Hepatitis B immune escape and drug resistance mutations among blood donors in Gabon during the year 2022

Hepatitis B virus (HBV) and specifically occult HBV infection (OBI) remains concerning in transfusion medicine in many countries. This study aimed to determine the burden of overt and occult HBV infections and characterize the circulating viral genotypes among blood donors in Gabon. A facility-based study was conducted among blood donors at the Gabon National Blood Transfusion Centre in 2022. Screening for HBsAg and anti-HBc was done using ELISA; characterization of OBI (defined serologically as HBsAg- but anti-HBc+) was done using HBV DNA viral load (VL); and HBV Pol/S sanger-sequencing was performed for the analysis of immune-escape and drug resistance mutations. Data were analyzed with p < 0.05 considered significant. Overall, 283 participants were enrolled: 218 (77.0%) males, median age 31 (26–35) years and 264 (93.3%) frequent donors. HBV seropositivity revealed 25.1% (71/283) overt infection (i.e. HBsAg + and anti-HBc+) and 5.7% (16/283) OBI (HBsAg- but anti-HBc+). All OBI cases (16/16) had HBV DNA VL < 10 IU/ml versus 37.5% (6/16) VL < 10 IU/ml, 25% (4/16) VL between ]10–500] IU/ml, and 37.5% (6/16) VL > 500 IU/ml among controls (overt infections). Genotyping was successful for 15.6% (5/32) participants with VL > 500 IU/ml (p = 0.02). Following genotyping, 80% (4/5) participants (VL > 2000 IU/ml) had at least one immune escape mutation (sT131N, sR122K, sG145A) and rtI169L mutation associated with drug resistance was detected in one donor. Molecular phylogeny revealed genotypes A (80%; 4/5) and E (20%; 1/5). HBV seropositivity was 25.1%, markedly higher than the estimated prevalence in the general population and therefore of significant concern. Likewise, the observed OBI prevalence of 5.7% represents a substantial risk to transfusion safety.