for a putative RNA

lowing the discovery of the "Australia" antigen (hepatitis B binding protein, and NS5 codes for the RNA-dependent RNA surface antigen, HBsAg) by Blumberg, Alter and Visnich in 1964 [3], it was recognized that many of the cases of "serum" hepatitis were due to infection with hepatitis B virus (HBV) [4], and that HBV was also an important cause of chronic active hepatitis and cirrhosis [reviewed in 5]. Unfortunately, by the late 1970s it was apparent that HBV was not the only cause of "serum" hepatitis, and that other "non-A-non-B" hepatitis viruses existed [6], which could be transmitted by blood products to humans and chimpanzees [7]. Using molecular biologic methods, Houghton and colleagues cloned and expressed portions of a RNA virus from the

polymerase [14]. Significant nucleotide and amino acid heteroge-

neity is present throughout the HCV genome, with a wellcharacterized hypervariable region in the E2 envelope glycoprotein domain [16]. This has led to the recognition of at least six HCV subtypes based on differences in the nucleotide sequence for NS5 [17].

HCV infection may be transmitted by blood products or as a consequence of intravenous drug abuse [13]. Transmission by sexual contact or by vertical transmission from mother to infant likely occurs but appears to be infrequent [13]. In as many as 20 plasma of an infected chimpanzee in 1989 [8, 9]. This virus, to 40% of cases, no known risk factor for HCV infection can be designated hepatitis C virus (HCV), is now known to be a major cause of both transfusion-associated and sporadic non-A-non-B found [13]. Infection is followed by an incubation period of 6 to 12 weeks

hepatitis [10, 11]. Infection with this virus is often persistent, and prior to the development of clinical hepatitis. In the majority of may result in chronic active hepatitis, cirrhosis or hepatocellular cases the hepatitis is mild and anicteric. Persistent viremia despite carcinoma [10—12, and reviewed in 13]. resolution of the acute hepatitis is seen in the majority of cases. The persistent and indolent nature of HCV infection often results in prolonged viremia in spite of a strong humoral immune Although many of these patients have persistent viremia despite minimal liver pathology, suggesting the presence of a "healthy" response [reviewed in 13, 14]. It is perhaps not surprising, then, carrier state, at least 50% of patients develop chronic hepatitis, of that chronic immune complex diseases may occur in this setting. which 20% progress to cirrhosis or chronic active hepatitis [13]. The relationship between immune complex disease of the kidney Epidemiologic studies suggest that HCV infection may also be an and hepatitis B infection, a long appreciated connection, has been recently reviewed [15]. In this paper, we will discuss some of the important cause of hepatocellular carcinoma [12]. Serologic assays are routinely used to diagnose HCV infection. more recently recognized extrahepatic manifestations of HCV The original first generation enzyme immunoassay (EIA-l), which infection, with particular emphasis on its association with glomermeasured antibodies to the nonstructural Cl00-3 antigen (coded ular disease. by the NS4 domain), lacked sensitivity and specificity, and was undetectable in 10 to 25% of patients with chronic HCV viremia Biology, clinical features, diagnosis and epidemiology of HCV and falsely present in both healthy individuals and patients with virus

chronic autoimmune hepatitis [18, 19]. The second generation HCV is a lipid enveloped, single stranded, positive-sense RNA enzyme immunoassay (EIA-2) measures antibodies to recombivirus in the family Flaviviridae, which also includes the flaviviruses nant core and NS3 antigens in addition to that coded by NS4, and (such as, yellow fever and dengue viruses) and pestiviruses (such has greatly improved sensitivity (—95%) and specificity. A supas, hog cholera virus) [reviewed in 13, 14]. The HCV genome is plemental serologic assay, the recombinant immunoblot assay approximately 9600 nucleotides in length and contains a single

(RIBA II test), measures antibody to four HCV antigens (the nonstructural antigens 5-1-1, C100-3, and C33, and the core antigen C22), and has comparable sensitivity and slightly more

specificity than the EIA-2 test [13]. However, diagnosis of acute HCV infection by measuring anti-HCV antibodies is compro-

Received for publication March 4, 1994 and in revised form May 4, 1994 Accepted for publication May 5, 1994

mised by the fact that the humoral response is often delayed.

© 1994 by the International Society of Nephrology

Indeed, both IgG and 1gM antibodies to HCV antigens may not

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Johnson et al: HCV and glomerulonephritis

Hepatitis C virus genome

I •i

histologically resembles SjOgren's syndrome [55]. Other syndromes possibly associated with chronic HCV infection include

5 -sv1dIC • env 1 i2ESJ NS3 NS4 NS5 F 3' Core

Envelope

antigen antigens I

C22—3

C

C

Nonstructural antigens

C33 C100-3 5-1-1

C

[59], and polyarteritis nodosa [60, 61]. There may also be an increased risk for lymphoproliferative disorders characterized by monoclonal gammopathy with chronic HCV infection [38, 39, and unpublished observations]. The rest of the discussion will concentrate on the associations of HCV infection with cryoglobulinemia and glomerulonephritis.

I

/I\

chronic corneal ulcerations (that is, Mooren's ulcer) [56], porphyria cutanea tarda [57], lichen planus [58], autoimmune thyroiditis

EIA-1

C C S EIA-ZIRIBA HT-PCA

Fig. 1. HCVgenome. The HCV genome consists of a single open reading frame with a 5' conserved region, and regions encoding the nucleocapsid (core), several envelope antigens (envi and env2/NS1) and several nonstructural proteins (NS2-NS5). Assays to detect HCV infection include the first and second generation enzyme immunoassays (EIA4 and EIA-2, respectively) and the recombinant immunoblot assay (RIBA) which detect

antibodies to various recombinant antigens derived from the HCV genome. A reverse transcriptase polymerase chain reaction (RT-PCR) assay using primers to the 5' conserved region is used to detect HCV RNA and is the best test to determine infectivity.

Mixed ciyoglobulinemia and HCV infection

Cryoglobulins are immunoglobulins that will precipitate in the cold, and are classified as type I if the cryoprecipitates contain a

single monoclonal antibody (such as in myeloma or Waldenstrom's macroglobulinemia), type II if they contain polyclonal IgG and a monoclonal 1gM, and type III if they contain polyclonal IgG

and polyclonal 1gM. In the "mixed cryoglobulinemias" (that is, types II and III) the 1gM typically has rheumatoid factor activity (that is, anti-IgG activity). Mixed cryoglobulinemias have been previously associated with connective tissue diseases (especially Sjogren's syndrome), infec-

tions, malignancies and chronic liver disease [62—66]. If no

underlying association could be found, mixed cryoglobulinemia was labeled "essential." Clinical manifestations of mixed cryooccur until 2 to 12 months following infection (that is, after the globulinemia are often chronic, and include palpable purpura clinical episode of hepatitis) [13, 20], and delayed or absent (from a leukocytoclastic vasculitis), Raynaud's phenomenon, leg seroconversion may develop in the setting of immunosuppression ulcers, arthralgias and/or arthritis, and peripheral neuropathy or viral mutation. The most definitive test for diagnosing active [62—66]. Seventy percent have abnormal liver function tests, and HCV infection is the reverse transcription polymerase chain in severe cases cardiomyopathy or abdominal pain requiring reaction (RT-PCR), which measures the presence of viral RNA in laparotomy may develop [66]. The development of renal disease, patient serum and hence determines potential infectivity [13, 21]. which occurs in half of the cases, carries the worst prognosis [66]. The vast majority of individuals with HCV infection test contin- The principal glomerular lesion is membranoproliferative glomeruously positive by RT-PCR for periods of 20 years or longer, and ulonephritis, but diffuse, focal or mesangial proliferative glomerspontaneous resolution of HCV viremia is unusual. Although ulonephritis has also been reported, especially in association with RT-PCR is technically difficult, expensive and often problematic type III mixed cryoglobulinemia [66—72]. Occasional patients may [22], an accurate, standardized assay is available from several also have granulomatous vasculitis of small and moderately sized reference laboratories [21, 23]. renal arteries [66, 67]. Epidemiologic studies have shown that chronic HCV infection Levo et al were the first to suggest that mixed cryoglobulinemia affects 0.3% of the population of Canada and Northern Europe, was a manifestation of chronic HBV infection [64, 65]. Two-thirds 0.6% of the United States and Central Europe, 1.2 to 1.5% of of patients with essential mixed cryoglobulinemia have abnormal Japan and Southern Europe, and 3.5 to 6.4% in some regions of liver function, and as many as 50% of patients had antibodies to Africa [24—26]. Interestingly, in Peru HCV infection appears to be

the HBsAg in their blood [64, 65]. When the cryoprecipitates were

extremely rare [27]. In high risk groups the prevalence of HCV

examined, 74% were positive either for the HBsAg or anti-HBs [64]. However, the association of cryoglobulinemia with HBV

infection is higher, being 60 to 90% of hemophiliacs, 60 to 70% of intravenous drug abusers, 15 to 25% of dialysis patients, and 4 to

infection could not be confirmed in another study [63]. The 8% of homosexual men [13, 241. However, the incidence of frequency of liver function abnormalities was also independent of post-transfusion HCV infection in the United States is decreasing; the HBV status [64, 66]. These data were consistent with the this is due in part to the screening of blood in blood banks in the hypothesis that a different hepatic virus was involved in the 1980's for "surrogate" markers for HCV infection (such as pathogenesis of the cryoglobulinemia. elevated alanine aminotransferase levels or the presence of antiIt is now apparent that HCV is the major cause of mixed HBc antibodies [28, 29]), and more recently by the screening of donor blood for specific anti-HCV antibodies [30], as well as by the avoidance of blood donation from high risk groups. Extrahepatic manifestations of HCV infection

cryoglobulinemia. HCV RNA (as detected by RT-PCR) and HCV antibodies (as detected by EIA-2 or RIBA-2) are present in the serum of the majority (>80%) of patients with mixed cryoglobu-

linemia [32, 33, 39-44]. In these patients, HCV RNA and

anti-HCV antibody have been shown to be concentrated in the Recently, several extrahepatic syndromes have been reported cryoprecipitates [41—46]. In some of the cryoprecipitates, the with chronic HCV infection. These include the mixed cryoglobu- monoclonal 1gM appears to have a stronger binding affinity for linemias [31—44], niembranoproliferative glomerulonephritis antibody to the HCV core antigen (C22) than to control IgG [45]. (MPGN) [31, 45—53], arthritis [54] and a sicca syndrome that While these data suggest an important role for HCV infection in

Johnson et al: HCV and glomendonephritis

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cryoglobulinemia, other viruses, such as HBV [64] or EpsteinBarr virus [73] may also be involved in some cases. Glomerulonephritis

Background. Glomerular disease often accompanies chronic liver disease, although frequently it is clinically silent [74—83]. In

addition to cryoglobulinemic MPGN, mesangial proliferative, membranoproliferative, membranous, diffuse proliferative, and sclerosing glomerulonephritis (ON) also have been reported [78—83]. A mesangial proliferative ON with IgA deposition is especially common [79, 82].

Although these glomerular diseases may occur in association with a wide variety of liver diseases [78—81], patients with chronic

HBV infection are particularly predisposed to develop membranous and membranoproliferative ON [reviewed in 15]. These

diseases are thought to be mediated by HBeAg and HBsAg immune complexes, respectively, although other pathogenic mechanisms have not been entirely excluded [15].

Several studies have documented an association of chronic HCV infection with MPGN [31, 45—53]. We have now studied the

clinical and virologic features of 35 of these patients (manuscript submitted).

Clinical and laboratory features. Patients presented with nephrotic syndrome or occasionally with non-nephrotic proteinuria and mild to moderate renal insufficiency. Whereas many of these patients have type II, or, more rarely, type III cryoglobulinemia [31, 45—51], 30 to 40% do not have detectable circulating cryoglobulins at presentation [45, and manuscript submitted]. Indeed, symptoms suggestive of cryoglobulinemia, such as purpura, arthritis, or neuropathy, were present in only one-half of HCV-infected

patients with MPON. In addition, only 20% of patients had physical signs of liver disease, although the majority (60 to 70%)

have mildly elevated transaminases. Other laboratory features of HCV-associated MPGN include hypocomplementemia (depressed CH5O, C4, and often C3), the presence of rheumatoid factors, and elevated Clq binding. Tests for antinuclear and anti-neutrophil cytoplasmic antibodies were generally negative. Pathology. Renal biopsy typically shows an increased cellularity

and accentuation of the lobular architecture of the glomerular tuft, often with double contours of the basement membrane noted by silver methenamine staining [45] (Fig. 2). Mesangial proliferation and sclerosis may also be present. By immunofluorescence, mesangial and capillary wall deposition of 1gM, IgO, and C3 can be demonstrated in most cases, although the deposition may be Fig. 2. HCV-associated MPGN. A By light microscopy, glomeruli display modest, and in as many as one-third of cases no or only trace IgG hypercellularity in a lobular pattern. B Immunofluorescence shows capilis found. Electron microscopy usually shows subendothelial de- laiy wall deposition of 1gM, often with IgG and C3. C Electron microscopy

posits characteristic of MPGN type I, although mesangial and subepithelial immune deposits are occasionally observed. In some cases the immune deposits have ultrastructural features of cryo-

usually shows immune deposits in the subendothelial and paramesangial spaces (arrows).

globulins such as granular, finely fibrillar, or immunotactoid structures. In addition to the glomerular disease, tubulointerstitial HCV-associated MPGN may also develop following liver [52] inflammation and scarring are common, and in two cases we have or renal transplantation. We have observed a proliferative gbmerulopathy with histologic features similar to MPON or transnoted vasculitis of small and medium sized renal arteries. Although the classic lesion is usually cryoglobulinemic or plant gbomerulopathy in two renal transplant patients with HCV noncryoglobulinemic MPON type I, the occasional presence of infection (manuscript in preparation). Both patients had subepithelial immune deposits may suggest a pattern of injury that nephrotic range proteinuria, a rising serum creatinine, mildly has been called MPON type III, and the relative lack of immune elevated liver function tests, hypocomplementemia, circulating deposits occasionally observed is similar to some cases of acute rheumatoid factors, and serum that was positive for HCV RNA exudative and proliferative ON. Areas of focal sclerosis may also and antibody. One patient had cryogbobulinemia, whereas the other had circulating immune complexes as detected by an be prominent.

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Johnson et a!: HCV and glomerulonephritis

elevated Clq binding test. Biopsy in both cases showed a membranoproliferative lesion with 1gM and C3 deposition, but no or only trace amounts of IgG, and with occasional subendothelial immune deposits by electron microscopy. These findings are consistent with MPGN, but are not clearly distinguishable from allograft glomerulopathy [84]. Virology. Evidence suggesting a causative role for HCV infec-

tion in the development of MPON has been based on the demonstration of HCV RNA and antibody in the serum, and, in those cases where cryoprecipitates were available, to demonstrate the concentration of the HCV RNA and antibody in the cryoglobulins [45—53]. Furthermore, immune complexes and cryoglobulins have been localized within glomeruli in the subendothehal space of the capillary walls. However, identification of the virus in the glomeruli has remained elusive, although one report claims to show virus-like particles in the mesangium [47]. Further evidence for a viral etiology may be provided as more effective methods for detecting HCV antigens and RNA in tissue become available [85—88].

How important is HCVas an etiologic factor for MPGN? Recent evidence suggests that HCV infection may be an important cause of MPON, especially in countries where HCV infection is highly prevalent. For example, in Northern Japan, HCV infection was noted in 6 of 10 random patients (60%) with MPGN, in one study, whereas it was present in only 1 of 58 patients with IgA nephropathy and in 0 of 12 patients with minimal change disease [51]. We found HCV RNA and antibody in 2 of 10 random patients with MPON type I [45], but our impression is that it may be significantly more common than this initial sampling suggests. Indeed,

one wonders if the decline in MPGN observed in Europe and North America in the 1970s and 1980's [89—91, and Daniel Cattran, personal communication] reflects the policies of some blood banks to exclude blood with "surrogate" markers of HCV infection, such as the presence of elevated transaminase activity or

of anti-HBc antibody [28, 29]. One may also speculate that the high incidence of MPGN observed in some developing countries, such as in Ethiopia [92] may relate to the relatively high prevalence of HCV infection in these areas [25, 26]. Other types of GN. The primary glomerular lesion associated with HCV infection is cryoglobulinemic or noncryoglobulinemic MPGN. However, as noted above, the lesion may also appear as an acute exudative and proliferative nephritis, MPGN type III, or, in transplant patients, as a lesion indistinguishable from allograft glomerulopathy. We have also noted six cases of HCV infection associated with membranous nephropathy (unpublished data), and several cases of HCV infection and membranous ON have been reported by others [93, 94]. These cases clinically present like classic idiopathic membranous nephropathy, and patients have normal complement levels, an absence of rheumatoid factor or cryoglobulinemia, and often normal liver function. The obser-

ing HCV antigens, anti-HCV antibodies, and rheumatoid factors (anti-IgG antibodies). Circulating HCV and anti-HCV immune complexes should occur in most HCV-infected patients as viremia is usually persistent despite a strong antibody response [12, 13]. We [45] and others [41, 42] have demonstrated that HCV RNA is concentrated over 100-fold relative to serum in the cryoprecipitates of our patients with HCV-associated cryoglobulinemia or MPGN. The lack of a neutralizing antibody response to HCV may

relate to the ability of the HCV virus to change its envelope antigens by mutation during the course of infection [95]. This would result in spontaneous changes in antibody affinity and avidity, and could potentially explain the chronic relapsing course frequently observed in untreated patients with mixed cryoglobulinemia [66, 96].

The mechanism for the development of an 1gM rheumatoid factor in these patients remains unclear. In those patients with type II cryoglobulinemia, the monoclonal 1gM can frequently be shown to be a specific serologically-defined rheumatoid factor cross-reactive idiotype termed WA [41], which is believed to be encoded by germline genes [97, 98]. Although the 1gM antibody frequently binds to normal pooled IgG, several of our patients had 1gM which appeared to bind more avidly to anti-HCV core (C22) IgO than nonspecific human IgG [45]. This raises the question as to whether the 1gM rheumatoid factor may bind preferentially to

anti-HCV IgG or to the IgG-HCV immune complex. Indeed, it has been reported that the 1gM rheumatoid factors in patients with mixed cryoglobulinemia have anti-idiotypic activity against homologous IgO [99]. If the 1gM anti-IgG activity were induced by the persistently elevated anti-HCV IgG in predisposed patients, then the binding of this 1gM to HCV-IgG immune complexes would potentiate immune complex formation and deposition, possibly resulting in a clinical presentation of either mixed cryoglobuhinemia or MPGN. Evidence supports the hypothesis that the circulating immune complexes localize to the glomerular capillaries where they deposit in the subendothelium and mesangium and initiate local cellular proliferation and leukocyte inifitration [45]. The variability in degree of immune deposits observed may be due to the balance between deposition and normal mechanisms of clearance. For example, it is known experimentally that, whereas immune complexes may persist in the subendothelial space [100], in some conditions it may be rapidly cleared from the glomerular subendothehium [101]. Studies of leukocytoclastic vasculitis in man have

also shown that immune deposits are cleared from the subendothelial space of the dermal capillaries within 24 to 48 hours [102]. Two alternative hypotheses should also be considered. First, it

is now recognized that chronic HCV infection may result in

vation in one study that 8% of patients with membranous

autoantibody formation, such as anti-GOR antibodies (directed to a host-derived nuclear antigen [103]), type 1 liver-kidney micro-

nephropathy in Northern Japan had HCV antibodies and HCV RNA as compared to less than 1% of patients with other types of ON (but excluding MPGN) suggests that this association is not strong but may well be significant [51].

mic antibodies (P-ANCA) [58, 104, 105]. It is possible that autoantibodies to native renal antigens may also develop that

Pathogenesis

The pathogenesis of HCV-associated ON likely relates to the glomerular deposition of circulating immune complexes contain-

somal antibodies, anti-smooth muscle antibodies, antinuclear antibodies, and occasionally perinuclear anti-neutrophil cytoplas-

could account for some of the glomerular pathology. Second, the observation that MPGN may occur in patients with HBV-negative and HCV-negative liver disease [81] suggests that chronic liver disease, perhaps via the impaired clearance of immune complexes, may contribute to the pathogenesis of MPGN directly.

Johnson et alt HCV and glomerulonephritis

Treatment and management Alpha interferon

Alpha interferon (a-IFN) is currently approved in the United States for the treatment of chronic HCV infection. Treatment with a-IFN (2 to 3 million U three times per week for 6 months) suppresses viremia and improves liver function and histology in 50% of patients with chronic HCV infection [106, 107]. Unfortunately, clinical relapses occur in at least 50% of patients after completing treatment [106, 107]. Given its ability to inhibit HCV viral replication, a-IFN could potentially be useful in the treatment of extrahepatic manifesta-

1259

67, 96]. However, in situations where the clinical manifestations are severe, immunosuppressive treatment with steroids, cytotoxic agents (that is, cyclophosphamide or chlorambucil), and/or plasmapheresis has been frequently recommended [reviewed in 66, 67, 96]. Unfortunately, most reports of beneficial responses have

been anecdotal, and relapses are common [66, 67]. However, there is evidence that pulse methylprednisolone therapy may significantly improve renal function in these patients, but most patients remain with significant proteinuria and low levels of circulating cryoglobulins [118].

We have not observed any spontaneous remissions of renal

disease in our patients with HCV-associated MPGN, and patients have either remained stable or progressed over a 6 month period.

tions of HCV infection, such as mixed cryoglobulinemia or MPGN. Indeed, a-IFN has been used to treat patients with We have also not observed any reduction in proteinuria in five essential mixed cryoglobulinemia [37, 108—114] and MPGN [45, patients who received various doses of oral corticosteroids, a!and manuscript submitted]. In patients with cryoglobulinemia, though it did appear to improve the skin lesions in the two a-IFN improves the clinical symptoms such as the purpura and arthralgias, and reduces the cryoglobulin levels in the majority of

patients who had purpura. The administration of "pulse" steroids

has resulted in improved renal function in two of our patients, although both have remained HCV RNA positive. We have also had five patients that received prednisone and cyclophosphamide Recently Misiani et al have reported the effect of a-IFN in 25 with or without plasma exchange. Three of these patients, howpatients with HCV-associated mixed cryoglobulinemia, of which ever, subsequently died from infectious complications, which are about three quarters had renal involvement [114]. Sixty percent known to be associated with this type of therapy [119]. We are (N = 15) became negative in their serum for HCV RNA by aware of one additional patient with HCV-associated MPGN who RT-PCR during therapy, and it was these patients who had had a complete remission with prednisone and cyclophosphamide; patients [37, 108—113]. However, clinical relapse is common after therapy is stopped [108—113].

significant improvements in cutaneous vasculitis, as well as signif-

however, serial blood samples during therapy also showed a rapid

icant decreases in ciyoglobulins, rheumatoid factor and serum increase in HCV RNA as determined by quantitative PCR (Quigg creatinine. Unfortunately, viremia and cryoglobulinemia recurred R, Gretch DR, unpublished observations). in all HCV RNA-negative patients after therapy was discontinued

Based on knowledge of other chronic viral infections, it is likely that cell mediated immunity plays an important role in controlling We have treated 17 American patients with both cryoglobuline- HCV infection. HCV-specific CD8+ lymphocytes can be identimic and non-cryoglobulinemic HCV-associated MPGN with fied in livers of infected chimpanzees and humans [120, 121]. Of a-IFN, of which 14 have been treated for 6 months or longer potentially greater significance, it has been shown that CD4+ T (manuscript in press). Treatment was associated with a significant lymphocytes proliferate in response to the HCV core antigen, and reduction (65%) in proteinuria, and normalization of liver func- that the T cell proliferative response is associated with a benign tion tests, but with no significant change in renal function. As with hepatic course [122]. Milder liver disease is also associated with the study of Misiani et al [114], a good clinical response correlated less HCV viremia relative to that observed in patients with with disappearance of HCV RNA from the blood as measured by advanced liver disease [123, 124]. This suggests that the T cell [114].

RT-PCR, however, relapse of viremia and renal disease were response can be correlated both with the degree of viremia and common after completing therapy. This suggests that future the severity of liver disease. protocols using a-IFN may need to consider higher doses or In circumstances where the T cell response to HCVis impaired, longer duration of therapy. as with immunosuppressive therapy, one might expect to see Side effects of a-IFN have included flu-like symptoms, insom- increased HCV viremia and worsening of liver disease. In most nia, and malaise. Two patients have developed erythema multi- liver transplant recipients HCV viremia recurs [125], and viral form requiring discontinuation of therapy. A reduction in diuretic

RNA titers increase rapidly (D. Gretch, manuscript submitted). In

dosage is often required in the first month. Rare patients with as many as 50% of liver transplant patients this is followed by cryoglobulinemia have had transient worsening of pre-existent recurrent liver disease within one year of transplant [126 and DG, peripheral neuropathies [110, 113, and unpublished observations]. manuscript submitted]. Nonetheless, although HCV is a major This may relate to the ability of a-IFN to up-regulate class I and cause of post-transplant hepatitis, many HCV-infected patients II antigens and to augment the immunologic response [115]. have a benign course following transplantation (at least in the Although a-IFN has been reported to occasionally induce pro- initial but often relatively short follow-up period) [127—131]. teinuria [116, 117], we have not observed worsening proteinuria in any of our patients. Immunosuppressive therapies

What is the role for immunosuppressive therapy in the management of extrahepatic HCV disease? Because of the waxing and waning nature of essential mixed ciyoglobulinemia and cryoglobulinemic GN, some investigators have suggested that no treatment is necessary unless the renal disease is progressive [reviewed in 66,

However, in some cases advanced liver disease may develop [127, 129]. One variable that appears to correlate with the development

of liver disease in these patients is the cumulative dose of anti-lymphoblast globulin administered [130]. If immunosuppressive medication is detrimental, then why do

some patients do well without evidence for worsening liver disease? One possibility is that immunosuppressive therapy may

not be able to impair a strong CD4+ response to HCV core antigen if it is already present. In contrast, if the CD4+ response

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Johnson et al: HCV and glomerulonephritis

was weak, such that the patient already had evidence of significant

4. PRINCE AM, HARGROVE RL, SZMUNESS W, CHERUBIN CE, FONTANA

viremia and liver disease, then the immunosuppression may be

VJ, JEFFRIES GH: Immunologic distinction between infectious and serum hepatitis. N Engl J Med 282:987—991, 1970 5. SHERLOCK 5: The natural history of hepatitis B. Postgrad Med J

enough to lead to a rapid increase in the viremia. This is consistent with recent observations that the risk for progressive liver disease in renal transplant patients is much greater if the pre-transplant liver biopsy shows chronic liver disease [132]. The degree of histocompatibility is also likely important, as recent studies in HCV-infected liver transplant patients suggest that the risk for development of progressive liver disease is greater if the donor and recipient are matched at the HLA-DQI3 locus [133]. Conclusion

63:7—11, 1987 6. FEINSTONE SM, KAPIKIAN AZ, PURCELL RH, ALTER HJ, HOLLAND

PV: Transfusion-associated hepatitis not due to viral hepatitis type A or B. N Engl J Med 292:767—770, 1975 7. BRADLEY DW, MCCAUSTLAND KA, COOK EH, SCHABLE CA, EBERT

JW, MAYNARD JE: Posttransfusion Non-A, Non-B hepatitis in chimpanzees. Gastroenterology 88:773—779, 1985

8. CHoo Q-L, Kuo G, WEINER Al, OVERBY LR, BRADLEY DW, HOUGHTON M: Isolation of a cDNA clone derived from a bloodborne non-A, non-B viral hepatitis genome. Science 244:359—361, 1989

HCV is a major cause of chronic liver disease, but it is also associated with extrahepatic manifestations, including mixed cryo-

globulinemia and glomerulonephritis. The principal type of gbmerulonephritis observed is either a cryoglobulinemic-type of MPGN, or MPGN type I. Initial epidemiologic studies suggest

that HCV infection may be a major cause of both types of glomerulonephritis. Patients with glomerulonephritis may have no

clinical evidence for systemic or liver involvement, and liver function tests may be normal. These patients usually have hypo-

complementemia, circulating rheumatoid factors, and in twothirds of cases, cryoglobulinemia. The pathogenesis of HCVassociated MPGN is likely to be mediated by the glomerular deposition of circulating HCV and anti-HCV antibodies. Treatment with a-interferon may be of benefit in suppressing the viremia, reducing the proteinuria and stabilizing the renal function, but long term and controlled studies are needed to prove this and to assess the risk for relapse. Although immunosuppressive treatment has been commonly used to treat mixed cryogbobulinemia and MPGN in the past, a re-evaluation of the effects of this

treatment on HCV viremia and antibody response, and on the liver and renal disease is indicated. RIO-lARD J. JOHNSON, RICHARD WIU.soN, HIDEAKI YANABE, WILLIAM COU5ER, CHARLES E. ALPER5,

MARK H. WENER, CONNIE DAVIS, AND

DAVID R. GRETCH

Seattle, Washington, USA and Hirosaki, Japan

Acknowledgments Support for this manuscript was provided by the U.S. Public Health Service grants DK 43422, DK 02142, and by an NIH George O'Brien

9. Kuo G, CHOO Q-L, ALTER EU, GITNICK GL, REDEKER AG, PURCELL RH, MIYAMURA T, DIENSTAG JL, ALTER MJ, STEVENS CE, TEGTMEtER GE, B0NIN0 F, COLOMBO M, LEE W-S, KUO C, BERGER K, SHUSTER JR, OVERBY LR, BRADLEY DW, HOUGHTON M: An assay

for circulating antibodies to a major etiologic virus of human non-A, non-B hepatitis, Science 244:362—364, 1989 10. ALTER HJ, PURCELL RH, SHIH JW, MELPOLDER JC, HOUGHTON M,

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