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HIV-1 evades immune detection by the cGAS-STING cytosolic DNA-sensing pathway during acute infection. STING is a critical mediator of type I IFN production, and STING agonists such as cGMP-AMP (cGAMP) and other cyclic dinucleotides elicit potent immune and antitumor response. In this article, we show that administration of cGAMP, delivered by an ultra–pH-sensitive nanoparticle (NP; PC7A), in human PBMCs induces potent and long-acting antiretroviral response against several laboratory-adapted and clinical HIV-1 isolates. cGAMP-PC7A NP requires endocytosis for intracellular delivery and immune signaling activation. cGAMP-PC7A NP-induced protection is mediated through type I IFN signaling and requires monocytes in PBMCs. cGAMP-PC7A NPs also inhibit HIV-1 replication in HIV+ patient PBMCs after ex vivo reactivation. Because pattern recognition receptor agonists continue to show more clinical benefits than the traditional IFN therapy, our data present important evidence for potentially developing cGAMP or other STING agonists as a new class of immune-stimulating long-acting antiretroviral agents.

TANK-binding kinase 1 (TBK1) is a serine/threonine protein kinase that plays a crucial role in innate immunity. Enhanced TBK1 function is associated with autoimmune diseases and cancer, implicating the potential benefit of therapeutically targeting TBK1. In this article, we examined a recently identified TBK1 inhibitor Compound II on treating autoimmune diseases. We found that Compound II is a potent and specific inhibitor of TBK1-mediated IFN response. Compound II inhibited polyinosinic-polycytidylic acid–induced immune activation in vitro and in vivo. Compound II treatment also ameliorated autoimmune disease phenotypes of Trex1−/− mice, increased mouse survival, and dampened the IFN gene signature in TREX1 mutant patient lymphoblasts. In addition, we found that TBK1 gene expression is elevated in systemic lupus erythematosus patient cells, and systemic lupus erythematosus cells with high IFN signature responded well to Compound II treatment. Together, our findings provided critical experimental evidence for inhibiting TBK1 with Compound II as an effective treatment for TREX1-associated autoimmune diseases and potentially other interferonopathies.

Mycoplasmas are a common cause of pneumonia in humans and animals, and attempts to create vaccines have not only failed to generate protective host responses, but they have exacerbated the disease. Mycoplasma pulmonis causes a chronic inflammatory lung disease resulting from a persistent infection, similar to other mycoplasma respiratory diseases. Using this model, Th1 subsets promote resistance to mycoplasma disease and infection, whereas Th2 responses contribute to immunopathology. The purpose of the present study was to evaluate the capacity of cytokine-differentiated dendritic cell (DC) populations to influence the generation of protective and/or pathologic immune responses during M. pulmonis respiratory disease in BALB/c mice. We hypothesized that intratracheal inoculation of mycoplasma Ag–pulsed bone marrow–derived DCs could result in the generation of protective T cell responses during mycoplasma infection. However, intratracheal inoculation (priming) of mice with Ag-pulsed DCs resulted in enhanced pathology in the recipient mice when challenged with mycoplasma. Inoculation of immunodeficient SCID mice with Ag-pulsed DCs demonstrated that this effect was dependent on lymphocyte responses. Similar results were observed when mice were primed with Ag-pulsed pulmonary, but not splenic, DCs. Lymphocytes generated in uninfected mice after the transfer of either Ag-pulsed bone marrow–derived DCs or pulmonary DCs were shown to be IL-13+ Th2 cells, known to be associated with immunopathology. Thus, resident pulmonary DCs most likely promote the development of immunopathology in mycoplasma disease through the generation of mycoplasma-specific Th2 responses. Vaccination strategies that disrupt or bypass this process could potentially result in a more effective vaccination.

Trex1−/− mice suffer from systemic inflammation caused largely by chronic activation of the cGAS-STING-TBK1-IRF3 signaling pathway. We showed previously that Trex1-deficient cells have reduced mTORC1 activity, although the underlying mechanism is unclear. Here, we performed detailed metabolic analysis in Trex1−/− mice and cells that revealed defects in mitochondrial respiration, reduced adiposity, increased energy expenditure and glycolysis. We also found that Trex1−/− mice and cells exhibit chronically suppressed mTORC1 activity. Furthermore, we provide genetic evidence corroborated with cellular and biochemical validation to show that metabolic dysregulation in Trex1−/− mice is caused by STING-dependent activation of TBK1, but not the downstream IRF3-mediated signaling and inflammation, and that TBK1 binds to the mTORC1 complex and inhibits its activity in Trex1−/− cells. Our data thus establish chronic STING-dependent activation of TBK1 as a novel regulatory axis of mTORC1 and cellular metabolism.

Mycoplasmas cause chronic respiratory diseases in animals and humans, and vaccine development has been problematic. T cell responses were shown to confer protection as well as promote immunopathology in murine mycoplasma pneumonia. Because T cells play a critical role, the role of antigen presenting cells (APC) was examined as they likely influence either an increase in disease severity or promote protective immunity. The roles of APC, such as dendritic cells (DC) and macrophages, in mycoplasma disease are currently unknown. In this study, we examined the ability pulmonary APC populations and their contribution to T cell responses during disease pathogenesis. Both macrophages and DC increased in the lungs of mice after infection. These cell populations showed different patterns of cytokine mRNA expression, supporting the idea that these cells have different impacts on immunity in response to infection. In fact, DC from the lungs of infected mice were most capable of stimulating mycoplasma-specific T helper (Th) cell responses in vitro. In vivo, DC cells were co-localized with Th cells in inflammatory lesions in the lungs of mycoplasma-infected mice. Intratracheal inoculation of mycoplasma antigen-pulsed DC resulted in increased disease severity after subsequent infection. Thus, DC appear to be the major APC population responsible for pulmonary T cell stimulation in mycoplasma-infected mice, and these DC likely contribute to responses impacting disease pathogenesis.