Mutations in the “a” Determinant Region of Hepatitis B Virus Genotype A among Voluntary Kenyan Blood Donors

Abstract

Background: Occurrence of mutations within the major antigenic alpha determinant region of hepatitis B surface antigen (HBsAg can alter HBV antigenicity resulting in   failures in diagnosis, vaccine and hepatitis B immunoglobulin therapy.

Objective: This study aimed at detection of mutations in the “a” determinant region of HBV surface antigen among voluntary blood donors in Kenya.

Design: A cross sectional study involving serology and molecular techniques

Settings: This study involved analysis of samples from blood transfusion centers

Subjects: A total of 301 blood samples from donor blood were collected for the study.

Methods: Sero-status for HBsAg was determined using Enzyme-Linked Immunosorbent Assay (ELISA). A fragment of the S gene including the "a" determinant was amplified by PCR from the HBsAg positive samples and sequenced for mutation analysis. Mutations and phylogenetic analyses were performed using Mega 6 software, Bioedit software and GENETYX^® software version 9.1.0.

Results: Out of the 301 samples tested 69/301 (22.9%) were Polymerase Chain Reaction (PCR) positive including 2/69(2.9%) were sero-negative for HBsAg. All isolates were genotype A, sub-genotype A1. A total of 29 mutations were observed of which 37.9% were located within the “a” determinant. Mutations T143M and K122R were the most frequent in this study. Escape mutations associated with diagnostic failure, vaccine and immunoglobulin therapy escape were also identified.

Conclusions: These findings are important for policies related to vaccine implementation and therapeutic and diagnostic guidelines.

Keywords: Escape mutants, genotype, hepatitis B virus, antigenic determinant, surface antigen.