Autophagy induced by human neutrophil exovesicles controls intracellular growth of Mycobacterium tuberculosis H37Rv in autologous macrophages

Abstract

Abstract We have previously shown that human neutrophils (NEU) stimulated with live Mycobacterium tuberculosis H37Rv (Mtb) release exovesicles, named EXO-Mtb. When autologous macrophages were incubated with EXO-Mtb, they increased the expression of CD86 and MHC II and produced inflammatory cytokines. Here we demonstrate that EXO-Mtb can also reduce the intracellular load of Mtb in autologous macrophages. Since autophagy has been shown to control mycobacterial growth, LC3II expression was measured on infected macrophages after incubation with EXO-Mtb (4, 6 and 24h). Control EXO preparations included those released spontaneously from NEU, or after stimulation with PMA or fMLP. Our results showed that of all EXO preparations used, EXO-Mtb induced the largest amounts of LC3II protein, which correlates with a significant reduction of colony forming units (CFU). This phenomenon could be reverted with the addition of Wortmannin, an autophagy inhibitor. It is important to remark that there was not a 100% control of intracellular mycobacterial growth. Further experiments should be done to better understand the role of ectosomes in NEU-macrophage communication through exovesicles.