Cell-mediated immune response evaluation of live in-vivo attenuated and killed vaccines against Babesia bigemina in calves

Abstract

Abstract The economic significance of babesiosis to the cattle population demands the adoption of alternate, effective and safe prophylactic measures. The current study aimed to develop an effective vaccine against babesiosis caused by B. bigemina. A total (n = 20) six months old, cattle calves were divided into four groups (A, B, C and D; five per group). Group A was inoculated with 2.5 x 106 B. bigemina-infected RBCs propagated and attenuated in-vivo in a rabbit model as a live attenuated vaccine, and Group B was subcutaneously administered with 2 x 106 B. bigemina merozoites as a killed vaccine having Montanide oil. Group C served as the B. bigemina-infected group, while Group D was an uninfected healthy control group. Group B was administered with a booster dose at the same dose on the 14th day post-primary immunization. Both groups, A and B, were challenged with exposure to five B. bigemina-infected Rhipicephalus microplus ticks on the 30th day post-vaccination. Blood samples were collected from all groups at day 0, 7th, and two-week intervals up to three months to evaluate cell-mediated immune response. Group A exhibited the highest cell-mediated immune response among all the groups, with higher protection at post-immunization and post-challenge stage. The significantly higher quantification of CD8 + and CD4 + T cells was associated with the protective potential of live attenuated B. bigemina vaccinated calves (Group A) than killed B. bigemina vaccinated calves (Group B) up to day 100 post-challenge. Based on these results, the live attenuated B. bigemina vaccine from local isolates can be used for prophylaxis against this disease to overcome the economic losses in cattle farming in the future.