Evaluation of Cell-mediated Immune Response in PBMCs of Calves Vaccinated by Capri Pox Vaccines Using ELISA and Real-time RT-PCR

Background: The analysis of antigen-specific cytokine expression has been considered to evaluate the immune responses and vaccines efficacy in recent years. The aim of this study was to compare the cell-mediated immune response characteristics of two Capri pox virus (CaPV) vaccines against lumpy skin disease in cattle. Materials and Methods: Two Capri pox virus vaccines were administered to dairy cows of two farms and followed up to 5 weeks post vaccination. These vaccines were live attenuated Goat pox virus (GTP) Gorgan strain (n=20) and Sheep pox virus (SPP) Romanian strain (n=20). Cell-mediated immune response of vaccinated calves was evaluated using in vitro lymphocyte proliferation and IFN-g and IL-4 release assay after stimulation with recall vaccine strains, and in vivo cytokine expression in PBMCs by real-time PCR. Results: Lymphocyte proliferation in GTP- and SPP-vaccinated groups began to increase till reached to its peak at third week post vaccination and then decreased in the weeks thereafter. Stimulation index in stimulated PBMCs in GTP-vaccinated calves was higher than SPP-vaccinated calves in all weeks, which indicated higher levels of immunogenicity produced by the GTP-vaccine in cattle. Also, in both vaccinated groups the peak release of IFN-g and IL-4 proteins in cultured PBMCs in response to recall antigen was detected at week 3 post vaccination. Although the mean of the cytokine release in GTP-vaccinated calves was higher than SPP-vaccinated calves in all weeks of experiment, a significant difference was only observed at week 3 post vaccination (P<0.05). In contrast, the IFN-g mRNA expression in PBMCs of vaccinated groups was induced early, peaked at week 1 post vaccination and decreased in the weeks thereafter, and this rate was higher in GTP-vaccinated calves compared with SPP-vaccinated calves in all weeks, but the significant difference was only found at week 3 post vaccination (P<0.05). However, the IL-4 mRNA expression showed delayed induction and peaked at week 3, and unlike the SPP group, it remained at this level in GTP group, until the end of experiment. Also this rate of expression in GTP-vaccinated calves was higher than SPP-vaccinated calves in all weeks and had a significant increase at week 5 post vaccination (P<0.05). Conclusion: The findings show that due to induction of high level cell-mediated immune response in live attenuated GTP vaccine compared to SPP vaccine, GTP vaccine has a good immunogenic response, and therefore can be a better choice for vaccination against lumpy skin disease.