THEILERIA-ANNULATA SPOROZOITE ANTIGEN FUSED TO HEPATITIS-B CORE ANTIGEN USED IN A VACCINATION TRIAL

A C terminal fragment (SR1) of SPAG-1, a sporozoite surface antigen of Theileria annulata, has been expressed as a fusion protein in the el loop of hepatitis B cope antigen (HBcAg), This recombinant antigen (HB cAg-SR1) is produced in the form of self-assembling polyhedral particl es which have been visualised under the electron microscope, Cattle im munised with HBcAg-SR1 produced high titres of neutralising antibodies , A significant T cell response to both the HBcAg and SR1 determinants was observed but evidence of a T suppressor determinant in SR1 was al so revealed Immunised cattle showed some evidence of protection to spo rozoite challenge as assessed by severity of the disease. The signific ance of these findings for the development of a sub-unit vaccine again st T, annulata is discussed.