Virological differences between patients infected with subtypes Ba and Bj of hepatitis B virus genotype B

Meta-analysis: The association of hepatitis B virus genotypes and hepatocellular carcinoma

BACKGROUND

A meta-analysis on the risk of hepatocellular carcinoma (HCC) among hepatitis B virus (HBV) genotypes is warranted as the current data are conflicting.

AIM

To investigate the relative risk of HCC among the four major HBV genotypes (A-D).

METHODS

A meta-analysis was performed based on literature search from electronic databases and bibliography between 1950 and 2012. All abstracts with keywords 'hepatitis B', 'hepatocellular carcinoma' and 'genotype' were screened. Studies were included if they reported HBV genotype as an exposure and HCC as an outcome.

RESULTS

Nine hundred and eighty-eight abstracts were found through literature search, among them 43 studies were eligible for this meta-analysis. A total of 14,545 patients with an average age of 43 years were included; 71% were male patients and 17% had cirrhosis. In 33 studies, HCC was found in 1541/6060 (25%) genotype C vs. 550/4417 (12%) genotype B HBV-infected patients [odds ratio (OR) = 2.05, 95% confidence interval (CI) = 1.52-2.76, P < 0.001]. No difference in the risk of HCC was found among genotype A (71/517, 14%) vs. genotype D (170/1506, 11%) HBV-infected patients in 14 studies (OR = 0.94, 95% CI = 0.67-1.32). In 10 studies, the risk of HCC was also found higher among genotype C (498/1659, 30%) than genotype A&D (103/1403, 7%) HBV-infected patients (OR = 2.34, 95% CI = 1.63-3.34, P < 0.001). Subgenotype Ce and Cs HBV-infected patients had similar risk on HCC (OR = 1.13, 95% CI = 0.76-1.67, P = 0.54). On funnel plot analysis, there was no significant publication bias in all comparisons.

CONCLUSION

Genotype C hepatitis B virus is associated with a higher risk of hepatocellular carcinoma than other major hepatitis B virus genotypes.

HBV genotypes: relevance to natural history, pathogenesis and treatment of chronic hepatitis B

Although chronic HBV infection is the leading cause of chronic liver disease and death worldwide, there are substantial differences in its clinical courses regarding prevalence, mode of transmission, characteristics of each phase, responses to antiviral therapy, and development of cirrhosis and hepatocellular carcinoma, according to geographical areas (Asia versus Western Europe and North America versus Africa). Furthermore, the clinical course in infected individuals depends on a complex interplay among various factors including viral, host, environmental and other factors. Recently, understanding of molecular characteristics of the prevailing HBV genotypes, frequently accompanied mutations and their clinical implications might explain these geographical differences more pertinently. Hence, in this article, we review the global epidemiology and the natural history of HBV infection, with emphasis on summarizing the different HBV genotypes according to regions.

JGH Foundation emerging leadership lecture. Significance of hepatitis B virus genotypes and mutations in the development of hepatocellular carcinoma in Asia

Advances in molecular biology technology in the last two decades have allowed detailed study of the viral mutations and genomic heterogeneity of hepatitis B virus (HBV). The first mutant discovered was precore stop codon mutation. It was reported in HBeAg-negative patients and initially thought to associate with fulminant hepatitis. Subsequent studies have suggested that it is merely one of the mechanisms of losing HBeAg by the virus. Another mutation that can downregulate the production of HBeAg is the basal core promoter mutation, which is located in the X gene upstream of the precore region. Based on the configuration of codon 15 and the stability of the epsilon of the precore region, these two mutants will be differentially selected during the course of HBeAg seroconversion. The most common HBV genotypes in South-East Asia are genotype B and C HBV. The higher hepatocellular carcinoma (HCC) risk of genotype C HBV has been confirmed by longitudinal studies in Hong Kong and Taiwan. One possible carcinogenic mechanism is its association with basal core promoter mutation, which has also been found to be a risk factor of HCC. Within genotype C HBV, subgenotype Cs is predominant in South-East Asia and subgenotype Ce is predominant in East Asia. Subgenotype Ce HBV has been found to have the highest risk of HCC as compared with subgenotype Cs or genotype B HBV. The understanding of the carcinogenic mechanisms of these HBV strains may shed light into future therapeutics in the prevention and treatment of HBV-related HCC.

The influence of hepatitis B virus genotype and subgenotype on the natural history of chronic hepatitis B

BACKGROUND

Chronic infection with hepatitis B virus (HBV) is associated with a high lifetime risk of developing hepatocellular carcinoma (HCC) and cirrhosis of the liver.

PURPOSE

To review the studies published to date regarding the association of HBV genotypes and subgenotypes in the development of adverse sequelae from HBV.

METHODS

Review of the literature for articles describing studies of HBV genotype/subgenotypes and development of HCC, cirrhosis, and liver-related death.

RESULTS

Eight genotypes of HBV (A through H), which differ from each other in viral genome sequence by more than 8%, and multiple subgenotypes, which differ from each other by 4-8% have been identified. Recently, studies investigating the association between the risks of developing HCC and cirrhosis by specific HBV genotypes and subgenotypes have reported marked differences in outcome. Certain HBV genotypes and subgenotypes, including genotype C, B2-5, and F1, appear to be associated with a higher risk of developing HCC, and others, including genotypes B1, B6, and A2, appear to be associated with a lower risk of complications of HBV. Our understanding of the role of HBV genotypes and subgenotypes on the outcome of HBV infection is limited, as few population-based prospective studies have been performed and most studies compare only the outcome in areas where two genotypes predominate whereas others have not examined subgenotypes.

CONCLUSIONS

Studies to date suggest that HBV genotypes/subgenotypes have important influences on the outcome of chronic HBV infection, but more population-based prospective studies examining multiple genotypes are needed.

Benign course of long-standing hepatitis B virus infection among Greenland Inuit?

OBJECTIVE

Chronic hepatitis B virus (HBV) infection can present in different ways, from inactive carrier to liver failure or cancer. The role of the virus subtype is controversial. The purpose of this study was to characterize HBV infection in detail and its impact on general health, body-build and liver biochemistry.

MATERIAL AND METHODS

The study comprised a population-based cohort of Inuit exposed to HBV 3-7 decades ago in the capital in West Greenland, a coastal town and four settlements in rural East Greenland. Participants included 95% of the invited Inuit: 229 men, 205 women, aged 50-69 years.

RESULTS

Only 25% of the participants had never had HBV infection. HBsAg was positive in 86 participants (20.0%), more being found positive in rural East Greenland than in the city in West Greenland (28.9% versus 2.7%; p < 0.001). HBV-DNA was positive in 61 of those with median HBV-DNA 40,000 copies/ml. HBV genotype could be determined in 52: 47 participants had genotype B, 4 genotype D, and 1 had both B and D. At sequencing, genotype B resembled subtype Bj, but with more than 5% diversity in the C-gene it could be a new subtype B. Pre-core mutation was found in 55 of 56 participants investigated. None of the participants had signs of liver disease, and HBV infection did not influence body-build or liver biochemistry.

CONCLUSIONS

More than 75% of participants had a marker of present or previous HBV infection but the infection seemed dormant. The majority harbored a special variant of genotype B that might be a new subtype giving a relatively benign disease. The role of detailed subtyping of HBV for prognostic evaluation should be investigated in more detail.

Classification of hepatitis B virus genotypes by the PCR-Invader method with genotype-specific probes

Hepatitis B virus is a worldwide public health problem. A simple and effective test to identify viral genotypes would greatly aid efforts to understand and control the spread of this disease. A serial invasive signal amplification reaction assay (PCR-Invader assay) was developed for distinguishing the known eight genotypes (A-H) and four subgenotypes (Aa, Ae, Ba, Bj) of hepatitis B virus (HBV). The preS/S and core regions were amplified by multiplex PCR and delivered to 12 wells containing genotype-specific Invader probes. By observing the fluorescence patterns in the wells, HBV sub/genotypes can be assigned. A total of 505 serum samples containing HBV/HBsAg in Japan was examined by PCR-Invader and compared the results with those from ELISA assays with monoclonal antibodies against epitopes on gene products of the preS2 region and with a genotype-specific probe assay (GSPA) based on the preS1 region. Genotypes determined by the PCR-Invader agreed with those of the ELISA method in 98.2% of cases and with the GSPA method in 97.1% of cases. Co-infection with two distinct genotypes was correctly identified by the PCR-Invader in four serum samples, as determined by GSPA. Thus, the PCR-Invader assay is a useful tool for detecting the 10 known HBV sub/genotypes.