Characterisation of putative immunomodulatory gene knockouts of lumpy skin disease virus in cattle towards an improved vaccine

• Published in: Vaccine 2018-07, Vol.36 (31), p.4708-4715
• Main Authors: Kara, Pravesh D., Mather, Arshad S., Pretorius, Alri, Chetty, Thireshni, Babiuk, Shawn, Wallace, David B.
• Format: Article
• Language: English
• Subjects: Animals; Attenuation; Calves; Capripoxvirus; Cattle; Cell culture; Economic impact; Gene knockout; Genes; Genomes; Homology; Immune response (humoral); Immunogenicity; Immunomodulation; Immunomodulators; Infections; Inoculation; Interferon; Interferon-gamma receptor-like gene (IFN-γR); Interleukin 10; Interleukin-10-like gene (IL-10); Lesions; Livestock farming; Lumpy skin disease; Mutation; Orf; Skin; Skin diseases; Trade restrictions; Vaccine; Vaccines; Viruses; γ-Interferon
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2018.06.017

•The putative interleukin-10-like and interferon-gamma receptor-like gene deleted from the genome of a LSDV field isolate.•Severe post-vaccinal reactions observed in calves at the site of inoculation, and fever, for both constructs.•Improved cellular and humoral immune responses recorded in calves following inoculation with either construct.•Following challenge none of the calves inoculated with either knockout construct showed any external clinical signs of LSD.•At high inoculation dose used either construct insufficiently attenuated for use in cattle. Lumpy skin disease virus (LSDV) is responsible for causing severe economic losses to cattle farmers throughout Africa, the Middle East, and more recently, South-Eastern Europe and Russia. It belongs to the Capripoxvirus genus of the Poxviridae family, with closely related sheeppox and goatpox viruses. Like other poxviruses, the viral genome codes for a number of genes with putative immunomodulatory capabilities. Current vaccines for protecting cattle against lumpy skin disease (LSD) based on live-attenuated strains of field isolates passaged by cell culture, resulting in random mutations. Although generally effective, these vaccines can have drawbacks, including injection site reactions and/or limited immunogenicity. A pilot study was conducted using a more targeted approach where two putative immunomodulatory genes were deleted separately from the genome of a virulent LSDV field isolate. These were open reading frame (ORF) 005 and ORF008, coding for homologues of an interleukin 10-like and interferon-gamma receptor-like gene, respectively. The resulting knockout constructs were evaluated in cattle for safety, immunogenicity and protection. Severe post-vaccinal reactions and febrile responses were observed for both constructs. Two calves inoculated with the ORF008 knockout construct developed multiple lesions and were euthanised. Following challenge, none of the animals inoculated with the knockout constructs showed any external clinical signs of LSD, compared to the negative controls. Improved cellular and humoral immune responses were recorded in both of these groups compared to the positive control. The results indicate that at the high inoculation doses used, the degree of attenuation achieved was insufficient for further use in cattle due to the adverse reactions observed.