Analysis of immunogenic interactions among recombinant antigens in experimental multicomponent vaccines against ticks

Ticks are obligate ectoparasites that are associated with pathogen transmission and economic losses in the cattle industry. In Brazil, there is only one available vaccine against Rhipicephalus microplus based on a single antigen (Bm86), which has variable efficacy (0-51%) influenced by factors such as tick population and geographical region, highlighting the need for alternative vaccine approaches. This study evaluated the immunogenic interaction among three recombinant proteins from R. microplus, previously evaluated individually for their immunogenicity (neprilysin, inositol monophosphatase and scoloptoxin 14-like) whether different antigen proportions could influence the antibody response in experimental cocktail formulations. The recombinant proteins were expressed separately in Escherichia coli strain BL21 (DE3) Star, purified using urea, and quantified. Vaccine formulations containing different concentrations of the three proteins were formulated and emulsified in Montanide ISA 61 VG adjuvant with shared antigen ratios to assess potential immunogenic interactions. New Zealand White rabbits (n = 1 per group) were subcutaneously immunized with three doses administrated at two-week intervals. Avidity and antibody levels for each antigen were evaluated by indirect ELISA from blood samples collected before first dose, after each dose and fifteen days following the third dose. The results indicate potential interactions among the antigens under the tested conditions, while the antibody response profile may support a two-dose vaccination regimen in future studies. Avidity test suggest that all formulations induced the production of antibodies with similar avidity against the three antigens, regardless of their proportions. The recombinant protein inositol monophosphatase exhibited lower antibody levels compared to other antigens, implying that adjustments in antigen proportion could be required to achieve a balanced humoral response. These findings support further investigation into the combined use of the three antigens for broader immunological coverage against R. microplus, and the present preliminary data are now guiding an ongoing experiment with four rabbits per group.