Title

The effect of kelch-like protein SPPV_19 on virulence of sheeppox virus

Date of Completion

January 2007

Keywords

Biology, Virology

Degree

Ph.D.

Abstract

Sheeppox virus (SPPV) is classified in the Capripoxvirus genus of the Poxviridae family of viruses, which include the closely related Goatpox virus (GTPV) and Lumpy Skin Disease virus (LSDV). Disease is characterized by; fever, anorexia, depression, respiratory distress, generalized skin lesions and internal lesions. Outbreaks of SPPV can result in substantial loss of animal life as well as economic loss due to the high cost of outbreak management and trade restrictions. Vaccine strains GTPV and LSDV have disruptions in members of a multigene family containing kelch-like repeats (Tulman, Afonso et al. 2002). However, little is known about the role these genes play in Capripoxvirus pathogenesis. A SPPV_19 kelch-like gene deletion mutant (ΔKLP) and its revertant (RvKLP) were constructed and characterized. ΔKLP does not display any growth defects in lamb kidney cell culture or in tracheal epithelial explant culture; however, it does show a decrease in Ca2+ independent cell adhesion compared to wild-type and RvKLP viruses. ΔKLP is attenuated in vivo after intranasal or intradermal inoculation. Lambs inoculated with ΔKLP display a reduction in mortality, fever, viremia, virus shedding and the appearance of lesions compared to wild-type and RvKLP infected animals. ^ A thymidine kinase (TK) deletion mutant (ΔTK) was also constructed and characterized. ΔTK did not show any growth defects in cell culture. However, lambs inoculated with ΔTK developed only a slight fever, and no other signs of clinical disease were evident. ^ A fluorogenic probe hydrolysis (TaqMan) based assay was developed for detection of CaPVs in this study. The assay can detect SPPV in blood buffy coats, nasal swabs, oral swabs, scabs, lesion biopsys as well as lung and lymph nodes collected at necropsy. The assay can be performed in 2 hours or less and can detect viral DNA prior to the onset of clinical disease. ^