<p>Extracellular vesicles released by J774A.1 macrophages reduce the bacterial load in macrophages and in an experimental mouse model of tuberculosis</p>

Abstract

BackgroundTuberculosis is the leading cause of death by an infectious microorganism worldwide. Conventional treatment lasts at least six months and has adverse effects; therefore, it is important to find therapeutic alternatives that reduce the bacterial load and may reduce the treatment duration. The immune response against tuberculosis can be modulated by several mechanisms, including extracellular vesicles (EVs), which are nano-sized membrane-bound structures that constitute an efficient communication mechanism among immune cells.MethodsThe EVs released by the J774A.1 mouse macrophage cell line, both spontaneously (S-EV) and after infection with Mycobacterium tuberculosis H37Rv (Mtb-EV), were purified by ultra-centrifugation and size-exclusion chromatography. The size distribution and chemical composition of these EVs were evaluated, and their effect on the bacterial load and the production of cytokines was determined in both in vitro and in vivo models of M. tuberculosis infection.ResultsMtb-EV are larger than S-EV, they contain M. tuberculosis-specific antigens (not detected in EVs released from M. fortuitum-infected J774A.1 cells) and are rich in phosphatidylserine, present in their outer membrane layer. S-EV, but not Mtb-EV, reduced the bacterial load and the production of MCP-1 and TNF-α in M. tuberculosis-infected macrophages, and these effects were reversed when phosphatidylserine was blocked with annexin V. Both S-EV and Mtb-EV significantly reduced the lung bacterial load in mice infected with M. tuberculosis after 60 days of treatment, but they had no effect on survival or on the lung pneumonic area of these mice.ConclusionJ774A.1 macrophages infected with M. tuberculosis H37Rv released EVs that differed in size and phosphatidylserine content from spontaneously released EVs, and these EVs also had different biological effects: S-EV reduced the mycobacterial load and the cytokine production in vitro (through a phosphatidylserine-dependent mechanism), while both EVs reduced the lung bacterial load in vivo. These results are the basis for further experiments to evaluate whether EVs improve the efficiency of the conventional treatment for tuberculosis.

The Role of Macrophages in Staphylococcus aureus Infection

“…Indeed, EV from macrophage infected with M. bovis modulated T lymphocytes responses ( 412 ). When macrophages were infected with M. tuberculosis , the content of the EV changed to confer decreased inflammatory cytokine release and decrease lung mycobacterial load ( 413 ). Furthermore, during infection with hepatitis C virus, macrophages secreted EVs that inhibited viral replication ( 414 ).…”

The emerging role of exosomal miRNAs as a diagnostic and therapeutic biomarker in Mycobacterium tuberculosis infection

“…In contrast, both EVs decreased the bacterial lung load in vivo. These results are the foundation for more investigations to assess whether EVs enhance the efficacy of the conventional therapy for tuberculosis (TB) (García-Martínez et al 2019 ) The recent evidence has indicated that the Mtb infection can enhance microvesicle generation in response to iron limitation. These microvesicles carry mycobactin, which can work as an iron donor and promotes the replication of iron-starved mycobacteria.…”

Annexin A1 Regulates NLRP3 Inflammasome Activation and Modifies Lipid Release Profile in Isolated Peritoneal Macrophages

“…The detection of this potential lipid biomarker in both AnxA1 -/supernatants (LPS and nigerin) can be related to the release of extracellular vesicles by macrophages. Macrophages can release extracellular vesicles after Mycobacterium tuberculosis infection, or spontaneously with a high concentration of phosphatidylserine [65].…”