Abstract
Background: Patients with pulmonary tuberculosis (TB) typically produce sputa, which are used to identify the pathogen. Sputum also contains host proteins that may aid in diagnosis. We hypothesized that sputa from TB patients will have unique proteomes when compared to other lung diseases. Methods: Sputa were collected from 219 patients with suspected TB. Neutrophil-derived protein calprotectin (CP), which was used as a marker for lung damage, was quantified and compared between TB and non-TB groups. Three sputa with high or low CP from each group were selected and analyzed using label-free proteomics. Results: There was no difference in CP amounts between TB and non-TB groups. However, TB samples had other differentially abundant neutrophil-associated proteins. Compared to low CP, samples with high CP had much smaller number of proteins that could differentiate between TB and non-TB groups. Only two proteins, MUC5AC and MMP8, were more abundant in TB samples, regardless of CP levels. Conclusions: Our findings suggest that TB sputa may have unique proteomes that depend on CP levels, which should be further validated due to the small sample size. Therefore, controlled and more advanced TB may need a different set of biomarkers to reliably distinguish TB from other lung diseases.