Evaluation of Cocktails with Recombinant Proteins of Mycobacterium bovis for a Specific Diagnosis of Bovine Tuberculosis

The Delayed type hypersensitivity skin test (DTH) and interferon-gamma assay are used for the diagnosis of bovine tuberculosis (TBB). The specificity of these diagnoses, however, is compromised because both are based on the response against purified protein derivative of Mycobacterium bovis (PPD-B). In this study, we assessed the potential of two cocktails containing M. bovis recombinant proteins: cocktail 1 (C1): ESAT-6, CFP-10 and MPB83 and cocktail 2 (C2): ESAT-6, CFP-10, MPB83, HspX, TB10.3, and MPB70. C1, C2, and PPD-B showed similar response by DTH in M. bovis-sensitized guinea pigs. Importantly, C1 induced a lower response than PPD-B in M. avium-sensitized guinea pigs. In cattle, C1 displayed better performance than PPD-B and C2; indeed, C1 showed the least detection of animals either vaccinated or Map-infected. To optimize the composition of the cocktails, we obtained protein fractions from PPD-B and tested their immunogenicity in experimentally M. bovis-infected cattle. In one highly reactive fraction, seven proteins were identified. The inclusion of FixB in C1 enhanced the recognition of M. bovis-infected cattle without compromising specificity. Our data provide a promising basis for the future development of a cocktail for TBB detection without interference by the presence of sensitized or infected animals with other mycobacteria.