Analysis of hepatitis B virus S gene in occult infection among patients with chronic hepatitis B

Abstract

Objective To further explore the occult hepatitis B virus(HBV) infection in patients with chronic hepatitis B(CHB) and analyze S gene mutations and the possible reasons of occult infection. Methods Sera of 10 CHB patients carrying HBsAg negative with HBV DNA positive after treatment were collected. Real-time polymerase chain reaction(PCR) was used.S gene amplification products were obtained by PCR, and clonal sequencing were then used for these samples. Results For 10 samples, ALT results were normal(23.3±13.3U/L), serological HBsAg results were negative by qualitative and quantitative reagents. HBV DNA quantitative results of 10 samples were positive and low (mean: 4.82×104 copies/ml). Sequencing disclosed S gene mutations in all 10 samples. Among them, co-existences of the different mutants or mutants with wild-type were found in 8 samples. The mutation points with high frequency included T47A、L98V、I/T126N/S、T131N、M133T/I、W172*、M198I、W199*、N207T. Conclusions Occult HBV infection existed in CHB patients after treatment. Factors contributing to the occult HBV infection include S gene mutations and low levels of circulating antigen which are below the assay limit of detection. The use of highly sensitive reagents for HBV DNA detection is beneficial to the detection of occult HBV infection in CHB patients after treatment. Key words: Hepatitis B virus (HBV); Occult infection; Chronic hepatitis B; S gene mutations