Genomic characterization of a Chinese bovine papillomavirus isolate and its L1-based phylogenetic placement in a...

Bovine papillomatosis (BP), caused by bovine papillomavirus (BPV), is characterized by proliferative epithelial lesions and is associated with significant economic losses in cattle populations. Despite its clinical and economic relevance, the molecular characteristics of BPV isolates circulating in China, as well as their phylogenetic relationships within the context of global BPV genetic diversity, remain inadequately characterized.

A BPV strain was isolated from a cattle farm in Fujian Province, China, and its complete genomic sequence was obtained. Using publicly available reference sequences, we analyzed the viral L1 gene through recombination screening, selection-pressure analysis (dN/dS ratio), and maximum-likelihood phylogenetic inference. Additional temporal signal analyses were conducted on the BPV2 subset to explore the presence of measurable temporal structure in the sequence data.

The newly identified strain, designated FJ-01, was classified as BPV2 and possessed a complete genome of 7,947 bp. No recombination was detected in the L1 gene. The overall dN/dS ratio indicated dominant purifying (negative) selection acting on the L1 gene (dN/dS = 0.0735). Maximum-likelihood phylogenetic analysis placed FJ-01 within the BPV2 clade in the final global L1 dataset. Exploratory temporal analyses of the BPV2 subset suggested weak temporal structure; however, estimates of absolute divergence dates were associated with high uncertainty and should be interpreted with caution.

This study provides a molecular characterization of a Chinese BPV isolate and integrates it into a global L1-based phylogenetic framework. Our findings support the genetic classification of FJ-01 within BPV2 and indicate the L1 gene is evolutionarily conserved. These results serve as a valuable reference for future molecular surveillance efforts and for more comprehensive studies utilizing geographically balanced and genome-complete BPV datasets.