Phylogenetic Analysis, Morphological Characteristics, and Cellular Tropism of Vaccine-Like Recombinant Strains of Lumpy Skin Disease Virus in China.

Lumpy skin disease virus (LSDV) causes lumpy skin disease (LSD), a highly contagious cattle disease that leads to substantial economic losses to the global cattle industry. Currently, it is imperative to further elucidate its biological characteristics and analyze the global epidemiological dynamics. In this study, two isolates of LSDV with genetic recombination were identified in Northern and Eastern China, which demonstrated broad host cell entry ability. Through electron microscopy, we further revealed its morphogenetic characteristics across its replication cycle for the first time. Viral particles sequentially formed crescent membranes, nucleoids, and lateral bodies, and ultimately developed into four types of mature virions: intracellular mature virions (IMVs), intracellular enveloped virions (IEVs), cell-associated enveloped virions (CEVs), and extracellular enveloped virions (EEVs). Whole-genome phylogenetic analysis revealed that both isolates belonged to Clade R4. Based on the global reference strains, our integrated analysis for temporal and geographical information revealed that LSDV has progressively expanded its endemic range, particularly in Asia, where recombinant Clade R4 strains have recently emerged as the predominant epidemic strains. Strikingly, recombination analysis detected a limited number of recombination signals between the LSDV isolates and goatpox virus (GTPV) or sheeppox virus (SPPV) strains, suggesting that the possibility of recombination between heterologous vaccines and LSDV cannot be fully excluded. These data may provide important information for prevention and control of LSD global outbreaks.