Immunization with an adjuvant hepatitis B vaccine after liver transplantation for hepatitis B–related disease

VIRAL HEPATITIS

Immunization With an Adjuvant Hepatitis B Vaccine After Liver Transplantation for Hepatitis B–Related Disease 1 Ruth Neuhaus,2 Pierre Vandepapeliere,3 Jens Vollmar,3 Andreas Lun,4 ¨ Ulrich Bienzle,1 Matthias Gunther, and Peter Neuhaus2

Patients who undergo transplantation for hepatitis B virus (HBV)-related diseases are treated indefinitely with hepatitis B hyperimmunoglobulin (HBIG) to prevent endogenous HBV reinfection of the graft. Active immunization with standard hepatitis B vaccines in these patients has recently been reported with conflicting results. Two groups of 10 liver transplant recipients on continuous HBIG substitution who were hepatitis B surface antigen (HBsAg) positive and HBV DNA negative before transplantation were immunized in a phase I study with different concentrations of hepatitis B s antigen formulated with the new adjuvants 3-deacylated monophosphoryl lipid A (MPL) and Quillaja saponaria (QS21) (group I/vaccine A: 20 ␮g HBsAg, 50 ␮g MPL, 50 ␮g QS21; group II/vaccine B: 100 ␮g HBsAg, 100 ␮g MPL, 100 ␮g QS21). Participants remained on HBIG prophylaxis and were vaccinated at weeks 0, 2, 4, 16, and 18. They received 3 additional doses of vaccine B at bimonthly intervals if they did not reach an antibody titer against hepatitis B surface antigen (anti-HBs) greater than 500 IU/L. Sixteen (8 in each group) of 20 patients (80%) responded (group I: median, 7,293 IU/L; range, 721-45,811 IU/L anti-HBs; group II: median, 44,549 IU/L; range, 900-83,121 IU/L anti-HBs) and discontinued HBIG. They were followed up for a median of 13.5 months (range, 6-22 months). The vaccine was well tolerated. In conclusion, most patients immunized with the new vaccine can stop HBIG immunoprophylaxis for a substantial, yet to be determined period of time. (HEPATOLOGY 2003;38:811-819.)

H

epatitis B virus (HBV) infection with acute liver failure or liver cirrhosis is the indication for liver transplantation in 10% to 20% of liver transplant recipients.1 These patients face a high risk of endogenous HBV reinfection without continuous postoperative immunoprophylaxis. The reinfection rate in preoperatively HBV DNA–positive patients is about 80% and about 50% in HBV DNA/hepatitis B e antigen (HBeAg)-negative recipients.2 Abbreviations: HBV, hepatitis B virus; HBeAg, hepatitis B e antigen; HBIG, hepatitis B hyperimmunoglobulin; anti-HBs, antibody against hepatitis B surface antigen; HBsAg, hepatitis B surface antigen; MPL, monophosphoryl lipid A; QS21, Quillaja saponaria Molina adjuvant. From the 1Institute of Tropical Medicine, 2Department of General, Visceral and Transplantation Surgery, and 4Institute of Laboratory Medicine and Pathobiochemistry, Charite´, Humboldt University, Berlin, Germany; and 3GlaxoSmithKline Biologicals, Rixensart, Belgium. Received February 14, 2003; accepted June 27, 2003. Address reprint requests to: Ulrich Bienzle, M.D., Institute of Tropical Medicine, Spandauer Damm 130, 14050 Berlin, Germany. E-mail: [email protected]; fax: (49) 30 30116710. Copyright © 2003 by the American Association for the Study of Liver Diseases. 0270-9139/03/3804-0006$30.00/0 doi:10.1053/jhep.2003.50396

Reinfection can be prevented in most liver transplant recipients by regular hepatitis B hyperimmunoglobulin (HBIG) substitution administered alone or in combination with nucleoside analogues.1,3-5 As a rule, antibody titers to hepatitis B surface antigen (anti-HBs) greater than 100 IU/L should continuously be maintained, whereas a trough level greater than 500 IU/L prevents reinfection in almost 100% of HBeAg-negative patients. Only a few patients on long-term HBIG prophylaxis develop HBV infection caused by mutations of the gene coding for hepatitis B surface antigen (HBsAg).6 HBIG substitution is safe and causes only mild and intermittent symptoms. Independently, Ba´rcena et al.7 and Sanchez-Fueyo et al.8,9 immunized patients after liver transplantation for HBV-related disease with repeated double doses of a recombinant HBV vaccine and reported significant anti-HBs antibody production in most of their vaccinees. In contrast, in an immunization study by Angelico et al.10 on 17 patients who underwent transplantation for HBV-related cirrhosis, only 2 patients developed protective antibody titers. 811

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Table 1. Demographic and Clinical Characteristics of 20 LTx Recipients for HBV-Related Disease Receiving a Hepatitis B Vaccine Formulated With a Novel Adjuvant System Patient (Group I/II)

Responder* 01(I) 02(I) 04(I) 05(I) 07(I) 08(I) 09(I) 10(I) 11(II) 12(II) 14(II) 16(II) 17(II) 18(II) 19(II) 20(II) Nonresponder 03(I) 06(I) 13(II) 15(II)

Age Sex

Underlying Disease

Interval Since LTx (y)

Immunosuppressive Drugs

35 M 51 M 53 M 58 M 55 M 45 M 55 M 57 M 41 M 45 M 65 M 51 M 56 M 61 F 43 M 54 M

Cirrhosis

10.5

C

Acute hepatitis, liver failure

6.5

T

Acute hepatitis, liver failure

7

T

Cirrhosis

8.5

C

Diabetes type II, LTx with splenectomy

Cirrhosis

4.5

T

V. portae thrombosis

Cirrhosis

7.5

T

Cirrhosis

3

Lamuvidine 150 mg/d Renal transplantation 1981

Cirrhosis

2.5

T MMF T

Cirrhosis

5

T

Diabetes type II Lamivudine 150 mg/d

Cirrhosis

9

T

Cirrhosis

10

C

Cirrhosis

13

C

Cirrhosis

6.5

T

Famciclovir 1,000 mg/d

Cirrhosis

4

T

Lamuvidine 150 mg/d

Cirrhosis

3.5

Cirrhosis, liver failure

7

T MMF T

Prednisolone 4 mg/d Renal transplantation 1999 Nephrotic syndrome

Cirrhosis

2.5

Cirrhosis

5

T MMF T

Cirrhosis

13

C

Cirrhosis

2

C

54 M 69 F 63 M 46 M

Other

Prednisolone 7.5 mg/d

Abbreviations: T, tacrolimus; C, ciclosporin; MMF, mycophenolate mofetil. *Anti-HBs ⬎ 500 IU/L.

In a preliminary communication,11 we presented data from a phase I, low-dose hepatitis B immunization trial in 10 patients who underwent transplantation for HBV-related disease.11 Patients who remained HBsAg and HBV DNA negative on HBIG immunoprophylaxis were immunized using recombinant HBsAg combined with a novel adjuvant system. The vaccine was well tolerated, and a sustained antibody response was observed in 5 of 10 patients and allowed termination of HBIG substitution. Since then, 10 more patients have been admitted to the study and the concentration of both HBsAg and the adjuvant system were increased to improve the response

rate. The data in the present report confirm and expand our previous findings.

Patients and Methods Study Group. Two groups of 10 liver transplant recipients from the Department of Surgery, Humboldt University, were admitted to this phase I hepatitis B vaccination study (Table 1). Eighteen patients underwent liver transplantation for HBV-related cirrhosis and 2 for acute hepatitis B and liver failure. Eligible patients were stable liver transplant recipients on reinfection prophy-

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laxis with HBIG. Four patients also received antiviral therapy to prevent reinfection (3 treated with lamivudine 150 mg/d and 1 treated with famciclovir 1,000 mg/d). Ciclosporin, tacrolimus, mycophenolate mofetil, and corticosteroids were used for immunosuppression. We excluded patients who underwent transplantation less than 12 months before enrollment, who were HBV DNA positive or HBeAg positive preoperatively, or who receive interferon or any other immunostimulating drug. Patients provided written informed consent. The trial protocol conformed to the ethical guidelines of the Declaration of Helsinki in force at the time of study and was approved by the ethics committee of Humboldt University. Before admission to the study, all patients had received between 500 and 1,500 IU of HBIG intravenously every 2 to 6 weeks since transplantation to maintain anti-HBs titers greater than 100 IU/L. HBIG prophylaxis was continued during the vaccination trial until participants developed an antibody response greater than 500 IU/L. Intervals between HBIG injections grew longer when active anti-HBs production started. Hematologic and biochemical parameters (prothrombin time; creatinine, amylase, bilirubin, transaminase, and alkaline phosphatase levels; and urinalysis) and serum levels of immunosuppressive drugs were measured using standard laboratory methods. Quantitative HBV DNA determination was performed by the Roche Monitor Amplicor assay (Roche Diagnostics, Belleville and Branchburg, NJ), and HBsAg was determined by enzyme immunoassay (ETIMAK-2; BykDiaSorin, Saluggia, Italy). Anti-HBs antibody titers were also determined by enzyme immunoassay (ETI-AB-AUK-3; BykDiaSorin). Vaccine and Study Design. All patients received a vaccine consisting of recombinant purified HBsAg, as contained in Engerix B (GlaxoSmithKline Biologicals, Rixensart, Belgium), formulated with sucrose and combined with the novel adjuvant system AS02. AS02 is composed of 3-deacylated monophosphoryl lipid A (MPL) and Quillaja saponaria Molina (QS21), a purified natural saponin molecule in an oil/water emulsion. The vaccine (0.5 mL) for patients in group I (vaccine A) contained 20 ␮g HBsAg, 50 ␮g MPL, 50 ␮g QS21, and 250 ␮L oil/water emulsion; the vaccine for patients in group II (vaccine B) contained 100 ␮g HBsAg, 100 ␮g MPL, 100 ␮g QS21, and 250 ␮L oil/water emulsion. The trial was designed as an open, sequential, nonrandomized, controlled phase I study. Vaccine doses were injected intramuscularly into the upper deltoid region at weeks 0, 2, 4, 16, and 18. Patients in both groups who failed to produce an anti-HBs antibody titer greater than 500 IU/L after the primary immunization series of 5 vaccinations received up to 3 additional injections of vaccine

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B at bimonthly intervals. Vaccination was performed at least 2 days before scheduled HBIG substitution. AntiHBs titers were tested just before HBIG injection and together with HBsAg, HBeAg, and HBV DNA at monthly intervals. Determination of immunosuppressive drug levels was performed at monthly intervals, and biochemical and hematologic parameters were tested every second week and at monthly intervals after the third vaccination and during the follow-up period. Local and systemic adverse events were closely observed at the time of vaccination and during the following 2 hours and were monitored during the subsequent week and for 3 months after the last injection. Pain at injection site was scored as mild if painful on touch, moderate if painful when the limb is moved, and severe if spontaneously painful. Redness and swelling were also scored as mild (⬍20 mm), moderate (20-50 mm), and severe (⬎50 mm). Other adverse events that were easily tolerated were considered mild. Moderate adverse events were sufficiently discomforting to interfere with normal everyday activities, and severe adverse events prevented everyday activities. Statistical Analysis. The ␹2 test was applied for comparison of proportions between groups, and Wilcoxon rank tests and the Mann-Whitney U test were applied for comparisons of quantitative variables. Log-transformed antibody titers for both groups as well as for responders and nonresponders were compared using the MannWhitney U test. All analyses were performed with SPSS software version 11.0 (SPSS, Chicago, IL).

Results Demographics. Twenty liver transplant recipients participated in the study (18 men and 2 women; age range, 35-69 years; median, 54 years). Nine men and one woman were assigned to group I (age range, 35-69 years; median, 54.5 years), and nine men and one woman were assigned to group II (age range, 41-65 years; median, 52.5 years). Demographic data are shown in Table 1. Immunosuppressive therapy was similar in both groups. Patients were on monotherapy with cyclosporine (n ⫽ 6), tacrolimus (n ⫽ 11), or a combination of tacrolimus and mycophenolate mofetil (n ⫽ 3). Corticosteroids were added in one patient treated with tacrolimus and mycophenolate mofetil and in one patient treated with cyclosporin. The time between liver transplantation and admission to the study was 2 to 13 years (group I: median, 5.75 years; group II: median, 6.75 years). All patients received HBIG substitution since transplantation. In the year preceding the study, patients needed a median of 22,500 IU HBIG (range, 6,000-31,500 IU HBIG) to maintain serum antibody titers greater than 100 IU/L

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Table 2. Data on Reinfection Prophylaxis With Hepatitis B Immunoglobulin and Number of Vaccinations to Achieve Maximal Antibody Titer in the 20 Study Participants Patient (Group I/II)

Prestudy HBIG (IU) per Year/ Number of Doses/ HBIG per Month

Expenses for HBIG Prophylaxis per Year (Dollar)

Total HBIG (IU) During the Study Period/ Number of Doses (n)

HBIG-Free Interval Since Last Dose of HBIG/Since Max Titer (Month)

Vaccinations to Achieve Max Titer (n)

Maximum Titer/ Titer at Last Follow-up Visit (IU/L Anti-HBs)

01(I) 02(I) 03(I) 04(I) 05(I) 06(I) 07(I) 08(I) 09(I) 10(I) 11(II) 12(II) 13(II) 14(II) 15(II) 16(II) 17(II) 18(II) 19(II) 20(II)

27,000/18/2,250 30,000/20/2,500 18,000/12/1,500 24,000/16/2,000 31,500/21/2,625 19,500/13/1,625 22,500/15/1,875 15,000/15/1,250 25,500/17/2,125 24,000/16/2,000 19,500/13/1,625 18,000/12/1,500 6,000/26/540 28,500/19/2,375 25,500/17/1,875 27,000/18/2,250 22,500/15/1,875 19,500/13/1,625 15,000/11/1,250 12,200/8/1,000

30,000 33,000 20,000 27,000 35,000 22,000 25,000 17,000 28,000 20,000 22,000 20,000 7,000 32,000 28,000 30,000 25,000 22,000 17,000 14,000

6,000/(4) 15,000/(10) 24,500/(15) 7,500/(5) 15,000/(10) 30,000/(17) 9,000/(6) 6,000/(4) 6,000/(4) 18,000/(11) 12,000/(6) 4,500/(3) 5,000/(10) 6,500/(4) 18,000/(10) 10,500/(6) 7,500/(5) 8,150/(5) 3,000/(2) 0/(0)

27/21 15/13 — 26/22 24/13 — 26/16 14/10 22/17 10/8 24/19 25/22 — 16/14 — 15/7 20/11 13/6 17/10 22/20

5 6 8 5 6 8 6 7 5 8 5 5 8 5 8 7 7 8 6 2

7,293/3,161 17,729/1,773 NR 459 45,811/3,830 50,918/6,042 NR 416 55,960/4,018 29,509/6,125 29,047/3,511 1,287/393 21,640/4,581 83,121/11,896 NR 465 44,549/5,021 NR 471 7,323/2,317 13,155/3,206 1,255/396 7,683/2,678 63,495/3,394

Abbreviation: NR, nonresponder.

(range, 77-514 IU/L; median, 174 IU/L anti-HBs). The total cost of HBIG prophylaxis per annum for the 20 patients was $474,000, with an average of $2,000 per month per patient (Table 2). There were no significant differences as to underlying disease, sex, age, time since transplantation, immunosuppressive therapy, and HBIG substitution between the 2 groups. Response to Immunization. All 20 patients completed the study. In group I, 5 patients (50%) developed antibody titers greater than 500 IU/L after 5 vaccinations with vaccine A (range, 721-45,811 IU/L; median, 7,239 IU/L anti-HBs). Another 3 subjects in this group responded after 3 additional doses of vaccine B (n ⫽ 8; 80% responders; range, 1,287-55,960 IU/L; median, 29,047 IU/L anti-HBs). In group II, 6 patients (60%) developed a protective response (range, 900-83,121 IU/L; median, 44,549 IU/L anti-HBs) after 5 vaccinations with vaccine B. Two more patients responded after one additional dose (n ⫽ 8; 80% responders; range, 1,255-83,121 IU/L; median, 17,397 IU/L anti-HBs)(Figs. 1-3). One patient (no. 20) responded after the first vaccination. He mounted an anti-HBs titer of 28,000 IU/L at day 18. We cannot exclude that he had seroconverted previously, masked by HBIG prophylaxis, and had an undetected active antiHBs production at a very low level. Four patients did not produce antibody titers greater than 500 IU/L. Three of these patients remain on HBIG prophylaxis. One of the nonresponders in group II (no. 13) showed an antibody

response close to 500 IU/L after 8 vaccinations. Although HBIG substitution was discontinued, his antibody titer has not decreased to less than 80 IU/L for more than 6 months. As of May 2003, none of the 16 responders had resumed HBIG prophylaxis or received an additional vaccination after the maximal antibody response (Table 2). Responders have been followed up (anti-HBs, HBsAg, HBV DNA) for a median of 13.5 months (range, 6-22 months) after maximal antibody response. In a 6-month follow-up period, median decline of titers was 75% (range, 22%-88%) in group I and 70% (range, 54%87%) in group II. Median intervals since last vaccination and last follow-up visit were 14.5 months (range, 8-23 months) and 18.5 months (range, 10-27 months) since last HBIG application, respectively. We found no obvious differences between responders and nonresponders with respect to age, time since transplantation, immunosuppressive therapy, and HBIG substitution as well as no correlation between the strength of antibody production in both groups (after 5 vaccinations) and the variables previously listed. Number of vaccinations and antibody response were not significantly different between patients on prophylaxis with HBIG alone and those on HBIG plus antivirals. Antibody titers were slightly but not significantly higher in patients immunized 5 times with vaccine A than with vaccine B, respectively. Safety. In both groups, no sign of graft rejection, endogenous HBV reinfection, or any significant alteration

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Fig. 1. Maximal antibody response and follow-up of antibody titers in responders of group I. }, patient 1; 䊐, patient 2; ‚, patient 4; ■, patient 5; F, patient 7; E, patient 8; ⫹, patient 9; Œ, patient 10.

of hematologic and biochemical parameters was observed. Eight patients reported that the incidence and severity of local and systemic adverse events decreased during the course of the study. In group I, mild local (general) adverse events were found in 32% (20%), moderate local (general) adverse events in 26% (20%), and severe local and general adverse events in 2%, respectively. In group II, local (general) adverse events were mild in 54% (40%),

moderate in 23% (23%), and severe in 19% (4%), respectively. No serious vaccine-related adverse event occurred. In patients in both groups, local and general adverse events disappeared after 1 to 13 days (median, 2 days).

Discussion Acute, self-limited hepatitis B and the various clinical forms of chronic illness represent the extremes of a bio-

Fig. 2. Maximal antibody response and follow-up of antibody titers in responders of group II. }, patient 11; 䊐, patient 12; ‚, patient 14; ■, patient 16; F, patient 17; E, patient 18; ⫹, patient 19; Œ, patient 20.

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Fig. 3. Development of anti-HBs titers in 2 early and 2 late responders. Œ, patient 2; ■, patient 8; ‚, patient 9; E, patient 11.

logical continuum. Regardless of the outcome of the disease, viral replication persists and is controlled by the strength of the cytotoxic T-lymphocyte response.12 Elimination or control of HBV infection depends on cytotoxic T-lymphocyte and T-helper cell and subsequent B-cell response. Anti-HBs specific T-helper cell response is low in chronic hepatitis B and may be even weaker in liver transplant recipients on immunosuppression.13 Although the course of infection and the immune response to HBV immunization is at least partly genetically determined, environmental host factors such as age, disease-related immunosuppression, and immunosuppressive therapy play a role.14 In HBsAg-positive liver transplant recipients, spontaneous seroconversion to anti-HBs is rare. In the vast majority, endogenous HBV reinfection from extrahepatic sites occurs.15 Patients with active viral replication (HBeAg positive, HBV DNA positive) have a much higher risk of endogenous reinfection than liver transplant recipients with fulminant disease or nonreplicative chronic hepatitis (HBeAg negative, HBV DNA negative). Reinfection can be prevented by long-term HBIG substitution. There is consensus that a level of anti-HBs greater than 100 IU/L should continuously be maintained. Few centers advocate target levels up to 500 IU/L.5,16 As a possible alternative to or in combination with HBIG substitution, the nucleoside analogues may be given. Primary hepatitis B immunization of healthy adults with commercially available recombinant subunit HBsAg vaccines consists of 3 doses (0, 1, and 6 months). The vaccines are highly immunogenic in healthy subjects and confer long-term protection.17 Antibody titers greater than 10 IU/L are considered protective in immunocompetent subjects. Immunosuppressive substances used in transplant recipients interfere with immune response to antigens in various ways.18 Therefore, immunocompro-

HEPATOLOGY, October 2003

mised patients are vaccinated with double doses of HBsAg. The antibody response rate in liver transplant recipients is low (⬍25%) and antibodies decline rapidly.18,19 Studies in murine models20,21 and in patients with chronic hepatitis B led to the assumption that immunization with hepatitis B vaccine may enhance the defective T-cell response and reduce HBV replication.22 Subsequent immunotherapeutic vaccination studies in patients with chronic hepatitis B showed a temporary decrease of the HBV viral load and stimulation of a CD4⫹ T-lymphocyte response but no lasting HBsAg negativation.23,24 By increasing the number of vaccinations and combining vaccination with antiviral drugs or cytokines, a sustained loss of HBV DNA and normalization of transaminase levels was achieved in a number of patients.25,26 Based on this experience, several groups adopted specific vaccine therapy for liver transplant recipients.7-10 Sanchez-Fueyo et al.9 vaccinated 22 patients who underwent transplantation because of HBsAg-positive/HBV DNA–negative HBV-related disease with 3 intramuscular double doses (40 ␮g HBsAg) of a standard recombinant HBV vaccine (Table 3). Nonresponders received 3 additional doses. Seroconversion (anti-HBs ⬎10 IU/L) was achieved in 14 subjects (63.6%). None of the responders developed HBV reinfection. Ba´rcena et al.7 immunized 5 HBV DNA–negative and HBsAg-positive liver transplant recipients with 3 monthly doses of 40 ␮g HBV vaccine. Seroconversion (anti-HBs ⬎10 IU/L) was observed in 4 of 5 patients. Angelico et al.10 performed a similar study with 17 patients who underwent transplantation for HBV-related cirrhosis (HBsAg positive, HBV DNA negative). All patients were started on lamivudine. They received up to 9 intramuscular and intradermal HBV vaccinations, but only 2 (11.8%) developed a titer greater than 100 IU/L and 3 a titer greater than 10 IU/L. As reported in a preliminary communication,11 the results of an anti-HBV immunization study in 10 patients who underwent transplantation for HBV-related disease (HBsAg positive, HBV DNA negative) were encouraging. In this (group I) and a subsequent series with 10 more patients (group II), 5 vaccinees (50%) in group I and 6 vaccinees (60%) in group II seroconverted (anti-HBs ⬎500 IU/L) after 5 intramuscular doses of anti-HBV vaccine A and B, respectively. With a maximum of 3 additional vaccinations with vaccine B, the number increased to 80% (Table 2 and Figs. 1 and 2). Seroconverting patients developed a strong antibody response. They have now been followed up for a median of 13.5 months; although a substantial decrease of antibody titers has been observed, they remain at high levels and do not receive HBIG. The first anti-HBs titer greater than 500 IU/L in a

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Table 3. Studies on Hepatitis B Immunization in LTx Recipients for HBV-Related Disease Number Male/female Age (y), median (range) Underlying HBV disease (acute/chronic) Immunosuppression (mono/combination therapy) HBIG prophylaxis during vaccination Seroconversion cutoff (anti-HBs IU/L) 10 IU/L anti-HBs (%) ⱖ100 IU/L anti-HBs (%) 500 IU/L anti-HBs (%) Maximum anti-HBs IU/L of responders, median (range) Observation period after immunization, months: median (range) Time of vaccination, months after LTx: median (range)

Sanchez-Fueyo et al.8,9

Barcena et al.7

Angelico et al.10

Bienzle et al.11

22 15/7 38 ⫾ 8* 41 ⫾ 9† 8/14

5 5/0 NA

17 15/2 53 (36–63)

20 18/2 54 (35–69)

NA

0/17

2/18

11/6 No 10 63.6 23.5 9.1

5/0 No 10 80 NA NA

17/0 No 100 17.6 11.8 5.9

16/4 Yes 500 – – 80

47 (10–1,000)

NA

258 (10–601)

25,344 (1,255–83,121)

41 (31–85)

5.5 (5–8)

66 (25–88)

13.5* (6–22)

33 (18–76)

⬎20 NA

48 (25–85)

78 (24–156)

*Responders (median ⫾ SD). †Nonresponders (median ⫾ SD).

responder certainly was a mixture of passive anti-HBs and actively produced antibody. However, the shortest interval between the last HBIG prophylaxis and the maximum anti-HBs titer was 6 weeks. We know from previous studies that the half-life of HBIG is about 2 weeks.27,28 Three of the 4 nonresponders resumed HBIG prophylaxis. Because HBIG substitution was continued during the study, we could not verify how many nonresponders had mounted an antibody response exceeding the standard seroconversion cutoff of 10 IU/L anti-HBs. Similarly to the participants of the studies previously described, our patients were HBsAg positive but HBV DNA and HBeAg negative before immunization and received long-term HBIG prophylaxis. The study group of Ba´rcena et al.7 was too small for meaningful comparison (Table 3). If a positive response to immunization is defined as an antibody titer greater than 10 IU/L, 63.6% of 22 vaccinees in the series of Sanchez-Fueyo et al. and 17.6% of 17 patients in the series of Angelico et al.10 seroconverted. Defining positive response at an anti-HBs greater than 100 IU/L, the percentage of responders in the series of Sanchez-Fueyo et al. was 23.5% and in the series of Angelico et al. was 11.8% (Table 3). Analyzing the predictors of response, Sanchez-Fueyo et al. noticed that 6 of 8 patients with acute HBV-related disease were responders, as were the 2 patients in our series. None of the patients in the study by Sanchez-Fueyo et al. on lamivudine responded. Our patients treated with lamivudine (n ⫽ 3) or famciclovir (n ⫽ 1) responded as well as the other participants. The patients in the study by Angelico et al. were all treated with lamivudine. The time from transplantation to immunization was much longer in our

patients. But, as in the other studies, we found no correlation to antibody response. The mode of vaccine application (intramuscular and intradermal), total HBsAg dose, number of vaccinations, length of the immunization study, and time from transplantation to immunization varied, but there was no obvious impact on the outcome of the studies. Local and systemic adverse events were more frequent and more severe in patients immunized with the new vaccine than would be expected after immunization with standard HBV vaccines. Our study was different in at least 2 important aspects. First, although the vaccine contained the same recombinant HBsAg, the antigen was formulated with 2 new potent adjuvants: MPL and QS21.29 MPL belongs to a class of immunostimulatory adjuvants that is derived from the lipopolysaccharide of gram-negative bacteria. Obtained from Salmonella minnesota, MPL exerts its effect at the cytokine level by stimulating the synthesis of interferon gamma and promoting a T-helper cell response. Vaccination trials in healthy adults showed significantly higher (up to 10-fold) anti-HBs titers compared with standard hepatitis B vaccine.30 QS21, a pure fraction of Quil A saponin derived from Q. saponaria (Chilean soap bark tree), strongly induces the production of interferon gamma and interleukin 2 and antibody formation of the immunoglobulin G2a isotype.31 In our vaccine, both adjuvants are formulated to oil-in-water emulsion, which is used as a delivery system to enhance the uptake by antigen-presenting cells. Second, HBIG prophylaxis in our patients was continued during immunization. The mechanism of protection against endogenous reinfection is not well understood.

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Polyclonal anti-HBs immunoglobulin may neutralize virus through immune precipitation and formation of immune complexes.32 Celis et al.33 assumed that antibodies forming immune complexes may increase cellular uptake, processing, and presentation of HBsAg. This process may stimulate T-helper cell activity and enhance the synthesis of anti-HBs.34 Based on such findings, Wen et al.34 even suggested the use of antigen-antibody complexes as a therapeutic vaccine for viral hepatitis B. Several conclusions and recommendations can be drawn from these immunization studies. Most importantly, successful hepatitis B vaccination in liver transplant recipients for acute and nonreplicative chronic hepatitis B is possible. Based on available data, up to 20% of the patients immunized with standard HBV vaccines will mount a protective response of anti-HBs greater than 100 IU/L. Vaccines with more potent adjuvants may induce an antibody response in up to 80% of subjects. Patients undergoing transplantation for acute hepatitis B and liver failure would probably show better results than liver transplant recipients for nonreplicative chronic hepatitis B. No data are available for patients with HBepositive and HBV DNA–positive chronic hepatitis. The potential impact of the time length from transplantation to immunization is not clearly determined, but immunization should not be started within the first 6 months because high-dose immunosuppression may inhibit response.18 There is no proof that type and dosage of immunosuppressive treatment influences the antibody response. However, it can be observed from the data of Sanchez-Fueyo et al. that patients on monotherapy may fare better. Concomitant treatment with lamivudine may interfere with antibody response. The number of vaccine doses necessary to achieve antibody response is not known. One of our patients seroconverted after the first vaccination, whereas others did not before the eighth injection. Antibody titers may decrease rapidly. Regular antibody testing is necessary, and booster vaccinations are advisable if the titer decreases to less than 100 IU/L. HBIG immunoprophylaxis has a good record of efficacy, safety, and tolerability, but the financial burden is heavy (Table 2).16,35 Active immunization with the new adjuvanted hepatitis B vaccine may offer a cost-effective, safe, and promising strategy to prevent endogenous reinfection. To confirm our findings, a multicenter, randomized controlled study on a larger number of patients with different risk of HBV recurrence is in preparation. Acknowledgment: The authors thank GlaxoSmithKline Biologicals (Rixensart, Belgium) for providing the vaccines.

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