Emergence and molecular characterization of bovine alphaherpesvirus 1 subtype 1.1 in China, with in vivo...

Bovine alphaherpesvirus 1 (BoAHV-1; formerly bovine herpesvirus 1, BoHV-1) remains endemic in China, whereas available surveillance and genomic data have largely suggested predominance of genotype 1.2. In this study, molecular subtyping using a 451-nt fragment from the UL44 carboxyl terminal region identified 15 genotype 1.1 viruses among 60 recent BoAHV-1 positive clinical specimens. This proportion (25%) contrasts with previous Chinese surveillance studies that have predominantly reported genotype 1.2, particularly subtype 1.2b, suggesting that genotype 1.1 may have been underrecognized in earlier molecular epidemiological surveys. On this basis, a genotype 1.1 strain, designated China BoAHV BC01, was isolated from a respiratory disease outbreak in an unvaccinated dairy herd and subjected to complete genome sequencing and annotation. The BC01 genome is 132,061 bp in length and has been deposited in GenBank under accession number PV550781.1. Whole-genome and gene-based phylogenetic analyses of UL27, UL44, and US6 consistently classified BC01 as genotype 1.1. Comparative analysis showed high overall genomic similarity to published BoAHV-1 strains, with localized sequence variation in specific genomic regions. Structure and epitope analysis of US6, together with docking to bovine nectin 1 based on the published 6LSA structure, indicated broadly similar surface features and receptor interface geometry between BC01 and a genotype 1.2 reference strain. In female rabbits, intranasal challenge with BC01 was associated with fever, respiratory signs, detectable viral DNA in nasal swabs and tissues, and histopathological changes, especially in the lung. To our knowledge, BC01 represents the first completely sequenced and systematically annotated domestic BoAHV-1.1 clinical isolate from China. Together with the exploratory rabbit data, this study provides a genomic resource for future molecular surveillance and comparative studies of BoAHV-1 subtype diversity.