New S19 Mutant to Improve Distinction Between Infected and Vaccinated Animals.

Background: Using 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.

Objectives: The aim of this study was to employ gene knockout S19 for the first time to eliminate diagnostic defects and obtain the attenuated mutant strain.

Material And Methods: The gene, which is one of the LPS O-chain coding genes, was knocked out in vaccinal S19. The proliferative response and immunoglobulin M production were analyzed in deletion strain-infected BALB/c mice.

Results: The loss of 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, mutant did not induce any IgM antibody response using the enzyme-linked immunosorbent assay.

Conclusions: 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.