Nucleic acid-containing immune complexes and immune activation - PROJECT SUMMARY/ABSTRACT The long-range goal of this research is to explore how HIV-1, when suppressed by anti-retroviral therapy (ART), sustains the immune activation and consequent accelerated aging that underlie the survival gap between people living with HIV (PLWH) and the general population. HIV-1 itself is likely a key driver of immune activation. However, in the setting of low levels of virus replication, it is unclear how HIV-1 continues to cause inflammation. We propose that monocyte activation by immune complexes (ICs) made of Gag, HIV-1 RNA, and anti-Gag IgG contribute to chronic inflammation and endothelial cell dysfunction in ART-treated PLWH. This notion arises from our preliminary data indicating that nucleic acid-containing ICs stimulate monocytes in vitro to produce inflammatory chemokines. Such ICs are likely to be present in ART-treated patients whose viremia is well controlled, because in addition to replicating virus, genomes of defective virus—which makes up >90% of the reservoir virus in treated patients—can transcribe RNA and encode Gag. Moreover, most individuals maintain anti-Gag antibodies despite undetectable plasma viremia. Consistent with the idea that nucleic acid-containing ICs promote immune activation is the intriguing observation that natural hosts of SIV, who resolve immune activation, have very low or undetectable anti-Gag antibodies, whereas such antibodies are readily measured in pathogenic SIV infection of macaques. In addition, patients with autoimmune disorders such as lupus, make IgG that binds to nucleic acids or to ribonucleoproteins. Like PLWH, patients with lupus have endothelial cell dysfunction and accelerated atherosclerosis. Analogous to what we propose for IgG-Gag-RNA ICs, nucleic acid- containing ICs in lupus are internalized by phagocytes through Fcγ receptors (FcγRs) where they engage TLRs and mediate inflammation. To test the hypothesis that ICs consisting of Gag, RNA and anti-Gag IgG mediate immune activation, we will accomplish two specific aims: Aim 1: Measure the inflammatory response to nucleic acid-containing ICs in healthy, human FcγR-transgenic mice. Mice will be treated with HIV-1 Gag (p55, which contains the RNA-binding domain NCp7) and HIV-1 RNA with or without anti-Gag human IgG1. Markers of immune activation and microbial translocation will be measured. Specific Aim 2: Using human vascularized micro-organs (VMO's), assess interactions between nucleic acid-containing ICs, monocytes, and endothelial cells (ECs). Since endothelial dysfunction plays a role in diseases contributing to mortality in ART-treated PLWH, we will use VMOs to assess the impact of ICs and monocytes on the vasculature. VMOs (three dimensional models allowing physiological flow, EC function and gene expression) will be treated with monocytes and ICs, and vascular permeability, cytokine expression, and in situ expression of adhesion molecules will be measured. The proposed research is designed to determine whether or not nucleic acid- containing ICs drive the immune activation and endothelial dysfunction that contribute to reduced life expectancy in PLWH. Novel therapeutic strategies to provide a functional cure for HIV may emerge from our research.
