Mutations in Core Gene Region of Hepatitis B Virus in Patients with Chronic Hepatitis B

The HBV core protein plays a major role in host immune response. Mutations occurring in the HBV core gene may cause alterations in the major epitopes being effective in the host immune response. Until now, the persistent effects of core gene mutations on HBV infections have not been fully understood. The aim of this study is to analyze the core gene mutations for epitopes in the T lymphocytes [T helper (Th) and cytotoxic (CTL)] and B cell and C terminal region in patients with chronic hepatitis using ultra-deep pyrosequencing (UDPS) method.

Eleven patients with chronic hepatitis B infection were included in the study. Amplification of the core gene was performed by a conventional PCR method. Mutations in the epitopes for T lymphocytes (Th and CTL) and B cell and in the C terminal region of HBV core gene were screened by UDPS. These mutations were analyzed in HBeAg positive and negative patients.

The minimum percentages of amino acid substitutions were found with 0.9% in HBeAg positive patients and 1.2% in negative patients. The number of missense mutation was higher in patients with HBeAg positive than negative patients (p < 0.005). The number of amino acid substitutions in the region of aa49 - 69 in the Th epitopes was found to be the highest in both HBeAg positive and negative patients. The mutation frequency was higher in the C-terminal region of the core protein compared to the Th, CTL, and B cell regions and these were more common in subjects with high-grade fibrosis. Some types of mutations (V27I, R47H, Y132I, R174STOP, S181P, Q182K) were only detected in subjects with liver cirrhosis.

Unlike literature, our results show that there is no significant increase in number of mutations in the core gene of the virus during the anti-HBe positive period. The role of low abundance variants and mutations in the immune system can be understood using methods such as UDPS in the near future.