Design principles for inflammasome inhibition by pyrin-only-proteins.

Inflammasomes are filamentous signaling platforms essential for host defense against various intracellular calamities such as pathogen invasion and genotoxic stresses. However, dysregulated inflammasomes cause an array of human diseases including autoinflammatory disorders and cancer. It was recently identified that endogenous pyrin-only-proteins (POPs) regulate inflammasomes by directly inhibiting their filament assembly.

Cross-reactive antibodies facilitate innate sensing of dengue and Zika viruses.

The Aedes aegypti mosquito transmits both dengue virus (DENV) and Zika virus (ZIKV) . Individuals in endemic areas are at risk for infection with both viruses, as well as for repeated DENV infection. In the presence of anti-DENV antibodies, outcomes of secondary DENV infection range from mild to life threatening.

Allosteric coupling between Mn2+ and dsDNA controls the catalytic efficiency and fidelity of cGAS.

Cyclic-G/AMP (cGAMP) synthase (cGAS) triggers host innate immune responses against cytosolic double-stranded (ds)DNA arising from genotoxic stress and pathogen invasion. The canonical activation mechanism of cGAS entails dsDNA-binding and dimerization. Here, we report an unexpected activation mechanism of cGAS in which Mn2+ activates monomeric cGAS without dsDNA.

Assessment of inflammasome and type I IFN responses to DNA viruses and DNA PAMPS.

The innate immune system is an evolutionarily conserved host defense system and is the first barrier to infection. The system utilizes genetically conserved receptors to identify the presence of microbial structures. Engagement of innate immune receptors by primarily by ligands that discriminate pathogens from the host activates programmed responses that limit pathogen expansion.

Bypassing the bottleneck: intentional hepatitis C transmission with organ transplant.

Solid organ transplantation from hepatitis C virus-positive (HCV-positive) deceased donors into HCV-negative recipients is a recent approach aimed to expand the donor organ pool in the setting of severe shortage. Good short-term outcomes have been reported with this approach in combination with direct-acting antivirals. In this issue of the JCI, Zahid and colleagues have characterized early viral kinetics and the genetic landscape of donor-to-recipient HCV transmission using single-genome sequencing.

CMPK2 and BCL-G are associated with type 1 interferon-induced HIV restriction in humans.

Type 1 interferons (IFN) are critical for host control of HIV and simian immunodeficiency virus. However, it is unknown which of the hundreds of interferon-stimulated genes (ISGs) restrict HIV in vivo. We sequenced RNA from cells that support HIV replication (activated CD4 T cells) in 19 HIV-infected people before and after interferon-α2b (IFN-α2b) injection.

Direct-Acting Antiviral Prophylaxis in Kidney Transplantation From Hepatitis C Virus-Infected Donors to Noninfected Recipients: An Open-Label Nonrandomized Trial.

Background: Given the high mortality rate for patients with end-stage kidney disease receiving dialysis and the efficacy and safety of hepatitis C virus (HCV) treatments, discarded kidneys from HCV-infected donors may be a neglected public health resource.

Objective: To determine the tolerability and feasibility of using direct-acting antivirals (DAAs) as prophylaxis before and after kidney transplantation from HCV-infected donors to non-HCV-infected recipients (that is, HCV D+/R- transplantation).

Design: Open-label nonrandomized trial.

HIV-antibody complexes enhance production of type I interferon by plasmacytoid dendritic cells.

Type I IFN production is essential for innate control of acute viral infection; however, prolonged high-level IFN production is associated with chronic immune activation in HIV-infected individuals. Although plasmacytoid DCs (pDCs) are a primary source of IFN, the mechanisms that regulate IFN levels following the acute phase are unknown. We hypothesized that HIV-specific Ab responses regulate late IFN production.

Systemic Elevation of Proinflammatory Interleukin 18 in HIV/HCV Coinfection versus HIV or HCV Monoinfection.

Background: HIV/HCV coinfection and elevated interleukin (IL)-18 levels are both associated with enhanced progression of hepatic inflammation and increased risk of diabetes, kidney disease, and cardiovascular disease. IL-18 is a proinflammatory cytokine made upon activation of the inflammasome, an innate sensing system. We assessed whether increased IL-18 could explain the increased incidence and progression of inflammatory conditions seen with HIV/HCV coinfection.

TGFβ1-Mediated SMAD3 Enhances PD-1 Expression on Antigen-Specific T Cells in Cancer.

Unlabelled: Programmed death-1 (PD-1) is a coinhibitory receptor that downregulates the activity of tumor-infiltrating lymphocytes (TIL) in cancer and of virus-specific T cells in chronic infection. The molecular mechanisms driving high PD-1 expression on TILs have not been fully investigated. We demonstrate that TGFβ1 enhances antigen-induced PD-1 expression through SMAD3-dependent, SMAD2-independent transcriptional activation in T cells in vitro and in TILs in vivo The PD-1 subset seen in CD8 TILs is absent in Smad3-deficient tumor-specific CD8 TILs, resulting in enhanced cytokine production by TILs and in draining lymph nodes and antitumor activity.

HIV and HCV activate the inflammasome in monocytes and macrophages via endosomal Toll-like receptors without induction of type 1 interferon.

Innate immune sensing of viral infection results in type I interferon (IFN) production and inflammasome activation. Type I IFNs, primarily IFN-α and IFN-β, are produced by all cell types upon virus infection and promote an antiviral state in surrounding cells by inducing the expression of IFN-stimulated genes. Type I IFN production is mediated by Toll-like receptor (TLR) 3 in HCV infected hepatocytes.

Monocytes activate natural killer cells via inflammasome-induced interleukin 18 in response to hepatitis C virus replication.

Background & Aims: Production of interferon (IFN)-γ by natural killer (NK) cells is attenuated during chronic infection with hepatitis C virus (HCV). We investigated whether this is due to intrinsic or extrinsic mechanisms of NK cells.

Methods: Peripheral blood mononuclear cells (PBMCs) were collected from patients with chronic HCV infection or uninfected blood donors (controls); NK cells and monocytes were isolated or eliminated.

High plasma interleukin-18 levels mark the acute phase of hepatitis C virus infection.

Background: Proinflammatory cytokines play a critical role in antiviral immune responses. Large-scale genome studies have found correlations between single-nucleotide polymorphisms (SNPs) in the interleukin (IL) 18 promoter and spontaneous control of hepatitis C virus (HCV), suggesting a role in clearance.

Methods: Plasma IL-18, IL-1β, IL-6, IL-8, IL-12, interferon-γ, tumor necrosis factor-α, alanine aminotransferase (ALT), and HCV RNA levels were assessed longitudinally in subjects with known dates of HCV acquisition and analyzed according to IL-18 SNPs and outcome, either spontaneous clearance (SC) (n = 13) or persistent infection (PI) (n = 25).

HIV-mediated phosphatidylinositol 3-kinase/serine-threonine kinase activation in APCs leads to programmed death-1 ligand upregulation and suppression of HIV-specific CD8 T cells.

Recent evidence demonstrates that HIV-1 infection leads to the attenuation of cellular immune responses, which has been correlated with the increased expression of programmed death (PD)-1 on virus-specific CD8(+) T cells. PD-1 is induced upon T cell activation, and its prolonged expression facilitates CD8(+) T cell inhibitory signals when bound to its B7 family ligands, PD-ligand (L)1/2, which are expressed on APCs. Importantly, early reports demonstrated that blockade of the PD-1/PD-L interaction by Abs may help to counter the development of immune exhaustion driven by HIV viral persistence.

DR5 activation of caspase-8 induces DC maturation and immune enhancement in vivo.

Non-homeostatic tissue apoptosis in vivo has been shown to induce inflammatory responses and facilitate the cross-presentation of proteins within apoptotic bodies. We hypothesize that in the presence of foreign antigens, the apoptotic-inflammatory process improves immune priming; further, molecules that trigger apoptosis may be adapted for use as immune adjuvants. One very attractive molecule in this context is the tumor necrosis factor receptor (TNFR) family molecule DR5/TRAIL-receptor 2.

Host cell killing by the West Nile Virus NS2B-NS3 proteolytic complex: NS3 alone is sufficient to recruit caspase-8-based apoptotic pathway.

The West Nile Virus (WNV) non-structural proteins 2B and 3 (NS2B-NS3) constitute the proteolytic complex that mediates the cleavage and processing of the viral polyprotein. NS3 recruits NS2B and NS5 proteins to direct protease and replication activities. In an effort to investigate the biology of the viral protease, we cloned cDNA encoding the NS2B-NS3 proteolytic complex from brain tissue of a WNV-infected dead crow, collected from the Lower Merion area (Merion strain).

HIV-1 Viral protein-r (Vpr) protects against lethal superantigen challenge while maintaining homeostatic T cell levels in vivo.

The HIV-1 accessory protein Vpr exhibits many interesting features related to macrophage and T cell biology. As a viral protein or as a soluble molecule it can suppress immune cell activation and cytokine production in vitro in part by targeted inhibition of NF-kappaB. In this regard we sought to test its effects in vivo on an NF-kappaB-dependent immune pathway.

Coimmunization with an optimized IL-15 plasmid results in enhanced function and longevity of CD8 T cells that are partially independent of CD4 T cell help.

DNA vaccines are a promising technology for the induction of Ag-specific immune responses, and much recent attention has gone into improving their immune potency. In this study we test the feasibility of delivering a plasmid encoding IL-15 as a DNA vaccine adjuvant for the induction of improved Ag-specific CD8(+) T cellular immune responses. Because native IL-15 is poorly expressed, we used PCR-based strategies to develop an optimized construct that expresses 80-fold higher than the native IL-15 construct.

Co-immunization with plasmid IL-12 generates a strong T-cell memory response in mice.

Plasmid encoded exogenous IL-12 delivered as a DNA vaccine adjuvant has been shown to improve vaccine-induced immunity. In particular, pIL-12 greatly improves antigen (Ag)-specific cytotoxic tlymphocyte (CTL) activity in immunized mice. The longevity of this response has not previously been studied in detail.

Costimulatory molecule immune enhancement in a plasmid vaccine model is regulated in part through the Ig constant-like domain of CD80/86.

There is great interest in understanding the role of costimulatory molecules in immune activation. In both the influenza and HIV DNA immunization models, several groups have reported that coimmunization of mice with plasmids encoding immunogen and CD86, but not CD80, effectively boosts Ag-specific T cell activation. This difference in immune priming provided an opportunity to examine the functional importance of different regions of the B.

Engineering cross-presentation in vivo.

Apoptotic bodies deliver antigens (Ags) to the cross-presentation pathways of dendritic cells (DCs), where their presentation has been associated with both the maintenance of tolerance as well as the induction of protective immunity. The manner in which apoptotic bodies are generated, their abundance in relation to local DCs, and the milieu in which they are generated appear to be the major factors determining whether apoptotic bodies will induce CD8(+) T cell activation or anergy. These observations have been extended to the field of vaccination, where the engineered apoptosis of Ag-bearing/loaded cells in vivo has been used to prime strong CD8(+) T cell immunity.