Autophagy induction targeting mTORC1 enhances Mycobacterium tuberculosis replication in HIV co-infected human macrophages

Abstract

To survive and replicate in macrophages Mycobacterium tuberculosis (Mtb) has developed strategies to subvert host defence mechanisms, including autophagy. Autophagy induction has the potential to clear Mtb, but little is known about its effect during controlled tuberculosis and HIV co-infection. Mammalian target of rapamycin complex1 (mTORC1) inhibitors were used to induce autophagy in human macrophages pre-infected with HIV-1BaL and infected with a low dose of Mtb (co-infected), or single Mtb infected (single infected). The controlled Mtb infection was disrupted upon mTOR inhibition resulting in increased Mtb replication in a dose-dependent manner which was more pronounced during co-infection. The increased Mtb replication could be explained by the marked reduction in phagosome acidification upon mTOR inhibition. Autophagy stimulation targeting mTORC1 clearly induced a basal autophagy with flux that was unlinked to the subcellular environment of the Mtb vacuoles, which showed a concurrent suppression in acidification and maturation/flux. Overall our findings indicate that mTOR inhibition during Mtb or HIV/Mtb co-infection interferes with phagosomal maturation, thereby supporting mycobacterial growth during low-dose and controlled infection. Therefore pharmacological induction of autophagy through targeting of the canonical mTORC1-pathway should be handled with caution during controlled tuberculosis, since this could have serious consequences for patients with HIV/Mtb co-infection.

Bacterial Pathogens versus Autophagy: Implications for Therapeutic Interventions

“…However, the differences in bacterial burden tend to be less than 2.5 fold[41,44,103,104]. In addition, a recent study found that in macrophages coinfected with HIV and M. tuberculosis , stimulation of autophagy with rapamycin actually led to increased M. tuberculosis survival[106]. Thus, it will be critical to determine the impact of comorbidities such as HIV when perusing options for clinical intervention.…”

Efferocytosis of Apoptotic Neutrophils Enhances Control of <b><i>Mycobacterium tuberculosis</i></b> in HIV-Coinfected Macrophages in a Myeloperoxidase-Dependent Manner

“…For GFP-expressing M. tuberculosis the medium was supplemented with 20 µg/mL of kanamycin, and for luciferase-expressing M. tuberculosis 100 µg/mL of hygromycin was used. For infection, the bacteria were prepared as previously described [28].…”

“…Macrophages were infected with 0.06 ng/mL HIV-1BaL (Lot p4238), produced as previously described [28], for 1 week prior to M. tuberculosis infection at MOI = 1-5. After M. tuberculosis infection the macrophages were incubated with apoptotic neutrophils (1: 2) for different time points, depending on the experiment.…”

“…Macrophages were infected for 1.5 h prior to washing and the addition of apoptotic neutrophils for a total of 24 h when the cells were collected and Western blot was performed as previously described [28]. The antibodies were: rabbit monoclonal anti-LC3B (D11; cat.…”

Interplay of human macrophages and Mycobacterium tuberculosis phenotypes

“…Autophagy is generally believed to be host beneficial and leads to a decrease of Mtb burden in mice [94,191], but pharmacological induction of autophagy has also been shown to facilitate bacterial growth inside macrophage infected with a low burden of Mtb [192].…”