Enhanced proinflammatory cytokine activity during experimental bluetongue virus-1 infection in Indian native sheep.

Abstract

Bluetongue disease has been causing variable morbidity and mortality in sheep in India and other countries of the world. The experimental infection with Indian BTV-1 strain induced mild to sub-acute infection in native sheep. There were low induction of IL-12, IFN-γ and TNF-α cytokine mRNA expressions determined by real time RT-PCR in draining lymph nodes (DLN), spleen, and PBMCs during the initial stages of infection (8 days post inoculation, DPI) and higher around 15 DPI. The reduced pro-inflammatory cytokine (IFN-γ and TNF-α) responses during the initial stage of infection (8 DPI) was also accompanied by similarly decreased T-cell populations and overt clinical symptoms. Later up regulation of these cytokines and substantial increase in the proportion of CD8(+) T-cells occurred with reduction of clinical signs and disappearance of BTV-1 antigen from tissues as determined by immunohistochemistry and RT-PCR. Thus there is definite involvement of pro-inflammatory cytokines and CD8(+) T cell activity in disease induced by BTV-1 strain.