Tick vaccines are important component of integrated pest management for sustainable control of tick and tick born diseases. Immune responses against rHaa86 (homologue of Bm86) recombinant Hyalomma tick antigen were determined in experimental crossbred calves. The humoral antibody responses of the calves were measured against rHaa86 in an optimized ELISA format. The expression of the interferon gamma (IFN-γ), was also evaluated in the culture supernatant of blood culture from blood samples of the experimental calves. The expression patterns were studied after stimulating the blood cells in vitro with rHaa86 antigen and subsequently optical density was measured against IFN-γ. The results were expressed as stimulation indices. All the rHaa86 immunized animal showed strong humoral antibody response just after 1st vaccination and reach to pick after 2nd booster and thereafter maintained up to days 120 from post primary immunization. The humoral antibody response was dominated by IgG1 against IgG2 throughout the period of antibody monitoring. The standard graph of bovine recombinant IFN-γ was plotted which showed a significant difference in SI and OD value up to 200 pg/ml. The lowest detectable value of IFN-γ was 20 pg/ml and SI at this level is 1.16 which is greater than maximum SI calculated from individual calf. The IFN-γ response never reached at significant level and the IgG1 response was dominated over IgG2 response throughout the period of experiment. Since IgG2 and IFN-γ are interlinked, the present study established the Th2 response as a possible mode of mechanism of conferring antibody mediated protection against challenged ticks.
Keywords: Hyalomma; IFN-γ; IgG1; IgG2; rHaa86.