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?

A reliable test to detect infection at various stages.
Options include biomarker detection of the host response or the organism.
To develop biosignatures (combination of biomarkers) that could inform on the latent/carrier status of an animal and evaluate the risk of Mb shedding and transmission .
Development of tools to identify animals at risk to transmit for targeted elimination to end massive herd culling

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

• Define the stages of infection, i.e., is it like human TB hypothesis?
• Current detection systems for cell-mediated immune responses need improvement.
• Trade-off between test antigen specificity and sensitivity.
• Detecting shedders.
• Differentiating infectious from infected animals. Current tests cannot distinguish exposure from infection; precautionary principle means all immunoreactive cases removed.
• Test should differentiate infected from vaccinated
• A deeper understanding of the host-pathogen interaction and the development of sensitive and specific biomarkers
• Understanding the dynamic nature of host immune responses during different stages of bTB infection is crucial.
• Combination of different biomarkers (mix omics) to define biosignatures of infection
• We need to understand the different clinical states of TB in cattle akin to what is now establish for human TB
• We need to develop easy and affordable tools to identify biosignatures
• We need to identify a biosignature in circulating blood (the easiest and less invasive procedures for sampling large numbers of animals)

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

• Improved skin test with characterised (molecular defined) antigens.
• Establishment of standard banks of tissue, cells and serum from animals with known infection status.
  Serological test.
• Interferon γ test with characterised antigens.
• Other tests of Cell-Mediated Immune responses.
• The identification of biomarkers that can differentiate between early-stage, latent, and active infections.
• Multiplexed analyte/antigen testing, e.g., Luminex.
• Machine learning to scan for biomarkers, e.g., infrared spectroscopy in milk and blood.
• We need to embrace the One Health approach and work together with human TB specialists
• Zoonotic (human) cases tend to be detected as MTBC. No structured surveillance for at risk groups; tend to present to health services with symptoms.

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

Known, preferably stage-specific antigens to which the host responds. We need to establish robust pipelines with all stakeholders￾including bTB surveillance programs- to ensure rigorous and longitudinal follow-up of animals in the field

Existing knowledge including successes and failures

Human biomarker panels. One Health Approach