Species-specific Interferon-Gamma Release Assay for the diagnosis of Mycobacterium abscessus complex infection in Cystic Fibrosis patients

Abstract

<i>Mycobacterium abscessus</i> complex (MABC) infection in Cystic Fibrosis (CF) patients has devastating impact on the course of CF disease. Diagnosis of MABC pulmonary disease in CF patients is challenging and current diagnostic approaches lack accuracy. In this study, we aimed to establish a MABC-specific interferon-gamma release assay to aid in the diagnosis of MABC infection in CF patients. Four species-specific proteins of MABC identified in former studies were overexpressed in an E. coli expression system. Purified proteins were used to stimulate study subjects’ peripheral blood mononuclear cells in an ELISpot assay. Interferon-γ response of 13 subjects with established diagnosis of MABC infection (10 CF, 3 non-CF) was compared to 18 controls distributed to three control groups, CF subjects without NTM infection, subjects with NTM infection other than MABC, and subjects with tuberculosis. Cellular in vitro responses in the MABC group were stronger than in the control groups, especially towards the protein MAB_0405c (50 vs. 11 spots per 300,000 PBMC, p=0.016; data represent mean values) and particularly for the subgroup of CF subjects (55 vs. 6 spots, p=0.008). In conclusion, this assay identifies MAB_0405c as a protein that may stimulate MABC-specific interferon-γ secretion and thus may add to the diagnosis of MABC infection in affected patients.