A chimeric vaccine based on peptides from salivary serpins for tick control

The cattle tick Rhipicephalus microplus causes significant economic losses to the livestock industry, underscoring the need for the development of effective control methods. Vaccination with tick antigens has been proposed as a promising strategy to induce a protective immune response, especially using tick salivary antigens, which play important roles in modulating the host immune response. It was previously demonstrated by our research group that three serpins (RmS-3, RmS-6 and RmS-17) are present in the saliva of the cattle tick Rhipicephalus microplus and are secreted during feeding, where they act by interfering in the host immune response. In addition, antibodies raised against theses serpins are able to neutralize their inhibitory functions. More recently, we identified neutralizing epitopes for RmS-17 using an in vitro approach. Based on these results, we developed a cost-effective strategy to identify neutralizing epitopes by combining epitope prediction algorithms with the spatial localization of the epitopes within the serpin structure. This strategy was applied to RmS-3 and RmS-6, and peptides were synthesized based on the predicted epitopes. Rabbits were immunized with these peptides to generate antisera against the respective peptides. Purified IgG was then used in a neutralization assay for RmS-6, which demonstrate that anti-p1RmS-6 neutralized rRmS-6 activity by 48%, anti-p3RmS-6 by 22% and a combination of both antibodies by 25%. Assays for RmS-3 are still ongoing. Based on the peptides identified for the three serpins, a chimeric protein it will be developed and evaluated for their capacity to generate a protective immune response against tick infestations.