Detection of circulating HBV QSA3/E recombinants and HDV genotype GT5 amongst blood donors in Senegal

Senegal has a high burden of hepatitis B virus (HBV); however, HBV molecular epidemiology is sparse, and coinfection with hepatitis delta virus (HDV) is poorly investigated. A blood donor panel was evaluated to characterize circulating HBV genotypes, HDV prevalence, and assess the performance of ultrasensitive HBsAg Next, HBV DNA, anti-HDV Total Ig, and HDV RNA diagnostic assays.

Pre-screened, non-transfused specimens (n = 320) were tested for HBV and HDV biomarkers on the Alinity i platform. Comparator HBsAg testing was assessed with Elecsys HBsAg II. Specimens reactive for HBsAg and/or anti-HDV were tested for HBV DNA and HDV RNA. Specimens with sufficient viral load underwent next-generation sequencing. Phylogenetic inference was assessed with maximum likelihood trees and recombination analysis conducted on basal sequences.

Testing revealed reactive results for HBsAg (87.2%), anti-HBc (92.8%), anti-HBs (6.9%), HBeAg (3.8%), and anti-HDV (1.3%). HBsAg Next Qualitative and Elecsys HBsAg II concordance was 311/319 (97.5%), with n = 8 (2.5%) samples not detected by Elecsys HBsAg II. Confirmatory testing verified HBsAg positivity for the 8 discordant specimens. Sequencing (n = 104) resulted in >70% genome coverage for n = 74 specimens and phylogenetic analysis identified HBV Quasi-subgenotype A3 (QSA3) (40.5%), A basal (1.4%), D (5.4%), E (52.7%), and 2 HDV GT5 genomes. Recombination analysis revealed two HBV QSA/E 3 recombinants.

This study provides, to our knowledge, the first HBV sequences from Senegal in 20 years and highlights a predominance of genotypes E, QSA3, and notably two unique QSA3/E recombinants. The improved detection of HBsAg Next Qualitative on samples with low levels of HBsAg highlights the importance of ultrasensitive assays.