A RECOMBINANT S19 Brucella abortus EXPRESSING A Babesia bovis ANTIGEN IS IMMUNOSTIMULATORY

SAVIO Y GARCIA J; MACEDO G; BARSANTE M; CARVALHO N; CARRICA M; FARBER M; CRAVERO S; CAMPOS E; COSTA S; ROSSETTI O

Pinamar, Bs. As.

Congreso; 41st Annual Meeting SAIB; 2005

Due to the strong cellular and humoral immune response that S19 Brucella abortus live vaccine elicits, it is an attractive vector for the delivery of heterologous antigens. The objective of the present study is to express antigens of pathogens that require the same type of immune response elicited by Brucella to control the desease they produce. S19 B. abortus expressing RAP1a (a conserved immunogenic antigen) of Babesia bovis were generated. rap1a was PCR-amplified as a complete version or without the sequence that encodes for its signal peptide. The amplicons were subcloned under different promoters and signal sequences: lacz, bp26 and omp19 to study diverse subcelular localizations. BP26 is a peri-plasmic protein and OMP19 is associated to the outer membrane of Brucella spp. RAP1a as a fusion with the first aminoacids of either ß-galactosidase or OMP19 resulted in the expresion of RAP1 in association to the membrane of S19. Even though there was a relatively lower stability of the plasmids containing rap1a, compared to the empty plasmid, mice inoculated with S19pRAP or S19p19RAP developed specific immune responses to RAP1, being IgG2a the prominant subisotype of antibodies (analysed by ELISA). As a fusion protein with BP26, RAP1a was toxic. Therefore it can be concluded that the expression of RAP1 in B. abortus S19 is possible and immunostimulatory. Lymphocyte stimulation assays are being performed.