A Rapid Blood Test to Differentiate Latent Tuberculosis from Active Disease 

Funding Mechanism: Congressionally Directed Medical Research Programs (CDMRP) Technology/Therapeutic Development Award  W81XWH-18-1-0253 

Background: Almost 2 billion individuals are infected with Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB). The human cost of TB is enormous. Despite the fact that excellent treatment is available, at least 1.4 million deaths annually are due to TB, and it is the world’s leading cause of death from infectious disease. The World Health Organization (WHO) estimates that >40% of the 10.7 million individuals who fell ill with active TB in 2015 were not diagnosed by their country’s healthcare system. WHO stakeholder analysis stated that the most urgent need is for an accurate, rapid, biomarker-based non-sputum TB triage test that uses a readily accessible sample (e.g., saliva, blood, urine). The desired TB triage test would minimally have 90% sensitivity and 70% specificity, which would significantly narrow the population that needs a costly confirmatory test for active TB disease.

Rationale: Recently, several reports have been published by ourselves and others on putative blood biomarkers that reflect the host response to Mtb infection through human gene expression patterns associated with TB disease. The transcriptional state of circulating blood cells reacts to Mtb infection, and this forms the foundation of a simple to administer blood test. We have discovered and preliminarily tested a gene expression signature based on three genes (GBP5, DUSP3, and KLF2) with excellent predictive powers to discriminate between healthy individuals, those with active TB, and those with other diseases (e.g., a triage TB test). Further, we have also discovered that our three-gene signature signals well before Mtb can be detected in sputum and in fact can differentiate active TB months before it becomes contagious (preclinical TB).

Objective: Our primary long-term objective is to develop a finger-stick triage test using non-stimulated blood that meets or exceeds WHO Target Product Profiles for a rapid biomarker-based non-sputum-based triage test for detecting TB (= 90% sensitivity when compared with the confirmatory test for pulmonary TB and = 70% specificity against a microbiological reference standard). Our secondary objective is to extend our finger-stick test to include biomarkers of preclinical TB.

Specific Aims: We will first use bioinformatics on our worldwide multi-cohort database of RNA expression to select 1-5 genes, which will increase the robustness and performance of our three-gene signature to discriminate active TB, preclinical TB, and healthy, uninfected individuals (Aim 1). We will validate our TB signature using blood from 100 TB Index Cases and 450 household contacts in the Republic of Moldova and transfer the TB signature to a cartridge useable by GeneXpert or Omni Systems (Cepheid Corp., Sunnyvale, California) (Aim 2). Finally, we will test our preclinical research prototype cartridge using blood collected from 1,000 individuals who are being screened for TB in the Republic of Moldova (Aim 3).

Impact: The long-term impact of a new, accurate triage test for TB will dramatically change the way millions of TB suspects are screened everywhere in the world and will likely lead to many more cases of TB being diagnosed and treated early. An accurate test for preclinical TB by diagnosing and treating TB before it becomes contagious would be a major step toward “the elimination of TB as a public health treat by 2050.” The WHO’s global plan to eliminate TB focuses on early diagnosis of TB and systematic screening of contacts and high-risk groups. Our test would facilitate both of these testing goals simultaneously and additionally provide for the identification of individuals who harbor TB but are not infectious to others. TB treatment is low-cost and effective, but new, highly accurate diagnostic tests are necessary to find and treat patients appropriately.

Relevancy: Our proposal is important and relevant to developing improvements in the diagnosis of TB, which is a Peer Reviewed Medical Research Program Fiscal Year 2017 Topic Area, and specifically our proposal targets the focus area of “Development of a diagnostic assay that can be used at the point of care to rapidly and accurately diagnose tuberculosis.” Early case detection and rapid treatment with appropriate drugs are considered the most effective control strategies to reduce TB transmission. Civilians are at increased risk for exposure to TB from many transmission routes including exposure to TB-infected persons entering the United States undetected, long airplane flights, and increased exposure to TB during international travel for leisure or business. US troops are at increased risk of transmission of TB in settings with extreme crowding or limited ventilation, such as berthing areas in ships, barracks, and/or prisons, as well as exposure from visitors to bases, and environments encountered on tactical or humanitarian missions. A new test that offers for the first time a reliable test that can diagnose TB before it becomes contagious is an innovative way to stop the TB epidemic and help the US Armed Forces, US, and WHO reach its goal of eradicating TB as a public health threat by 2050.