Characterization of Babesia bovis glycosylphosphatidylinositol-(GPI)-anchored antigens as vaccine candidates

FLORES, DANIELA; RODRIGUEZ, ANABEL E; LANGELLOTTI, CECILIA; SORIA, VIVIANA; ZAMORANO, PATRICIA; TOMAZIC, MARIELA L; FLORIN-CHRISTENSEN, MÓNICA; SCHNITTGER, LEONHARD

Cairns, Queensland

Conferencia; One Health 9th Tick and Tick-borne Pathogen Conference & 1st Asia Pacific Rickettsia; 2017

Babesia bovis is an obligate tick-transmitted hemoparasite causing bovine babesiosis, a disease of cattle associated with significant economic losses. Currently used live vaccines entail major disadvantages which would be overcome by the development of a subunit vaccine. To this aim, we have identified GPI-anchored antigens in silico representing potential vaccine candidates in the B. bovis-proteome and two of yet unknown function, designated GPI-4 and GPI-5, were selected for further studies. By sequencing amplicons of geographic isolates originating from Argentina, Brazil, United States, Mexico, and Australia, an identity of > 90% could be determined for both antigens. The antigens were expressed in a prokaryotic system and used in immunoblots to verify the presence of specific antibodies in a panel of sera from 14 B. bovis-naturally infected bovines. Altogether 11 of the 14 tested sera specifically recognized the GPI-4 and GPI-5 antigen, demonstrating their immunodominance. Specific murine sera raised against the recombinant proteins significantly inhibited parasite propagation in an in vitro neutralization assay. Expression of both antigens on the surface of the parasite was demonstrated by live immunofluorescence. Finally, cellular immune responses were studied in lymphocyte proliferation assays using spleen cells of immunized mice. Specific proliferation was observed against recombinant and native GPI-5 demonstrating the presence of T cell specific epitopes in this antigen. The results obtained encourage the inclusion of both antigens in a subunit vaccine formulation. Financed by INTA PNBIO 1131034, PICT 2010-0438 and PICT 2013-1708.