Roadmap for the development of diagnostic test for bTB

What are we trying to achieve and why? What is the problem we are trying to solve?

To exploit the M. bovis whole-genome sequence to identify antigens with diagnostic potential.

What are the scientific and technological challenges
(knowledge gaps needing to be addressed)?

• Challenge to understand how TB benefits from major antigens being highly conserved and under purifying selection.
• Relatively limited genome diversity within the major M. bovis clonal complexes; some are fixed by location.
• Development of standardised nomenclature linking MLVA(Multiple-Locus Variable number tandem repeat Analysis) and spoligotyping with Whole Genome Sequencing data.
• Whole-genome sequencing provides unprecedented resolution; MLVA and spoligo data are highly correlated with it, although rare homoplasy evident.

What approaches could/should be taken to address the research question?

• Ongoing genome annotation, identification of ORFs, gene expression and regulation (epigenetics), post-translational modification etc.
• Comparative genomics within the MTBC (Mycobacterium Tuberculosis Complex) and beyond.
• Bioinformatics T- and B-cell epitope mapping.
• Structure and function prediction.
• Identification of potential DIVA (Differentiation of Infected from Vaccinated Animals) diagnostic reagents.
• Identification of molecularly defined PPDs.
• Comparative genomics to investigate and control cross-reactivity.

What else needs to be done before we can solve this need?

Existing knowledge including successes and failures

A 24-loci MIRU-VNTR (Mycobacterial Interspersed Repetitive Units – Variable Number Tandem Repeat)genotyping is the gold standard for human TB diagnosis.
Reference and research labs increasingly transitioning to whole genome-enabled approaches.