Hepatitis B virus genetic diversity and its impact on diagnostic assays

Atypical serologic profiles of hepatitis B virus infection across clinical cohorts of patients in Southwestern Nigeria

Hepatitis B virus (HBV) infection follows a natural course of events predicted by a dynamic interaction between viral antigen and the host immune system, which forms the basis for HBV serological diagnosis. These interactions may deviate from the typical serologic patterns. This study investigates the types of atypical HBV serologic profiles (AHBSP) across clinical cohorts of patients with HBV infection in southwestern Nigeria. This is a cross-sectional, hospital-based, multi-centered study. Patients' sera were analyzed for HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc IgM, and anti-HBc IgG by ELISA from 279 study participants attending selected gastroenterology clinics between August 2019 and December 2020. The prevalence of atypical HBV serologic profiles was 27% (n = 76). The mean age of patients was 35.7 ± 11.2 years. The gender distribution involved 183 females (65.6%) and 96 males (34.4%). Across clinical cohorts of patients with atypical serologic profiles, HBeAg Negative, anti-HBe positive with detectable HBV DNA had the highest prevalence of 21% followed by isolated anti-HBc antibody positive, HBsAg negative and detectable HBV DNA, 5%. The atypical serologic profiles, HBeAg positive, HBsAg negative with detectable HBV DNA and concurrent anti-HBs with HBsAg, had the lowest prevalence, 0.4%, respectively. This study identified the considerable presence of atypical HBV serologic profiles across clinical cohorts of HBV infection in southwestern Nigeria.

In vitro characterization of six hepatitis B virus genotypes from clinical isolates using transfecting linear HBV genomes

Hepatitis B virus (HBV) infection is a global public health problem with about 257 million chronically infected people and over 887000 deaths annually. In this study, 32 whole HBV genomes of various genotypes were amplified from clinical isolates to create transfection clones. The clones were sequenced, and their biological properties characterized by transfecting linear HBV clones into HepG2 cells. We analysed the SPI and SPII promotor regions, X-gene, BCP/PC sequences, core, preS/S and HBV polymerase sequences. HBV clones analysed in this study revealed differential replication kinetics of viral nucleic acids and expression of proteins. Sequence analysis of HBV clones revealed mutations in preS1, preS2 and S genes; deletion and insertion and point mutations in BCP/PC region; including novel and previously reported mutations. Among the patient samples tested, HBV genotype B clones were more likely to have higher frequencies of mutations, while sub-genotype A1 and A2 clones tended to have fewer mutations. No polymerase drug resistant mutations were seen. HBeAg mutations were primarily in the BCP/PC region in genotype B, but core truncations were found in genotype E. S gene mutations affecting HBsAg expression and detection were seen in all genotypes except A2. Using an HBV clone with repetitive terminal sequences and a SapI restriction site allowed us to analyse HBV analyte production in cell culture and characterize the genetics of viral phenotypes using complete HBV genomes isolated from serum/plasma samples of infected patients.

HBV S antigen evolution in the backdrop of HDV infection affects epitope processing and presentation

INTRODUCTION

HBV can evolve under selection pressure exerted by drugs and/or host immunity, resulting in accumulation of escape mutations that can affect the drug or the immune activity. Hepatitis delta virus (HDV) coinfection is also known to exert selection pressure on HBV, which leads to selective amplification of certain mutations, especially in genes that are required for HDV pathogenesis, such as HBsAg. However, little is known about the function of these mutations on HBV or HDV life cycle. The purpose of this study is to determine mutations selectively amplified in the backdrop of HDV, and how these mutations affect processing of CD4- and CD8-T cell epitopes.

METHODS

HBsAg was successfully amplified from 49/50 HBV mono- and 36/50 coinfected samples. The sequences were used to identify mutations specific to each study group, followed by an in silico analysis to determine the effect of these mutations on (1) proteasomal degradation, (2) MHC-I and MHC-II biding, and (3) processing of T-cell epitopes.

RESULTS

HBV-HDV coinfected sequences exhibited certain unique mutations in HBsAg genes. Some of these mutations affected the generation of proteasomal sites, binding of HBsAg epitopes to MHC-I and -II ligands, and subsequent generation of T- cell epitopes.

CONCLUSION

These observations suggest that HBV selectively amplifies certain mutations in the backdrop of HDV coinfection. Selective amplification of these mutations at certain strategic locations might not only enable HBV to counteract the inhibitory effects of HDV on HBV replication but also facilitate its survival by escaping the immune response.

A Highly Prevalent Polymorphism in the Core Region Impairs Quantification of Hepatitis B Virus (HBV) by the cobas TaqMan HBV Assay

The high genetic variability of hepatitis B virus (HBV) can impair DNA quantification. Here, we investigate a major underquantification of HBV by the cobas TaqMan HBV assay (CTM; Roche). In France, between 2005 and 2017, HBV DNA was detected in 3,102 blood donations by use of the CTM (95% limit of detection [LOD₉₅], 4.8 IU/ml). HBV strains were sequenced in the S region (LOD₉₅, ∼30 IU/ml). Concordant (n = 120) and discordant (n = 45) samples were identified according to the agreement between the plasma viral load (pVL) determined by the CTM and sequencing; all samples were also quantified using the RealTime HBV assay (RTH; Abbott). The viral signature, cloning, and mutagenesis were used to characterize the polymorphism responsible for CTM misquantification. A CTM-RTH discordance (>1 log IU/ml) was found in 14/45 samples that had low pVLs and were successfully genotyped (pVL^low genoS⁺). PreC/C clones of concordant (C1, C2) and discordant (D1, D2) strains were used to challenge the CTM. Strains D1 and D2 were highly underquantified (42- and 368-fold). In clones, mutating the region corresponding to the CTM reverse primer from a discordant sequence to a concordant sequence restored the levels of quantification to 24% (D1→C1) and 59% (D2→C1) of theoretical levels, while mutating the sequence of a concordant strain to that of a discordant strain led to 78-fold (C1→D1) and 146-fold (C1→D2) decreases in quantification. Moreover, mutating positions 1961 and 1962 was enough to induce a 5-fold underquantification. We conclude that the CTM underestimates pVLs for HBV strains with mutations in the reverse primer target. Specifically, the polymorphism at nucleotides 1961 and 1962 is naturally present in 4.79 and 4.22% of genotype A and D strains, which are highly frequent in Europe, leading to a 5-fold decrease in quantification. Quantification using the new-generation Roche C4800 assay is not affected by this polymorphism.

Entecavir-resistant hepatitis B virus decreases surface antigenicity: A full genome and functional characterization

BACKGROUND AND AIM

Since polymerase and surface genes overlap in hepatitis B virus (HBV), an antiviral-induced mutation in the polymerase gene may alter the surface antigenicity in patients with chronic hepatitis B (CHB), but this possibility has not been clearly confirmed. This study aimed to determine the drug susceptibility and surface antigenicity of the patient-derived mutants.

PATIENTS AND METHODS

Full-length HBV genomes isolated from four entecavir-resistant CHB patients were cloned and sequenced. Around 10 clones of full-length HBV obtained from each patient were analysed and registered in the NCBI GenBank. Representative clones were further characterized by in vitro drug susceptibility and surface antigenicity assays.

RESULTS

The rtL180M + rtM204V mutations were common among all the clones analysed. Additionally, the ETV resistance mutations rtT184A/L, rtS202G and rtM250V were found among three patients. Most of the ETV-resistant mutants had amino acid alterations within the known epitopes recognized by T- and B-cells in the HBV surface and core antigens. The in vitro drug susceptibility assay showed that all tested clones were resistant to ETV treatment. However, they were all susceptible to ADV and TDF. More importantly, the rtI169T mutation in the RT domain, led to the sF161L mutation in the overlapping S gene, which decreased in surface antigenicity.

CONCLUSIONS

The ETV resistance mutations can affect the antigenicity of the HBsAg proteins due to changes in the overlapping sequence of this surface antigen. Thus, the apparent decline or disappearance of HBsAg needs to be interpreted cautiously in patients with previous or current antiviral resistance mutations.

Comprehensive analysis of hepatitis B virus infections in blood donors in southern China that are surface antigen positive but nucleic acid testing negative

BACKGROUND

Hepatitis B virus (HBV) infection is one of the major concerns for the safety of blood transfusion in high-prevalent countries such as in China. Prior studies outside of China have shown hepatitis B surface antigen (HBsAg) false-reactive rate of 0.02% to 0.04%. Similarly, false-negative HBsAg and HBV DNA results may occur in infected donors. Our study analyzed HBsAg enzyme-linked immunosorbent assay (ELISA)-reactive but NAT-negative donations in Shenzhen Blood Center, China.

STUDY DESIGN AND METHODS

HBsAg ELISA-positive/NAT-negative plasma samples identified from screening 101,025 donations during 2017-2018 were analyzed by molecular and serologic tests including neutralization, chemiluminescence immunoassays, and various HBV DNA amplification assays. Molecular characterizations of HBsAg-positive/NAT-negative samples were determined by quantitative polymerase chain reaction (qPCR) and nested PCR amplification of the basic core and precore promotor regions (295 base pairs) and HBsAg (S) region (496 base pairs).

RESULTS

Screening of 101,025 eligible blood donations identified 157 (0.16%, 95% confidence interval, 0.13%-0.18%) HBsAg ELISA-positive/NAT-negative plasma samples; of those, 71 (45.2%) were HBsAg confirmed positive by further HBsAg testing and DNA positive by molecular tests with increased sensitivity. Of the 71, all but one was antibody to hepatitis B core antigen reactive without antibody to hepatitis B surface antigen, yielding one recent (window-period) HBV infection. Of the remaining donations, 80 (51%) were not considered as HBV-infected donors, and 6 (3.8%) were interpreted as indeterminate since HBsAg results were discordant with unconfirmed HBV DNA results. In the 71 confirmed positives, HBsAg levels ranged from 0.05 to 400 IU/mL and HBV DNA from 6 to 2654 IU/mL; however, the correlation between the two was weak (R² = 0.24).

CONCLUSION

Fewer than half of HBsAg ELISA-positive/NAT-negative samples were confirmed as HBsAg positive. Our study demonstrates that in highly HBV-endemic countries, assays with high sensitivity and specificity may be required.

Intra-host diversity of hepatitis B virus during mother-to-child transmission: the X gene may play a key role in virus survival in children after transmission

Mother-to-child transmission of hepatitis B virus (HBV) is the main route of transmission in Asia, and characterization of HBV quasispecies is needed to further understand virus evolution and adaptation. To understand changes in HBV during mother-to-child transmission, we enrolled nine pairs of mothers and children in the study, including a set of twins. Three groups were infected with HBV genotype C, and six groups were infected with HBV genotype B. The full-length HBV genome was amplified by PCR from serum samples before antiviral treatment, the whole viral genomes from each pair were sequenced, and the complexity and diversity of the quasispecies were analyzed. The entropy of transmitted HBV in children was found to be lower than their mothers, suggesting that there was a bottleneck effect during HBV transmission from the mother to the child. Selective evolution was shown by calculating πN and πS in the whole genomes, and the highest values were obtained for the X gene, which plays a role in viral replication and immune escape. All genotype C patients and only one genotype B pair had a πN/πS greater than 1 ratio, indicating that positive selection had occurred. In addition, quasispecies were found to be different between the twin children despite having the same mother, indicating that virus evolution is host-specific.

Current progress in the prevention of mother-to-child transmission of hepatitis B and resulting clinical and programmatic implications

There is currently no cure for hepatitis B chronic infections. Because new hepatitis B infections result mainly from perinatal transmission, preventing mother-to-child transmission is essential to reach by 2030 the goal of hepatitis B elimination set by the World Health Organization. The universal administration of hepatitis B vaccine to all infants, regardless of maternal status, starting with the birth dose, is the cornerstone of the strategy for elimination. Additional interventions, such as hepatitis B immune globulin administered to newborns and antiviral prophylaxis administered to hepatitis B infected pregnant women, may contribute to reaching the goal earlier. Hepatitis B immune globulin may remain out for reach of many pregnant women in low- and middle-income countries due to cost and logistic issues, but antivirals are cheap and do not require a cold chain for distribution. However, it has been observed that some viruses harbor mutations associated with escape from vaccine-elicited antibodies following immunization or administration of hepatitis B immune globulin. Also, resistance associated mutations have been described for several drugs used for treatment of hepatitis B infected patients as well as for the prevention of mother-to-child transmission. Whether these mutations have the potential to compromise the prevention of mother-to-child transmission or future treatment of the mother is a question of importance. We propose a review of important recent studies assessing tenofovir disoproxil fumarate for the prevention of mother-to-child transmission, and provides detailed information on the mutations possibly relevant in this setting.

Hepatitis B Virus Blood Screening: Need for Reappraisal of Blood Safety Measures?

Over the past decades, the risk of HBV transfusion–transmission has been steadily reduced through the recruitment of volunteer donors, the selection of donors based on risk-behavior evaluation, the development of increasingly more sensitive hepatitis B antigen (HBsAg) assays, the use of hepatitis B core antibody (anti-HBc) screening in some low-endemic countries, and the recent implementation of HBV nucleic acid testing (NAT). Despite this accumulation of blood safety measures, the desirable zero risk goal has yet to be achieved. The residual risk of HBV transfusion–transmission appears associated with the preseroconversion window period and occult HBV infection characterized by the absence of detectable HBsAg and extremely low levels of HBV DNA. Infected donations tested false-negative with serology and/or NAT still persist and derived blood components were shown to transmit the virus, although rarely. Questions regarding the apparent redundancy of some safety measures prompted debates on how to reduce the cost of HBV blood screening. In particular, accumulating data strongly suggests that HBsAg testing may add little, if any HBV risk reduction value when HBV NAT and anti-HBc screening also apply. Absence or minimal acceptable infectious risk needs to be assessed before considering discontinuing HBsAg. Nevertheless, HBsAg remains essential in high-endemic settings where anti-HBc testing cannot be implemented without compromising blood availability. HBV screening strategy should be decided according to local epidemiology, estimate of the infectious risk, and resources.

Ultra-deep sequencing reveals high prevalence and broad structural diversity of hepatitis B surface antigen mutations in a global population

The diversity of the hepatitis B surface antigen (HBsAg) has a significant impact on the performance of diagnostic screening tests and the clinical outcome of hepatitis B infection. Neutralizing or diagnostic antibodies against the HBsAg are directed towards its highly conserved major hydrophilic region (MHR), in particular towards its “a” determinant subdomain. Here, we explored, on a global scale, the genetic diversity of the HBsAg MHR in a large, multi-ethnic cohort of randomly selected subjects with HBV infection from four continents. A total of 1553 HBsAg positive blood samples of subjects originating from 20 different countries across Africa, America, Asia and central Europe were characterized for amino acid variation in the MHR. Using highly sensitive ultra-deep sequencing, we found 72.8% of the successfully sequenced subjects (n = 1391) demonstrated amino acid sequence variation in the HBsAg MHR. This indicates that the global variation frequency in the HBsAg MHR is threefold higher than previously reported. The majority of the amino acid mutations were found in the HBV genotypes B (28.9%) and C (25.4%). Collectively, we identified 345 distinct amino acid mutations in the MHR. Among these, we report 62 previously unknown mutations, which extends the worldwide pool of currently known HBsAg MHR mutations by 22%. Importantly, topological analysis identified the “a” determinant upstream flanking region as the structurally most diverse subdomain of the HBsAg MHR. The highest prevalence of “a” determinant region mutations was observed in subjects from Asia, followed by the African, American and European cohorts, respectively. Finally, we found that more than half (59.3%) of all HBV subjects investigated carried multiple MHR mutations. Together, this worldwide ultra-deep sequencing based genotyping study reveals that the global prevalence and structural complexity of variation in the hepatitis B surface antigen have, to date, been significantly underappreciated.

Hepatitis B immunopathogenesis and immunotherapy

Worldwide there are over 248 million chronic carriers of HBV of whom about a third eventually develop severe HBV-related complications. Due to the major limitations of current therapeutic approaches, the development of more effective strategies to improve therapeutic outcomes in chronic hepatitis B (CHB) patients seems crucial. Immune activation plays a critical role in spontaneous viral control; therefore, new modalities based on stimulation of the innate and adaptive immune responses could result in the resolution of infection and are promising approaches. Here, we summarize the HBV immunopathogenesis, and discuss the encouraging results obtained from the promising immune-based innovations, such as therapeutic vaccination, cytokine therapy, cell-based therapies and blocking inhibitory receptors, as current and future immunotherapeutic interventions.

Molecular epidemiology and genetic diversity of hepatitis B virus in Ethiopia

Although hepatitis B virus (HBV) infection is hyperendemic in Ethiopia and constitutes a major public health problem, little is known about its genetic diversity, genotypes, and circulation. The aim of this study was to determine the molecular epidemiology and genetic diversity of HBV in Ethiopia, using 391 serum samples collected from HBsAg-positive blood donors living in five different geographic regions. The HBV S/pol gene was amplified, sequenced, and HBV genotypes, subgenotypes, serotypes, and major hydrophilic region (MHR) variants were determined. Phylogenetic analysis of 371 samples (95%) revealed the distribution of genotypes A (78%) and D (22%) in Ethiopia. Further phylogenetic analysis identified one subgenotype (A1) within genotype A, and 4 subgenotypes within genotype D (D1; 1.3%, D2; 55%, D4; 2.5%, and D6; 8.8%). Importantly, 24 isolates (30%) of genotype D formed a novel phylogenetic cluster, distinct from any known D subgenotypes, and two A/D recombinants. Analysis of predicted amino-acid sequences within the HBsAg revealed four serotypes: adw2 (79%), ayw1 (3.1%), ayw2 (7.8%), and ayw3 (11.6%). Subsequent examination of sequences showed that 51 HBV isolates (14%) had mutations in the MHR and 8 isolates (2.2%) in the reverse transcriptase known to confer antiviral resistance. This study provides the first description of HBV genetic diversity in Ethiopia with a predominance of subgenotypes A1 and D2, and also identified HBV isolates that could represent a novel subgenotype. Furthermore, a significant prevalence of HBsAg variants in Ethiopian population is revealed.

Occult hepatitis B virus co-infection in human immunodeficiency virus-positive patients: A review of prevalence, diagnosis and clinical significance

The prevalence of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) co-infection is high as they share similar mechanisms of transmission. The development and widespread use of highly sensitive tests for HBV diagnosis has demonstrated that a significant proportion of apparently healthy individuals with evidence of exposure to HBV continue to carry fully functional HBV DNA in their hepatocytes, a situation that predisposes them to the development of progressive liver disease and hepatocellular carcinoma. The presence of co-infections frequently influences the natural evolution of each of the participating infections present by either facilitating their virulence or competing for resources. Furthermore, the drugs used to treat these infections may also contribute to changes in the natural course of these infections, making the analysis of the impact of co-infection more difficult. The majority of studies has examined the impact of HIV on overt chronic hepatitis B, finding that co-infection carries an increased risk of progressive liver disease and the development of hepatocellular carcinoma. Although the effect of HIV on the natural history of occult hepatitis B infection (OBI) has not been fully assessed, all available data suggest a persisting risk of repeated flares of hepatitis and progressive liver disease. We describe studies regarding the diagnosis, prevalence and clinical significance of OBI in HIV-positive patients in this short review. Discrepancies in worldwide prevalence show the urgent need for the standardization of diagnostic criteria, as established by the Taormina statements. Ideally, standardized protocols for testing should be employed to enable the comparison of data from different groups. Additional studies are needed to define the differences in risk for OBI without HIV and in HIV-HBV co-infected patients with or without overt disease.

Hepatitis B virus large surface protein: function and fame

Chronic infection with hepatitis B virus (HBV) is the leading cause of liver cirrhosis and hepatocellular carcinoma worldwide. HBV life cycle begins with viral attachment to hepatocytes, mediated by the large HBV surface protein (LHBs). Identification of the sodium-taurocholate cotransporting polypeptide (NTCP) as a HBV receptor has revealed a suitable target for viral entry inhibition. Analysis of serum hepatitis B surface antigen (HBsAg) level is a non-invasive diagnostic parameter that improves HBV treatment opportunities. Furthermore, HBsAg plays an important role in manipulation of host immune response by HBV. However, observations in patients with chronic hepatitis B under conditions of immune suppression and in transgenic mouse models of HBV infection suggest, that in absence of adaptive immune responses cellular mechanisms induced by HBV may also lead to the development of liver diseases. Thus, the multifaceted pathological aspects of HBsAg predetermine the design of new therapeutical options modulating associated biological implications.

Seroepidemiology and occult hepatitis B virus infection in young adults in Banjarmasin, Indonesia

Hepatitis B virus (HBV) infection remains a public health problem in Indonesia. There has been limited data regarding HBV infection in young adult population. This study aimed to evaluate the seroepidemiology of HBV infection and characterize occult HBV variants in healthy young adults in Banjarmasin, Indonesia, who were born before the implementation of the universal infant hepatitis B vaccination. Serum samples of 195 healthy young adults were tested for HBsAg, anti-HBc, and anti-HBs. The prevalence of HBsAg, anti-HBc, and anti-HBs was 9 (4.6%), 62 (31.8%), and 96 (49.2%), respectively. Seventy four (37.9%) samples were seronegative for all three parameters, indicating the susceptibility to HBV infection. Among 66 samples positive for HBsAg and/or anti-HBc, 13 (19.7%) were HBV DNA positive; of these, four were HBsAg positive and nine were HBsAg negative, and categorized as occult HBV infection. Most occult HBV cases had high-level anti-HBs (>100 IU/l), suggesting that blood with positive anti-HBs and anti-HBc could not be regarded as noninfectious. Thirteen amino acid substitutions were identified: T126S, P127S, Q129R, T131N, M133T, and Y161S in the HBsAg-positive group; P120T, T126I, G145S, Y161F, E164V, and V168F in the occult-HBV group; and T143S in both groups. More studies are required to provide data on the prevalence and characteristics of mutants to ensure reliable diagnosis. The occult HBV infection, combined with the HBsAg prevalence, could indicate the high HBV carriage among young adults in this area. The high percentage of individuals susceptible to HBV infection reiterates the need for catch-up immunization strategies targeted at young adults.

Individualized management of pregnant women with high hepatitis B virus DNA levels

Hepatitis B is a major health concern in the Asia-Pacific region, and is endemic in China, Southeast Asia, and Africa. Chronic hepatitis B virus (HBV) infection may cause hepatic cirrhosis and liver cancer. It is estimated that there are more than 350 million chronic HBV carriers worldwide, of whom approximately one quarter will die of chronic hepatitis B-related liver diseases. HBV is transmitted horizontally through blood and blood products or by sexual transmission, and vertically from mother to infant. Perinatal infection is the predominant mode of transmission in countries with a high prevalence of hepatitis B surface antigen (HBsAg) carriage, and perinatal transmission leads to high rates of chronic infection. Therefore, it is important to prevent the mother-to-child transmission (MTCT) of HBV. Research has shown that pregnant women with high HBV DNA levels have an increased risk of MTCT. However, most of the obstetrics guidelines do not make a distinction between pregnant women with high HBV DNA levels and those who are HBsAg positive only. This review addresses the management of pregnant women with high levels of HBV viremia, in terms of antiviral therapy, use of hepatitis B immunoglobulin (HBIG), the combined application of hepatitis B vaccine and HBIG, choice of delivery mode and feeding practices.

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.

Prevalence and molecular analysis of occult hepatitis B virus infection isolated in a sample of cryptogenic cirrhosis patients in iran

OBJECTIVES

The aims of this study are to investigate the prevalence of occult hepatitis B virus infection among patients with cryptogenic cirrhosis and to analyze the relationship between surface protein variability and occult hepatitis B virus infection, which may be related to the pathogenesis of occult hepatitis B virus infection in cryptogenic cirrhosis. Occult hepatitis B virus infection is a well-recognized clinical entity characterized by the detection of hepatitis B virus DNA in serum and/or liver in the absence of detectable hepatitis B virus surface antigen, with or without any serological markers of a past infection.

METHODS

Sera from patients with cryptogenic chronic liver disease were tested for hepatitis B virus DNA using both real-time and nested PCR. In the detected hepatitis B virus DNA samples, the surface gene was analyzed for mutations.

RESULTS

Hepatitis B virus DNA was detected in 38% of patients, all of whom had a viral load below 10,000 copies/mL. All hepatitis B virus belonged to genotype D. There were no significant associations between occult hepatitis B virus infection status and age, gender, ALT/AST levels, viral load or serologic markers of previous hepatitis B virus infection. There were 14 mutations found in 5 patients; 6 were in the major hydrophilic region, of which 4 were Y134F assigning for the "a" determinant region. All patients who acquired Y134F contained S207R (within HLA-A2-restricted CTL epitope) as a combination.

CONCLUSION

Hepatitis B virus surface antigen variants may arise as a result of natural selection to evade the immune surveillance of the infected host, and subsequently may go undetected by conventional hepatitis B virus surface antigen screening tests. Etiological diagnosis of cryptogenic cirrhosis is significantly underestimated with current serology testing methods alone.

Molecular characterization of hepatitis B virus (HBV) strains circulating in the northern coast of the Persian Gulf and its comparison with worldwide distribution of HBV subgenotype D1

Iran is a large country that covers the northern coast of the Persian Gulf. Iranian residents of this coastal region interact closely with people from neighboring countries because of historical and cultural relationships, as well as economic activities. In addition, the inhabitants of this border region have experienced several wars, which have affected public health infrastructures. This study characterized for the first time, the evolution of the full-length genome of HBV strains in asymptomatic carrier patients living in this particular region. In addition, this study was compared and complemented by a comprehensive evolutionary analysis of the worldwide geographical distribution of HBV subgenotype D1. Evolutionary analysis demonstrates that patients living in the northern coast of the Persian Gulf are mainly infected with HBV subgenotype D1, subtype ayw2. Specific mutations related to advanced liver disease were found more frequently in these strains compared to other strains isolated from asymptomatic carriers from other regions of Iran. This global comprehensive analysis showed that HBV subgenotype D1 strains have a worldwide distribution and that human mobility and immigration had a large impact on dispersal of HBV subgenotype D1, subtype ayw2 in Middle Eastern countries such as Iran, Syria, and Turkey. In addition to association of subtype ayw2 with subgenotype D1, it was demonstrated that other HBV subtypes like adw2, ayw1, and ayw3 are associated with HBV subgenotype D1 in different regions of the world. This study also revealed a remarkable distribution of subgenotype D1, subtype ayw4 although this particular subtype is associated with subgenotype D4 of HBV in European countries.

Quasispecies structure, cornerstone of hepatitis B virus infection: Mass sequencing approach

Hepatitis B virus (HBV) is a DNA virus with complex replication, and high replication and mutation rates, leading to a heterogeneous viral population. The population is comprised of genomes that are closely related, but not identical; hence, HBV is considered a viral quasispecies. Quasispecies variability may be somewhat limited by the high degree of overlapping between the HBV coding regions, which is especially important in the P and S gene overlapping regions, but is less significant in the X and preCore/Core genes. Despite this restriction, several clinically and pathologically relevant variants have been characterized along the viral genome. Next-generation sequencing (NGS) approaches enable high-throughput analysis of thousands of clonally amplified regions and are powerful tools for characterizing genetic diversity in viral strains. In the present review, we update the information regarding HBV variability and present a summary of the various NGS approaches available for research in this virus. In addition, we provide an analysis of the clinical implications of HBV variants and their study by NGS.

A recombinant multiepitope protein for hepatitis B diagnosis

Hepatitis B is a liver inflammation caused by hepatitis B virus (HBV) and can be diagnosed in clinical stage by hepatitis B core antibody from IgM class (anti-HBcIgM). Hepatitis B core antibody from IgG class (Anti-HBcIgG) appears quickly after IgM, reaching high titers in chronic hepatitis, and remains even after cure. Since hepatitis B core antibody (anti-HBc) is the first antibody identified and sometimes the only marker detected during the course of infection, it can be used both to indicate HBV acute infection (anti-HBc-IgM) and to identify individuals who have come into contact with the virus (anti-HBc-IgG). In this work we propose a recombinant hepatitis B core multiepitope antigen (rMEHB) to be used for diagnosis of hepatitis B. For this purpose, a synthetic gene coding for rMEHB was designed and cloned into vector pET21a with a 6xHis tag at the C-terminal. Time course induction in E. coli showed an induced protein with an apparent molecular mass of ~21 kDa. Protein purification was performed by a single step with affinity chromatography Ni-NTA. Circular dichroism spectroscopy indicated rMEHB as a thermal stable protein at pH 7.0 and 8.0. In these conditions rMEHB was successfully used to perform an enzyme linked immuno sorbent assay (ELISA) with positive and negative sera.

Hepatitis B virus surface protein mutations clustered mainly in CTL immune epitopes in chronic carriers: results of an Iranian nationwide study

Mutations within the coding region of hepatitis B surface antigen (HBsAg) have been found naturally in chronic carriers. To characterize the mutations of HBsAg from Iranian chronic carriers who were vaccine and/or medication naive. The surface genes from 360 patients were amplified and directly sequenced. The distribution of amino acid substitutions was classified according to different immune epitopes of the surface protein. All isolates belonged to genotype D. 222 (61.6%) of 360 patients contained at least one amino acid substitution. 404 (74.5%) of 542 amino acid changes occurred in different immune epitopes of HBsAg, of which 112 (27.7%) in 32 residues of B-cell epitopes (62 in the 'a' determinant); 111 (27.4%) in 32 residues of T helper; and 197 (48.7%) in 32 residues inside cytotoxic T lymphocyte (CTL) epitopes. One Th (186-197) and two CTL (28-51 and 206-215) epitopes were found to be hotspot motifs for the occurrence of 213 (52.7%) substitutions. 20 stop codons were identified in different epitopes. There was a significant association between amino acid substitutions and anti-HBe seropositivity; however, the correlation between such changes with viral load and ALT levels was not significant. In chronic hepatitis B virus(HBV) carriers, positive selection in particular outside the 'a' determinant appeared to exert influence on the surface proteins. These changes could be immune escape mutations naturally occurring due to the host immune surveillance especially at the T-cell level.

Quasispecies and pre-existing drug-resistant mutations of hepatitis B virus in patients with chronic hepatitis B

Background/Aims

To investigate pre-existing hepatitis B virus (HBV) quasispecies and the genotypic evolution of several variants.

Methods

From six patients with lamivudine (LAM) failure, serum samples at pretreatment, 6 months of LAM therapy, and virologic breakthrough were obtained. One hundred clones with HBV inserts in each patient were sequenced at each time point. Pretreatment serum samples were also analyzed from six patients who achieved good responses to LAM therapy.

Results

Among the six patients with LAM failure, the analysis of 100 clones from patient 1 revealed the substitutions L180M in 1% of clones and V173L in 2% of clones. Patient 2 had substitutions of L80V, W153Q, and L180M. In patient 3, mutations conferring resistance to adefovir at V84I (5%), I169L (1%), and N236H (7%) and entecavir at S202G (2%) were detected. Patient 4 had mutations at T128N (1%), I169L (1%), V173L (2%), A181V (1%), and Q215H (1%). In patient 5, M204V/I was detected in 1% and 2% of clones, respectively. L80I and V173L were also identified in patient 6. In the six patients who responded to LAM, the degree of overall quasispecies was less than those with LAM failure.

Conclusions

Various HBV quasispecies associated with drug resistance existed before treatment, and the quasispecies dynamically changed through LAM therapy.

Sequence conservation of the region targeted by the Abbott RealTime HBV viral load assay in clinical specimens

The Abbott RealTime HBV assay targets the N-terminal region of the S gene. Here we analyzed the sequence variability of the assay target region from >2,100 clinical specimens. Thermodynamic modeling of the percentage of bound primer/probe at the assay annealing temperature was performed to assess the potential effect of sequence variability.

Tracing hepatitis B virus to the 16th century in a Korean mummy

A rare find of a mummified child from the 16th century AD, in Korea, with relatively preserved organs, enabled a search for ancient hepatitis B virus (aHBV) DNA sequences from laparoscopic-derived liver biopsies. Analysis of the complete aHBV genome (3,215 base pairs) revealed a unique HBV genotype C2 (HBV/C2) sequence commonly spread in Southeast Asia, which probably represents an HBV that infected the Joseon Dynasty population in Korea. Comparison of the aHBV sequences with contemporary HBV/C2 DNA sequences revealed distinctive differences along four open reading frames. Genetic diversity between contemporary and recovered aHBV/C2 DNA may be the result of immunologic, environmental, and/or pharmacologic pressures. The calculated time of most recent common ancestor suggests that the Korean HBV sequence origin dates back at least 3,000 years and possibly as long as 100,000 years. This isolate most likely represents the earliest human HBV sequence that colonized Southeast Asia by human migration.

CONCLUSION

This study describes the complete sequence of the oldest HBV isolate and the most ancient full viral genome known so far.

Analysis of mutations in the S gene of hepatitis B virus strains in patients with chronic infection by online bioinformatics tools

Hepatitis B virus (HBV) genomes show a high rate of mutations. This can lead to a variety of amino acid changes in the surface and polymerase genes, causing changes in viral protein conformation that can result in diminished antibody binding or decreased secretion of surface antigen (HBsAg). HBV monitoring increasingly relies on HBsAg detection and quantification, and therefore epidemiological data on HBsAg mutations are needed. We therefore analyzed the frequency of HBsAg mutations possibly influencing the quantification of HBsAg (MUPIQHs) in an unselected patient collective. To this end, we determined the HBV surface and polymerase gene sequences of an unselected patient collective of 237 individuals chronically infected with HBV and analyzed the MUPIQHs in these sequences using three different online HBV sequence analysis tools. We found that 17 or 34% of the patients, depending on the online interpretation algorithm used, harbored MUPIQHs and that MUPIQHs were not significantly associated with the duration of disease, treatment, or HBV genotype. Thus, this study shows that a substantial amount of HBV sequences derived from unselected patients chronically infected with HBV carry MUPIQHs, and therefore the reliability of routine quantitative and qualitative HBsAg tests needs to be reevaluated.

High prevalence of occult hepatitis B virus infection in children born to HBsAg-positive mothers despite prophylaxis with hepatitis B vaccination and HBIG

BACKGROUND & AIMS

Occult hepatitis B virus (HBV) infection is a well-recognized clinical entity characterized by the detection of HBV DNA in serum and/or liver in the absence of detectable hepatitis B surface antigen (HBsAg). The frequency of the diagnosis depends on the relative sensitivity of both HBsAg and HBV DNA assays. We aimed at determining the prevalence of occult HBV infection in a high risk group of children who developed HBV infection despite immunoprophylaxis.

METHODS

The sera of 75 children born to HBsAg-positive mothers previously immunized by HBIG and prophylaxic vaccine regimen were assayed for HBV DNA by real-time PCR. Subsequently, the samples were tested using a sensitive standard PCR, with an independent set of primers for all HBV genes, and analyzed by direct sequencing.

RESULTS

HBV DNA was detected in 21/75 (28%) children, and ranged between 77 and 9240 copies/ml. All were positive for anti-HBs. Five (24%) children were found to be positive for anti-HBc, while anti-HBc-only positive individuals were not observed. Eight isolates (38%) did not carry any mutation. Thirteen infected children (62%) had at least one mutation in regions known to be involved in functional and/or immune epitope activity. Ten had G145R mutations.

CONCLUSIONS

HBV occult infection seems to be relatively frequent in immunized children born to HBsAg-positive mothers. HBsAg negativity is not sufficient to completely exclude HBV DNA presence. These findings emphasize the importance of considering occult HBV infection in hypo-endemic areas.

Viral quasispecies evolution

Evolution of RNA viruses occurs through disequilibria of collections of closely related mutant spectra or mutant clouds termed viral quasispecies. Here we review the origin of the quasispecies concept and some biological implications of quasispecies dynamics. Two main aspects are addressed: (i) mutant clouds as reservoirs of phenotypic variants for virus adaptability and (ii) the internal interactions that are established within mutant spectra that render a virus ensemble the unit of selection. The understanding of viruses as quasispecies has led to new antiviral designs, such as lethal mutagenesis, whose aim is to drive viruses toward low fitness values with limited chances of fitness recovery. The impact of quasispecies for three salient human pathogens, human immunodeficiency virus and the hepatitis B and C viruses, is reviewed, with emphasis on antiviral treatment strategies. Finally, extensions of quasispecies to nonviral systems are briefly mentioned to emphasize the broad applicability of quasispecies theory.

Dynamics of hepatitis B virus quasispecies in association with nucleos(t)ide analogue treatment determined by ultra-deep sequencing

BACKGROUND AND AIMS

Although the advent of ultra-deep sequencing technology allows for the analysis of heretofore-undetectable minor viral mutants, a limited amount of information is currently available regarding the clinical implications of hepatitis B virus (HBV) genomic heterogeneity.

METHODS

To characterize the HBV genetic heterogeneity in association with anti-viral therapy, we performed ultra-deep sequencing of full-genome HBV in the liver and serum of 19 patients with chronic viral infection, including 14 therapy-naïve and 5 nucleos(t)ide analogue(NA)-treated cases.

RESULTS

Most genomic changes observed in viral variants were single base substitutions and were widely distributed throughout the HBV genome. Four of eight (50%) chronic therapy-naïve HBeAg-negative patients showed a relatively low prevalence of the G1896A pre-core (pre-C) mutant in the liver tissues, suggesting that other mutations were involved in their HBeAg seroconversion. Interestingly, liver tissues in 4 of 5 (80%) of the chronic NA-treated anti-HBe-positive cases had extremely low levels of the G1896A pre-C mutant (0.0%, 0.0%, 0.1%, and 1.1%), suggesting the high sensitivity of the G1896A pre-C mutant to NA. Moreover, various abundances of clones resistant to NA were common in both the liver and serum of treatment-naïve patients, and the proportion of M204VI mutants resistant to lamivudine and entecavir expanded in response to entecavir treatment in the serum of 35.7% (5/14) of patients, suggesting the putative risk of developing drug resistance to NA.

CONCLUSION

Our findings illustrate the strong advantage of deep sequencing on viral genome as a tool for dissecting the pathophysiology of HBV infection.

Diagnostic strategy for occult hepatitis B virus infection

In 2008, the European Association for the study of the liver (EASL) defined occult hepatitis B virus infection (OBI) as the “presence of hepatitis B virus (HBV) DNA in the liver (with detectable or undetectable HBV DNA in the serum) of individuals testing hepatitis B surface antigen (HBsAg) negative by currently available assays”. Several aspects of occult HBV infection are still poorly understood, including the definition itself and a standardized approach for laboratory-based detection, which is the purpose of this review. The clinical significance of OBI has not yet been established; however, in terms of public health, the clinical importance arises from the risk of HBV transmission. Consequently, it is important to detect high-risk groups for occult HBV infection to prevent transmission. The main issue is, perhaps, to identify the target population for screening OBI. Viremia is very low or undetectable in occult HBV infection, even when the most sensitive methods are used, and the detection of the viral DNA reservoir in hepatocytes would provide the best evaluation of occult HBV prevalence in a defined set of patients. However, this diagnostic approach is obviously unsuitable: blood detection of occult hepatitis B requires assays of the highest sensitivity and specificity with a lower limit of detection < 10 IU/mL for HBV DNA and < 0.1 ng/mL for HBsAg.

Unique hepatitis B virus subgenotype in a primitive tribal community in eastern India

Hepatitis B virus (HBV) strains isolated from members of the primitive Paharia ethnic community of Eastern India were studied to gain insight into the genetic diversity and evolution of the virus. The Paharia tribe has remained quite separate from the rest of the Indians and differs culturally, genetically, and linguistically from the mainstream East Indian population, whose HBV strains were previously characterized. Full-length HBV DNA was PCR amplified, cloned, and sequenced. Phylogenetic relationships between the tribal sequences and reference sequences from the mainstream population were assessed, and divergence times of subgenotypes of HBV genotype D were estimated. HBV was found in 2% of the Paharias participating in the study. A predominance of hepatitis B e antigen-negative infection (73%) was observed among the Paharias, and the genome sequences of the HBV strains exhibited relative homogeneity, with a very low prevalence of mutations. The novel feature of Paharia HBV was the exclusive presence of the D5 subgenotype, which was recently identified in Eastern India. Analysis of the four open reading frames (ORFs) of these tribal HBV D5 sequences and comparison with previously reported D1 to D7 sequences enabled the identification of 27 specific amino acid residues, including 6 unique ones, that could be considered D5 signatures. The estimated divergence times among subgenotypes D1 to D5 suggest that D5 was the first to diverge and hence is the most ancient of the D subgenotypes. The presence of a specific, ancient subgenotype of HBV within an ethnically primitive, endogamous population highlights the importance of studies of HBV genetics in well-separated human populations to understand viral transmission between communities and genome evolution.

Detection of hepatitis B virus DNA among accepted blood donors in Nanjing, China

Background

Posttransfusion hepatitis B virus (HBV) infection still occurs although its incidence has been substantially reduced since the introduction of screening of hepatitis B surface antigen (HBsAg) in blood donors. This study aimed to investigate the occult HBV infection in accepted blood donors in Nanjing, China.

Results

The lower detection limit of the nested PCR in this study was estimated to be 20 copies/ml HBV DNA. The positive rate of occult HBV infection was 0.13% (5 of 2972) in the accepted blood donors. Sequencing data showed that the amplified HBV sequences were not identical each other and to the known sequences cloned in our laboratory, excluding the false-positive caused by cross-contamination. Phylogenetic analysis showed that the HBV in all five donors was genotype B; a single base deletion was detected in the S region of HBV DNA from one donor, and no mutation was observed in the "a" determinant of HBsAg from four other donors. All five donors were negative for anti-HBs and one was positive for anti-HBc.

Conclusions

The prevalence of occult HBV infection in the accepted blood donors in Nanjing, China is relatively high. The data would be meaningful in adapting strategy to eliminate posttransfusion HBV infection in China.

Detection of highly prevalent hepatitis B virus coinfection among HIV-seropositive persons in Ghana

Simple hepatitis B surface antigen (HBsAg) tests may facilitate ascertainment of hepatitis B virus (HBV) infection in settings with high endemicity but limited infrastructure. We evaluated two rapid HBsAg tests and characterized HBV coinfection in a Ghanaian HIV-positive cohort. Samples from 838 patients were tested by the rapid assays Determine and Vikia and the reference assays Architect, Murex version 3, and Liaison Ultra. The assays were also evaluated using the 2nd International Standard, a seroconversion panel, and two mutant panels. HBsAg-positive samples underwent HBV DNA quantification by real-time PCR and surface and polymerase gene population sequencing. Overall, 140/838 patients (16.7%; 95% confidence interval, 14.2 to 19.2%) were HBsAg positive, and of these, 103/140 (73.6%) were e-antigen negative and 118/140 (84.3%) showed an HBV DNA level of >14 IU/ml (median, 8,279 IU/ml). Assay sensitivities and specificities were as follows: Architect, 97.9 and 99.6%; Liaison, 97.1 and 99.4%; Murex, 98.6 and 99.3%; Determine, 69.3 and 100%; and Vikia, 70.7 and 100%. With Determine, the limit of detection was >1.5 to 3.4 HBsAg IU/ml, and the median HBV DNA loads were 598 and 10,905 IU/ml in Determine-negative and -positive samples, respectively (P = 0.0005). Results were similar with the Vikia assay. HBV DNA sequencing indicated infection with genotype E in 82/86 (95.3%) patients. HBsAg mutations affected assay performance, including a T123A mutant that escaped detection by Architect. Major drug resistance mutations were observed in 4/86 patients (4.6%). The prevalence of HBV coinfection was high in this HIV-positive Ghanaian cohort. The two rapid assays identified HBsAg-positive patients at risk for liver disease with high specificity, albeit with only moderate sensitivity.

The underlying mechanisms for the "isolated positivity for the hepatitis B surface antigen (HBsAg)" serological profile

During HBV infection, four structural antigen/antibody systems are observed: hepatitis B surface antigen (HBsAg) and its antibody (anti-HBs); the pre-S antigens associated with HBsAg particles and their antibodies; the particulate nucleocapsid antigen (HBcAg) and anti-HBc; and an antigen structurally related to HBcAg, namely HBeAg and its antibody (anti-HBe). Through the examination of this antigen-antibodies system, hepatitis B infection is diagnosed and the course of the disorder may be observed. Isolated HBsAg seropositivity is a peculiar serological pattern in HBV infection observed some times in routine laboratory. In most cases is not clear how this profile should be interpreted neither its significance. This pattern, however, may be associated with some clinical and laboratorial situations of great relevance, some of which will be addressed in this article.

Molecular evolutionary analysis and mutational pattern of full-length genomes of hepatitis B virus isolated from Belgian patients with different clinical manifestations

Molecular evolutionary patterns of 62 HBV full-length genomes obtained from Belgian patients were characterized. Phylogenetic analysis revealed diverse HBV subgenotypes including A2 and A6 (46.8%), D1-D4 (38.8%), E (9.7%), C1 (1.6%), and B2 (1.6%). The study population consisted of patients with different ethnic origin (Caucasian, Turkish, Asian, Arab, and African). One HBV D/C recombinant isolate was identified, which encoded subtype adw2. An HBV subgenotype D4 with an aberrant subtype ayw4 was detected. Although none of the genotypes was associated with a specific disease outcome, several nucleotide substitutions, deletions and insertions were observed within the HBV preS1/S and X genes, particularly among patients with active chronic hepatitis B infection and patients with cirrhosis. Within the immunological domain of the HBsAg gene, the most frequent substitutions were sT125M and sT118A. High rates of precore and basal core promoter mutations were detected in patients infected with genotype D of HBV. Almost half of the patients who received lamivudine therapy for at least 1 year had HBV variants associated with lamivudine drug resistance. In conclusion, the most common HBV genotypes in West Europe (A and D) also prevail in Belgium. The highest degree of genetic diversity was detected in HBV genotype D. In addition, this study reveals the circulation of exotic HBV genotypes B, C, and E in Belgium. J. Med. Virol. 82:379-389, 2010. (c) 2010 Wiley-Liss, Inc.

Occult hepatitis B virus infection: a covert operation

Detection of occult hepatitis B requires assays of the highest sensitivity and specificity with a lower limit of detection of less than 10 IU/mL for hepatitis B virus (HBV) DNA and <0.1 ng/mL for hepatitis B surface antigen (HBsAg). This covert condition is relatively common in patients with chronic hepatitis C virus (HCV) that seems to exert some influence on the replicative capacity and latency of HBV. Detection of virus-specific nucleic acid does not always translate into infectivity, and the occurrence of primer-generated HBV DNA that is of partial genomic length in immunocompetent individuals who have significant levels of hepatitis B surface antibody (anti-HBs) may not be biologically relevant. Acute flares of alanine aminotransferase (ALT) that occur during the early phase of therapy for HCV or ALT levels that remain elevated at the end of therapy in biochemical nonresponders should prompt an assessment for occult hepatitis B. Similarly, the plasma from patients with chronic hepatitis C that is hepatitis B core antibody (anti-HBc) positive (+/-anti-HBs at levels of <100 mIU/mL) should be examined for HBV DNA with the most sensitive assay available. If a liver biopsy is available, immunostaining for hepatitis B surface antigen (HBsAg) and hepatitis B core antigen (HBcAg) should be contemplated and a portion of the sample tested for HBV DNA. This is another reason for optimal collection of a specimen (e.g. two passes with a 16-guage needle under ultrasound guidance). Transmission of HBV to immunosuppressed orthotopic liver transplant recipients by donors with occult hepatitis B (OHB) will continue to occupy the interests of the transplant hepatologist. As patients with OHB may have detectable HBV DNA in serum, peripheral blood mononuclear cells (PBMC) and/or liver that can be reactivated following immunosuppression or intensive cytotoxic chemotherapy, the patient needs to be either monitored or treated depending on the pretreatment serological results such as an isolated anti-HBc reaction or a detectable HBV DNA.

The pre-S1 and antigenic loop infectivity determinants of the hepatitis B virus envelope proteins are functionally independent

The hepatitis B virus (HBV) envelope proteins bear two determinants of viral entry: a receptor-binding site (RBS) in the pre-S1 domain of the large envelope protein and a conformation-dependent determinant, of unknown function, in the antigenic loop (AGL) of the small, middle, and large envelope proteins. Using an in vitro infection assay consisting of susceptible HepaRG cells and the hepatitis delta virus (HDV) as a surrogate of HBV, we first investigated whether subelements of the pre-S1 determinant (amino acids 2 to 75), i.e., the N-terminal myristoyl anchor, subdomain 2-48 (RBS), and subdomain 49-75, were functionally separable. In transcomplementation experiments, coexpression of two distinct infectivity-deficient pre-S1 mutants at the surface of HDV virions failed to restore infectivity, indicating that the myristoyl anchor, the 2-48 RBS, and the 49-75 sequence, likely cooperate in cis at viral entry. Furthermore, we showed that as much as 52% of total pre-S1 in the HDV envelope could bear infectivity-deficient lesions without affecting entry, indicating that a small number of pre-S1 polypeptides-estimated at three to four per virion-is sufficient for infectivity. We next investigated the AGL activity in the small or large envelope protein background (S- and L-AGL, respectively) and found that lesions in S-AGL were more deleterious to infectivity than in L-AGL, a difference that reflects the relative stoichiometry of the small and large envelope proteins in the viral envelope. Finally, we showed that C147S, an AGL infectivity-deficient substitution, exerted a dominant-negative effect on infectivity, likely reflecting an involvement of C147 in intermolecular disulfide bonds.

The blood donor in sub-Saharan Africa: a review

The high prevalence of numerous endemic and epidemic diseases such as malaria, HIV infection and viral hepatitis in some areas of sub-Saharan Africa (SSA) affects the health status of blood donors. Considering the difficulties in ensuring sufficient and safe blood supply, analysing epidemiological factors that impact blood donors in this community may further bring light on issues of supply and safety, and help in planning for its rational use. This review does not aim to propose new strategies but describes the main characteristics of blood donors in SSA as collected from different reports. Data were mainly obtained from the reports of the World Health Organization and national blood transfusion programmes and also from relevant literature and conference reports. Several characteristics are common in blood donors, such as the predominance of young adult males, the high frequency of Transmission-transmitted Infections (TTIs) and some erythrocytic phenotypes. The data indicate variations in the level of improvement of blood collection and blood safety from one area to another, particularly in the field of donor motivation or screening strategies for TTIs. These data could be useful to supplement previous reports and to provide updates for governments and international organizations' programs involved in the improvement of blood safety in Africa.

Prevalence of hepatitis B virus and risk factors in Brazilian non-injecting drug users

Non-injecting drug users are at high-risk for acquiring hepatitis B virus (HBV), although the factors contributing to this increased risk are not known. In the present study, the overall and occult HBV infection prevalence rates were determined in a large population of non-injecting drug users in the Central-West region of Brazil. HBV genotypes and predictors of infection were also identified. A total of 852 individuals in 34 drug treatment centers were interviewed, and their serum samples were tested for the presence of HBV markers by ELISA. HBsAg and anti-HBc-positive samples were tested for HBV DNA by PCR. Samples with HBV DNA were genotyped by restriction fragment length polymorphism (RFLP). The overall prevalence of HBV infection was 14% (95% CI: 11.7-16.5). A multivariate analysis of risk factors showed that age >30 years, non-white race/ethnicity, duration of drug use >10 years, lifetime number of sexual partners >10, non-use of condoms, and HCV and HIV status were associated significantly with HBV infection. Of the 9 (1%) HBsAg-reactive samples, HBV DNA was present in 2/2 of HBeAg-positive and in 5/7 anti-HBe-positive samples. An occult HBV infection rate of 2.7% (3/110) was found among anti-HBc-positive individuals. All HBV DNA-positive samples were genotyped: seven were genotype A, two were genotype D, and one was genotype F. Finally, few individuals (8%) had serological evidence of a previous HBV vaccination. These findings indicate that preventive interventions are needed for both sexual and drug-related high-risk behavior. Additionally, non-injecting drug users should be targeted for HBV vaccination.