Comparative Analysis on Proteomics Profiles of Intracellular and Extracellular M.tb and BCG From Infected Human Macrophages

Abstract

Tuberculosis is the second cause in infectious diseases leading to human death. Understanding the virulence mechanism is inevitable if the disease needs to be fully cured. Therefore, this study aimed to reveal this mechanism by comparing proteomic profiles of intracellular and extracellular virulent strainM.tband bacille Calmette–Guérin (BCG) from infected THP-1cells. First,M.tband BCG infected THP-1 at MOI 10:1. Twelve hours postinfection, intracellular bacteria ofM.tband BCG were collected, whereas the two bacilli cultured in 7H9 broth media were used as the control. Then four groups of bacilli were subjected to proteomic analysis, and differential proteomic profiles betweenM.tband BCG were comparatively analyzed with bioinformatics tools. As a result, we identified a total of 1,557 proteins. Further, they were divided into four groups for comparison ofM.tbversus BCG under 7H9 culture (shorten as out),M.tbin (intracellular) versusM.tbout, BCG in versus BCG out andM.tbin versus BCG in. BetweenM.tbin versus BCG in, a total of 211 differentially expressed proteins were found. Eight proteins like ESAT-6 distributed in six RDs and some known proteins related to virulence. Besides, five uncharacterized proteins were differentially expressed. Further analysis revealed enriched pathways were associated with glyoxylate and dicarboxylate metabolism pathways. InM.tbout versus BCG out, a total of 144 differential proteins were identified and mainly involved in metabolism pathways. Then, 121 differential proteins in the group ofM.tbin versusM.tbout were enriched in ribosome and oxidative phosphorylation related to adaptation to the host environment. The group of BCG in versus BCG out shared the same trend of different pathways to theM.tbin versusM.tbout. Finally, 42 proteins were identified to be up-regulated only in intracellularM.tbincluding eight RD proteins, whereas 22 up-regulated uniquely in intracellular BCG. Besides, only two proteins (Pks13 and Rv1405c) were commonly up-regulated in intracellularM.tband BCG. Further, some unknown proteins were uniquely up-regulated in the intracellularM.tband BCG. These findings provide valuable data for further exploration of molecular mechanism forM.tbvirulence and BCG immune response.