Isolation, identification and phylogenetic analysis of a lumpy skin disease virus strain from diseased beef cattle in China

Abstract Lumpy skin disease (LSD) is a highly contagious viral disease in cattle caused by lumpy skin disease virus (LSDV), which belongs to the genus Capripoxvirus (CaPVs) within the family Poxviridae . Since its first outbreak in China in August 2019, LSD has spread widely across mainland China, posing significant threats to the cattle industry. This study aimed to isolate and identify a clinical strain of LSDV via Vero cells. Skin tissue samples from lump lesions were homogenized and inoculated onto cell cultures. After 7 passages, the inoculated cells exhibited typical cytopathic effects (CPEs). PCR amplification of the LSDV132 gene confirmed the presence of LSDV nucleic acid. In addition, quantitative PCR (qPCR) demonstrated a significant increase in viral copy number over time. Transmission electron microscopy (TEM) revealed typical brick-shaped viral particles. Furthermore, an indirect immunofluorescence assay (IFA) of infected Vero cells exhibiting CPEs produced a positive reaction with antiserum from cattle naturally infected with LSDV. Additionally, nucleotide similarity analysis of 123 LSDV strains revealed a high degree of similarity (98.4%-100%) among different geographic lineages. Nucleotide sequencing and recombination analysis of the LSDV011 gene from LSDV/China/HB01/2020 revealed close similarity to Asian strains and revealed a recombination event. Furthermore, similarity plot analysis confirmed two genomic exchange sites at nucleotide positions 120 and 762 within the LSDV011 gene. Recombination events between 65 Asian LSDV strains and 13 goatpox virus (GTPV) strains have raised safety concerns regarding the use of attenuated goatpox vaccines, highlighting the need for novel and safer LSDV vaccines. In summary, this study successfully isolated a clinical LSDV strain, demonstrating its evolutionary status and providing crucial insights for LSD control in the cattle industry.