HBV genotype distribution and S gene mutations in HIV-HBV co-infected patients: insights from North India

Purpose Effective HBV therapy and immunisation require knowledge of HBV mutation rate and genetic variability. This study aimed to characterize HBV genotypes, serotypes, and surface (S) gene mutations among HBV–HIV co-infected and HBV mono-infected patients in North India. Methods A total of 100 HBV–HIV co-infected and 50 HBV mono-infected patients were enrolled. HBV DNA was extracted from serum using the QIAamp DNA Blood Mini Kit (QIAGEN). HBV viral load was quantified by real-time PCR. The HBV surface gene was amplified using conventional and nested PCR, followed by Sanger sequencing for genotyping, serotyping, and mutational analysis. Genotypes were additionally confirmed using type-specific multiplex PCR. Results The mean age of HIV-HBV co-infected and HBV mono-infected patients was 36.6 and 34.9 years, respectively. HBeAg positivity was observed in 17% of co-infected and 10% of HBV mono-infected cases. HBV surface gene was successfully amplified in 19 (19%) HIV-HBV co-infected and 20 (40%) HBV mono-infected samples. Genotype D predominated (35/39, 89.7%), with subgenotypes D1 and D3 detected at comparable frequencies, while genotype A was identified in 4 (10.3%) samples, all belonging to subgenotype A1. Serotype analysis showed exclusive association of genotype D with ayw2 and genotype A with adw2. Mutations within the HBsAg ‘a’ determinant region were identified in 36.8% of HBV–HIV co-infected patients, including nonsynonymous substitutions, whereas no such mutations were observed in HBV mono-infected individuals. Genotype D sequences clustered with subgenotypes D2, D3, and D9 (from West Bengal), as well as D3 (from Russia, Madhya Pradesh, Delhi and Brazil). Conclusion This study confirms the predominance of HBV genotype D with serotype ayw2 in North India and demonstrates a higher frequency of HBsAg immune escape–associated mutations in HBV–HIV co-infected patients. These findings underscore the importance of ongoing molecular surveillance to inform diagnostic strategies, vaccination effectiveness, and clinical management of HBV, particularly in HIV-affected populations.