The continuous circulation of pseudorabies virus (PRV) variants persists in causing substantial economic losses within China's swine industry. Nevertheless, the molecular characteristics and pathogenic potential of the recently emerged variants remain poorly understood, and the cross-protective effectiveness of the newly developed vaccines based on these variants against the circulating strains is still uncertain. In this study, two novel PRV strains, designated WK631 and WK1157, were isolated from clinical samples collected in 2022 and 2024 during investigations of suspected pseudorabies outbreaks. Comparative genomic analysis indicated that both strains share high sequence homology with previously reported PRV variants and harbor sporadic amino acid mutations. Moreover, a small-fragment recombination event was detected in WK631. Pan-genomic alignment has identified genotype-specific molecular signatures: 33 proteins for genotype I, 5 for classical genotype II, and 10 for variant genotype II strains. Subsequently, 14 days after immunization with the PRV variant vaccine, the animals were challenged with WK631, WK1157, or the highly virulent control strain HeN1. Unvaccinated mice exhibited characteristic PRV-induced pruritus and succumbed to infection with 100% mortality within 6 days postchallenge. High viral loads were detected in brain tissues by quantitative PCR and immunohistochemistry, accompanied by typical neuropathological lesions. In contrast, all vaccinated mice survived without exhibiting any clinical symptoms, viral replication, or pathological alterations. This study not only broadens our understanding of the genomic characteristics of PRV variants but also confirms the pathogenic potential of recent isolates and validates the effectiveness of variant-based vaccines, thereby reinforcing their potential use in PRV control strategies.

Keywords: cross-protection effect; molecular signatures; novel PRV variants; pathogenicity.