New Brucella abortus S19 Mutant to Improve Distinction Between Infected and Vaccinated Animals

Abstract

<strong>Background:</strong> Using <em>Brucella abortus</em> Strain 19 (S19) to control bovine brucellosis is restricted due to induce antibodies to the O-side chain of the smooth lipopolysaccharide (LPS) which may be difficult to differentiate vaccinated and infected animals. Furthermore, it is virulent for humans and can induce abortion to cattle.<br /> <strong>Objectives:</strong> The aim of this study was to employ gene knockout <em>B. abortus</em> S19 for the first time to eliminate diagnostic defects and obtain the attenuated mutant strain.<br /> <strong>Material and Methods:</strong> The <em>wbkA</em> gene, which is one of the LPS O-chain coding genes, was knocked out in vaccinal <em>Brucella abortus</em> S19. The proliferative response and immunoglobulin M production were analyzed in<em> wbkA</em> deletion strain-infected BALB/c mice.<br /> <strong>Results:</strong> The loss of <em>wbkA</em> gene function resulted in induction of the splenocyte proliferative response in mice infected by the mutant S19 strain compare to those induced by parental S19 and RB51 strains. Moreover, <em>wbkA</em> mutant did not induce any IgM antibody response using the enzyme-linked immunosorbent assay.<br /> <strong>Conclusions:</strong> As a result, the new mutant S19 strain had deficiency in its LPS O-chain structure, besides cannot induce IgM response then, reduce mistakes to discriminate between vaccinated and infected animal, and also can be considered as a new vaccine candidate.