Rhipicephalus microplus voraxin-alpha contains B-cell epitopes that reduce ticks' biological fitness in immunized...

Rhipicephalus microplus ticks are a serious pest of cattle in tropical and subtropical regions, mainly due to the losses they cause by reducing meat and milk production, as well as causing hide damage, in addition to their role as vectors of babesiosis and anaplasmosis. Integrated tick control must include the use of anti-tick vaccines to reduce tick populations and mitigate the ecological impact associated with the extensive use of acaricides. To develop improved vaccines, evaluation of new tick antigens is essential. Voraxin, mainly described as a testes-derived protein, is transferred from males to females during copulation, and it is crucial for stimulating engorgement in female ticks and for the development of their organs. In this study, R. microplus voraxin-alpha (voraxin-α) was amplified and sequenced, four peptides with predicted B-cell epitopes were designed and their immunogenic properties were evaluated. Each peptide was mixed with a commercial adjuvant and inoculated into two cattle from a tick-free region to corroborate if they were truly immunogenic. The antibody responses to each peptide were assessed using indirect ELISA. Two peptides were immunogenic and were selected for further testing involving immunization and experimental infestation with 10,000 larvae and two cattle per evaluated peptide. Immunization with peptide 3 reduced tick survival in 17 %, oviposition in 14 % and egg hatching in 22 %, while peptide 4 impaired oviposition in 18 % and egg hatching in 18 %. No effect on weight was observed. In conclusion, ticks fed on cattle producing specific antibodies against voraxin-α B-cell epitopes, have a reduced survival, oviposition and fertility, which are important biological parameters, related to tick fitness. Vaccine trials are required to evaluate this antigen as a vaccine candidate against R. microplus.