Gut membrane proteins as candidate antigens for immunization of mice against the tick Amblyomma sculptum.

Amblyomma sculptum is widely distributed in Brazil and is the main vector of Rickettsia rickettsii, the causative agent of the Brazilian spotted fever (BSF). Tick gut proteins play an essential role in blood feeding, digestion, and protection of gut epithelium. Therefore, many of these were investigated as potential vaccine targets for tick-control strategies. The present study aimed to select transcripts corresponding to putative immunogenic proteins in the A. sculptum gut epithelial membrane, produce recombinant proteins and evaluate them as antigens against A. sculptum infestations. Three gut proteins - AsMucin, AsAPP, and AsLAMP - and a chimeric protein (rAsChimera) based on 22 peptides containing putative B cell epitopes from seven different gut proteins were evaluated as anti-A. sculptum antigens. Mice immunizations revealed that all recombinant targets elicited humoral response with significantly increased IgG levels compared to controls. For rAsChimera, IgG levels remained significantly higher than controls up to 75 days after the end of the immunization. Challenge trials revealed that vaccination with the chimeric protein was the most effective against A. sculptum, inducing 100 % nymph mortality and reaching 80.8 % efficacy against females. The other three proteins did not induce relevant protection, as AsAPP had only 26.6 % efficacy, whereas AsMucin and AsLAMP induced no protection. These data indicate that targeting gut protein immunogenic regions may be an effective strategy for a vaccine formulation againstA. sculptum.