Key mutations in the C-terminus of the HBV surface glycoprotein correlate with lower HBsAg levels in vivo, hinder HBsAg secretion in vitro and reduce HBsAg structural stability in the setting of HBeAg-negative chronic HBV genotype-D infection

Prevalence and molecular characteristics of occult hepatitis B virus infection among blood donors in Huzhou City, eastern China

Occult hepatitis B virus (HBV) infection (OBI) is a significant challenge for HBV prevention and control. We investigated the prevalence and surface (S) gene mutations of OBI among blood donors in Huzhou City, eastern China. The hepatitis B surface antigen (HBsAg) was routinely screened among 44,256 blood donors. HBV-DNA was detected using the Roche cobas®system. Serum samples that were HBsAg negative and HBV-DNA positive were selected, and the HBV S gene was amplified and sequenced. HBV genotype and S gene mutations were analyzed. The OBI rate in these blood donors was 0.070 % (31/44,256). Among the blood donors with OBI, only two cases (2/31, 6.5 %) were anti-HBc negative. The S gene sequences of 28 samples were successfully obtained, and we found that HBV genotype C (21/28, 70 %) was predominant among blood donors with OBI. Most S gene mutations were associated with OBI, and the high frequency mutations included N40S, G44E, Q51R/P, T113A/S,T118K/M, P120Q/S/T, and Y161F/S. Notably, amino acid substitutions at some sites differed from those reported previously, such as Y72F, G102V, P127L, Q129P, and S143T. Additionally, six novel mutations (S31I/N/R, P46L, S58C, C76Y, Y200F/C, and I208T) that may be associated with OBI were found. OBI was detected in a certain proportion of blood donors in Huzhou City. S gene mutations play an important role in OBI development. Further research is required to explore the functions of novel S gene mutants in OBI pathogenesis. The findings of this study may provide important insights to prevent HBV transmission through blood transfusions.

Molecular Characterization of Hepatitis B Virus in People Living with HIV in Rural and Peri-Urban Communities in Botswana

(1) Background: Hepatitis B virus (HBV) sequencing data are important for monitoring HBV evolution. We aimed to molecularly characterize HBV sequences from participants with HBV surface antigen-positive (HBsAg+) serology and occult hepatitis B infection (OBI+). (2) Methods: We utilized archived plasma samples from people living with human immunodeficiency virus (PLWH) in Botswana. HBV DNA was sequenced, genotyped and analyzed for mutations. We compared mutations from study sequences to those from previously generated HBV sequences in Botswana. The impact of OBI-associated mutations on protein function was assessed using the Protein Variation Effect Analyzer. (3) Results: Sequencing success was higher in HBsAg+ than in OBI+ samples [86/128 (67.2%) vs. 21/71 (29.2%)]. Overall, 93.5% (100/107) of sequences were genotype A1, 2.8% (3/107) were D3 and 3.7% (4/107) were E. We identified 13 escape mutations in 18/90 (20%) sequences with HBsAg coverage, with K122R having the highest frequency. The mutational profile of current sequences differed from previous Botswana HBV sequences, suggesting possible mutational changes over time. Mutations deemed to have an impact on protein function were tpQ6H, surfaceV194A and preCW28L. (4) Conclusions: We characterized HBV sequences from PLWH in Botswana. Escape mutations were prevalent and were not associated with OBI. Longitudinal HBV studies are needed to investigate HBV natural evolution.

A review of epidemiology and clinical relevance of Hepatitis B virus genotypes and subgenotypes

BACKGROUND

Hepatitis B virus (HBV) infection is a global public health burden, affecting nearly 300 million people around the world. Due to HBV population is considered to be represented as a viral quasispecies with genetic diversity, some reports showed that different genotypes of HBV have different viral effects, though the emergence of antiviral drugs that effectively inhibit viral replication, however, HBV infection has still not been eradicated and further research is needed.

SUMMARY

HBV has been classified into at least ten genotypes (A-J)  and more than 40 subgenotypes based on an intergroup or intragroup nucleotide difference across the whole genome, respectively. Inter genotypic recombinants were also observed during the HBV evolution. HBV genotypes and subgenotypes have distinct ethno-geographical distributions, as well as evident differences in their biological characteristics. HBV genotypes and subgenotypes also have close association with disease severity, long-term clinical outcomes, and response to antiviral therapy.

KEYMESSAGES

In this review, we up-dated the epidemiological characteristics, clinical features and prognosis of HBV infection with dissimilar genotype/subgenotypes, to better understanding and developing individualized prevention and treatment strategies.

Hepatitis B Virus Genotype D: An Overview of Molecular Epidemiology, Evolutionary History, and Clinical Characteristics

The hepatitis B virus (HBV) genotype D (HBV/D) is the most extensively distributed genotype worldwide with distinct molecular and epidemiological features. This report provides an up-to-date review on the history of HBV/D subgenotyping and misclassifications, along with large-scale analysis of over 1000 HBV/D complete genome sequences, with the aim of gaining a thorough understanding of the global prevalence and geographic distribution of HBV/D subgenotypes. We have additionally explored recent paleogenomic findings, which facilitated the detection of HBV/D genomes dating back to the late Iron Age and provided new perspectives on the origins of modern HBV/D strains. Finally, reports on distinct disease outcomes and responses to antiviral therapy among HBV/D subgenotypes are discussed, further highlighting the complexity of this genotype and the importance of HBV subgenotyping in the management and treatment of hepatitis B.

Research Progress on the Mechanism of Persistent Low-Level HBsAg Expression in the Serum of Patients with Chronic HBV Infection

Among HBV-infected persons, there is a group of people with hepatitis B surface antigen (HBsAg) showing persistently low levels of expression. The production of low-level HBsAg does not mean a good outcome of chronic HBV infection. Patients still have virus replication and sustained liver damage, and they have the potential to transmit the infection. This risk poses a challenge to clinical diagnosis and blood transfusion safety and is a major concern of experts. However, the mechanism behind persistent low-level HBsAg expression in serum is not completely clear, and complete virus clearance by the host is vital. In this review, we summarize the research progress on the mechanism behind low-level expression of HBsAg in patients with chronic HBV infection in recent years.

Biological Characterization of Hepatitis B virus Genotypes: Their Role in Viral Replication and Antigen Expression

Hepatitis B virus (HBV) inter-host evolution has resulted in genomic diversification reflected in the existence of nine genotypes (A-I) and numerous subgenotypes. There is growing evidence that genotypes influence HBV natural history, clinical outcomes, and treatment response. However, the biological characteristics underlying these differences have not yet been established. By transfecting HuH-7 cells with unit-length constructs of genotypes A2, B2, C1, D1, and F1b, we identified major differences in HBV replicative capacity and antigen expression across genotypes. Genotypes B2 and F1b showed a 2-fold increase in cccDNA levels compared to the other genotypes (p<0.005). Genotype A2 expressed the lowest pgRNA levels, with a 70-fold decrease in relation to the other genotypes (p<0.0001), while genotype B2 showed the lowest Precore RNA levels, with a 100-fold reduction compared to genotype A2 (p<0.0001). The highest intracellular HBV DNA levels were observed for genotype B2 and the lowest for genotypes A2 and C1 (p<0.0001). Regarding antigen expression, genotype F1b secreted the highest HBsAg levels and genotype D1 the lowest (p<0.0001), while genotypes A2 and B2 showed the highest intracellular HBsAg levels (p<0.0001). Interestingly, genotype C1 secreted the highest HBeAg levels, while genotype A2 showed the highest intracellular levels (p<0.0001). Finally, the analysis of the intra/extracellular antigen ratios revealed that most genotypes retained intracellularly 5-20% of the antigens, except the genotype A2 that retained 50% of the total expressed antigens. In conclusion, this study provides new insights into the biological characteristics of HBV genotypes, being the first study to comparatively analyze European (A and D) and Asian (B and C) genotypes with the Latin American (F) genotype. The differences in HBV replication and antigen expression might contribute to understand the differential role of genotypes in pathogenesis.

Transcriptomic analysis of livers of Inactive Carrier HBV patients with differential HBsAg

Inactive Carrier phases in chronic hepatitis B virus (HBV) infection present minimal liver disease and HBV replication activity suggesting a partial immune-reconstitution although the mechanisms responsible remain elusive. Moreover, HBsAg production -hypothesized to modulate the immune response- is unaltered. Here, we assessed the intrahepatic transcriptome in Inactive Carrier patients vs healthy liver donors, also in the context of diverse HBsAg levels (serum and liver), to better understand the phenomenon of immune control. We found a de-regulated liver transcriptome in Inactive Carrier patients vs healthy controls despite normal liver function. Moreover, diverse HBsAg levels impacted minimally at the liver transcriptome in Inactive Carrier patients although gene correlation analysis revealed leukocyte activation, recruitment and innate responses genes to correlate with liver HBsAg levels. These findings provide more insight into the mechanisms underlying anti-HBV strategies that are currently under development aimed at interfering with HBsAg production or at inducing a state of immune control.