A protein signature associated with active tuberculosis identified by plasma profiling and network-based analysis

Objectives: Tuberculosis (TB) is a bacterial infectious disease caused by Mycobacterium tuberculosis. Annually, an estimated 10 million people are diagnosed with active TB, and approximately 1.4 million dies of the disease. If left untreated, each person with active TB will infect 10 to 15 new individuals every year. Therefore, interrupting disease transmission by accurate early detection and diagnosis, paired with appropriate treatment is of major importance. In this study, we aimed to identify biomarkers associated with the development of active TB that can then be further developed for clinical testing. Methods: We assessed the relative plasma concentration of 92 proteins associated with inflammation in individuals with active TB (n=19), latent TB (n=13), or healthy controls (n=10). We then constructed weighted protein co-expression networks to reveal correlations between protein expression profiles in all samples. After clustering the networks into four modules, we assessed their association with active TB. Results: One module consisting of 16 proteins was highly associated with active TB. We used multiple independent transcriptomic datasets from studies investigating respiratory infections and non-TB diseases. We then identified and removed genes encoding proteins within the module that were low expressed in active TB or associated with non-TB diseases, resulting in a 12-protein plasma signature associated with active TB. Conclusion: We identified a plasma protein signature that is highly enriched in patients with active TB but not in individuals with latent TB or healthy controls and that also had minimal cross-reactivity with common viral or bacterial lower respiratory tract infections.