First evaluation of the peptide RmS-17 immunization against Rhipicephalus microplus: a controlled trial in cattle.

Abstract

Rhipicephalus microplus is the most significant tick affecting cattle globally. Chemical acaricides are the main control method, but improper use has led to resistant tick strains. In this context, anti-tick vaccines offer a sustainable alternative for integrated tick management, helping to reduce tick infestation in cattle production. Therefore, it is important to evaluate promising antigens for developing anti-tick vaccines. This study evaluated the efficacy of the peptide RmS-17 on R. microplus tick biology through a controlled trial in cattle. Fifteen Bos taurus calves were distributed into three experimental groups (n&#xa0;=&#xa0;5): Group 1: pRmS-17, Group 2: Bm86 antigen (control +), and Group 3: saline/adjuvant (control). Cattle received three immunizations of 100&#xa0;&#x3bc;g/dose at weeks 0, 4, and 6, followed by a challenge infestation with 5000 R. microplus larvae at week 7. IgG antibody levels were measured using ELISA and confirmed with Western blot; also, the reproductive performance of R. microplus was assessed. Animals immunized with the pRmS-17 showed a significant effect on tick biological parameters, with reductions in adult female tick numbers (40&#xa0;%), oviposition (28&#xa0;%), and larvae hatching (31&#xa0;%) (P&#xa0;<&#xa0;0.05), resulting in an overall efficacy of 70&#xa0;%. The Bm86 antigen showed an overall efficacy of 67&#xa0;%. The pRmS-17-immunized calves developed a strong humoral immune response, characterized by high IgG levels, and Western blot confirmed the immunogenicity of the peptide. Additionally, the negative correlation between antibody levels and reduction in the number of ticks collected indicated that the effect of pRmS-17 was a result of the antibody response in cattle. Bm86-immunized calves had results similar to previous reports. In conclusion, the results indicate that the pRmS-17 antigen has the potential to induce immune protection, making it a promising candidate for a next-generation tick vaccine, and support further studies to validate its usefulness under diverse production systems.