Late Breaking Abstract - Use of non-tuberculous mycobacteria (NTM) specific antigens to detect NTM infection

Diagnosing non-tuberculous mycobacteria (NTM) infection is important to discard tuberculosis (TB) infection when test results are discordant and could be useful to handle patients with pulmonary infectious diseases (PID) with NTM isolations of unclear clinical relevance. This study, describes an immunological NTM-Interferon-gamma (IFN-γ) Release Assay (IGRA) that we have developed using specific NTM antigens to detect NTM sensitization. We enrolled 342 patients: 90 latently TB infected (LTBI), 69 active TB, 60 NTM culture positive, 13 NTM infection suspicion (positive TST, negative IGRA and no BCG vaccination record), 53 HIV positive (4 also LTBI), 32 unknown etiology lymphadenopathies, 3 non-NTM lymphadenopathies, and 22 uninfected controls with no TB exposure record. Peripheral blood mononuclear cells were isolated from whole blood samples. Cells were then stimulated overnight with NTM specific antigens. Detection of IFN-γ producing cells was evaluated by ELISPOT. NTM positive and suspicion groups had a significantly higher count of INF-γ-producing cells after NTM-antigen sensitization. Using ROC curve analysis, a positivity cut-off of 6 spots was determined. NTM suspicion, NTM positive and non-culture confirmed lymphadenopathies groups, had a higher number of positive results than LTBI, HIV positive, and active TB patients (76.9%, 73.3% and 37.5%, 26.7%, 22.6%, 17.4%, respectively). Uninfected individuals and those with non-NTM lymphadenopathies were negative. NTM-IGRA could serve as an NTM infection diagnosis test aiding clinicians in the patient’s clinical evaluation and treatment decision-making. Ongoing studies are focused on characterizing the immune response against these antigens.