Interferon-γ-response to mycobacterial glycopeptidolipids in patients with pulmonary non-tuberculous mycobacterial infection.

The understanding of host responses to pulmonary infection with non-tuberculous mycobacteria (NTM) is incomplete and immunodiagnostic tools are not established. Unlike mycobacteria of the Mycobacterium tuberculosis complex, several NTM express glycopeptidolipids (GPLs) in their cell wall. Here, we investigate the interferon-γ response to mycobacterial GPLs and its diagnostic use in patients with pulmonary NTM infection. M. avium-derived GPLs were used for in vitro stimulation of peripheral blood mononuclear cells in an ELISpot assay of patients with pulmonary NTM infection and 3 control groups, (1) patients with tuberculosis (TB), (2) patients with cystic fibrosis without evidence of NTM infection (CF) and (3) healthy controls (HC). Immune responses were compared between the groups and for the subgroup of NTM patients with either M. avium complex (MAC) or M. abscessus complex (MABC). Interferon-γ responses of 31 patients with NTM (16 MABC, 11 MAC, 1 MABC & MAC, and 3 other NTM) were compared to 43 controls (15 TB, 15 CF, 13 HC). Responses to GPLs were significantly stronger in the NTM group compared to controls (13.5 vs. 1.5 spots per 300,000 PBMC, p < 0.0001, data represent median values). MAC patients had an overall stronger reaction than MABC patients. Assay sensitivity and specificity were 64 and 98% for MAC, 19 and 95% for MABC, and 32 and 98% for all NTM, respectively. Mycobacterial GPLs are potent drivers of interferon-γ-responses. Patients with pulmonary NTM infection show stronger immune responses to GPLs compared to uninfected participants, making GPLs a promising target for the development of NTM immune diagnostic tools.