Abstract

Introduction Tuberculosis (TB) is an infectious airborne disease caused by Mycobacterium tuberculosis (Mtb). Active TB diagnosis requires direct detection of Mtb in usually difficult-to-obtain clinical samples. Therefore, better and non-invasive diagnostic tools are urgently required. We aimed to evaluate the humoral immunity in saliva from patients with active pulmonary TB to reveal possible biomarkers of TB disease. Methods Nineteen subjects with confirmed pulmonary TB (active TB) and 49 controls (uninfected individuals) were recruited. Saliva samples were processed and stored at -80ºC until measurement. A multiplexed Luminex-based immunoassay was developed to detect immunoglobulins (IgA) against twelve immunogenic Mtb antigens in saliva. Fluorescence signals were read with MAGPIX. Statistical analysis was performed with the Mann–Whitney U test (p<0.05 was considered as statistically significant). Results Significantly higher specific IgA levels were found in active TB for all Mtb antigen compared to control group. The highest discriminatory value were obtained for IgA anti-cell membrane fraction (p<0.0001; AUC=0.85) and IgA anti-lipoarabinomannan (LAM) (p<0.0001; AUC=0.82). Conclusions Our Luminex-based immunoassay successfully detected specific anti-Mtb antigens IgA in saliva from patients with active TB with higher fluorescence values than control. The best discriminatory performance to differentiate active TB from control was for IgA anti-cell membrane fraction and anti-LAM. Additional larger studies are necessary to validate these results. FONDECYT Regular 1171570 and 1191874.