The cattle ticks, Rhipicephalus (Boophilus) spp., affect cattle production in tropical and subtropical regions of the world. Tick
vaccines constitute a cost-effective and environmentally friendly alternative to tick control. The recombinant Rhipicephalus microplus Bm86
antigen has been shown to protect cattle against
tick infestations. However, variable efficacy of Bm86-based
vaccines against geographic tick strains has encouraged the research for additional tick-protective
antigens. Herein, we describe the analysis of R. microplus
glutathione-S transferase,
ubiquitin (UBQ),
selenoprotein W, elongation factor-1 alpha, and subolesin (SUB) complementary DNAs (cDNAs) by RNA interference (RNAi) in R. microplus and Rhipicephalus annulatus. Candidate protective
antigens were selected for vaccination experiments based on the effect of gene knockdown on tick mortality, feeding, and fertility. Two
cDNA clones encoding for UBQ and SUB were used for cattle vaccination and infestation with R. microplus and R. annulatus. Control groups were immunized with recombinant Bm86 or adjuvant/saline. The highest
vaccine efficacy for the control of
tick infestations was obtained for Bm86. Although with low immunogenic response, the results with the SUB
vaccine encourage further investigations on the use of recombinant subolesin alone or in combination with other
antigens for the control of cattle
tick infestations. The UBQ
peptide showed low immunogenicity, and the results of the vaccination trial were inconclusive to assess the protective efficacy of this
antigen. These experiments showed that RNAi could be used for the selection of candidate tick-protective
antigens. However, vaccination trials are necessary to evaluate the effect of recombinant
antigens in the control of
tick infestations, a process that requires efficient
recombinant protein production and formulation systems.