Different vaccine strategies used to protect against Theileria annulata.

SPAG-1, a sporozoite surface antigen of T. annulata, has previously been shown to elicit partial protection when used, as an hepatitis B core antigen fusion, to immunize cattle. The objective of this study was to try and improve the protective capacity of this antigen by enlisting different vaccine strategies. Cattle were immunized with SPAG-1, as a fusion protein with a His6 tag, either incorporated into ISCOMs, with or without the merozoite antigens TAMS 1-1 and 1-2, or with RWL as adjuvant three times at monthly intervals. Another group of cattle were immunized with p67, the T. parva sporozoite antigen, in RWL to assess whether any cross-protection could be induced. The animals were then challenged with an estimated LD50 of T. annulata sporozoites, and their ability to resist the infection was investigated. Serum responses and T-cell proliferative responses were analyzed throughout the trial. Post-challenge analyses included lymph node biopsies and blood smears to check for the presence of parasites, routine hematological parameters, and observation for clinical manifestations of the disease. The results of this trial will be discussed.