Brucellosis is an important zoonotic disease causing huge economic losses worldwide. Currently no effective immunotherapy for Brucellosis or any biomarker to monitor the efficacy of therapy is available. Treatment is ineffective and animals remain carrier lifelong. S19 and RB51 are live attenuated vaccine strains of Brucella abortus. However, S19 induces only antibody, ineffective for intracellular pathogen. RB51 induces cell mediated immunity (CMI) but it is Rifampicin resistant. Both organisms are secreted in milk and can infect humans and cause abortions in animals. Phage lysed bacteria (lysates) retain maximum immunogenicity as opposed to killing by heat or chemicals. We report here the successful immunotherapy of bovine Brucellosis by phage lysates of RB51 (RL) and S19 (SL). The SL induced strong antibody response and RL stimulated CMI. In vitro restimulation of leukocytes from RL immunized cattle induced interferon gamma production. A single subcutaneous dose of 2 ml of cocktail lysate (both RL and SL), eliminated live virulent Brucella from Brucellosis affected cattle with plasma level of Brucella specific 223 bp amplicon undetectable by RT-PCR and blood negative for live Brucella by culture in 3 months post-immunization. This is the first report on minimally invasive monitoring of the efficacy of antibacterial therapy employing plasma RNA specific for live bacteria as a biomarker as well as on the use of RB51 phage lysate for successful immunotherapy of Brucellosis in cattle.
Brucellosis is an important re-emerging zoonotic disease caused by Brucella organisms. In the absence of a Differentiation of Infected from Vaccinated Animal (DIVA) assay for bovine Brucellosis, it becomes difficult to assess whether the anti-Brucella antibody response in an animal is due to vaccination or infection. We compared the anti-Brucella antibody titers of naturally Brucellosis affected unvaccinated cows, previously vaccinated infected cows, normal healthy vaccinated cows and healthy unvaccinated calves. The titers of anti-Brucella antibodies were estimated by indirect ELISA. The mean titer (log 10 ) was found to be 1.518 ± 0.005 in case of naturally Brucellosis affected cattle which had been vaccinated during calf hood. The mean titer in case of naturally infected cattle which had never been vaccinated was 1.5441 ± 0.005. The mean titer in healthy unaffected cattle vaccinated during calf hood was 1.504 ± 0.002 and that of unvaccinated healthy calves was 0.560 ± 0.016. It was interesting to find that the antibody titers in naturally affected cattle which had never been vaccinated were very significantly (p < 0.01) higher than those of Brucellosis affected cows which had been vaccinated during calf hood. The titer in vaccinated infected cattle was very significantly (p < 0.01) higher than that of uninfected vaccinated cows.
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