cyclic-guanosine-monophosphate-adenosine-monophosphate and HIV-Infections

HIV-1 replicates in cells that express a wide array of innate immune sensors and may do so simultaneously with other pathogens. How a coexisting innate immune stimulus influences the outcome of HIV-1 sensing, however, remains poorly understood. Here, we demonstrate that the activation of a second signaling pathway enables a cyclic GMP-AMP synthase (cGAS)-dependent type I interferon (IFN-I) response to HIV-1 infection. We used RNA sequencing to determine that HIV-1 alone induced few or no signs of an IFN-I response in THP-1 cells. In contrast, when supplemented with suboptimal levels of bacterial lipopolysaccharide (LPS), HIV-1 infection triggered the production of elevated levels of IFN-I and significant upregulation of interferon-stimulated genes. LPS-mediated enhancement of IFN-I production upon HIV-1 infection, which was observed in primary macrophages, was lost by blocking reverse transcription and with a hyperstable capsid, pointing to viral DNA being an essential immunostimulatory molecule. LPS also synergistically enhanced IFN-I production by cyclic GMP-AMP (cGAMP), a second messenger of cGAS. These observations suggest that the DNA sensor cGAS is responsible for a type I IFN response to HIV-1 in concert with LPS receptor Toll-like receptor 4 (TLR4). Small amounts of a TLR2 agonist also cooperate with HIV-1 to induce type I IFN production. These results demonstrate how subtle immunomodulatory activity renders HIV-1 capable of eliciting an IFN-I response through positive cross talk between cGAS and TLR sensing pathways.

Topics: HIV Infections; HIV-1; Humans; Immunity, Innate; Interferon Type I; Macrophages; Nucleotides, Cyclic; Nucleotidyltransferases; Signal Transduction; Toll-Like Receptor 4

Functional HIV-1-specific CD8

Topics: CD8-Positive T-Lymphocytes; Epitopes, T-Lymphocyte; Granzymes; HIV Infections; HIV Seronegativity; HIV-1; HLA-B52 Antigen; HLA-C Antigens; Humans; Ligands; Membrane Proteins; Nucleotides, Cyclic; Perforin; Virus Replication

Pathogen recognition receptor (PRR) agonists are currently being developed and tested as adjuvants in various formulations to optimize the immunogenicity and efficacy of vaccines. Using an original in vitro approach to prime naive precursors from unfractionated human peripheral blood mononuclear cells, we assessed the influence of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), a ligand for the stimulator of interferon genes (STING), on the induction of antigen-specific CD8+ T cells. We found that 2'3'-cGAMP and 3'3'-cGAMP were especially potent adjuvants in this system, driving the expansion and maturation of functionally replete antigen-specific CD8+ T cells via the induction of type I IFNs. The biological relevance of these findings was confirmed in vivo using two mouse models, in which 2'3'-cGAMP-adjuvanted vaccination elicited protective antitumor or antiviral CD8+ T cell responses. These results identify particular isoforms of cGAMP as effective adjuvants that may find utility in the development of novel immunotherapies and vaccines.

Topics: Adjuvants, Immunologic; Animals; Cancer Vaccines; CD8-Positive T-Lymphocytes; Cell Line, Tumor; Cells, Cultured; Disease Models, Animal; Female; HIV Infections; HIV-1; Humans; Immunogenicity, Vaccine; Interferon Type I; Ligands; Membrane Proteins; Mice; Nucleotides, Cyclic; Primary Cell Culture; Thymoma; Thymus Neoplasms; Vaccination; Viral Vaccines

Infected cells detect viruses through a variety of receptors that initiate cell-intrinsic innate defense responses. Cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS) is a cytosolic sensor for many DNA viruses and HIV-1. In response to cytosolic viral DNA, cGAS synthesizes the second messenger 2'3'-cyclic GMP-AMP (cGAMP), which activates antiviral signaling pathways. We show that in cells producing virus, cGAS-synthesized cGAMP can be packaged in viral particles and extracellular vesicles. Viral particles efficiently delivered cGAMP to target cells. cGAMP transfer by viral particles to dendritic cells activated innate immunity and antiviral defenses. Finally, we show that cell-free murine cytomegalovirus and Modified Vaccinia Ankara virus contained cGAMP. Thus, transfer of cGAMP by viruses may represent a defense mechanism to propagate immune responses to uninfected target cells.

Topics: Animals; Chlorocebus aethiops; Cytosol; Dendritic Cells; Genetic Vectors; HeLa Cells; Herpesviridae Infections; HIV Infections; HIV-1; Humans; Immunity, Innate; Mice; Mice, Inbred C57BL; Muromegalovirus; Nucleotides, Cyclic; Second Messenger Systems; Vaccinia; Vaccinia virus; Vero Cells; Virion; Virus Assembly

Cyclic GMP-AMP synthase (cGAS) detects cytosolic DNA during virus infection and induces an antiviral state. cGAS signals by synthesis of a second messenger, cyclic GMP-AMP (cGAMP), which activates stimulator of interferon genes (STING). We show that cGAMP is incorporated into viral particles, including lentivirus and herpesvirus virions, when these are produced in cGAS-expressing cells. Virions transferred cGAMP to newly infected cells and triggered a STING-dependent antiviral program. These effects were independent of exosomes and viral nucleic acids. Our results reveal a way by which a signal for innate immunity is transferred between cells, potentially accelerating and broadening antiviral responses. Moreover, infection of dendritic cells with cGAMP-loaded lentiviruses enhanced their activation. Loading viral vectors with cGAMP therefore holds promise for vaccine development.

Topics: AIDS Vaccines; Dendritic Cells; Genes, Reporter; Genetic Vectors; HEK293 Cells; Herpes Simplex; Herpes Simplex Virus Vaccines; Herpesvirus 1, Human; HIV Infections; HIV-1; Humans; Immunity, Innate; Interferon-beta; Nucleotides, Cyclic; Promoter Regions, Genetic; Second Messenger Systems; Transcriptional Activation; Virion