Abstract
Bovine brucellosis caused by B. abortus is endemic in cattle in Bangladesh. It is a top priority zoonotic disease in Bangladesh. There is an urgent need to control brucellosis in livestock of Bangladesh. Although vaccination is employed in many countries to control bovine brucellosis but Brucella vaccines are not available to use in livestock in Bangladesh. The objective of this study was to develop inactivated B. abortus vaccines using B. abortus biovar 3 isolated from cattle in Bangladesh. Two inactivated B. abortus vaccine: B. abortus vaccine was prepared. Preclinical efficacy trail of the vaccines were conducted in mice. BALB/c mice at 6-8 weeks of age were immunized subcutaneously with B. abortus alum and oil adjuvant vaccines. Booster vaccine was administered at 28 days post vaccination (DPV). Challenge infection of vaccinated and control mice was given at 42 DPV with virulent B. abortus biovar 3. Sera were collected from five randomly selected mice at 7, 14, 21, 28, 35 and 42 DPV for detection of antibody response by rose Bengal plate test (RBPT), Indirect ELISA. Bacterial load in the spleen of mice were determined at 7 days post challenge. Cell mediated immune response (CMI) in vaccinated mice was measured by delayed type hypersensitivity (DTH) reaction. B. abortus specific antibody response was detected in 80% vaccinated mice by RBPT. The ELISA OD value of sera of alum and oil adjuvant vaccinated mice were (0.152±0.06 and 0.244±0.02),(0.155±0.02 and 0.252±0.003),(0.45±0.02 and 0.546±0.030), (0.65±0.01 and 0.575±0.009),(0.69±0.11 and0.696±0.005), (0.626±0.08 and 0.702±0.061) and (0.616±0.08) and 0.782±0.083) at 0, 7, 14, 21, 28, 35 and 42 DPV, respectively (p<0.05). Bacterial load of alum and oil adjuvant vaccinated mice (log105.64±0.43 cfu/g and and log105.35±0.50 cfu/g ) was significantly reduced as compared to unvaccinated control (log106.45±0.78 cfu/g) (p<0.05). Swelling of footpad of mice was observed (1.16±0.13 mm, 1.14±0.16 mm and 0.96± 0.10 mm at 24hr, 48hr and 72hr, respectively). Data of this study indicates that inactivated B. abortus vaccine induces both humoral and CMI response and confer protection in mice against virulent challenge infection. Field trail of the inactivated vaccines in dairy cattle is under progress.
