Mechanism of Interferon-Stimulated Gene Induction in HIV-1-Infected Macrophages.

Viruses manipulate the complex interferon and interferon-stimulated gene (ISG) system in different ways. We have previously shown that HIV inhibits type I and III interferons in its key target cells but directly stimulates a subset of >20 ISGs in macrophages and dendritic cells, many of which are antiviral. Here, we examine the mechanism of induction of ISGs and show this occurs in two phases. The first phase was transient (0 to 24 h postinfection [hpi]), induced mainly by extracellular vesicles and one of its component proteins, HSP90α, contained within the HIV inoculum. The second, dominant, and persistent phase (>48 hpi) was induced via newly transcribed HIV RNA and sensed via RIGI, as shown by the reduction in ISG expression after the knockdown of the RIGI adaptor, MAVS, by small interfering RNA (siRNA) and the inhibition of both the initiation and elongation of HIV transcription by short hairpin RNA (shRNA) transcriptional silencing. We further define the induction pathway, showing sequential HIV RNA stimulation via Tat, RIGI, MAVS, IRF1, and IRF7, also identified by siRNA knockdown. IRF1 also plays a key role in the first phase. We also show that the ISGs IFIT1 to -3 inhibit HIV production, measured as extracellular infectious virus. All induced antiviral ISGs probably lead to restriction of HIV replication in macrophages, contributing to a persistent, noncytopathic infection, while the inhibition of interferon facilitates spread to adjacent cells. Both may influence the size of macrophage HIV reservoirs in vivo Elucidating the mechanisms of ISG induction may help in devising immunotherapeutic strategies to limit the size of these reservoirs.IMPORTANCE HIV, like other viruses, manipulates the antiviral interferon and interferon-stimulated gene (ISG) system to facilitate its initial infection and establishment of viral reservoirs. HIV specifically inhibits all type I and III interferons in its target cells, including macrophages, dendritic cells, and T cells. It also induces a subset of over 20 ISGs of differing compositions in each cell target. This occurs in two temporal phases in macrophages. Extracellular vesicles contained within the inoculum induce the first, transient phase of ISGs. Newly transcribed HIV RNA induce the second, dominant ISG phase, and here, the full induction pathway is defined. Therefore, HIV nucleic acids, which are potent inducers of interferon and ISGs, are initially concealed, and antiviral ISGs are not fully induced until replication is well established. These antiviral ISGs may contribute to persistent infection in macrophages and to the establishment of viral reservoirs in vivo.

Airway ß-Defensin-1 Protein Is Elevated in COPD and Severe Asthma.

BACKGROUND: Innate immune antimicrobial peptides, including ß-defensin-1, promote the chemotaxis and activation of several immune cells. The role of ß-defensin-1 in asthma and chronic obstructive pulmonary disease (COPD) remains unclear. METHODS: Induced sputum was collected from healthy controls and individuals with asthma or COPD. ß-defensin-1 protein in sputum supernatant was quantified by ELISA. Biomarker potential was examined using receiver operating characteristic curves. ß-defensin-1 release from primary bronchial epithelial cells (pBECs) was investigated in culture with and without cigarette smoke extract (CSE). RESULTS: Airway ß-defensin-1 protein was elevated in COPD participants compared to asthma participants and healthy controls. Inflammatory phenotype had no effect on ß-defensin-1 levels in asthma or COPD. ß-defensin-1 protein was significantly higher in severe asthma compared to controlled and uncontrolled asthma. ß-defensin-1 protein could predict the presence of COPD from both healthy controls and asthma patients. Exposure of pBECs to CSE decreased ß-defensin-1 production in healthy controls; however in pBECs from COPD participants the level of ß-defensin-1 remanied unchanged. CONCLUSIONS: Elevated ß-defensin-1 protein is a feature of COPD and severe asthma regardless of inflammatory phenotype. ß-defensin-1 production is dysregulated in the epithelium of patients with COPD and may be an effective biomarker and potential therapeutic target.

HIV-1 infection of human macrophages directly induces viperin which inhibits viral production.

Macrophages are key target cells for HIV-1. HIV-1(BaL) induced a subset of interferon-stimulated genes in monocyte-derived macrophages (MDMs), which differed from that in monocyte-derived dendritic cells and CD4 T cells, without inducing any interferons. Inhibition of type I interferon induction was mediated by HIV-1 inhibition of interferon-regulated factor (IRF3) nuclear translocation. In MDMs, viperin was the most up-regulated interferon-stimulated genes, and it significantly inhibited HIV-1 production. HIV-1 infection disrupted lipid rafts via viperin induction and redistributed viperin to CD81 compartments, the site of HIV-1 egress by budding in MDMs. Exogenous farnesol, which enhances membrane protein prenylation, reversed viperin-mediated inhibition of HIV-1 production. Mutagenesis analysis in transfected cell lines showed that the internal S-adenosyl methionine domains of viperin were essential for its antiviral activity. Thus viperin may contribute to persistent noncytopathic HIV-1 infection of macrophages and possibly to biologic differences with HIV-1-infected T cells.