Immunization with Brucella abortus S19Δper Conferred Protection in Water Buffaloes against Virulent Challenge with B. abortus Strain S544

Abstract

Vaccination of cattle and buffaloes with Brucella abortus strain 19 has been the mainstay for control of bovine brucellosis. However, vaccination with S19 suffers major drawbacks in terms of its safety and interference with serodiagnosis of clinical infection. Brucella abortus S19∆per, a perosamine synthetase wbkB gene deletion mutant, overcomes the drawbacks of the S19 vaccine strain. The present study aimed to evaluate the potential of Brucella abortus S19Δper vaccine candidate in the natural host, buffaloes. Safety of S19∆per, for animals use, was assessed in guinea pigs. Protective efficacy of vaccine was assessed in buffaloes by immunizing with normal dose (4 × 1010 colony forming units (CFU)/animal) and reduced dose (2 × 109 CFU/animal) of S19Δper and challenged with virulent strain of B. abortus S544 on 300 days post immunization. Bacterial persistency of S19∆per was assessed in buffalo calves after 42 days of inoculation. Different serological, biochemical and pathological studies were performed to evaluate the S19∆per vaccine. The S19Δper immunized animals showed significantly low levels of anti-lipopolysaccharides (LPS) antibodies. All the immunized animals were protected against challenge infection with B. abortus S544. Sera from the majority of S19Δper immunized buffalo calves showed moderate to weak agglutination to RBPT antigen and thereby, could apparently be differentiated from S19 vaccinated and clinically-infected animals. The S19Δper was more sensitive to buffalo serum complement mediated lysis than its parent strain, S19. Animals culled at 6-weeks-post vaccination showed no gross lesions in organs and there was comparatively lower burden of infection in the lymph nodes of S19Δper immunized animals. With attributes of higher safety, strong protective efficacy and potential of differentiating infected from vaccinated animals (DIVA), S19Δper would be a prospective alternate to conventional S19 vaccines for control of bovine brucellosis as proven in buffaloes.

DIVA (Differentiating Infected from Vaccinated Animals) Aşı ve Stratejileri

“…Then S19Δper DIVA capability was assessed by using Rose Bengal Plate Test. As a result the mutant S19Δper with a moderately similar phenotype showed a significant similarity to the S19 vaccine strain with improved immunogenicity, safety and DIVA properties for the bovine brucellosis control, and can thus be used as the DIVA vaccine (Lalsiamthara et al 2015;Chaudhuri et al 2021).…”

Facing the Human and Animal Brucellosis Conundrums: The Forgotten Lessons

“…Still, the quality of controlled studies depends on several experimental requisites that are not easy to implement ( Table 2 ) and, unfortunately, a good understanding of the methodology established many years ago by workers with extensive experience on animal brucellosis is vanishing. This unfortunate event is shown in recent publications that claim the safety and/or efficacy in cattle of influenza virus vectors carrying genes of Brucella L7/L12 or Omp16 [ 138 , 139 , 140 ], a mutant (wrongly characterized as deleted in the perosamine synthetase gene) in buffaloes [ 141 ] and a 16MΔ vjbR mutant in small ruminants [ 142 , 143 ]. Likewise, some recent meta-analyses of controlled experiments use publications that do not meet the requisites in Table 2 and apply elaborated statistics to data that are not amenable to quantification and statistical comparisons because of their qualitative character.…”