Comparison of humoral immune responses between cattle and buffaloes immunized with commercial brucella abortus strain RB51 vaccine in Bangladesh

Background: The effective control and eradication of brucellosis can be achieved by rapid and accurate diagnosis and effective vaccination but both have limitations. Therefore, brucellosis research is currently focused on the improvement of the diagnosis and vaccine induced prophylaxis. Moreover, diagnostic tests and immunization have not been thoroughly studied in buffaloes and even not compared with cattle. Therefore, the comparative evaluation of the immunological responses of Brucella vaccinated cattle and buffaloes would be required for both the diagnosis and vaccine induced efficacy. Objectives: The main objective of this study was to compare the humoral immune response (HIR) between cattle and buffalo cows immunized with B. abortus RB51 vaccine by using indirect ELISA Materials and Methods: Each of the three randomly selected B. abortus sero-negative native cows and three buffaloes received 2.0 ml imported commercial B. abortus SRB51 vaccine subcutaneously in the neck region at day 0 and then booster dose at 60 days after first vaccination with similar dose and route. Each of the collected serum samples of both the cattle and buffaloes was tested to detect the antibody status by using commercial indirect ELISA kit. Results: The results showed that the OD value of the serum of cows and buffalos before inoculation of RB51 B. abortus vaccine was 0.088 ± 0.009 and 0.096  0.011 at 0 week and 0.124 ± 0.018 and 0.111  0.010 at 1st week, near about the negative control OD value (0.106). After that, the OD value started to rise from the 2nd week (OD value (0.144 ± 0.023 and 0.1333  0.007) and reached to a peak level at 90 days (OD value 0.376  0.0080 and 0.316  0.219) and then started to decline from 120 days (OD value 0.2963  0.0416 and 0.2863  0.070) to 180 days (OD value 0.1943 0.073 and 0.176 0.172) in cows and buffalos respectively. Conclusion: This study suggests that the RB51 vaccination has induced satisfactory HIR with initial inoculation but significantly higher immune responses with booster immunization which enhancing immunity against both in the cattle and buffaloes. The CMI plays major role in protection against brucellosis needs further investigation in both cattle and buffaloes in Bangladesh.