THE CENTRAL REGION OF THE B646L GENE SUPPORTS AFRICAN SWINE FEVER VIRUS GENOTYPE II IDENTIFICATION

Abstract

The B646L gene encoding the major capsid protein p72 is the standard genetic marker for African swine fever virus (ASFV) genotyping, with classification conventionally based on sequencing the C-terminal region. In contrast, the central region is routinely amplified during diagnostic PCR but has not been systematically evaluated for genotype assignment. Here, we assessed the genotyping utility of the central B646L region using laboratory-generated ASFV-positive sequences together with representative complete ASFV genomes. Phylogenetic analyses of the complete B646L coding sequence (CDS), central region, and C-terminal region consistently assigned the laboratory-generated sequences to genotype II. Comparative sequence analyses further identified seven parsimony-informative sites within the central region that distinguished genotype II from its closest neighboring genotype, despite the fragment containing fewer informative sites than the complete CDS and the conventional C-terminal region. These findings demonstrate that the routinely amplified central B646L fragment retains sufficient sequence variation for ASFV genotype II identification and represents a practical source of molecular information that can complement routine molecular surveillance.