Virological and Clinical Characteristics of Hepatitis B Virus Genotype A

ELISA genotyping of hepatitis B virus in China with antibodies specific for genotypes B and C

Hepatitis B virus (HBV) causes hepatitis B (HB) and distinct HBV genotypes can lead to different prognoses. However, HBV genotyping is rarely done in clinics, because the traditional method by PCR-based DNA sequencing is impractical for clinical diagnosis with tedious process and low success rate. Herein, we have established an ELISA-based genotyping method to quickly determine the HBV genotypes of HB patients in China. First, two commercial antibodies, 16D12 and 6H3 specific for HBV genotypes B and C respectively, are chosen as capture antibodies, since these two genotypes dominate in China. Then two home-made genotype-specific antibodies, B19 and C04, are used as the detection antibodies for genotypes B and C in sandwiched ELISA. The ELISA kit shows high sensitivity (> 95%) and specificity (> 95%) in detecting genotypes B and C of Chinese HB patients. Moreover, the ELISA kit has demonstrated higher success rate (98.7%) than PCR-based DNA sequencing (93.5%) and a commercial PCR-based genotyping kit (92.2%) for sera with HBV DNA ≥ 1000 IU/mL and HBsAg ≥ 250 IU/mL. Such an advantage is more obvious for the sera with HBV DNA < 1000 IU/mL. The kappa analysis between the ELISA and PCR-based DNA sequencing results exhibits a kappa of 0.836, indicating a good correlation.

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.

Global prevalence and molecular characteristics of three clades within hepatitis B virus subgenotype C2: Predominance of the C2(3) clade in South Korea

Hepatitis B Virus (HBV) genotypes reflect geographic, ethical or clinical traits and are currently divided into 10 genotypes (A–J). Of these, genotype C is mainly distributed in Asia, is the largest group and comprises more than seven subgenotypes (C1–C7). Subgenotype C2 is divided into three phylogenetically distinct clades, C2(1), C2(2), and C2(3), and is responsible for most genotype C infections in three East Asian nations, including China, Japan, and South Korea, which are major HBV endemic areas. However, despite the significance of subgenotype C2 with regard to clinical or epidemiologic aspects, its global distribution and molecular characteristics remain largely unknown. Here, we analyze the global prevalence and molecular characteristics between 3 clades within subgenotype C2 using 1,315 full genome sequences of HBV genotype C retrieved from public databases. Our data show that almost all HBV strains from South Korean patients infected with genotype C belong to clade C2(3) within subgenotype C2 [96.3%] but that HBV strains from Chinese or Japanese patients belong to diverse subgenotypes or clades within genotype C, suggesting clonal expansion of a specific HBV type, C2(3), among the Korean population. Our genome sequence analysis indicated a total of 21 signature sequences specific to the respective clades C2(1), C2(2), and C2(3). Of note, two types of four nonsynonymous C2(3) signature sequences, sV184A in HBsAg and xT36P in the X region, were detected in 78.9 and 82.9% of HBV C2(3) strains, respectively. In particular, HBV strains C2(3) versus C2(1) and C2(2) show a higher frequency of reverse transcriptase mutations related to nucleot(s)ide analog (NA) resistance, including rtM204I and rtL180M, suggesting an increased possibility of C2(3) infection in those with NA treatment failure. In conclusion, our data show that HBV subgenotype C2(3) is extremely prevalent in Korean patients with chronic HBV infection, which is distinct from two other East Asian nations, China and Japan, where diverse subgenotypes or clades within genotype C coexist. This epidemiologic trait might affect distinct virological and clinical traits in chronic HBV patients in Korea, where exclusively C2(3) infection is predominant.

[Neutralization of hepatitis B virus with vaccine-escape mutations by novel hepatitis B vaccine with large-HBs antigen]

Although the current hepatitis B (HB) vaccine comprising yeast-derived small hepatitis B surface antigen (HBsAg) is potent and safe and used worldwide, specific concerns should not be ignored, such as the attenuated prophylaxis against hepatitis B virus (HBV) infection with specific amino acid polymorphisms, called vaccine-escape mutations (VEMs). We investigated a novel HB vaccine consisting of large-HBsAg that covers the shortcomings of the current HB vaccine in a nonhuman primate model. The yeast-derived large-HBsAg was mixed with the adjuvant and used to immunize rhesus macaques, and the induction of antibodies to HBsAg was compared with that of the current HB vaccine. The current HB vaccine predominantly induced antibodies to small-HBsAg, whereas immunization with the large-HBsAg vaccine mainly induced antibodies to the preS1 region. Although the antibodies induced by the current HB vaccine could not prevent infection of HBV with VEMs, the large-HBsAg vaccine-induced antibodies neutralized infection of HBV with VEMs at levels similar to those of the wild type. The HBV genotypes that exhibited attenuated neutralization by induced antibodies differed between these vaccines. In conclusion, the novel HB vaccine consisting of large-HBsAg was revealed to be useful to compensate for shortcomings of the current HB vaccine. The combined use of these HB vaccines may be able to induce antibodies that can neutralize HBV strains with VEMs or multiple HBV genotypes.

Trends of hepatitis B virus genotype distribution in chronic hepatitis B patients in Japan

BACKGROUND

Hepatitis B virus (HBV) is one of the most prevalent chronic viral infections that causes chronic hepatitis B (CHB). In Japan, genotypes B and C account for most of acute and chronic cases of hepatitis. However, previous studies showed that the prevalence of genotype A in CHB gradually increased every 5 years. Therefore, we have conducted a nationwide survey to comprehensively investigate the trends of HBV genotype distribution in CHB patients in Japan.

METHODS

4421 CHB patients were recruited between 2015 and 2016. Clinical characteristics and distribution of CHB patients among different age groups and genotypes in 2015-2016 was compared with those in 2000-2001, 2005-2006, and 2010-2011.

RESULTS

The percentages of genotype A, B, C, and D were 4.0, 16.2, 79.1, and 0.7%, respectively. While the overall percentage of CHB patients with genotype A did not change in the past 5 years, CHB with genotype A increased in young adults. On the other hand, the peak distribution of CHB with genotypes B and C, two genotypes with the largest patient population, has shifted to an older age group.

CONCLUSIONS

In Japan, the peak distribution for CHB with genotypes B and C advanced to an older age group while CHB with genotype A expanded in a younger age group. Given the universal HBV vaccination launch in Japan in 2016, these pre-vaccination survey data provide important baseline information for comparative studies of the impact of universal vaccination on HBV genotypes.

Hepatitis B Virus Genotype G: The Odd Cousin of the Family

With a widespread distribution but low prevalence worldwide, the hepatitis B virus (HBV) genotype G (HBV/G) is a recently described genotype for which the origin and biology are poorly understood. Some unique features make HBV/G the most peculiar of all genotypes. In this review, we reflect on the major milestones in HBV/G research, highlighting the main aspects of its discovery, molecular epidemiology, and virological and clinical characteristics. We also illustrate common pitfalls in the routine detection, which may lead to underestimated rates of HBV/G infection. Large-scale analysis of data from dozens of articles was further performed, with the aim of gaining comprehensive insights into the epidemiological aspects of HBV/G. Finally, we point out recent findings on HBV/G origins and discuss new perspectives regarding the evolutionary history of HBV/G and the plausibility of an African geographic re-emergence of this genotype.

Genetic diversity of hepatitis B virus in Yunnan, China: identification of novel subgenotype C17, an intergenotypic B/I recombinant, and B/C recombinants

Yunnan is considered to be a geographical hotspot for the introduction, mutation and recombination of several viruses in China. However, there are limited data regarding the genotypic profiles of hepatitis B virus (HBV) in this region. In this study, we characterized 206 HBV strains isolated from chronic hepatitis B patients in Yunnan, China. Initial genotyping based on 1.5 kb sequences revealed that genotype C was the most prevalent at 52.4 % (108/206), followed by genotype B at 30.6 % (63/206) and unclassified genotypes at 17.0 % (35/206). To characterize the 35 unclassified strains, 32 complete HBV genomes were amplified and analysed; 17 isolates were classified within a known subgenotype, 8 were classified as B/C recombinants, 1 was classified as a B/I recombinant and 6 constituted a potentially novel C subgenotype that we designated as C17, based on the characteristics of a monophyletic cluster, >4 % genetic distances, no significant evidence of recombination and no epidemiological link among individuals. Thus, multiple subgenotypes - namely B1, B2, B4, C1, C2, C3, C4, C8 and C17 - and two distinct intergenotypic recombinants exist in Yunnan, China, highlighting the complex and diverse distribution pattern of HBV genotypic profiles.

Characterization of a novel hepatitis B virus subgenotype B10 among chronic hepatitis B patients in Yunnan, China

Diversity and complexity of Hepatitis B Virus (HBV) may be related to clinical outcome, disease prognosis, and response to antiviral treatment in infected patients. HBV has been classified into ten genotypes (A-I) and over 50 subgenotypes. However, there are still some variants of HBV that need to be classified. Here, we investigated genotypic profiles of HBV among 150 patients with chronic hepatitis B in Yunnan, China, and characterized a novel HBV subgenotype B10. Multiple subgenotypes were identified in 146 subjects with successful sequencing for the S gene, including genotype B2 (48.6%, 71/146), C1 (34.2%, 50/146), B4 (8.9%, 13/146), C2 (0.7%, 1/146), C5 (0.7%, 1/146) and an unclassified group (6.8%,10/146). To characterize the unclassified group, seven HBV complete genomes were successfully amplified and analyzed. The seven strains constituted a potentially novel B subgenotype that we designated as B10 based on the characteristics of a monophyletic cluster, > 4% genetic distances, no significant evidence of recombination, and no epidemiologic link among individuals. Moreover, Bayesian analyses showed that HBV B10 originated around the B·C 1.80 thousand years old, suggesting a much ancient HBV strain. This findings highlighted the importance of continual monitoring of genetic diversity of HBV strains in Yunnan, China.

Retrospective analysis of acute HBV infections occurred in 1978-79 and 1994-95 in North-East Italy: increasing prevalence of BCP/pre-core mutants in sub-genotype D3

Background

At the end of the 1970s, in Italy more than 2% of the general population was HBsAg carrier. In the late ‘70s and late ‘80s, two remarkable events might have impacted on HBV strains transmitted in North-East Italy: (a) the increased HBV incidence due to parenteral drugs between 1978 and 1982; (b) the preventive anti-HIV educational campaign, started locally in 1985.

Methods

To address if those events impacted on circulating HBV variants, acute cases occurred in North-East Italy in 1978–79 (n = 50) and 1994–95 (n = 30) were retrospectively analysed. HBV sequences obtained from serum samples were subjected to phylogenetic analysis and search for BCP/pre-core and S mutations.

Results

HBV-D was the most prevalent genotype in both 1978–79 (43/50, 86%) and 1994–95 (24/30, 80.0%), with HBV-A in all but one remaining cases. Among HBV-D cases, sub-genotype HBV-D3 was the most prevalent (25/29, 86.2% in 1978–79; 13/16, 81.2% in 1994–95), with HBV-D1 and HBV-D2 in the remaining cases. All HBV-A cases were sub-genotype A2.

Single and multiple BCP/pre-core mutations, responsible for HBeAg(−) hepatitis, were detected in 6/50 (12%) cases in 1978/79 vs. 12/30 (40.0%) in 1994/95 (p = 0.006). They were found exclusively in HBV-D; in the most abundant sub-genotype, HBV-D3, they were detected in 2/25 (8%) cases in 1978–79 vs. 6/13 (46%) in 1994–95 (p = 0.011). No vaccine escape S mutations were observed. The IDU risk factor was significantly more frequent in 1994–95 (8/30, 26.7%) than in 1978–79 (4/50, 8%) (p = 0.048).

Conclusions

The above mentioned epidemiological and public health events did not affect the proportion of genotypes and sub-genotypes that remained unchanged over 16 years. In contrast, the proportion of BCP/pre-core mutants increased more than three-fold, mostly in HBV-D3, a sub-genotype highly circulating in IDUs; drug abuse likely contributed to the spread of these mutants.

The findings contribute to explain a previously described major change in HBV epidemiology in Italy: the proportion of HBeAg(−) cases in the carrier cohort changed from low in late 1970s, to high at the beginning of the 2000s. In addition to other recognized factors, the increased circulation of BCP/pre-core mutants likely represents a further factor that contributed to this change.

Long-term follow-up of a Japanese patient with hepatitis B virus genotype H and human immunodeficiency virus coinfection

Hepatitis B virus (HBV) genotypes affect the pathogenesis of disease progression during the course of HBV infection. In Japan, HBV genotype H is one of the rare HBV genotypes. We recovered HBV genotype H from a blood sample from a Japanese HIV-infected patient with acute exacerbation of chronic HBV infection. Due to the development of drugs for treating HBV and HIV, HBV genotype H and HIV coinfection has been well controlled by nucleos(t)ide analogs and highly active antiretroviral therapy, respectively, from 2002 to 2019. Further study is needed with regard to HBV genotype H and its pathogenesis.

Comparison of intracellular responses between HBV genotype A and C infection in human hepatocyte chimeric mice

BACKGROUND AND AIMS

The clinical course and responsiveness to antiviral treatments differs among hepatitis B virus (HBV) genotypes. However, the cause of these differences is unclear. In the present study, we compared mRNA expression profiles in human hepatocyte chimeric mice infected with HBV genotypes A and C.

METHODS

Fifteen chimeric mice were prepared and divided into the following three groups: uninfected control mice, HBV genotype A-infected mice, and HBV genotype C-infected mice. Human hepatocytes were collected from these mouse livers and gene expression analyses were performed using next-generation RNA sequencing.

RESULTS

Although similar pathways were influenced by HBV infection, including inflammation mediated by chemokine and cytokine signaling, p53, and integrin signaling pathways, expression levels of up-regulated genes by HBV genotype A or C infection were quite different. In HBV genotype A-infected hepatocytes, 172 genes, including KRT23 and C10orf54, were significantly more highly expressed than in HBV genotype C-infected cells, whereas 10 genes, including SPX and IER3, were expressed at significantly lower levels. Genes associated with the p53 pathway and the inflammation mediated by chemokine and cytokine signaling pathway were more highly expressed in cells with HBV genotype A infection, whereas genes associated with CCKR signaling map and oxidative stress response were more highly expressed in cells with HBV genotype C infection.

CONCLUSION

Several differences in gene expression with respect to HBV genotype A and C infection were detected in human hepatocytes. These differences might be associated with genotypic difference in the clinical course or responsiveness to treatment.

Management of Hepatitis B Virus Infection: 2018 Guidelines from the Canadian Association for the Study of Liver Disease and Association of Medical Microbiology and Infectious Disease Canada

Hepatitis B virus (HBV) infection is an important public health problem in Canada. In keeping with evolving evidence and understanding of HBV pathogenesis, the Canadian Association for the Study of Liver Disease periodically publishes HBV management guidelines. The goals of the 2018 guidelines are to (1) highlight the public health impact of HBV infection in Canada and the need to improve diagnosis and linkage to care, (2) recommend current best-practice guidelines for treatment of HBV, (3) summarize the key HBV laboratory diagnostic tests, and (4) review evidence on HBV management in special patient populations and include more detail on management of HBV in pediatric populations. An overview of novel HBV tests and therapies for HBV in development is provided to highlight the recent advances in HBV clinical research. The aim and scope of these guidelines are to serve as an up-to-date, comprehensive resource for Canadian health care providers in the management of HBV infection.

Hepatitis B Virus Genotype C is Predominant in Myanmar

Myanmar is adjacent to India, Bangladesh, Thailand, Laos and China. In Myanmar, the prevalence of hepatitis B virus (HBV) infections is 6.5% and accounts for 60% of hepatocellular carcinoma. HBV has nine genotypes that have been identified by molecular genetic analysis. HBV genotypes are associated with several clinical features. We reviewed the prevalence of HBV genotypes in Myanmar and neighboring countries. We also reviewed HBV genotypes in refugees from Myanmar. HBV subgenotype C1 is predominant in Myanmar. As HBV genotype C is associated with hepatocellular carcinoma (HCC), it is important to screen for cirrhosis and HCC and to prevent their development in HBV-infected individuals of Myanmar.