Avaliação de um teste imunoenzimático indireto (ELISAi) na detecção de anticorpos anti Brucella abortus em novilhas imunizadas com vacina amostra B19

Abstract

Bovine brucellosis is an infectious disease caused traditionally by the bacteria Brucella abortus. Diagnosis by serological methods and vaccination with the B. abortus B19 strain are the conventional and traditional forms of disease control. The standard official serological screening test in Brazil is Acidified Antigen (AAT), however, it is not accepted internationally and further tests are necessary for its validation. Given the above, the objective was to evaluate and validate an indirect ELISA protocol using serum from vaccinated animals having, as an antigen for sensitizing the polystyrene plate, soluble molecules extracted from a commercial vaccine of Brucella abortus sample B19. In parallel, the AAT test was used as a control for the results obtained. For this purpose, sera were collected from 22 heifers vaccinated with B19 in rural properties in the municipalities of Jerônimo Monteiro, Alegre and São José do Calçado, Espírito Santo, Brazil, at the maximum times of eight, 12 and 16 months after vaccination with B19 and submitted to indirect ELISA and AAT tests to verify the qualitative presence of antibodies. The results were evaluated using the Chi-square statistical tests of two variables to verify the association between the results. The Kappa agreement index was calculated, as well as sensitivity and specificity, and positive and negative predictive values. The ELISAi protocol, using soluble antigens from the commercial vaccine of Brucella abortus in this experiment, showed sensitivity (0.7826) and specificity (0.3023), reaching the objective of this experiment to detect anti-brucella antibodies in impoverished females vaccinated with B19 at the time eight, 12 and 16 months after vaccination. However, it was observed that there is no significant association between the results of the AAT and ELISAi tests as shown by the chi-square test for the 2x2 contingency table (χ2 = 0.545, p = 0.46).