INDUCTION OF PROTECTIVE IMMUNITY TO THEILERIA-ANNULATA USING 2 MAJOR MEROZITE SURFACE-ANTIGENS PRESENTED BY DIFFERENT DELIVERY SYSTEMS

Allelic forms (Tams1-1 and Tams1-2) of the major merozoite surface ant igen gene of Theileria annulata have recently been expressed in Escher ichia coli and in Salmonella typhimurium aroA vaccine strain SL3261. T o test the potential of subunit vaccines against T. annulata infection , we immunized four groups of three calves with either recombinant (re -) (Tams1-1 and Tams1-2) proteins or naked DNA encoding these antigens . Group I was immunized intramuscularly with both re-proteins incorpor ated into immunostimulating complexes (ISCOMs). Group II was inoculate d intramuscularly with naked plasmid DNA encoding Tams1-1 and Tams1-2 Groups III and IV received S. typhimurium SL3261 [pSTams1-1][pIP5] and SL3261 [pSTams1-2][pIP5] subcutaneously and orally, respectively. A f inal group of three animals (Group V) served as an unimmunized control group. Four weeks after the last immunization all calves were challen ged with a T. annulata stabilate generated from blood of an infected a nimal with 30% piroplasm parasitaemia. All calves vaccinated with ISCO Ms proved to be protected from T. annulata infection and had generated antibodies against both re-(Tams1-1 and Tams1-2) at the time of chall enge. In two of these animals the antibody had a surface binding profi le by IFAT. Two of three calves immunized with naked DNA also proved t o be protected, but none of the animals had generated any detectable a ntibodies against the recombinants. Salmonella-based delivery of the r ecombinants did not induce any protection; two of six animals died of theileriosis and there was no difference between subcutaneous or oral administration. These preliminary results show that re-(Tams1-1 and/or Tams1-2) may elicit protective immune responses in cattle, depending on the antigen delivery system. (C) 1997 Elsevier Science Ltd.