DEVELOPING NEW DIAGNOSTIC TOOLS FOR BOVINE BABESIOSIS: COMPARISON OF TWO INDIRECT ELISAS BASED ON BABESIA BOVIS RECOMBINANT ANTIGENS

DOMINGUEZ, M; PETRIGH, R.; ECHAIDE, I; WILKOWSKY, S; FLORIN-CHRISTENSEN, M; FARBER, M

Neuchâtel, Suiza

Conferencia; 5th International Conference on Ticks and Tick-borne Pathogens (TTP5); 2005

University of Neuchâtel, Switzerland

Periodical diagnosis of bovine babesiosis in areas of enzootic instability allows to evaluate the immunological status of herds, and determine the need of vaccination. The most common diagnostic methods currently used are immunofluorescence and indirct ELISAs based on crude parasite antigens. In the case of Babesia bovis, recombinant rhoptry associated protein-1 (RAP-1) has also been exploited in the development of diagnostic kits. Lately, our group has shown that another immunodominant and highly conserved B. bovis antigen, Merozoite Surface Antigen 2-c (MSA-2c), constitutes a promising diagnostic candidate. In this work, we have compared the performance of recombinant MSA-2c with that of RAP-1 to detect anti-B. bovis antibodies present in field samples when used in indirect ELISAs. Both antigens were produced in the prokaryotic pBAD/thioTOPO expression system and purified by affinity chromatography. In the case of RAP-1, a C-terminal fragment was used, to avoid cross-reactivity to B. bigemina-infected sera. Optimal conditions for the ELISAs were set, adjusting antigen concentration; blocking agent, peroxidase substrate and incubation conditions. One hundred serum samples from B. bovis endemic areas of Northwestern Argentina and 50 negative samples from an Argentine Southern province were tested using the ELISAs based on MSA-2c and C-terminal RAP-1 here developed. Cut-off values were calculated as the average of the values obtained for negative sera + 2.5 standard deviations. Prevalence of B. bovis-positive sera in the geographical region studied was evaluated with both assays and the results are discussed.