Abstract
Lumpy skin disease virus (LSDV) causes a severe emerging and transboundary disease in cattle. Infection with LSDV leads to the development of widespread dermal nodules. In addition to the skin, LSDV resides in multiple internal organs and can be isolated from the blood of infected cattle. We have characterised the tropism, replication, and dissemination of both a field isolate of LSDV and an attenuated vaccine strain in vitro. To study virus infection and dissemination in living cells, we generated recombinant viruses that express a green fluorescent protein (GFP) under a synthetic viral promoter. The recombinant LSDVs expressing GFP displayed replication kinetics similar to their parental strains in a bovine kidney cell line. These LSDV-GFP strains also replicated effectively in a bovine macrophage cell line and primary bovine foreskin cells, showing no apparent differences between the field isolate and the vaccine strain. Bovine peripheral blood mononuclear cells (PBMCs) infected with either LSDV-GFP strain displayed specific viral-driven GFP fluorescence and significant viral gene expression. However, these infected PBMCs did not support substantial viral DNA replication or the release of infectious progeny. Further analysis of the anti-viral response revealed that heat-treated LSDV, but not infectious viruses, induced the expression of interferon-stimulated genes (ISGs) in PBMCs. Thus, although LSDV did not replicate productively in PBMCs, it evaded the anti-viral response of these cells. Finally, we demonstrated that despite the lack of productive replication, infected PBMCs effectively transmitted LSDV to recipient permissive cells in co-culture, leading to the formation of infection foci. This suggests a potential role for PBMCs in the dissemination of LSDV.