Hepatitis B virus surface mutations associated with infection after liver transplantation

Occurrence of occult hepatitis B virus infection associated with envelope protein mutations according to anti-HBs carriage in blood donors

OBJECTIVES

Occult hepatitis B virus infection (OBI) carries a risk of hepatitis B virus (HBV) transmission and hepatocellular carcinoma. As previous studies have had a limited sample size, the characteristics of OBI with genotype B and C (OBI_B and OBI_C) mutations relating to hepatitis B surface antibody (anti-HBs) elicited by vaccination or a limited host immune response to HBV have not been fully explored.

METHODS

In this study, the occurrence of OBI_B or OBI_C strains associated with envelope protein (pre-S/S) amino acid substitutions obtained from 99 blood donors stratified according to anti-HBs carriage were characterized extensively.

RESULTS

According to the presence of anti-HBs within each genotype, the number and frequency of substitution sites specific for anti-HBs(-) OBI_B were higher than those specific for anti-HBs(+) OBI_B strains (67 vs 31; 117 vs 41), but the reverse pattern was found in OBI_C strains (3 vs 24; 3 vs 26). Mutations pre-s₁T68I and sQ129R/L were found uniquely in 15-25% of anti-HBs(+) OBI_B carriers and mutation pre-s₁A54E was found preferentially in anti-HBs(+) OBI_C, while 17 substitutions were found preferentially in 11-38% of anti-HBs(-) OBI_B strains. In the major hydrophilic region (MHR) region, mutations sS167 in OBI_B, sT118 in OBI_C, and sA166 in both genotypes were possibly immune-induced escape mutation sites.

CONCLUSIONS

Several mutations in pre-S/S of OBI appeared to be associated with carrier anti-HBs pressure, which might be risk factors for potential reactivation of viruses under anti-HBs selection in OBI carriers.

Hepatitis B virus PreS/S gene variants: pathobiology and clinical implications

The emergence and takeover of hepatitis B virus (HBV) variants carrying mutation(s) in the preS/S genomic region is a fairly frequent event that may occur spontaneously or may be the consequence of immunoprophylaxis or antiviral treatments. Selection of preS/S mutants may have relevant pathobiological and clinical implications. Both experimental data and studies in humans show that several specific mutations in the preS/S gene may induce an imbalance in the synthesis of the surface proteins and their consequent retention within the endoplasmic reticulum (ER) of the hepatocytes. The accumulation of mutated surface proteins may cause ER stress with the consequent induction of oxidative DNA damage and genomic instability. Viral mutants with antigenically modified surface antigen may be potentially infectious to immune-prophylaxed patients and may account for cases of occult HBV infection. In addition, preS/S variants were reported to be associated with cases of fulminant hepatitis as well as of fibrosing cholestatic hepatitis, and they are associated with cirrhosis and hepatocellular carcinoma development.

An improved method for the isolation of hepatitis B virus DNA from human serum

Studies show that hepatitis B virus (HBV) DNA isolation methods vary in their efficiency to extract DNA from serum samples. The purpose of the present study was to develop an improved method for isolation of HBV DNA and compare it with commonly used HBV DNA isolation protocols. In order to develop HBV DNA isolation protocol, serum samples were collected from patients and screened for the presence of hepatitis B surface antigen, hepatitis B e antigen and HBV DNA. Highly viremic samples were pooled and used to compare commonly used HBV DNA isolation methods; namely alkaline lysis, microwave treatment, organic, inorganic with modified inorganic method. DNA isolated by these methods was detected qualitatively by polymerase chain reaction and quantitatively with competitive polymerase chain reaction (cPCR). The modified inorganic method gave maximum yield of HBV DNA followed by inorganic, organic, microwave treatment and alkaline lysis method. Our data also demonstrated a critical role of proteinase K in HBV DNA isolation. DNA isolation method described here, in combination with a reproducible and sensitive quantitative technique would further help in accurate classification of HBV infected patients, designing suitable drug regimen for treatment and monitoring antiviral treatment as well as emergence of drug resistant mutants.

Prophylaxis of hepatitis B infection in solid organ transplant recipients

Rates of transmission of hepatitis B virus (HBV) infection from organ donors with HBV markers to recipients along with reactivation of HBV during immunosuppression following transplantation have fallen significantly with the advent of hepatitis B immune globulin (HBIg) and effective antiviral therapy. Although the availability of potent antiviral agents and HBIg has highly impacted the survival rate of HBV-infected patients after transplantation, the high cost associated with this practice represents a major financial burden. The availability of potent antivirals with high genetic barrier to resistance and minimal side effects have made it possible to recommend an HBIg-free prophylactic regimen in selected patients with low viral burden prior to transplant. Significant developments over the last two decades in the understanding and treatment of HBV infection necessitate a re-appraisal of the guidelines for prophylaxis of HBV infection in solid organ transplant recipients.

Epidemiology of HBV S-gene mutants in the Liguria Region, Italy: Implications for surveillance and detection of new escape variants

HBV surface antigen (HBsAg) variants may impair diagnosis or allow the virus to escape vaccine-induced immunity and their circulation in the population can represent a Public Health threat. Their prevalence, however, is not yet completely established. Evidence indicates that amino acid substitutions within HBsAg can lead to conformational changes which allow mutated HBV to escape the vaccine-induced antibodies used in the screening tests. In such scenario, the aim of this study was to investigate the prevalence of HBV S-Gene escape mutants by sequencing the gene in a cohort of Ligurian patients monitored for viral load, genotype and drug resistance and to evaluate the risk of false negative HBsAg detection by routine screening tests. From 2007 to 2011, in 256 consecutive samples from Ligurian HBV positive patients sequencing assay for detection of RT/S-Gene mutations using Trugene HBV Genotyping kit (Siemens Healthcare Diagnostics Inc., Tarrytown, NY) was performed. Serological HBV tests and viral load were also performed. Analyzed sequences revealed G145R mutation in 8/256 (3.1%) examined sequences, it was alone in 5 patients and accompanied by other HBsAg mutations in 3 samples. HBsAg resulted undetectable by 3 of the 8 samples, derived from patients with multiple mutations: T126I-T131A-C139Y-E/D144G, T126I-M133L, and P120Q-T126I. The emergence of these mutants, at least the G145R, has already been addressed as a public health concern because of its capability of escaping the immune system. In the present study we point out a second aspect connected with their existence and with similar potential negative impact on public health, that is their capability of escape punctual detection.

Hepatitis B virus S gene escape mutants

Hepatitis B virus (HBV) can be classified into nine immunological subtypes or eight genotypes. The most prevalent genotypes in Asia are genotypes B and C. HBV is transmitted parenteraly and can produce either asymptomatic or symptomatic disease. Although the consequences of acute hepatitis B can be severe, serious sequelae are associated with chronic infections. HBV seroprevalence ranges from intermediate (2%-7%) to high (≥8%) levels in Asia. Several strategies for the control and prevention of HBV infection have been found to be efficacious. They include vaccination and the administration of HBIG, interferon-a and nucleoside/nucleotide analogues. However, these procedures also apply selective pressures on HBV in infected individuals leading to the generation and accumulation of mutations in the S gene. Most of these mutations occur in the major hydrophilic region (MHR) of the S gene. These mutations create public health concerns as they can be responsible for reactivation of hepatitis B and occult hepatitis B infection. The inability to detect occult infections means that these individuals may become blood donors. This suggests that new strategies for donor evaluation and selection may need to be developed to protect the blood supply.

Clinical course of de novo hepatitis B infection after pediatric liver transplantation

The characteristics of hepatitis B virus (HBV) in vaccinated children who acquire de novo HBV infections after orthotopic liver transplantation (OLT) remain largely unknown. The aim of this study was to explore HBV mutants in pediatric OLT recipients with de novo HBV infections. In all, 50 recipients underwent OLT between December 1997 and October 2005, and they were regularly checked for HBV serum markers from November 2005 to April 2009. Before OLT, all were hepatitis B surface antigen (HBsAg)-negative and under the coverage of the universal infant HBV vaccination program. Those who became HBsAg-positive after OLT were diagnosed with de novo HBV infection. HBV viral loads and full-length genome sequencing were determined when the diagnosis of de novo HBV infection was established. Nine patients (9/50, 18%) acquired de novo HBV infections after OLT. None had graft loss or fulminant hepatitis. Five cleared HBsAg, and 4 of the 5 even recovered with antibody to hepatitis B surface antigen (anti-HBs) formation. The other 4 were persistently HBsAg-positive. Mutations in the major S gene (681 base pairs) were discovered in 8 (88.9%) of the de novo HBV-infected children. Six of them harbored mutations within the "a" determinant region (codons 124-147), whereas the other 2 had mutations outside this region. These 2 cleared HBsAg and recovered with anti-HBs formation. HBV DNA levels were not different between those who cleared HBsAg and those who did not. In conclusion, surface mutants are frequent among pediatric liver transplant recipients with de novo HBV infections, but their clinical relevance requires further study.

Differential impact of immune escape mutations G145R and P120T on the replication of lamivudine-resistant hepatitis B virus e antigen-positive and -negative strains

Immune escape variants of the hepatitis B virus (HBV) represent an emerging clinical challenge, because they can be associated with vaccine escape, HBV reactivation, and failure of diagnostic tests. Recent data suggest a preferential selection of immune escape mutants in distinct peripheral blood leukocyte compartments of infected individuals. We therefore systematically analyzed the functional impact of the most prevalent immune escape variants, the sG145R and sP120T mutants, on the viral replication efficacy and antiviral drug susceptibility of common treatment-associated mutants with resistance to lamivudine (LAM) and/or HBeAg negativity. Replication-competent HBV strains with sG145R or sP120T and LAM resistance (rtM204I or rtL180M/rtM204V) were generated on an HBeAg-positive and an HBeAg-negative background with precore (PC) and basal core promoter (BCP) mutants. The sG145R mutation strongly reduced HBsAg levels and was able to fully restore the impaired replication of LAM-resistant HBV mutants to the levels of wild-type HBV, and PC or BCP mutations further enhanced viral replication. Although the sP120T substitution also impaired HBsAg secretion, it did not enhance the replication of LAM-resistant clones. However, the concomitant occurrence of HBeAg negativity (PC/BCP), sP120T, and LAM resistance resulted in the restoration of replication to levels of wild-type HBV. In all clones with combined immune escape and LAM resistance mutations, the nucleotide analogues adefovir and tenofovir remained effective in suppressing viral replication in vitro. These findings reveal the differential impact of immune escape variants on the replication and drug susceptibility of complex HBV mutants, supporting the need of close surveillance and treatment adjustment in response to the selection of distinct mutational patterns.

Hepatitis B virus variants

HBV replicates through reverse transcription of an RNA intermediate; the inherent lack of proofreading causes a high mutation frequency. Mutations in the precore and core promoter regions that abolish or reduce the production of hepatitis B e antigen occur most commonly. Patients with these HBV variants remain viremic and can develop progressive liver disease. Mutations in the core promoter region are associated with an increased risk of hepatocellular carcinoma. Exogenous selection pressure might favor certain mutations. Mutations in the HBV polymerase that confer resistance to nucleoside and nucleotide analog treatments are a major barrier to the success of therapy for hepatitis B. The development of antiviral drug resistance negates the initial treatment response and can lead to hepatitis flares and hepatic decompensation. Prompt addition of another drug to which the virus is not cross-resistant is required. Mutations in the HBV surface protein that facilitate escape from host immunity are responsible for the failure of immune prophylaxis in infants who received HBV vaccine and in liver transplant recipients who received hepatitis B immune globulin.

Viral persistence after liver transplantation for hepatitis B virus: a cross-sectional study

BACKGROUND

Prophylaxis to prevent recurrent HBV infection in liver transplant (LT) recipients has evolved over time, and we manage patients who receive lamivudine monoprophylaxis, lamivudine with HBV immunoglobulin (HBIg), and lamivudine and adefovir with HBIg.

METHODS

Serum was examined with sensitive assays to detect the persistence of HBV, and to identify mutations that might confer resistance to the antiviral prophylaxis. Forty patients were studied, and sera were collected 20 days to 13.3 years after LT.

RESULTS

Overall, HBV DNA was detected in serum of 67.5% of patients (8 of 10 of lamivudine monoprophylaxis patients, 15 of 24 of those receiving lamivudine and HBIg, and 4 of 6 of those receiving lamivudine, adefovir and HBIg). Thus, HBV infection persists for most of the patients despite successful prophylaxis after LT. Of those patients with detectable serum HBV DNA, three of eight of the lamivudine monoprophylaxis group had sequences associated with resistance to lamivudine (YMDD mutants), compared with only 1 of 15 of the lamivudine and HBIg cohort. Three of the lamivudine and HBIg cohort had the I126A Hepatitis B surface antigen escape variant. In those serum HBV DNA-positive patients who were receiving lamivudine, adefovir, and HBIg, only one of four had YMDD mutant, and none had Hepatitis B surface antigen escape variants. None of the 40 patients suffered clinical HBV recurrence.

CONCLUSIONS

Our observations imply that the selection of resistant virus may be essential, but is not sufficient to cause overt failure of prophylaxis with development of clinical disease. It seems likely that the patients' immune response contributes, at least partially, to the long-term control of infection in these patients.

Prevention of hepatitis B virus recurrence after liver transplantation

Liver transplantation for hepatitis B virus (HBV)-related liver disease has changed from a contraindication to outcomes comparable with non-HBV-related liver transplantations during the last two decades. Mainly the implementation of immunoprophylaxis with hepatitis B immunoglobulin (HBIG) and the use of nucleoside analogs such as lamivudine and adefovir account for this dramatic change. The standard of care in most centers today consists of lamivudine treatment in replicating hepatitis B pre-orthotopic liver transplantation (OLT) and a combination regimen of lamivudine and HBIG post-OLT. With adefovir, a potent antiviral drug became available in recent years that allows for the treatment of patients with lamivudine-resistant tyrosine-methionine-aspartate-aspartate (YMDD)-mutant HBV. In the transplantation setting, first studies indicate that a triple prophylactic therapy consisting of lamivudine, adefovir, and HBIG will become the standard of care for YMDD-mutant-related hepatitis B. With new drugs emerging for the treatment of chronic HBV, there is optimism for new options also in the transplant setting.

Evolution of multi-drug resistant hepatitis B virus during sequential therapy

Multi-drug resistant hepatitis B virus (HBV) has been reported in hepatitis B patients who received sequential antiviral therapy. In vitro studies showed that HBV constructs with mutations resistant to lamivudine and adefovir have marked reduction in sensitivity to combination of lamivudine and adefovir, whereas constructs with mutations resistant to either drug remain sensitive to the other drug. We conducted this study to determine whether mutations conferring resistance to multiple antiviral agents co-locate on the same HBV genome in vivo and to describe the evolution of these mutations. Sera from six patients who had been found to have multi-drug resistant HBV mutations to lamivudine+adefovir, lamivudine+hepatitis B immunoglobulin (HBIG), or lamivudine+entecavir on direct sequencing were cloned after nested polymerase chain reaction (PCR). Analysis of 215 clones from 11 samples with multi-drug resistant mutations on direct sequencing showed that 183 (85%) clones had mutations to both therapies on the same genome; 31 clones had lamivudine-resistant mutants only. Clonal analysis of serial samples from three patients showed progressive evolution from all clones with lamivudine-resistant HBV mutations only to mixtures of clones that have multi-drug resistant mutations and clones that have lamivudine-resistant HBV mutations only, and ultimately all clones having multi-drug resistant HBV mutations. In conclusion, mutations conferring resistance to multiple antiviral agents co-locate on the same viral genome, suggesting that combination therapy directed against mutants resistant to each treatment may not be adequate in suppressing multi-drug resistant HBV. De novo combination therapy may prevent the emergence of multi-drug resistant mutants.

A new HBsAg screening assay designed for sensitive detection of HBsAg subtypes and variants

The design of a new HBsAg screening assay, the Hepanostika HBsAg Ultra is based on the use of monoclonal antibodies raised against native wild-type HBsAg and reactive with HBsAg in which the common 'a'-determinant is modified by site-directed mutagenesis of four of the cysteine moieties. The design was checked using the same cysteine variants and samples from patients known to be infected with HBsAg variants. The results found were compared with other state-of-the-art commercial screening assays. The design of the Hepanostika HBsAg Ultra enabled detection of all variant HBsAg-positive samples in contrast to the other commercial assays. An additional 980 samples were tested to assess the specificity and sensitivity of the Hepanostika HBsAg Ultra. Screening of presumed negative serum and plasma samples resulted in a specificity of 100%. This makes the Hepanostika HBsAg Ultra the first screening assay with a design able to detect HBsAg variants with high sensitivity and specificity.

Complete genomic sequence and phylogenetic relatedness of hepatitis B virus isolates from Iran

Hepatitis B virus (HBV) is one of the main etiological agents of acute and chronic liver disease that is still a major public health problem in the world. Numerous HBV isolates have grouped into eight genotypes, A to H, based on the complete genome sequence. To date, no study has been carried out on the complete HBV genome sequence in Iran. The objective of this study was to investigate the complete genome sequence organization and phylogenetic analysis of the five HBV strains, which obtained from Iranian chronic infected patients. Results showed that Iranian strains were closely related to each other, with 97-100% nucleotide similarity. Phylogenetic analysis based on the complete genome sequences and the precore/core gene sequences revealed that all strains were of genotype D, sub-genotype D1 with bootstrap value 100 and 99%, respectively. The S gene encoded Arg122, Pro127, and Lys160 corresponding to subtype ayw2. Iranian HBV isolates had closely related with Turkish HBV strains. All strains had a nucleotide length of 3,182 base pair (bp) except IR-P4 strain, with a 3,185 bp in length and with a unique Phe89 insertion in the X gene. The intragenotypic divergence of the complete genome sequence of Iranian strains was 1.8% and the intergenotypic in genotype D was 3.8% and with the other genotypes was 7.9-15.4%. In conclusion, this study revealed that the HBV genotype D, sub-genotype D1, subtype ayw2 dominates in the Iranian infected patients. A single Phe89 insertion in the X gene of the one Iranian strain with an unforeseen length of 3185 bp was identified.

Hepatitis B and C Virus Variants in Long-Term Immunosuppressed Renal Transplant Patients in Latvia

The incidence of genome variants of hepatitis B and hepatitis C viruses among 38 long-term (2-15 years) immunosuppressed patients after renal transplantation and 10 patients undergoing dialysis was investigated. Twelve patients had only HBV infection, 9 had only HCV infection and 14 were co-infected. Regions corresponding to the HBV X/EnII/BCP, preC/C, preS/S and to the HCV core were sequenced for molecular characterization of the HBV and HCV genomes. Fifty-seven percent of HBV DNA isolates belonged to genotype D and 42% to genotype A, whereas 77% of HCV RNA isolates belonged to genotype 1b and only 17% to genotype 3a. One sample (6%) was of genotype 2c. Detailed analysis of the above-mentioned HBV genome regions revealed the presence of nucleotide point mutations, which, in some cases, resulted in amino acid substitutions. The clinical significance of such mutations is discussed.

Prevalence of HBsAg mutants and impact of hepatitis B infant immunisation in four Pacific Island countries

The prevalence rate of hepatitis B virus (HBV) infection in Pacific Island countries is amongst the highest in the world. Hepatitis B immunisation has been incorporated into national programmes at various times, often with erratic supply and coverage, until a regionally co-ordinated programme, which commenced in 1995 ensured adequate supply. The effectiveness of these programmes was recently evaluated in four countries, Vanuatu and Fiji in Melanesia, Tonga in Polynesia and Kiribati in Micronesia. That evaluation established that the programmes had a substantial beneficial impact in preventing chronic hepatitis B infection [Vaccine 18 (2000) 3059]. Several studies of hepatitis B vaccination programmes in endemic countries have identified the potential significance of surface gene mutants as a cause for failure of immunisation. In the study outlined in this paper, we screened infected children and their mothers for the emergence and prevalence of these variants in specimens collected from the four country evaluation. Although the opportunity for the emergence of HBV vaccine escape mutants in these populations was high due to the presence of a considerable amount of the virus in the population and the selection pressure from vaccine use, there were no "a" determinant vaccine escape mutants found. This suggests that vaccine escape variants are not an important cause for failure to prevent HBV transmission in this setting. Other HBsAg variants were detected, but their functional significance remains to be determined. The failure to provide satisfactory protection during such immunisation programmes reflects the need for achieving and sustaining high vaccine coverage, improving the timeliness of doses as well as improving 'cold-chain' support, rather than the selection of vaccine-escape mutants of HBV.

Hepatitis B virus infection after renal transplantation in the presence of antibody to hepatitis B surface antigen immunity

BACKGROUND AND AIM

Hepatitis B virus (HBV) infection has been known to be hampered by immunity against hepatitis B surface antigen (HBsAg). However, HBV with mutations within the common antigenic epitope of HBsAg, the "a" determinant region, can escape from humoral immunity. Moreover, HBV infection by "a" determinant mutants in chronic HBV patients has been reported after renal transplantation. In the present study, the authors investigated HBV infection after renal transplantation despite passive immunization or resolved HBV infection.

METHODS

A total of 1682 patients who underwent a renal transplant between 1979 and 1998 at the Severance Hospital, Yonsei University College of Medicine, Korea, were enrolled. The sequence of the HBV genome was analyzed from two patients with antibody to HBsAg (anti-HBs) immunity.

RESULTS

Of 1682 patients who were HBsAg negative before transplantation, 21 patients were found to be HBsAg positive, with elevated aspartate aminotransferase and alanine aminotransferase levels after transplantation. Interestingly, six of 21 (28.6%) patients were anti-HBs positive before the transplantation. Sequence analysis of the cloned HBV from two of six patients with anti-HBs immunity showed no evidence of significant mutations within the "a" determinant region, suggesting a wild-type of HBV. Their donors were not exposed to HBV before transplantation (all HBV markers were negative). Seven deaths of 21 patients were ascribed to HBV-related complications.

CONCLUSIONS

Regardless of anti-HBs immunity, HBV infection occurred in immunosuppressed patients in a high endemic area. The molecular mechanism and clinical impact of HBV infection after renal transplantation in patients with anti-HBs immunity should be further reappraised.

Deficiency in virion secretion and decreased stability of the hepatitis B virus immune escape mutant G145R

Hepatitis B virus with a G145R mutation in the small surface protein is considered the quintessential immune escape mutant because it frequently is found in vaccinated individuals with breakthrough infections and liver transplant recipients under anti-hepatitis B surface antigen (HBsAg) immunoglobulin prophylaxis. Nowadays the prevalence of the variant progressively increases. However, because spread of a virus depends not only on immune pressure but also on the viral phenotype, we investigated the biologic properties of the G145R variant. The G145R mutation was introduced into wild-type (Wt) virus genome by in vitro mutagenesis. After transfection into human hepatoma cells, the DNA, RNA, and protein synthesis and viral secretion ability of the mutant were studied. Furthermore, cotransfection studies were performed with the G145R variant and a Wt virus S-protein expressing construct and vice versa. Production and stability of viral messenger RNAs (mRNAs), DNA, and proteins were not affected by the G145R mutation. In contrast, secretion of mutant virions was reduced significantly. Only 20% of virions were found in the medium of G145R variant-transfected cells compared with Wt virus. Furthermore, mutant virions were more sensitive to detergent treatment suggesting a diminished stability. In cotransfection studies, Wt virus S-protein rescued secretion of mutant virions, whereas mutant S-protein had a transdominant negative effect on secretion of Wt virus. Both mechanisms may support persistence of the defective mutant in a mixed population with Wt virus. In conclusion, the significant defect of the G145R mutant for secretion of infectious virions and the diminished stability of mutant virions may limit global spread of the mutant.

Selection of a secretion-incompetent mutant in the serum of a patient with severe hepatitis B

BACKGROUND AND AIMS

A secretion-incompetent, highly replicating hepatitis B variant was previously found as the dominant viral population in the serum of a liver transplant recipient with severe hepatitis B reinfection. The secretion block resulted from mutations in the S protein, including the Gly145Arg substitution known to emerge under antibody to hepatitis B surface antigen immunoglobulin treatment. Here we investigated the mechanisms that allow selection of a secretion-incompetent virus as the predominant strain in the serum.

METHODS

To reproduce the interaction of viral quasispecies occurring in vivo, cotransfection experiments were performed with full-length genomes containing wild-type or mutant sequences. In addition, the relevance of mutations in the common S part of the surface proteins for the competence of L and S protein to support viral secretion was studied.

RESULTS

A small amount of wild-type virus or of a wild-type S protein-expressing variant rescued secretion of the defective mutant. In the secreted virions, the high-replicating mutant genome was predominant. Selection of the defective mutant was further supported by a transdominant negative effect of mutant S protein on wild-type virion secretion. In contrast, mutant L protein with the same c-terminal mutations as mutant S protein efficiently supported virion formation and secretion.

CONCLUSIONS

Interaction of the variant with a small amount of wild-type virus can reverse its secretion-defective phenotype. Mutations in the common region of S and L protein have different consequences for the ability of the envelope proteins to support virion assembly and secretion.

Hepatitis B immune globulin preparations and use in liver transplantation

Hepatitis B immune globulin remains a central component of prophylaxis in HBV-infected patients undergoing liver transplantation. HBIG monotherapy given at a high dosage and indefinitely can prevent recurrence in 65% to 80% of patients. Because treatment failures occur and combination therapy using HBIG plus a nucleoside analog is more uniformly effective, the current standard of care is combination HBIG plus a nucleoside analog. These combination protocols have reduced the rate of virologic breakthrough to 10% or less. Several questions remain. The optimal dose and duration of HBIG use is unclear. Moreover, the development of resistance to lamivudine (and other nucleoside analogs) before transplantation increases the risk for virologic breakthrough post-transplantation. For patients with pre-transplant evidence of active HBV replication caused by the presence of nucleoside analog resistance, HBIG may be the main or only form of prophylaxis. For these patients, HBIG doses sufficient to maintain anti-HBs titers comparable to the days of HBIG monotherapy seem warranted. New HBIG formulations have made anti-HBs therapy more safe and tolerable to patients but the cost of the drug remains significant. The cost factor is particularly important in developing countries or countries with more limited resources for management of liver transplant recipients. Thus, there remains a need to develop and test new forms of anti-HBs therapy, so that effective but less expensive forms of immunoprophylaxis can be made available.

Molecular epidemiology and immunology of hepatitis B virus infection - an update

Hepatitis B virus (HBV) continues to be one of the most important viral pathogens in humans. This review provides an update on the molecular epidemiology and immunology of HBV infection. DNA sequencing has allowed replacement of the initial serotypic classification of HBV strains by a more systematic genotype system that currently consists of 7 members (genotypes A-G). More recently, sequence analysis of virus isolates from many individual patients has revealed the occurrence of certain mutational hot spots in the genome, some of which appear to correlate with the patient's immunological and/or disease status; however, cause and effect are not always easily discernible. This holds particularly for the issue of whether virus variants exist that have, per se, an increased pathogenic potential; due to the scarcity of appropriate experimental in vivo models, such hypotheses are difficult to prove. Similarly, because of the compact organization of the HBV genome, almost every single mutation may have pleiotropic phenotypic effects. Nonetheless, there is accumulating evidence that at least some frequently observed mutations are causally related to viral escape from selective pressures, such as the presence of antibodies against dominant B cell epitopes, or drugs that inhibit the viral reverse transcriptase; possibly, this is also true for the cellular immune response. Therefore, despite the availability of an effective prophylactic vaccine, further extensive efforts are required to monitor the emergence of vaccination- and therapy-resistant HBV variants and to prevent their spread in the general population.

A 'first loop' linear epitope accessible on native hepatitis B surface antigen that persists in the face of 'second loop' immune escape

Murine monoclonal antibodies (mAbs) were raised following immunization with native mutant hepatitis B surface antigen (HBsAg) purified from human sera. A set of antibodies binding to a linear epitope carried between residues 121 and 129 of the s region was demonstrated. These antibodies were shown by cross-competition assays to bind to a single epitope whose antigenicity was influenced by the TTP motif lying between residues 125 and 127. This first loop epitope remained accessible on the surface of HBsAg in spite of major second loop mutations abrogating the normal a conformational epitopes. The mAb and its binding region in the first loop are important diagnostically and may represent an importance immunological target, one that is stable in the face of immunologically driven escape.

Genetic variation of hepatitis B surface antigen coding region among infants with chronic hepatitis B virus infection

Variants in the amino acid composition of the primary antibody-binding site of hepatitis B surface antigen (HBsAg) have been identified in a number of populations with chronic hepatitis B virus (HBV) infection. Direct sequencing of amplified or cloned PCR products, solid phase detection of sequence-specific PCR products (SP-PCR), and limiting dilution cloning PCR (LDC-PCR) were compared to determine their sensitivity in detecting differing concentrations of HBsAg variants. LDC-PCR had the greatest sensitivity and could detect HBsAg variants at a concentration of 0.1% of the total viral population. HBsAg variants were detected in 51% of infants with chronic HBV infection acquired after postexposure prophylaxis, and more than half of the variants were detected only by the most sensitive methods.

Comparison of commercial assays for the quantification of HBV DNA load in health care workers: calibration differences

Until recently, carriers of hepatitis B virus (HBV) were allowed to undertake exposure prone procedures providing their serum did not contain HBeAg. However, the recent description of hepatitis B transmission events occurring from HBV-infected health care workers who conduct exposure prone procedures demonstrated that the then current Department of Health guidelines needed to be revised. As part of a series of studies carried out to determine if viral load measurements are a more secure means of assessing the conduct of exposure prone procedures, the suitability of commercially available assays for HBV DNA detection and quantification were investigated. This study describes a comparative analysis on the performances of three assays each based on a different methodology. The assays included the QUANTIPLEX HBV DNA Assay (bDNA), (Chiron Diagnostics Ltd.), the AMPLICOR HBV Monitor Test, (Roche Diagnostics Systems) and the Digene Hybrid Capture System HBV DNA Assay (Digene Corporation). Calibration curves from experiments using the Eurohep ad and ay HBV DNA standard controls indicated a close correlation between the three assays over the dynamic ranges claimed by the manufacturers, although the Quantiplex assay did appear to be over-reporting. This became more apparent when testing patients undergoing anti-viral therapy where the Quantiplex assay consistently over-reported by 0.5 log(10) when compared with the Amplicor assay. The results of this study indicate that based on its dynamic range, the Amplicor HBV Monitor test is the most appropriate assay for the routine investigation of anti-HBe carriers, which will have lower levels of HBV DNA. The investigation also highlights the need for using accepted standard HBV DNA control sera. This will be essential when using an assay to establish whether health care workers who are hepatitis B carriers can be allowed to perform exposure prone procedures under the new guidelines of the UK Department of Health.

A concise update on the status of liver transplantation for hepatitis B virus: the challenges in 2002

Significant improvements in both patient and graft survival after orthotopic liver transplantation (OLT) for hepatitis B virus (HBV)-related liver failure have been made during the last decade. Recurrence of HBV infection has decreased, even in high-risk patients. Despite ongoing progress, challenges remain for the next millennium, including the determination of cost-effective dosing strategies, treatment of HBV infection in liver transplant recipients, and ramifications of the use of new antiviral agents, specifically, the appearance of resistant strains. This review summarizes the relevant history of OLT for chronic viral hepatitis B, details accepted preventive and therapeutic treatments, and discusses ongoing experimental trials. Emphasis also is placed on new approaches in transplantation as they impact on the care of HBV-infected patients.

Structural and functional heterogeneity of naturally occurring hepatitis B virus variants

Most organisms have developed sophisticated machineries to preserve their genomic integrity. On the contrary hepatitis B virus (HBV), like a lot of other viruses can undergo rapid and drastic sequence changes, especially if the virus has to cope with natural or therapy induced antiviral mechanisms in the host. Here, we try to summarize possible implications for the molecular pathogenesis of HBV based on the extensive research on the genetic variants of HBV.

Vaccine- and hepatitis B immune globulin-induced escape mutations of hepatitis B virus surface antigen

Hepatitis B virus surface antigen (HBsAg) vaccination has been shown to be effective in preventing hepatitis B virus (HBV) infection. The protection is based on the induction of anti-HBs antibodies against a major cluster of antigenic epitopes of HBsAg, defined as the 'a' determinant region of small HBsAg. Prophylaxis of recurrent HBV infection in patients who have undergone liver transplantation for hepatitis B-related end-stage liver disease is achieved by the administration of hepatitis B immune globulins (HBIg) derived from HBsAg-vaccinated subjects. The anti-HBs-mediated immune pressure on HBV, however, seems to go along with the emergence and/or selection of immune escape HBV mutants that enable viral persistence in spite of adequate antibody titers. These HBsAg escape mutants harbor single or double point mutations that may significantly alter the immunological characteristics of HBsAg. Most escape mutations that influence HBsAg recognition by anti-HBs antibodies are located in the second 'a' determinant loop. Notably, HBsAg with an arginine replacement for glycine at amino acid 145 is considered the quintessential immune escape mutant because it has been isolated consistently in clinical samples of HBIg-treated individuals and vaccinated infants of chronically infected mothers. Direct binding studies with monoclonal antibodies demonstrated a more dramatic impact of this mutation on anti-HBs antibody recognition, compared with other point mutations in this antigenic domain. The clinical and epidemiological significance of these emerging HBsAg mutants will be a matter of research for years to come, especially as data available so far document that these mutants are viable and infectious strains. Strategies for vaccination programs and posttransplantation prophylaxis of recurrent hepatitis need to be developed that may prevent immune escape mutant HBV from spreading and to prevent these strains from becoming dominant during the next decennia.

Novel immunoassay for the detection of hepatitis B surface 'escape' mutants and its application in liver transplant recipients

Hepatitis B virus (HBV) strains with mutations in the surface gene are responsible for the failure of prophylaxis with hepatitis B immunoglobulin (HBIG) in a proportion of patients transplanted for HBsAg positive cirrhosis. So far, the emergence and evolution of these 'surface antibody escape' mutants have been studied by DNA sequencing. In this study the use of an immunoassay is described for diagnosis and characterisation of HBV recurrence after liver transplantation (OLT), based on a monoclonal antibody able to recognise both wild-type and mutant HBsAg. Pre- and post-transplant samples from 22 patients transplanted for HBsAg positive cirrhosis were studied: Group A: 12 patients who reinfected the graft despite receiving HBIG; Group B: 6 patients with no HBV recurrence with continuous HBIG; Group C: 4 patients with HBV recurrence without prophylaxis. By running the new assay in parallel with an immunoassay that is susceptible to HBsAg mutants, 4 of 12 cases were identified in Group A with HBV recurrence due to surface antibody escape mutants, whereas in 8 patients this was due to the wild-type HBV. The results from the immunoassays were confirmed in all cases by HBV DNA sequencing. The surface gene mutations in the 4 patients affected codons 144 and 145 and in one of these 4 patients HBV strains with mutations in both codons were detected before and after transplantation. The epitope recognised by the new monoclonal antibody that reacts with both wild-type and mutant HBsAg seems to remain stable in the HBIG-induced HBV mutants. This serological approach allows rapid and cost-effective screening for HBsAg escape mutants in the liver transplant setting and may be helpful in the selection of appropriate prophylaxis.

Mechanisms of hepatitis B virus escape after immunoglobulin therapy

Passive immunoprophylaxis with hepatitis B immunoglobulin is used to reduce the risk of infection of grafts after liver transplantation and also to protect newborn children of hepatitis B virus-infected mothers. The use of hepatitis B immunoglobulin is associated with the emergence of variant viruses or escape mutants that have specific amino acid substitutions in immunodominant epitopes. Under these circumstances, high serum titres of the virus may be observed in the context of apparently protective levels of antibody to hepatitis B surface antigen. The potential impact of hepatitis B surface antigen variation on vaccination strategies remains a contentious issue. As the burden of hepatitis B virus is dramatically reduced by major vaccination programmes, a greater proportion of carriers will demonstrate hepatitis B surface antigen variation from wild-type. The degree of protection afforded by current vaccines from subsequent infection by variants of the virus is unknown. Concern is raised over the potential impact of hepatitis B surface antigen variation on hepatitis B virus polymerase inhibitor susceptibility, and the reduced sensitivity of current antigen assays for detection of hepatitis B surface antigen variants.

Reactivity of 13 in vitro expressed hepatitis B surface antigen variants in 7 commercial diagnostic assays

The primary marker of current hepatitis B infection is the surface antigen (HBsAg), however HBsAg negativity does not exclude hepatitis B viremia. HBsAg variants can be responsible for such diagnostic failures. Here 13 different HBsAg variants were cloned, variant protein produced in a mammalian expression system, and tested using 7 commercial HBsAg diagnostic assays. Of 12 variants analyzed, 6 samples displayed similar reactivity to the positive control (containing standard HBsAg sequence) in most of the assays, but 6 samples, containing various mutations throughout the entire major hydrophilic region (MHR), showed reduced reactivity. It was found that the loss of cysteine at amino acid (aa) 124 in 1 sample affected the secretion as well as the reactivity of HBsAg in the expression system. Thus, not all assays are equally able to detect HBsAg variants, implying that, to attain an acceptable level of sensitivity, the antibody repertoire of the current assays should be extended.

Characterization of the reactivity pattern of murine monoclonal antibodies against wild-type hepatitis B surface antigen to G145R and other naturally occurring "a" loop escape mutations

The hepatitis B surface antigen (HBsAg) "a" domain harbors major B-cell epitopes. Viruses with mutations in this region emerge after vaccination or during hepatitis B immune globulin (HBIg) prophylaxis. A strain with G145R replacement has been almost invariably isolated as a major escape mutant. We investigated mutant antigen-antibody interactions with direct binding assays. G145R and 16 other naturally occurring recombinant HBsAg mutants were expressed in mammalian Cos-1 cells. The reactivity of a panel of 28 murine anti-hepatitis B surface antigen (anti-HBs) monoclonal antibodies to mutant antigens was measured with enzyme immunoassay and expressed as percentage compared with the wild-type (wt) HBsAg signal for each antibody. All point-mutated proteins displayed diffuse intracellular immunofluorescent labeling corresponding to a secretory pathway. Monoclonal antibodies (mAbs) were classified according to different binding patterns. The effect of mutations on antibody binding differs depending on the amino acid involved and on the location within the "a" loop. As expected, most antibodies had absent or negligible binding (<40%), notably with residue 145 replacements. However, we identified antibodies that reacted with conformational epitopes but nevertheless had adequate reactivity (>40%) with all mutant antigens, including G145R. The effect of G145R was more pronounced than that of G145A. A subgroup of antibodies had substantially increased recognition (>120%) of antigens with mutations in the first loop. We demonstrated that antibodies can be selected or combined that react with all mutants investigated, including G145R. These data offer perspectives for improving anti-HBs-based protection against hepatitis B.

Hepatitis B virus mutants

During hepatitis B virus (HBV) infection, selection and takeover of mutant viruses are frequent events driven by both humoral and cellular host-immune response and antiviral therapy. Therefore, dynamic studies of the variations of viral mutants over time within the overall viral population in relation with the host-virus interactions are extremely important to better understand the biological and pathogenic role of each mutant. With these premises, we review the more frequent mutations detected in each of the 4 open reading frames of HBV. A detailed analysis of the pathobiologic implications of pre-C region mutations which suppress the expression of the hepatitis B 'e' antigen, will be presented, as these mutations induce a specific change in virus biology and the variations of the ratio between wild-type and mutant correlate with significant events in host-virus interactions.

Evidence that anti-HBc but not HBV DNA testing may prevent some HBV transmission by transfusion

Blood donor screening for antibody to hepatitis B core antigen (anti-HBc) implemented in some countries as a surrogate marker for non-A, non-B hepatitis has been superseded by anti-HCV screening. To assess the value of anti-HBc screening for the detection of hepatitis B surface antigen-negative blood donations that might contain infectious HBV, HBV genomic detection and recipient testing were used. Blood donations were screened and confirmed by multiple anti-HBc assays. Donations containing isolated anti-HBc and those with anti-hepatitis B surface antigen (anti-HBs) level < 0.1 IU/ml were tested for the presence of HBV DNA. Recipients of previous donations from the corresponding donors during the previous 5 years were traced and tested for markers of HBV infection. Of 103 869 donations screened, 586 (0.56%) were anti-HBc positive, two of which contained HBsAg, and 413 (0.4%) had protective (>/= 0.1 IU/ml) levels of anti-HBs. Anti-HBs < 0.1 IU/ml was found in 102 of these donations (0.1%) and isolated anti-HBc in 69 (0.07%). No donations with isolated anti-HBc were HBV DNA confirmed positive. Of 278 recipients of previous donations from 171 donors at risk of HBV carriage, 12 had markers of HBV infection. Six recipients had other identified risk factors. An association with blood transfusion was considered probable in two and possible in four recipients. None of the six corresponding donors had detectable HBV DNA 6-40 months after the implicated donation. The frequency of HBV transmission by chronic carriers negative for hepatitis B surface antigen was estimated in this study to be 1 in 52,000 donations (CI 0.3-7.8/100,000) from HBsAg-negative donors. Such HBV infectious donations may not be detected by DNA amplification.

Licensed recombinant hepatitis B vaccines protect chimpanzees against infection with the prototype surface gene mutant of hepatitis B virus

The emergence in vaccinated individuals of hepatitis B virus (HBV) mutants with amino acid substitutions within the a determinant of the surface protein has raised the possibility that such variants represent neutralization escape mutants. We previously demonstrated that one such mutant HBV, strain AS, with an arginine substituted for glycine at surface gene codon 145, was infectious and pathogenic in seronegative chimpanzees. In the present study, the protective efficacy of licensed hepatitis B vaccines was evaluated against challenge with this mutant virus. Four chimpanzees were immunized with 1 of 2 licensed recombinant hepatitis B vaccines. Shortly after the chimpanzees developed antibodies to hepatitis B surface antigen (anti-HBs), they were challenged intravenously with mutant HBV strain AS. Two unvaccinated chimpanzees served as positive controls. The 4 vaccinated chimpanzees did not develop evidence of HBV infection or hepatitis during 2 years following virus challenge. In contrast, the 2 unvaccinated chimpanzees developed HBV infection and hepatitis. Serum anti-HBs in the vaccinated chimpanzees reacted not only with wild-type surface antigen, but also with mutant surface antigen by competition enzyme-linked immunosorbent assay (ELISA). Thus, immunization of chimpanzees with licensed recombinant hepatitis B vaccines stimulates anti-HBs that is broadly reactive and affords protection against infection with a surface gene mutant of HBV, suggesting that properly immunized individuals are not at significant risk of infection with this prototype variant strain of HBV.

Antigenic characterization of pre- and post-liver transplant hepatitis B surface antigen sequences from patients treated with hepatitis B immune globulin

BACKGROUND/AIMS

The success of treatment with hepatitis B hyperimmune globulin in preventing recurrence of hepatitis B virus infection in patients undergoing orthotopic liver transplantation depends on maintaining levels of anti-HBs sufficient to neutralise hepatitis B virus and also on patient compliance. Breakthrough infections may occur, and these have been associated with the emergence of variants in HBsAg.

METHODS

Three patients, two who relapsed and one who had no evidence of hepatitis B virus infection post-orthotopic liver transplantation were studied. Polymerase chain reaction and sequencing of pre- and post-orthotopic liver transplantation samples was followed by antigenic analysis of the in vitro expressed cloned sequences.

RESULTS

In two patients who were treated with hyperimmune globulin, amino acid variation in the region of the immunodominant B cell epitopes of HBsAg occurred. Sequencing of clones revealed fluctuating variant sequences over time. One had clinical relapse and immune escape was evident on in vitro antigenic analysis. Patient two lost HBsAg reactivity post-orthotopic liver transplantation. There was loss of an antigenically critical cysteine molecule; sequencing of clones revealed that this was the dominant species. The third patient relapsed when protective levels of anti-HBs were not maintained; HBsAg showed no variation compared to a standard subtype sequence.

CONCLUSION

These data provide strong experimental evidence of immune escape. It appears that hyperimmune globulin provides the selection pressure. In these patients, HBsAg negativity does not exclude infection of the transplanted liver.

Fibrosing cholestatic hepatitis in renal transplant recipients with hepatitis C virus infection

Fibrosing cholestatic hepatitis (FCH) has been described as a specific manifestation of hepatitis B virus (HBV) infection in liver allograft recipients characterized by a rapid progression to liver failure. Only sporadic cases have been reported in other immunocompromised groups infected with HBV and in a few transplant recipients with hepatitis C virus (HCV) infection. We present the occurrence of FCH in 4 HCV-infected renal transplant recipients within a series of 73 renal transplant recipients with HCV infection followed up closely serologically and with consecutive liver biopsies. All 4 patients received the triple-immunosuppressive regimen (azathioprine, cyclosporine A, methylprednisolone). The interval from transplantation to the appearance of liver dysfunction was 1 to 4 months and to histological diagnosis, 3 to 11 months. The biochemical profile was analogous to a progressive cholestatic syndrome in 3 patients, whereas the fourth patient had only slightly increased alanine aminotransferase and gamma-glutamyl transferase (gammaGT) levels. Liver histological examination showed the characteristic pattern of FCH in 2 patients, whereas the other 2 patients had changes compatible with an early stage. All patients were anti-HCV negative at the time of transplantation, whereas 2 patients, 1 with incomplete and 1with complete histological FCH features, seroconverted after 3 and 31 months, respectively. The patients were HCV RNA positive at the time of the first liver biopsy and showed high serum HCV RNA levels (14 to 58 x 10(6) Eq/mL, branched DNA). HCV genotype was 1b in 3 patients and 3a in 1 patient. After histological diagnosis, immunosuppression was drastically reduced. Two patients died of sepsis and liver failure 16 and 18 months posttransplantation, whereas the seroconverted patients showed marked improvement of their liver disease, which was histologically verified in 1 patient. In conclusion, FCH can occur in HCV-infected renal transplant recipients. It seems to develop as a complication of a recent HCV infection during the period of maximal immunosuppression and is associated with high HCV viremia levels. There are indications that drastic reduction of immunosuppression may have a beneficial effect on the outcome of the disease.

Genetic alterations in the S gene of hepatitis B virus in patients with acute hepatitis B, chronic hepatitis B and hepatitis B liver cirrhosis before and after liver transplantation

BACKGROUND

Several studies have shown that hepatitis B immunoglobulin (HBIG) imposes a selection pressure on the hepatitis B virus (HBV) S gene, and that the emergence of mutations in this region would make reinfection after orthotopic liver transplantation (OLT) possible.

AIMS

This study was undertaken to analyze the presence of HBV S-gene mutations in the different stages of HBV infection and the relationship between HBIG therapy and the emergence of mutations in liver transplant recipients.

METHODS

The frequency and location of mutations in the coding region of the HBV S gene were studied by PCR and direct sequencing in 30 patients (7 with acute self-limited hepatitis B, 16 with chronic hepatitis B and 7 recipients of (OLT) for HBV-related end stage liver disease who became reinfected).

RESULTS

The average number of amino acid changes was higher in patients with a more advanced stage of disease, 0.57 mutations/100 positions in acute hepatitis B and 1.57 in chronic hepatitis B (1.28 in HBeAg-positive and 1.8 in anti-HBe-positive patients). The average number of substitutions in the transplanted patients was 2.7 before OLT and 3 after OLT. No amino acid substitutions were detected in the "a" determinant of HBsAg in acute hepatitis B, however, 8 substitutions were observed in 6 chronic patients. In 3 OLT patients, 4 substitutions were observed in samples before and after OLT. One of these patients, who had protective levels of anti-HBs, showed 3 additional new amino acid substitutions after OLT, suggesting escape mutant selection by the effect of HBIG therapy. No changes were observed between the consensus sequences obtained several years before and after transplantation, indicating consensus sequence stability.

CONCLUSION

These results show that there is an accumulation of HBV S-gene mutations in HBV-related end-stage liver disease. Prophylaxis with HBIG mainly obtained from acute self-limited hepatitis patients who have a highly homogeneous viral population, may be one factor underlying the reinfection after liver transplantation.

Liver transplantation and HBsAg-positive postnecrotic cirrhosis: adequate immunoprophylaxis and delta virus co-infection as the significant determinants of long-term prognosis

BACKGROUND/AIMS

The place of liver transplantation in hepatitis B viral (HBV)-related diseases remains controversial because of the high rate of reinfection. The aim of this study was to define the determinants of long-term prognosis after transplantation.

METHODS

Fifty-eight patients were transplanted during the period February 1984-September 1996. Six patients died during the early (< 3 months) posttransplant period from causes unrelated to HBV infection. All 52 long-term (> 3 months) survivors were evaluated in relation to the mode of presentation, viral replication at time of transplantation, absence of hepatocellular cancer at time of transplantation and use of adequate immunoprophylaxis (IP). Adequate immunoprophylaxis, defined as maintenance of anti-HBs levels over 100 mUI/ml, was introduced in December 1989. Intention-to-treat IP analysis compared patients transplanted before and after this date. The median follow-up was 74 months (range 4 to 131). Forty-seven patients (90%) had a minimal follow-up of 3 years.

RESULTS

Five-year actuarial survival rates of 58 patients and of 52 long-term survivors were 72 +/- 6% and 80 +/- 6%, respectively. Univariate analysis showed that delta co-infection (n = 25) significantly improved survival (p < 0.001) [96 +/- 4% vs 63 +/- 10% in HBV patients (n = 27) at 5 years] as did absence of hepatocellular cancer (n = 36) (p = 0.020) [89 +/- 5% vs 61 +/- 12% in 16 non-cancer patients]. IP, however, significantly influenced 5-year survival in the HBV-patient group (n = 17) (p = 0.001) [85 +/- 10% vs 30 +/- 14% in 10 patients without IP). Multivariate analysis selected delta co-infection (p = 0.002) and IP (p = 0.01) as the significant determinants of prognosis independently influencing survival. Uni- and multivariate analyses showed that survival without reinfection was significantly influenced by IP (p = 0.002) [73 +/- 8% (n = 31) versus 33 +/- 12% in 15 non-treated patients).

CONCLUSIONS

Delta virus co-infection and immunoprophylaxis are the most important prognostic factors after transplantation for postnecrotic HBsAg-positive cirrhosis. Transplantation can be proposed as a therapeutic tool only if life-long adequate adjuvant therapy can be achieved. Under this condition good results can even be obtained if there is viral replication at the time of transplantation.

Distribution of hepatitis B virus genotypes in two different pediatric populations from Argentina

Differences in pathogenesis and the probability of becoming a chronic carrier depend on the age at which hepatitis B virus (HBV) infection is acquired, ranging from 82% in infants less than 6 months of age to 15 to 30% in older children. HBV genotypes from 22 pediatric patients from two areas that differ in prevalence have been determined. Phylogenetic analysis shows a clear difference between the genotype distribution in Buenos Aires, a low-prevalence area, and that found in Gualeguay, Entre Ríos, a high-prevalence area. While the analysis allocated the sequences in the Buenos Aires group to genotypes A (36%), D (9%), and F (55%), the Gualeguay group presented exclusively genotype A isolates with very low nucleotide divergence, which suggests a strong founder viral population. The high prevalence of genotype F in the Buenos Aires group and its high intragroup heterogeneity agree with the American origin of this genotype.

Incidence and clinical consequences of surface and polymerase gene mutations in liver transplant recipients on hepatitis B immunoglobulin

Mutations in the "a" determinant of the surface gene have been associated with failure of hepatitis B immunoglobulin (HBIg) prophylaxis. We compared sequences from the surface and polymerase regions of hepatitis B virus (HBV) from 4 patients who failed high-dose HBIg therapy with two control groups: HBIg-treated patients who remained hepatitis B surface antigen (HBsAg)-negative (n = 4) and HBV-infected transplant recipients who never received HBIg (n = 4). Mutations within the surface and overlapping polymerase region were more common in patients failing HBIg than controls (P = .03), and mutations in the region of the "a" determinant were present only in patients failing HBIg. To examine the relationship between HBIg failure and duration of therapy, five additional treatment failures from a second transplantation center were sequenced (total with HBIg failure = 9). Mutations in the "a" determinant developed in 1 of 3 patients receiving HBIg for less than 6 months compared with 5 of 6 patients failing HBIg after 6 months of therapy (P = .23). The most frequently identified amino acid substitution was glycine to arginine at position 145 (present in 4 of 6 patients who failed HBIg after at least 6 months of treatment). A unique mutation within the YMDD motif (methionine to leucine) was present in 1 patient who failed HBIg treatment and who received a short course of ganciclovir. We conclude that the emergence of mutations in the "a" determinant accounts for some, but not all, treatment failures in patients receiving HBIg prophylaxis. Mutations in other regions of the S gene were more common in patients failing HBIg than controls, suggesting that domains other than the "a" determinant may be important.

Improved clinical outcomes with liver transplantation for hepatitis B-induced chronic liver failure using passive immunization

OBJECTIVE

The goals were to summarize the results of liver transplantation for chronic hepatitis B disease (HBV) at the University of Virginia, correlate pretransplant viral markers with posttransplant hepatitis B immunoglobulin (HBIg) requirements, and identify the relation between viral protein in the liver and clinical reinfection.

SUMMARY BACKGROUND DATA

Liver transplantation is an accepted treatment for end-stage liver disease from chronic HBV infection, although lifelong antiviral treatment (with HBIg or antiviral agents) is still necessary. Patients with evidence of active viral replication (detectable serum HBV-DNA or e antigen) at the time of transplant have a higher rate of allograft infection. Whether clinically stable patients receiving HBIg immunoprophylaxis have detectable viral products in their grafts remains unknown.

METHODS

Forty-four transplants performed for HBV disease at the University of Virginia since March 1990 were reviewed. Most patients underwent aggressive passive immunoprophylaxis with HBIg to maintain serum HBV surface antibody (HBsAb) levels > or =500 IU/l for the first 6 months after the transplant, and > or =150 IU/l thereafter. Patients had viral markers quantified, underwent pharmacokinetic analysis of HBsAb levels to adjust dosing, and were biopsied routinely every 3 to 6 months and when indicated.

RESULTS

Forty-four transplants were performed in 39 patients. Actual 1-year and 3-year graft survival was 95% and 81%, respectively, and 1-year and 3-year patient survival was 98% and 96%, respectively. After the adoption of indefinite HBIg prophylaxis, nine grafts became infected (all in recipients positive for HBV e antigen). Three occurred within 8 weeks of transplantation and were associated with a short HBsAb half-life and a wild-type virus. Six occurred >8 months after the transplant, and most of these were associated with viral mutation. Quantification of pretransplant markers was an overall poor predictor of HBIg requirements after the transplant. Immunohistochemistry demonstrated transient low-level expression of core protein in the liver in 23% of patients without serum or clinical evidence of recurrent hepatitis.

CONCLUSIONS

An excellent outcome is possible after liver transplantation for chronic HBV disease using HBIg dosed by pharmacokinetic parameters. Currently, quantification of pretransplant serum markers of the HBV antigen load does not predict the intensity of posttransplant treatment required for good clinical outcomes. Because HBV is not eradicated from the patient, some form of indefinite antiviral therapy continues to be warranted.

Nucleoside analogue therapy in fibrosing cholestatic hepatitis--a case report in an HBsAg positive renal transplant recipient

A 45-year-old HBsAg carrier (HBeAb positive with normal liver function tests) underwent renal transplantation for mesangioproliferative glomerulonephritis. Sixteen months later he developed jaundice. Investigations showed he remained HBeAb positive, but HBV-DNA levels were 99 pg/ml, indicating active replication of a HBV pre-core mutant. He was commenced on lamivudine therapy with a subsequent rapid fall in HBV-DNA levels to 2.8 pg/ml, but liver function tests continued to deteriorate and he developed hepatorenal failure. Liver biopsy showed fibrosing cholestatic hepatitis. He underwent liver transplantation, which was complicated by lactic acidosis. Lamivudine was withdrawn and HBV prophylaxis with HB immunoglobulin was commenced. Unfortunately he died 38 days post-transplant of surgical complications with no evidence of HBV recurrence. We discuss the use of nucleoside analogues in fibrosing cholestatic hepatitis and review the literature.