Characterisation of virus-specific peripheral blood cell cytokine responses following vaccination or infection with classical swine fever viruses

Existing live attenuated classical swine fever virus (CSFV) vaccines provide a rapid onset of complete protection but pose problems in discriminating infected amongst vaccinated animals. With a view to providing additional information on the cellular mechanisms that may contribute to protection, which in turn may aid the development of the next generation of CSFV vaccines, we explored the kinetics of the cytokine responses from peripheral blood cells of pigs vaccinated with an attenuated C-strain vaccine strain and/or infected with a recent CSFV isolate. Peripheral blood cells were isolated over the course of vaccination/infection and stimulated in vitro with C-strain or UK2000/7.1 viruses. Virus-specific responses of peripheral blood cells isolated from C-strain vaccinated pigs were dominated by the production of IFN-?. IFN-? production in response to the C-strain virus was first detected in vaccinates 9 days post-vaccination and was sustained over the period of observation. In contrast, cells from challenge control animals did not secrete IFN-? in response to stimulation with C-strain or UK2000/7.1 viruses. Supernatants from UK2000/7.1 infected animals contained significant levels of pro-inflammatory cytokines from day 8 post-infection and these cytokines were present in both virus and mock stimulated cultures. The results suggest that the C-strain virus is a potent inducer of a type-1 T cell response, which may play a role in the protection afforded by such vaccines, whereas the pro-inflammatory cytokine responses observed in cultures from infected pigs may reflect a pathological pro-inflammatory cascade initiated in vivo following the replication and spread of CSFV.