Antigen mining with iterative genome screens identifies novel diagnostics for the Mycobacterium tuberculosis complex

Area of Science:

• Immunology and Veterinary Diagnostics
• Bacteriology and Genomics

Background:

• Accurate diagnosis of bovine tuberculosis (TB) is critical, especially when used with Mycobacterium bovis (M. bovis) BCG vaccination.
• Distinguishing between M. bovis infection and BCG vaccination is a significant challenge for current diagnostic tools.

Purpose of the Study:

• To identify novel M. bovis-specific antigens for improved TB diagnosis in cattle.
• To develop diagnostic reagents that can differentiate M. bovis-infected from BCG-vaccinated animals.

Main Methods:

• Comparative genomic analysis of M. bovis, M. avium, and S. coelicolor to identify 42 potential M. bovis-specific antigens.
• High-throughput peptide-based screening of these antigens in cattle experimentally infected with M. bovis, vaccinated with BCG, or unvaccinated (naïve).
• Characterization of immunodominant peptides, including their Major Histocompatibility Complex (MHC) class II restriction.

Main Results:

• Three antigens (Mb2555, Mb2890, Mb3895) showed strong recognition in infected cattle but minimal response in BCG-vaccinated and naïve cattle.
• These antigens were also recognized in animals vaccinated against Johne's disease, indicating potential cross-reactivity with M. avium subsp. paratuberculosis.
• Eight immunodominant peptides from these antigens were identified and characterized for MHC class II restriction (DR and DQ).

Conclusions:

• Mb2555, Mb2890, and Mb3895 are promising candidates for developing specific diagnostic tests for bovine tuberculosis.
• The identified peptides and understanding of cross-reactivity are vital for refining diagnostic strategies and in silico prediction methods.
• Further evaluation in larger field studies is recommended to validate these findings for practical application.