Genotyping and hepatitis B virus in liver disease patients from Kerala, India
Keyter, Mark Andrew Robson
India is classified as an intermediate hepatitis B virus (HBV) endemic zone, with an estimated 50 million HBV carriers, thereby forming the second largest pool of chronic HBV infection in the world. Kerala, in south-west India is the most densely populated state of India, with a population of 33 million. There is currently a paucity of information on the prevalence of HBV genotypes and the respective subgenotypes in Kerala. Therefore the aim of this study was to molecularly characterise HBV isolated from liver disease patients in Kerala, and to determine the clinical implications of HBV genotypes and mutations on liver disease progression. Seventy HBV DNApositive serum samples belonging to the three disease groups: Chronic Hepatitis (CH), cirrhosis (CR) and hepatocellular carcinoma (HCC) were used in the present study. Analysis of 50 complete S region sequences, 57 BCP/PreC sequences and 9 representative complete HBV genome sequences was performed. Irrespective of disease status, the predominant genotype was A (64%), with 97% belonging to subgenotype A1, followed by genotype D (34%) and a single strain of genotype C. All subgenotype A1 isolates clustered within the ‘Asian’ clade as a separate branch, together with sequences from Asia, Africa and South America. A significantly higher prevalence of subgenotype A1 was found in HCC patients, with these patients being significantly younger than those infected with genotype D (p<0.05). Nine pre-S deletion mutants were detected (8 subgenotype A1; 1 subgenotype D2). Although a higher frequency of pre-S deletion mutants where found in subgenotype A1 isolates from HCC patients, this did not reach statistical significance (p=0.4). The ps2: M1I/T was found exclusively in subgenotype A1 isolates, and this was significantly associated with HCC as compared to other disease groups in patients infected with subgenotype A1(p=0.0072). The ps2: F22L was found in genotypes A and D, and was significantly associated with HCC in genotype D (p=0.0098). The G1862T was significantly associated with subgenotype A1 (90%), and in combination with the A1762T/G1764A double mutation, was significantly associated with HCC in subgenotype A1 (p<0.05). Subgenotype A1 was predominant in liver disease patients from Kerala, with a high prevalence in HCC patients. This study confirms the association shown from previous studies, that subgenotype A1 is significantly associated with HCC, and also showed a strong correlation between subgenotype A1 and the development of HCC at a younger age.