Testing Efficacy of a Conserved Polypeptide from the Bm86 Protein against <i>Rhipicephalus microplus</i> in the Mexican Tropics

• Published in: Vaccines
• Main Authors: Raymundo Coate, Miguel Ángel Alonso-Díaz, Moisés Martínez-Velázquez, Edgar Castro-Saines, Rubén Hernández-Ortiz, Rodolfo Lagunes-Quintanilla
• Format: Article
• Language: English
• Published: MDPI AG 2023-07-01
• Subjects: anti-tick vaccine; Bm86; polypeptide; <i>Rhipicephalus microplus</i>
• Online Access: https://www.mdpi.com/2076-393X/11/7/1267

<i>Rhipicephalus microplus</i> economically impacts cattle production in tropical and subtropical countries. Application of acaricides constitutes the major control method; however, inadequate use has increased resistant tick populations, resulting in environmental and cattle product contamination. Anti-tick vaccines based on the Bm86 antigen are an environmentally friendly, safe, and economically sustainable alternative for controlling <i>R. microplus</i> infestations. Nevertheless, variable efficacy has been experienced against different geographic tick strains. Herein, we evaluated the efficacy of a conserved polypeptide Bm86 derived from a Mexican <i>R. microplus</i> strain previously characterized. Twelve cows were assigned to three experimental groups and immunized with three doses of the polypeptide Bm86 (pBm86), adjuvant/saline alone, and Bm86 antigen (control +), respectively. Specific IgG antibody levels were measured by ELISA and confirmed by Western blot. In addition, the reproductive performance of naturally infested <i>R. microplus</i> was also determined. The more affected parameter was the adult female tick number, with a reduction of 44% by the pBm86 compared to the controls (<i>p</i> < 0.05), showing a vaccine efficacy of 58%. Anti-pBm86 IgG antibodies were immunogenic and capable of recognizing the native Bm86 protein in the eggs, larvae, and guts of <i>R. microplus</i>. The negative correlation between antibody levels and the reduction of naturally tick-infested cattle suggested that the effect of the polypeptide Bm86 was attributed to the antibody response in immunized cattle. In conclusion, the polypeptide Bm86 showed a specific immune response in cattle and conferred protection against <i>R. microplus</i> in a Mexican tropical region. These findings support further experiments with this antigen to demonstrate its effectiveness as a regional vaccine.