Primary bovine white blood cells support dissemination of Lumpy Skin Disease Virus while suppressing viral replication
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Lumpy skin disease (LSD) is a severe infectious, emerging transboundary disease of cattle, caused by a Pox family DNA virus. Lumpy skin disease virus (LSDV) infection is associated with a febrile response followed by emergence 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. LSDV is suggested to be mechanically transmitted by biting arthropods. Live attenuated vaccines are commonly used to control disease and its spread. We have characterized the tropism, replication, and dissemination of a LSDV field isolate and of an attenuated vaccine strain using in vitro systems. To follow virus infection and dissemination in living cells, we have generated recombinant viruses expressing green fluorescent protein (GFP) under a synthetic viral promoter. Recombinant, GFP-expressing, LSDVs demonstrated similar replication kinetics to their corresponding parental LSDV strains in a bovine kidney cell line (MDBK). We further demonstrated that LSDV-GFP productively replicated in a bovine macrophage cell line and in primary bovine foreskin cells with no apparent differences between the field isolate and the vaccine strain. When bovine peripheral blood mononuclear cells (PBMCs) were infected with either LSDV recombinant strain, we observed specific viral driven GFP fluorescence as well as significant viral gene expression. However, infected PBMCs failed to support substantial viral DNA replication and release of infectious progeny. Subsequent analysis of the anti-viral response revealed that heat treated (HT) LSDV induced the expression of interferon- stimulated genes (ISGs) in PBMCs, but this response was suppressed by infectious viruses. Finally, we show that despite failed replication, LSDV infected PBMCs transmitted the virus to recipient co-cultured MDBK cells and produced infectious foci, suggesting a potential role of PBMCs in LSDV dissemination.
Highlights
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Virulent and attenuated LSDV productively replicated in bovine kidney and bovine macrophage cell lines as well as in primary fibroblasts.
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Adherent white blood cells were susceptible to LSDV field and attenuated vaccine infection.
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LSDV showed active viral transcription in PBMCs yet no significant viral genome replication or production of infectious progeny.
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PBMCs infected with heat-treated LSDV but not with fully infectious viruses upregulated ISGs’ RNA.
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PBMCs transmitted and disseminated LSDV to contacting permissive cells.
