Orf132: A Critical Gene for LSDV Replication and Its Role in ER Stress-Related Apoptosis

Lumpy skin disease (LSD), caused by lumpy skin disease virus (LSDV), is an emerging infectious disease in China that primarily affects cattle. LSDV and goatpox virus (GTPV) belong to the Capripoxvirus genus and exhibit high genomic homology, enabling cross-immunogenicity. Comparative genome analysis revealed that LSDV contains a unique gene, Orf132 , whose function remains uncharacterized. In this study, we first confirmed that the recombinant ORF132 protein exhibits immunoreactivity against sera from LSDV-infected cattle and GTPV-vaccinated cattle, and this cross-reactivity excluded the possibility of using the ORF132 protein to distinguish between LSDV and GTPV. To investigate the biological role of Orf132 , we generated an Orf132 deletion strain (LSDV-Δ Orf132 ). Compared with that of the wild-type LSDV, the replication capacity of LSDV-Δ Orf132 was reduced approximately tenfold, indicating that Orf132 is critical for viral replication. Transcriptomic analysis of infected MDBK cells revealed significant alterations in Endoplasmic reticulum(ER) protein processing and unfolded protein response(UPR) pathways following Orf132 deletion. RT-qPCR validation showed marked upregulation of ER stress markers including Grp78 , Chop , and Gadd34 . Subsequent apoptosis assays established that Orf132 deletion triggers CHOP-Caspase12-mediated apoptotic pathways. This dysregulated stress response cascade culminates in premature apoptotic scenarios, possibly resulting in a weakening of viral replication. Our findings collectively revealed that Orf132 is a critical gene for LSDV replication, plays an essential role in the virus's life cycle, and its deletion significantly impairs viral replication while inducing ER stress-related apoptosis.