Evaluation of a novel microbiological test for latent tuberculosis infection in Ethiopia

An estimated one-third of the global population is believed to be infected with tuberculosis (TB). However, only 10-20% of these infected develop clinical TB. The two tests currently in use for the diagnosis of infection, the tuberculin skin test or the interferon-gamma release assay, do not discriminate these 10 - 20% who harbor the bacilli from those who have no infection. The current project aims to develop qRT-PCR to detect Mycobacterium tuberculosis complex (MTBC) DNA in CD34+ peripheral mononuclear cells (PBMC). The main objective is to determine whether MTBC DNA can be detected by qRT-PCR in CD34+ PBMC isolated from asymptomatic Ethiopian adults and establish correlation between results of the qRT-PCR assay and IGRA in the study population. The study is cross-sectional with nested prospective component. Four cohorts (n = 100 each) of TB index cases, healthy contacts, healthy contacts of bovine index cases, and HIV-infected adults about to receive isoniazid preventive therapy will be selected from DOTS centers in Addis Ababa, Ethiopia. Each cohort will be selected based on specific inclusion criteria but all study participants will be of age 18 years or above and must give a written consent to participate in the study. The study involves the following activities: screening and enrollment of potential participants; collection and storage of data; comparative intradermal tuberculin test; slaughter and post-mortem examination of cattle; collection and culturing of sputum; IGRA tests; CD34+ cell isolation and qRT-PCR assay; HIV serology; CD4+ count; Biomarker identification from IGRA supernatants; next generation sequencing and preparation of amplicons libraries; urine, serum/plasma biomarker identification; RNA biomarker identification; and radiology assessment. Results of the study will have a significant contribution to achieve WHO`s target of TB elimination by 2050.