Abstract:
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. This study aimed at detection of mutations in the “a” determinant region of HBV surface antigen among
voluntary blood donors in Kenya. This was a cross sectional study involving serology and molecular techniques.
This study involved analysis of samples from blood transfusion centers. A total of 301 blood samples from donor
blood were collected for the study. 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. 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. These findings are important for policies related to vaccine implementation and therapeutic
and diagnostic guidelines.
