IFN-γ-independent control of M. tuberculosis requires CD4 T cell-derived GM-CSF and activation of HIF-1α

Abstract

The prevailing model of protective immunity to tuberculosis is that CD4 T cells produce the cytokine IFN-γ to activate bactericidal mechanisms in infected macrophages. Although IFN-γ-independent CD4 T cell based control of M. tuberculosis infection has been demonstrated in vivo it is unclear whether CD4 T cells are capable of directly activating macrophages to control infection in the absence of IFN-γ. We developed a co-culture model using CD4 T cells isolated from the lungs of infected mice and M. tuberculosis-infected murine bone marrow-derived macrophages (BMDMs) to investigate mechanisms of CD4 dependent control of infection. We found that even in the absence of IFN-γ signaling, CD4 T cells drive macrophage activation, M1 polarization, and control of infection. This IFN-γ-independent control of infection requires activation of the transcription factor HIF-1α and a shift to aerobic glycolysis in infected macrophages. While HIF-1α activation following IFN-γ stimulation requires nitric oxide, HIF-1α-mediated control in the absence of IFN-γ is nitric oxide-independent, indicating that distinct pathways can activate HIF-1α during infection. We show that CD4 T cell-derived GM-CSF is required for IFN-γ-independent control in BMDMs, but that recombinant GM-CSF is insufficient to control infection in BMDMs or alveolar macrophages and does not rescue the absence of control by GM-CSF-deficient T cells. In contrast, recombinant GM-CSF controls infection in peritoneal macrophages, induces lipid droplet biogenesis, and also requires HIF-1α for control. These results advance our understanding of CD4 T cell-mediated immunity to M. tuberculosis, reveal important differences in immune activation of distinct macrophage types, and outline a novel mechanism for the activation of HIF-1α. We establish a previously unknown functional link between GM-CSF and HIF-1α and provide evidence that CD4 T cell-derived GM-CSF is a potent bactericidal effector.

CD30 co-stimulation drives differentiation of protective T cells during Mycobacterium tuberculosis infection

“…T cells in granulomas expressed higher levels of both CSF2/GM-CSF and CSF1/M-CSF. GM-CSF production by T cells has been implicated in control of Mtb infection in murine models ( Rothchild et al, 2014 ; Rothchild et al, 2017 ; Van Dis et al, 2022 ), but far less is known about the role of T cell–derived M-CSF during TB. Granuloma T cells expressed higher levels of IL-10 and OSM.…”

Transcriptional analysis of human peripheral blood mononuclear cells stimulated by Mycobacterium tuberculosis antigen

“…It has previously been reported using a “co-culture” model that CD4 + T cells activate the transcription factor HIF-1α by secreting granulocyte-macrophage colony-stimulating factor (GM-CSF/CSF2), thereby establishing a link between GM-CSF and HIF-1α. The link between GM-CSF and HIF-1α was established, demonstrating the bactericidal activity of CSF2 in this “pathway” and assisting CD4 + T cells in suppressing Mtb infection ( Van Dis et al., 2022 ). CSF2 promotes Tfh1 cell polarization by activating dendritic cells (DCs) in a CD40-dependent manner ( Korniotis et al., 2022 ), and also up-regulates anti-apoptosis-related genes such as Bcl-2 and HSP27 to maintain the survival of macrophages that have been infected with Mtb.…”

Impact of SIV infection on mycobacterial lipid-reactive T cell responses in Bacillus Calmette-Guérin (BCG) inoculated macaques

“…Interestingly, the dominant proportions of CD8-positive and CD4/CD8-double negative T cell subsets in the mycobacterial lipid-reactive T cells suggest that majority of these cells are CD4-negative and thus non-targets for direct HIV/SIV infection. This is critical in the setting of HIV coinfection since HIV-induced increase in TB risk is mainly attributed to loss of CD4 T cell functions ( 57 , 58 ) and the residual anti-mycobacterial T cell responses are dependent on non-CD4 T cell effector functions. Given the presence of human CD4 T cell responses to the mycobacterial cell wall lipids including mycolic acid (MA) and glucose monomycolate (GMM) ( 48 , 59 , 60 ), our results suggest that the dominant lipid antigens presented in total lipid fractions of M. bovis and Mtb are recognized by CD8 T cells and DNT cells.…”