The intradermal skin test for diagnosis of bovine tuberculosis has been used the purified protein derivative (PPD) of Mycobacterium bovis, that is able to induce a hypersensitivity reaction in infected animals. However, shows low specificity due to the occurrence of cross reactions with other mycobacteria. Thus, the aim of this study was to produce recombinant proteins (ESAT-6, PE13, PE5 and ESX-1) of Mycobacterium bovis and assess them as antigens in skin test using guinea pigs (Cavia porcellus) as a model, and check if the conditions employed in the purification (native or denaturing condition) interfere in the antigenic performance of these proteins. The proteins were tested in guinea pigs previously sensitized with inactivated M. bovis strain AN5, individually (160 µg/µl), or as a mixed cocktail (40 µg each). The cocktail of proteins induced hypersensitivity reactions in sensitized animals significantly (p=0.002) higher than those observed in non-sensitized animals, allowing differentiation. On the other hand, the proteins individually were not able to promote this differentiation. The conditions of solubilization and purification influenced the antigenic performance of the protein ESAT-6, since, when produced in denaturing condition triggered nonspecific reaction in non-sensitized animals. Whereas when produced under native conditions and used at concentrations (6, 12, 24 and 48µg/µl) induced a significant response only in sensitized animals, confirming its potential as antigen.
Bovine PPD; skin test; bovine tuberculosis; Mycobacterium bovis; solubility cattle
