Vaccination against Babesia bovis: T cells from protected and unprotected animals show different cytokine profiles

Vaccination of cattle against the haemoprotozoan parasite, Babesia bovis, with the recombinant antigen 11C5 resulted in 9 of 15 cattle being protected against challenge infection. The cellular immune responses of protected and unprotected cattle were compared in order to identify differences in response. No differences were observed in the pattern of change in various blood leukocyte populations throughout challenge infection. FACScan analysis revealed an increase in the proportion of cells bearing the CD2 marker in both protected and unprotected cattle over the course of infection. There were no observable differences in the frequency of various cell-surface markers between the unprotected and protected cattle. During the period of patent parasitaemia, in vitro cultures of peripheral blood mononuclear cells (PBMC) from protected cattle produced significantly more TNF-alpha (P < 0.05) than cultures from unprotected cattle. TNF-alpha concentrations remained at pre-challenge levels until day 10, when levels in the unvaccinated control and vaccinated/unprotected animals dropped. By peak parasitaemia, TNF-alpha production in vitro was significantly greater (P < 0.05) in cultures of PBMCs from protected cattle. Interferon production showed an initial peak at day 5 in all cattle, followed by a decrease and a second peak at days 10-13 in protected cattle only, which coincided with resolution of the infection.