Clinical significance of genotypes and precore/basal core promoter mutations in HBV related chronic liver disease patients in North India

A Narrative Review on the Specific Pattern of HBV Genotype in Bangladesh: Clinical Implications for Management

Background and aims

Bangladesh's unique epidemiological landscape presents an intriguing puzzle. This South Asian nation, with its complex sociodemographic and environmental factors, is home to a diverse array of hepatitis-B virus (HBV) genotypes, identified as Genotype C, with Genotypes D and A also making a significant contribution to the viral landscape. Reviewing such insights is necessary not only to underscore the country's regional diversity in HBV strains but also to bring into focus the clinical implications these genetic variations may have on disease progression and management.

Methods

A thorough database search covered various sources using relevant keywords like "Hepatitis B virus genotypes", "HBV genotypes in Bangladesh", and "HBV clinical implications". The review synthesized findings and analyzed HBV genotype prevalence and clinical implications in Bangladesh.

Results

Genotypes C and D collectively represent 82% of chronic hepatitis-B infection (CHB) cases in Bangladesh, underscoring their regional prevalence. The geographic context is pivotal in understanding HBV infection dynamics and disease progression in this area. Notably, genotype C and the presence of A1762T/G1764A mutations appear to have a distinct impact on disease development, potentially affecting the immune response in CHB patients. This highlights the need for tailored management approaches in this specific region. Further research is vital to confirm and elaborate on these findings, particularly in relation to how these mutations influence the host's immune response.

Conclusion and clinical significance

In summary, studies on HBV genotypes in Bangladesh stress the need for genotype-specific clinical considerations and more research to improve diagnostics and therapies.

How to cite this article

Raihan R, Akbar SMF. A Narrative Review on the Specific Pattern of HBV Genotype in Bangladesh: Clinical Implications for Management. Euroasian J Hepato-Gastroenterol 2023;13(2):152-158.

Review on hepatitis B virus precore/core promoter mutations and their correlation with genotypes and liver disease severity

Of 350 million people worldwide are chronically infected with hepatitis B virus (HBV) and are at risk of developing cirrhosis and hepatocellular carcinoma (HCC) later in life. HBV is the most diverse DNA virus, and its genome is composed of four open reading frames: Presurface antigen/surface antigen gene (preS/S), precore/core gene (preC/C), polymerase gene (P), and the X gene (X). HBV produces quasispecies naturally or in response to antiviral agents because of the absence of proofreading activity amid reverse transcription and a high replication rate. The virus has 10 genotypes (A to J) with different geographical distributions. There are various HBV mutations in the HBV genome, including preC/C mutations, preS/S mutations, P gene mutations, and X gene mutations. The core promoter region plays a vital part in the replication, morphogenesis and pathogenesis of the virus. The precore region also plays a crucial role in viral replication. Both core promoter and precore mutations rescue the virus from host immune surveillance and result in the formation of mutated strains that may have altered pathogenicity. preC/C mutations are associated with liver disease progression. Precore mutations stop hepatitis B e antigen (HBeAg) production and basal core promoter mutations downregulate HBeAg production. Mutations in the basal core promoter are also associated with increased HBV replication and an increased incidence of advanced liver diseases such as cirrhosis and HCC. The emergence of antiviral-resistant mutations is the main reason for treatment failure. This review focuses mainly on preC/C promoter mutations and their correlation with genotypes and liver disease severity. Thorough perception and knowledge of HBV genetic variety and mutants could be vital to discover techniques for the prognosis and control of HBV infection.

Molecular epidemiology of HBV among HIV infected individuals in Chennai, south India

Hepatitis B is a major co-infection among people with HIV (PWHIV) worldwide. There is a paucity of data on HBV genetic diversity in India, which would be useful for targeted preventive and management interventions. To characterize the distribution of HBV genotypes and sub-genotypes, samples of 180 HIV-HBV co-infected individuals from a study previously conducted to estimate the prevalence of HBV co-infection were analyzed. Nested PCR using type-specific primers was used to identify the various HBV genotypes. Partial HBV S sequences were generated for a subset of samples using Sanger sequencing. Mutation analysis was done using the online HBVseq program. PCR based genotyping documented D (69.4 %) and A (5.6 %) to be the major genotypes in the study population. Infection with multiple genotypes was observed in 25 % co-infected individuals. D2, D5, A2, and A1 were the sub-genotypes detected. Mutations 184K and 173L were identified. HBV genotypes/ sub-genotypes play a pivotal role in the clinical outcome of chronic hepatitis B (CHB). Therefore, monitoring of CHB cases is needed to track disease progression, including early detection of hepatocellular carcinoma.

LCR based quick detection of hotspot G1896A mutation in patients with different spectrum of hepatitis B

G1896A switch is one of the hotspots in subjects affected with hepatitis B. This hotspot mutation is observed in all the different spectrum of hepatitis B, and it has a very dangerous and a long lasting effect. The major purpose of the study was to screen G1986A mutations at a large scale and also to establish ligase chain reaction as a mutation testing tool. Polymerase chain reaction (PCR) and Nucleotide Sequencing was done to identify the G1896A mutation in the precore region of the genome. All the 331 HBV positive patients were screened. Almost 29% (24/82) of the cases remarkably had the presence of G1896A mutation confirmed by LCR and direct sequencing. The precore G1896A mutation is responsible for one third of the patients suffering from precore stop codon mutation. It clearly exhibits that LCR is 100% in sync with direct sequencing and is extremely reliable and the results are highly reproducible.

How viral genetic variants and genotypes influence disease and treatment outcome of chronic hepatitis B. Time for an individualised approach?

Chronic hepatitis B virus (HBV) infection remains a global problem. Several HBV genotypes exist with different biology and geographical prevalence. Whilst the future aim of HBV treatment remains viral eradication, current treatment strategies aim to suppress the virus and prevent the progression of liver disease. Current strategies also involve identification of patients for treatment, namely those at risk of progressive liver disease. Identification of HBV genotype, HBV mutants and other predictive factors allow for tailoured treatments, and risk-surveillance pathways, such as hepatocellular cancer screening. In the future, these factors may enable stratification not only of treatment decisions, but also of patients at risk of higher relapse rates when current therapies are discontinued. Newer technologies, such as next-generation sequencing, to assess drug-resistant or immune escape variants and quasi-species heterogeneity in patients, may allow for more information-based treatment decisions between the clinician and the patient. This article serves to discuss how HBV genotypes and genetic variants impact not only upon the disease course and outcomes, but also current treatment strategies. Adopting a personalised genotypic approach may play a role in future strategies to combat the disease. Herein, we discuss new technologies that may allow more informed decision-making for response guided therapy in the battle against HBV.

Current Scenario of Hepatitis B and Its Treatment in India

Hepatitis B is a significant public health problem in India, yet disease awareness is very low among the general population. The disease is mostly acquired horizontally, but the role of vertical transmission should not be underestimated. In spite of the fact that the majority of cases are e negative disease, most patients present in the advanced stage and even with hepatocellular carcinoma, the leading cause of which is hepatitis B. High-risk groups (especially tribals) also harbour significant disease burden and have a high prevalence of occult infection, supporting the potential of unknowingly spreading the disease. Findings on the relation of genotypes with disease severity or drug action have been conflicting. Though recently, oral antivirals with high genetic barrier to resistance have shown good viral suppression in the long term, e and s seroconversion is poor and relapse is universal upon therapy discontinuation. As no cure is possible with the currently available therapy, the target is long-term viral suppression by prolonged administration of oral antivirals; unfortunately, this leads to poor treatment adherence, which along with the high cost of therapy results in disease progression and spread of infection. At present, therefore, emphasis should be put on health education of the general and high-risk populations, along with health care workers to increase knowledge on such preventive measures as avoiding unsafe injection practices, high-risk sex, performing unnecessary injection and blood transfusion and providing proper screening of blood products; these efforts should be combined with intensive screening and aggressive vaccination programs, especially in high-risk groups and areas of high endemicity. Vaccination strategies are still below par and logistics should be developed for wider coverage; in addition, further research should be carried out on the efficacy and mode of usage for different types of vaccine.

Natural history of acute and chronic hepatitis B: The role of HBV genotypes and mutants

Molecular epidemiologic studies reveal remarkable differences in the geographical distribution of hepatitis B virus (HBV) genotypes. The frequency of mutants among HBV genotypes also varies. The role of HBV genotypes/mutants in the pathogenesis of HBV infection and natural history of HBV infection has been extensively investigated. The distribution of HBV genotypes in acute hepatitis B patients reflects the predominant genotypes in a given geographic area. In chronic hepatitis B patients, genotype C and D have a higher frequency of basal core promoter A1762T/G1764A mutations than genotype A and B. HBV genotypes C, D and F carry a higher lifetime risk of cirrhosis and HCC development than genotype A and B. HBV pre-S/S gene mutations were associated with immune escape of hepatitis B immunoglobulin or vaccine-induced immunity. Mutations in the pre-S, core promoter and X regions correlate with an increased risk of cirrhosis and HCC. In summary, HBV genotypes and mutants are associated with the disease progression and long-term outcome of HBV infection. They may serve as viral genetic markers for risk stratification of chronic hepatitis B patients in clinical practice.

Treatment strategies according to genotype for chronic hepatitis B in children

This review article was requested by editor-in-chief of this journal as 'pediatric CHB treatment' for the upcoming special issue. The main objective of chronic hepatitis B (CHB) treatment is diminishing the risk of complications related to chronic liver disease. In Asia, there are already some reports about hepatocellular carcinoma (HCC) in hepatitis B virus (HBV) infected children. The key points of treatment in children with CHB infections are selection of which patients to treat and conformation of the optimal therapy time that would reduce viral resistance. The choice of therapy is determined by the district (Western/Eastern), HBV genotype, medical accessibility, and economic state of the country. Newly developed nucleos(t)ide analogues (NAs) are potent in children with CHB. However, to improve therapeutic efficacy, physicians are recommended to follow treatment guidelines and determine the specific genotype in the CHB patient. In this article, the treatment of pediatric CHB is reviewed according to differences in genotype.

Hepatitis B virus precore G1896A mutation in chronic liver disease patients with HBeAg negative serology from North India

Hepatitis B with precore stop codon mutation is related with severe liver damage in HBeAg negative patients. It is of utmost importance to screen the G1896A precore mutation. The study was designed to assess the impact of G1986A mutations in patients with different clinical spectra of the liver disease by PCR–LCR. 210 HBV positive patients with HBeAg negative serology of different kind of liver diseases (AVH = 72, FH = 21, CH = 79, Cirrhosis = 20 and HCC = 18) were screened. Patients were screened for the presence or absence of precore G1896A mutation by PCR–LCR. Direct nucleotide sequencing was done to confirm the results of LCR. Precore mutant in HCC was 94.4% (17/18), 85.7% (18/21) in FH, 60% (12/20) in liver cirrhosis, 48.1% (38/79) in chronic hepatitis and 27.7% (20/72) in AVH cases. The serum ALT level was statistically significant between HBeAg negative WT and G1896A mutants in chronic hepatitis cases. ALT level and HBV DNA level was slightly raised in the pre core mutant but and was not significant. Genotype D had a higher prevalence (79.5%) as compared to genotype A (20.5%). The mutations detected by PCR–LCR were in 100% concordance with direct sequencing. The exceptionally high prevalence of G1896A in FH and HCC demonstrates that the precore mutants are strongly associated with the progression of liver diseases in patients with HBeAg negative serology. The findings are also suggestive of screening HBV precore G1896A mutation particularly in HBeAg negative cases. The precore G1896A mutation increases proportionately in severe form of liver diseases. LCR can be a suitable tool for screening of G1896A mutations.

Relationship between hepatitis B virus genotypes and hepatocellular carcinoma

Hepatitis B virus (HBV) genotype is closely related to response to antiviral therapy and the development of liver diseases. In this paper, we will review HBV genotypes, geographic distributions, their modes of transmission, and the occurrence of hepatocellular carcinoma (HCC). HBV genotypes have extensive connections with clinical pathology of HCC. Genotype B HBV is closely related to large-sized HCC, multiple tumors and vascular invasion. Patients with genotypes A or B HBV infection have better responses to interferon therapy, but genotypes seem not to influence the response to nucleotide analogue treatment. Therefore, HBV genotypes can be used as a genetic marker to predict the occurrence of HCC, and help practicing physicians choose optimal anti-viral therapy to prevent the occurrence of HCC.

Asian-Pacific clinical practice guidelines on the management of hepatitis B: a 2015 update

Worldwide, some 240 million people have chronic hepatitis B virus (HBV), with the highest rates of infection in Africa and Asia. Our understanding of the natural history of HBV infection and the potential for therapy of the resultant disease is continuously improving. New data have become available since the previous APASL guidelines for management of HBV infection were published in 2012. The objective of this manuscript is to update the recommendations for the optimal management of chronic HBV infection. The 2015 guidelines were developed by a panel of Asian experts chosen by the APASL. The clinical practice guidelines are based on evidence from existing publications or, if evidence was unavailable, on the experts' personal experience and opinion after deliberations. Manuscripts and abstracts of important meetings published through January 2015 have been evaluated. This guideline covers the full spectrum of care of patients infected with hepatitis B, including new terminology, natural history, screening, vaccination, counseling, diagnosis, assessment of the stage of liver disease, the indications, timing, choice and duration of single or combination of antiviral drugs, screening for HCC, management in special situations like childhood, pregnancy, coinfections, renal impairment and pre- and post-liver transplant, and policy guidelines. However, areas of uncertainty still exist, and clinicians, patients, and public health authorities must therefore continue to make choices on the basis of the evolving evidence. The final clinical practice guidelines and recommendations are presented here, along with the relevant background information.

Hepatitis B virus genotypes and variants

At least 10 hepatitis B virus (HBV) genotypes (A to J) with distinct geographic distributions and several HBV mutants, including precore/core promoter mutations and pre-S/S deletion mutations, have been recognized to be not only predictive of liver disease progression but also associated with response to antiviral therapy. HBV genotype-specific pathogenesis may contribute to heterogeneous clinical outcomes in chronic hepatitis B patients across the world. For example, patients with HBV genotypes C and D infection have a lower rate of spontaneous HBeAg seroconversion. In addition, HBV genotypes C and D have a higher frequency of core promoter and pre-S mutations than genotypes A and B. Genotypes C and D also carry a higher lifetime risk of cirrhosis and HCC development than genotypes A and B. Core promoter and pre-S mutations also correlate with an increased risk of hepatocellular carcinoma (HCC). Therapeutically, genotypes A and B patients have a better response to interferon-based therapy than genotypes C and D patients, but the response to nucleos(t)ide analogs is comparable across different HBV genotypes. In conclusion, HBV genotypes and variants may serve as viral genetic markers to predict disease progression as well as help practicing physicians optimize individualized antiviral therapy in clinical practice.

Genotypes and viral variants in chronic hepatitis B: A review of epidemiology and clinical relevance

The Hepatitis B Virus (HBV) has a worldwide distribution and is endemic in many populations. It is constantly evolving and 10 genotypic strains have been identified with varying prevalences in different geographic regions. Numerous stable mutations in the core gene and in the surface gene of the HBV have also been identified in untreated HBV populations. The genotypes and viral variants have been associated with certain clinical features of HBV related liver disease and Hepatocellular carcinoma. For example Genotype C is associated with later hepatitis B e antigen (HBeAg) seroconversion, and more advanced liver disease. Genotype A is associated with a greater risk of progression to chronicity in adult acquired HBV infections. Genotype D is particularly associated with the precore mutation and HBeAg negative chronic hepatitis B (CHB). The genotypes prevalent in parts of West Africa, Central and South America, E, F and H respectively, are less well studied. Viral variants especially the Basal Core Promotor mutation is associated with increased risk of fibrosis and cancer of the liver. Although not currently part of routine clinical care, evaluation of genotype and viral variants may provide useful adjunctive information in predicting risk about liver related morbidity in patients with CHB.

Molecular epidemiology of hepatitis B virus in Asia

Although safe and effective vaccines against hepatitis B virus (HBV) have been available for three decades, HBV infection remains the leading cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) worldwide, especially in Asian countries. HBV has been classified into at least 9 genotypes according to the molecular evolutionary analysis of the genomic DNA sequence and shown to have a distinct geographical distribution. Novel HBV genotypes/subgenotypes have been reported, especially from Southeast Asian countries. The clinical characteristics and therapeutic effectiveness of interferon (IFN) and nucleos(t)ide analogues vary among different HBV genotypes. Mutations at T1653C in subgenotype C2 from Japan and South Korea, C/A1753T and C1858T in subgenotype C1 from Vietnam, and C1638T and T1753V in subgenotype B3 from Indonesia were reported to be associated with advanced liver diseases including HCC. Genotype distribution in Japan has been changed by an increasing ratio of subgenotype A2 in chronic hepatitis B. While a large number of epidemiological and clinical studies have been reported from Asian countries, most of the studies were conducted in developed countries such as Taiwan, China, South Korea and Japan. In this review, the most recent publications on the geographical distribution of genetic variants of HBV and related issues such as disease progression and therapy in Asia are updated and summarized.

Molecular epidemiology and genetic characterization of hepatitis B virus in the Indian subcontinent

BACKGROUND

Hepatitis B virus (HBV) is a gradually evolving virus. The aim of this study was to characterize the distribution pattern of HBV genotypes and subgenotypes and HBsAg subtypes in chronic hepatitis B subjects from the Indian subcontinent. We also sought to investigate the genetic diversity of HBV genotypes and its influence on the therapeutic response.

METHODS

A total of 295 chronic hepatitis B subjects were studied. HBV genotypes and subgenotypes were determined using the generated HBV reverse transcriptase (rt) sequences. HBsAg subtypes were predicted using a newly developed automated program in Microsoft Visual Basic (VB6). Genetic diversity was characterized by calculating the mean genetic distance (d), the number of synonymous substitutions per synonymous site (dS), and the number of non-synonymous substitutions per non-synonymous site (dN). The virological response was measured by HBV DNA levels.

RESULTS

In southern India, the predominant HBV subgenotype/subtype was D2/ayw3 (79.1%). In eastern India, C1/adr (28.2%) was found to be the predominant subgenotype/subtype, followed by A1/adw2 (25.4%). In the north-eastern region, C2/adr, D2/ayw3, and D5/ayw3 were predominant and were each identified in 20.8% of subjects. In treatment-naïve subjects, the d, dS, and dN of genotype D sequences were higher compared to genotypes C and A. Additionally, the d, dS, and dN of HBV rt sequence were higher in subjects who subsequently showed a virological response to nucleos(t)ide analogues as compared to non-responders, irrespective of the genotypes tested (p=0.014 to p<0.0001).

CONCLUSIONS

We have described the distribution of HBV genotypes and subgenotypes and HBsAg subtypes in three major regions of the Indian subcontinent. HBV genetic diversity may play a pivotal role in the clinical outcome of chronic hepatitis B.

Hepatitis B virus subgenotype A1 predominates in liver disease patients from Kerala, India

AIM: To molecularly characterize hepatitis B virus (HBV) isolates from Kerala and to relate them to the clinical manifestation of infection.

METHODS: Sera and clinical data were collected from 91 patients diagnosed with chronic HBV infection and HBV-related hepatocellular carcinoma (HCC). HBV from 44 HCC, 22 cirrhotic and 25 chronic hepatitis patients were genotyped by sequencing of the complete S region or by restriction fragment length polymorphism assays. The basic core promoter/precore region was sequenced. The complete surface DNA sequences were assembled and aligned manually, and then compared with the sequences of HBV of genotypes (A-J) from GenBank. The evolutionary history was inferred using the Neighbor-Joining method and the evolutionary distances computed using the Kimura 2-parameter method. Bootstrapping was performed using 1000 replicates. The TaqMan BS-1 probe was used to quantify HBV DNA at a lower detection limit of approximately 20 IU/mL. Continuous variables were compared using an independent Student’s t test. The χ² test or Fisher’s exact test was used to compare categorical variables. The differences were considered statistically significant at P < 0.05.

RESULTS: Irrespective of disease status, the predominant genotype was A (72%); 95% belonging to subgenotype A1, followed by genotypes D (27%) and C (1%). HCC patients infected with subgenotype A1 were significantly younger than those infected with D. Mutation A1762T/G1764A was significantly associated with HCC in both genotypes A and D. Mutation G1862T was more frequent in subgenotype A1 (P < 0.0001), and in combination with A1762T/G1764A, it was significantly associated with HBV from HCC patients. Mutation C1766T/T1768A was significantly associated with genotype A (P = 0.05) and HCC (P = 0.03). The preS2 start codon M1T/I mutation was unique to genotype A strains (15.6%) from all disease groups and occurred at a higher frequency in isolates from HCC patients (P = 0.076). A higher frequency of preS deletion mutants (33.3%) was observed in genotype A from HCC compared with non-HCC patients, but did not reach statistical significance. The preS2:F22L mutation was found in genotypes A and D.

CONCLUSION: Kerala is the first Indian state in which subgenotype A1 has been found to predominate in liver disease patients who developed HCC at a relatively young age.

High frequency of genotype D and spontaneous hepatitis B virus genomic mutations among Haitians in a multiethnic North American population

GOALS/BACKGROUND

The importance of hepatitis B virus (HBV) genotype and mutations has been increasingly recognized. We aimed to determine HBV genotype, precore (PC), and basal core promoter region (BCP) mutations in a HBV multiethnic South Florida population.

STUDY

Samples from 213 patients were tested for HBV-DNA using Abbott RealTime HBV IUO assay, and for mutations using INNO-LiPA assay.

RESULTS

Patients were predominantly male (67%); 61 (31%) were African American, 60 (28%) Hispanic, 37 (17%) Haitian, 27 (19%) white non-Hispanic, and 14 (6.6%) Asian. Genotype A was found in 101 (69%), D in 25 (17%), F in 9 (6%), G in 7 (5%), C and E in 6 (4%) each, B in 4 (3%), and H in 2 (1%) patients. Mixed genotypes were detected in 11 patients. Genotype A was more prevalent in all ethnicities except for Asian. Among hepatitis B e antigen (HBeAg)-negative patients (59%), BCP, PC, and combined BCP/PC mutations were found in 30 (37.5%), 13 (16.3%), and 14 (17.5%), respectively. Genotype D was associated with higher frequency of HBeAg-negative status [18/24 (75%) vs. 62/121 (51%) P=0.03] and mutations [16/19 (84%) vs. 40/67 (60%) P=0.04] compared with others. Genotype A was negatively associated with mutations [26/31 (84%) vs. 30/55 (55%), P=0.009]. PC mutations were more common in genotype D (14/19, 73%) compared with genotype A (7/54, 13%, P<0.0001). One-hundred percent and 79% of Asians and Haitians had spontaneous mutations, respectively. All Haitians with genotype D had PC mutations and 3 (50%) had BCP/PC.

CONCLUSIONS

The present study shows that HBeAg-negative status and spontaneous mutations were more common with genotype D; the presence of genotype D in Haitians was always associated with spontaneous mutations.

Hepatitis B virus genotyping: is the time ripe for routine clinical use?

Hepatitis B is one of the major causes of end-stage liver disease and liver cancer worldwide. A number of host and viral factors influence the disease course and outcomes. One such viral factor is hepatitis B virus (HBV) genotypes. There are eight major HBV genotypes described from various geographic regions of the world. Although direct sequencing appears to be the gold standard for HBV genotyping, it is expensive and laborintensive and therefore cannot be applied for routine clinical use. The newer molecular methods including serotyping have made genotyping easier and simple to apply to large number of samples rapidly. The data collected mainly over the last decade have suggested that HBV genotypes may have a bearing over the natural course of the disease and its response to therapy. This review summarizes the available literature and highlights how genotyping could be incorporated into routine clinical practice in order to improve delivery of care to HBV-infected individuals.

Is there any value to hepatitis B virus genotype analysis?

Hepatitis B may cause a varying spectrum of diseases ranging from an asymptomatic or mild anicteric acute illness, to severe or fulminant hepatitis. Similarly, the outcome of chronic hepatitis B is variable. Viral factors associated with outcome of chronic hepatitis B virus (HBV) infection include hepatitis B e antigen status, HBV DNA, genotype, and HBV variants. HBV genotypes and subgenotypes have been associated with differences in clinical and virological characteristics, indicating that they may play a role in the virus-host relationship. A total of ten hepatitis B virus genotypes have been defined with a distinct geographical distribution. Hitherto, genotypes A, B, C and D have been studied most extensively. The HBV genotype appears to influence not only the natural history of HBV related liver disease but also the response to HBV treatment. HBV genotypes are also linked with both core promoter and BCP mutations. Progression to chronic infection appears to occur more frequently following acute infection with genotypes A and D than with the other studied genotypes. Genotypes A and B appear to have higher rates of spontaneous HBeAg seroconversion. More advanced liver disease and progression to HCC is more often seen in chronic infection with genotypes C and D in contrast to genotypes A and B. More specifically, genotypes A1, C, B2-B5 and H appear to be associated with more serious complications than genotypes A2, B1 and B6. These observations suggest important pathogenic differences between HBV genotypes. Genotypes A and B have higher response rates to interferon based therapy than genotypes C and D. Knowledge of HBV genotype enables clinicians to identify those patients at increased risk of disease progression whilst aiding the selection of appropriate antiviral therapy. Genotyping and monoclonal subtyping can provide useful information for epidemiological studies. In conclusion, genotyping of chronic HBV infections can help practicing physicians identify those at risk of disease progression and determine optimal anti-viral therapy.

Prevalence of Genotype D and Precore/Core Promoter Mutations in Hepatitis B Virus-infected Population of North India

Hepatitis B virus (HBV) isolates (21) from Punjab (North India) were studied for genotype distribution and precore/core promoter mutations. Assays of alanine aminotransaminase (ALT) and HBeAg were performed in all isolates. Genotypes were determined in all the samples by restriction fragment length polymorphism and the precore/core promoter mutations were studied by amplification and by direct sequencing of precore/core promoter region. Sixty-two percent of the isolates had higher ALT levels and 57% of the isolates were HBeAg negative. It was observed that 90% of the isolates were HBV D genotype (subgenotype D1 and D2) and 10% of the isolates were HBV A genotype (subgenotype A1). Amplification and sequencing of the precore/core promoter region showed 1762(A-T) and 1764(G-A) mutations in 29% and 19% of the isolates, respectively. 1809(C/T) mutation was observed in 71% of the isolates under study. Novel precore and core promoter mutations like 1690(A), 1695(A/T/G), 1700(A/C), 1703(c), 1850(A) and 1915(A/G) were observed in HBV-infected population of the state of Punjab (North India). Deletion and insertional mutations were also observed in some patients. (J CLIN EXP HEPATOL 2011;1:73-76).

The clinical implications of hepatitis B virus genotype: Recent advances

Outcomes of chronic hepatitis B virus (HBV) infection are heterogeneous. Estimates of annual incidence of cirrhosis and hepatocellular carcinoma (HCC) are 2-10% and 1-3%, respectively. Several viral factors, including HBV genotype, viral load and specific viral mutations, have been associated with disease progression. Among these, HBV genotype is not only predictive of clinical outcomes but has also been associated with response to interferon treatment. Currently, at least 10 HBV genotypes and several subtypes have been identified; they have distinct geographic distribution. Acute infection with genotypes A and D results in higher rates of chronicity than genotypes B and C. Compared to genotype A and B cases, patients with genotypes C and D have lower rates of spontaneous hepatitis B e antigen (HBeAg) seroconversion; when this occurs, it tends to be delayed. HBV genotype C has a higher frequency of basal core promoter (BCP) A1762T/G1764A mutation, pre-S deletion and is associated with higher viral load than genotype B. Similarly, genotype D has a higher prevalence of BCP A1762T/G1764A mutation than genotype A. These observations suggest important pathogenic differences between HBV genotypes. These may contribute to more severe liver disease, including cirrhosis and HCC with genotypes C and D HBV infection. In addition, genotype A and B patients have better responses to interferon-based therapy than genotypes C and D, but there are few consistent differences for direct HBV antivirals. In conclusion, genotyping of chronic HBV infections can help practicing physicians identify those at risk of disease progression and determine optimal anti-viral therapy.