Epstein-Barr virus (EBV), an oncogenic gammaherpesvirus, causes acute infectious mononucleosis (AIM) and is linked to the development of several human malignancies. There is an urgent need for a vaccine that is safe, prevents infection and/or limits disease. Unique among human herpesviruses, glycoprotein (gp)350/220, which initiates EBV attachment to susceptible host cells, is the major ligand on the EBV envelope and is highly conserved. Interaction between gp350/220 and complement receptor type 2 (CR2)/CD21 and/or (CR1)/CD35 on B-cells is required for infection. Potent antibody responses to gp350/220 occur in animal models and humans. Thus, gp350/220 provides an attractive candidate for prophylactic subunit vaccine development. However, in a recent Phase II clinical trial immunization with soluble recombinant gp350 reduced the incidence of AIM, but did not prevent infection. Despite various attempts to produce an EBV vaccine, no vaccine is licensed. Herein we describe a sub-unit vaccine against EBV based on a novel Newcastle disease virus (NDV)-virus-like particle (VLP) platform consisting of EBVgp350/220 ectodomain fused to NDV-fusion (F) protein. The chimeric protein EBVgp350/220-F is incorporated into the membrane of a VLP composed of the NDV matrix and nucleoprotein. The particles resemble native EBV in diameter and shape and bind CD21 and CD35. Immunization of BALB/c mice with EBVgp350/220-F VLPs elicited strong, long-lasting neutralizing antibody responses when assessed in vitro. This chimeric VLP is predicted to provide a superior safety profile as it is efficiently produced in Chinese hamster ovary (CHO) cells using a platform devoid of human nucleic acid and EBV-transforming genes.
EBV; NDV; VLP; Vaccine; Neutralization
Influenza A virus (IAV) is a major cause of morbidity and mortality throughout the world. Current antiviral therapies include oseltamivir, a neuraminidase inhibitor that prevents the release of nascent viral particles from infected cells. However, the IAV genome can evolve rapidly, and oseltamivir resistance mutations have been detected in numerous clinical samples. Using an in vitro evolution platform and whole-genome population sequencing, we investigated the population genomics of IAV during the development of oseltamivir resistance. Strain A/Brisbane/59/2007 (H1N1) was grown in Madin-Darby canine kidney cells with or without escalating concentrations of oseltamivir over serial passages. Following drug treatment, the H274Y resistance mutation fixed reproducibly within the population. The presence of the H274Y mutation in the viral population, at either a low or a high frequency, led to measurable changes in the neuraminidase inhibition assay. Surprisingly, fixation of the resistance mutation was not accompanied by alterations of viral population diversity or differentiation, and oseltamivir did not alter the selective environment. While the neighboring K248E mutation was also a target of positive selection prior to H274Y fixation, H274Y was the primary beneficial mutation in the population. In addition, once evolved, the H274Y mutation persisted after the withdrawal of the drug, even when not fixed in viral populations. We conclude that only selection of H274Y is required for oseltamivir resistance and that H274Y is not deleterious in the absence of the drug. These collective results could offer an explanation for the recent reproducible rise in oseltamivir resistance in seasonal H1N1 IAV strains in humans.
Osteolysis of bone following total hip replacements is a major clinical problem. Examination of the areas surrounding failed implants has indicated an increase in the bone-resorption-inducing cytokine, interleukin 1β (IL-1β). NALP3, a NOD-like receptor protein located in the cytosol of macrophages, has been shown to signal the cleavage of pro-IL-1β into its mature, secreted form, IL-1β. Here we show that titanium particles stimulate the NALP3 inflammasome. We demonstrate that titanium induces IL-1β secretion from macrophages and this response is dependent on the expression of components of the NALP3 inflammasome, including NALP3, ASC, and Caspase-1. We also show that titanium particles trigger the recruitment of neutrophils and that this acute inflammatory response is dependent on the expression of the IL-1 receptor and IL-1α/β. Moreover, administration of the IL-1 receptor antagonist (IL-1Ra) diminished neutrophil recruitment in response to titanium particles. Together, these results suggest that titanium particle-induced acute inflammation is due to activation of the NALP3 inflammasome, which leads to increased IL-1β secretion and IL-1-associated signaling, including neutrophil recruitment. Efficacy of IL-1Ra treatment introduces the potential for antagonist based-therapies for implant osteolysis.
Titanium; inflammasome; neutrophils; IL-1; NALP3
Polymeric microparticles have been widely investigated as platforms for delivery of drugs, vaccines, and imaging contrast agents, and are increasingly used in a variety of clinical applications. Microparticles activate the inflammasome complex and induce the processing and secretion of IL-1β, a key innate immune cytokine. Recent work suggests that while receptors are clearly important for particle phagocytosis, other physical characteristics especially shape, play an important role in the way microparticles activate cells. We examined the role of particle surface texturing not only on uptake efficiency but also on the subsequent immune cell activation of the inflammasome. Using a method based on emulsion processing of amphiphilic block copolymers, we prepared microparticles with similar overall sizes and surface chemistries, but having either smooth or highly micro-textured surfaces. In vivo, textured (budding) particles induced more rapid neutrophil recruitment to the injection site. In vitro, budding particles were more readily phagocytosed than smooth particles and induced more lipid raft recruitment to the phagosome. Remarkably, budding particles also induced stronger IL-1β secretion than smooth particles, through activation of the NLRP3 inflammasome. These findings demonstrate a pronounced role of particle surface topography in immune cell activation suggesting that shape is a major determinant of inflammasome activation.
RIG-I and MDA5 have emerged as key cytosolic sensors for the detection of RNA viruses, leading to antiviral interferon (IFN) production. Recent studies highlighted the importance of posttranslational modification for controlling RIG-I antiviral activity. However, the regulation of MDA5 signal-transducing ability remains unclear. Here we show that MDA5 signaling activity is regulated by a dynamic balance between phosphorylation and dephosphorylation of its CARD domains. Employing a phosphatome RNAi screen, we identified PP1α and PP1γ as primary phosphatases responsible for MDA5 and RIG-I dephosphorylation, leading to their activation. Silencing of PP1α and PP1γ enhanced RIG-I and MDA5 CARD phosphorylation and reduced antiviral IFN-β production. PP1α and PP1γ depleted cells were impaired in their ability to induce interferon-stimulated gene expression, which resulted in enhanced RNA virus replication. This work identifies PP1α and PP1γ as regulators of antiviral innate immune responses to various RNA viruses, including influenza virus, paramyxovirus, dengue virus and picornavirus.
The pathogenesis of malaria, an insect-borne disease that takes millions of lives every year, is still not fully understood. Complement receptor 1 (CR1) has been described as a receptor for Plasmodium falciparum, which causes cerebral malaria in humans. We investigated the role of CR1 in an experimental model of cerebral malaria. Transgenic mice expressing human CR1 (hCR1+) on erythrocytes were infected with Plasmodium berghei ANKA and developed cerebral malaria. No difference in survival was observed in hCR1+ mice compared to wild-type mice following infection with P. berghei ANKA; however, hCR1 detection was significantly diminished on erythrocytes between days 7 and 10 postinfection. hCR1 levels returned to baseline by day 17 postinfection in surviving animals. Immunoblot assays revealed that total erythrocyte hCR1 levels were diminished, confirming that immune complexes in association with erythrocyte hCR1 were likely removed from erythrocytes in vivo by clearance following immune adherence. Decreases in hCR1 were completely dependent on C3 expression, as mice treated with cobra venom factor (which consumes and depletes C3) retained hCR1 on erythrocytes during C3 depletion through day 7; erythrocyte hCR1 decreases were observed only when C3 levels recovered on day 9. B-cell-deficient mice exhibit a marked increase in survival following infection with P. berghei ANKA, which suggests that immune complexes play a central role in the pathogenesis of experimental cerebral malaria. Together, our findings highlight the importance of complement and immune complexes in experimental cerebral malaria.
Cerebral malaria is a deadly complication of infection with Plasmodium falciparum. Despite its high prevalence, relatively little is understood about its pathogenesis. We have determined that immune complexes are generated and deposited on erythrocytes specifically expressing human complement receptor 1 in a mouse model of cerebral malaria. We also provide evidence demonstrating the importance of immunoglobulins in the pathogenesis of cerebral malaria in mice. These findings may have important implications in human cerebral malaria.
The challenge of distinguishing genetic drift from selection remains a central focus of population genetics. Time-sampled data may provide a powerful tool for distinguishing these processes, and we here propose approximate Bayesian, maximum likelihood, and analytical methods for the inference of demography and selection from time course data. Utilizing these novel statistical and computational tools, we evaluate whole-genome datasets of an influenza A H1N1 strain in the presence and absence of oseltamivir (an inhibitor of neuraminidase) collected at thirteen time points. Results reveal a striking consistency amongst the three estimation procedures developed, showing strongly increased selection pressure in the presence of drug treatment. Importantly, these approaches re-identify the known oseltamivir resistance site, successfully validating the approaches used. Enticingly, a number of previously unknown variants have also been identified as being positively selected. Results are interpreted in the light of Fisher's Geometric Model, allowing for a quantification of the increased distance to optimum exerted by the presence of drug, and theoretical predictions regarding the distribution of beneficial fitness effects of contending mutations are empirically tested. Further, given the fit to expectations of the Geometric Model, results suggest the ability to predict certain aspects of viral evolution in response to changing host environments and novel selective pressures.
In recent years, considerable attention has been given to the evolution of drug resistance in the influenza A H1N1 strain. As a major annual cause of morbidity and mortality, combined with the rapid global spread of drug resistance, influenza remains as one of the most important global health concerns. Our work here focuses on a novel multi-faceted population-genetic approach utilizing unique whole-genome multi-time point experimental datasets in both the presence and absence of drug treatment. In addition, we present novel theoretical results and two newly developed and widely applicable statistical methodologies for utilizing time-sampled data – with a focus on distinguishing the relative contribution of genetic drift from that of positive and purifying selection. Results illustrate the available mutational paths to drug resistance, and offer important insights in to the mode and tempo of adaptation in a viral population.
Prepatellar bursitis is typically a monomicrobial bacterial infection. A fungal cause is rarely identified. We describe a 61-year-old man who had received a renal transplant 21 months prior to presentation whose synovial fluid and surgical specimens grew Phomopsis bougainvilleicola, a pycnidial coelomycete.
Epstein-Barr virus (EBV) attachment to primary B-cells initiates virus entry. While CD21 is the only known receptor for EBVgp350/220 a recent report documents EBV infects B-cells from a patient genetically deficient in CD21. On normal resting B-cells CD21 forms two membrane complexes, one with CD19 another with CD35. Whereas the CD21/CD19 complex is widely retained on immortalized and B-cell tumor lines, the related complement-regulatory protein CD35 is lost. To determine the role(s) of CD35 in initial infection, we transduced a CD21-negative pre-B-cell and myeloid leukemia line with CD35, CD21 or both. Cells expressing CD35 alone bound gp350/220 and became latently infected when the fusion receptor HLA II was co-expressed. Temporal, biophysical and structural characteristics of CD35-mediated infection were distinct from CD21. Identification of CD35 as an EBV receptor uncovers a salient role in primary infection, addresses unsettled questions of virus tropism, and underscores the importance of EBVgp350/220 for vaccine development.
Type I interferons (IFNs), predominantly IFN-α and -β, play critical roles in both innate and adaptive immune responses against viral infections. Interferon regulatory factor 7 (IRF7), a key innate immune molecule in the type I IFN signaling pathway, is essential for the type I IFN response to many viruses, including lymphocytic choriomeningitis virus (LCMV). Here, we show that although IRF7 knockout (KO) mice failed to control the replication of LCMV in the early stages of infection, they were capable of clearing LCMV infection. Despite the lack of type I IFN production, IRF7 KO mice generated normal CD4+ T cell responses, and the expansion of naïve CD8+ T cells into primary CD8+ T cells specific for LCMV GP33–41 was relatively normal. In contrast, the expansion of the LCMV NP396-specific CD8+ T cells was severely impaired in IRF7 KO mice. We demonstrated that this defective CD8+ T cell response is due neither to an impaired antigen-presenting system nor to any intrinsic role of IRF7 in CD8+ T cells. The lack of a type I IFN response in IRF7 KO mice did not affect the formation of memory CD8+ T cells. Thus, the present study provides new insight into the impact of the innate immune system on viral pathogenesis and demonstrates the critical contribution of innate immunity in controlling virus replication in the early stages of infection, which may shape the quality of CD8+ T cell responses.
(See the editorial commentary by Cunningham and Booth, on pages 1645–7.)
Background. Herpes simplex virus type 1 (HSV-1) infects >70% of the United States population. We identified a 3-megabase region on human chromosome 21 containing 6 candidate genes associated with herpes simplex labialis (HSL, “cold sores”).
Methods. We conducted single nucleotide polymorphism (SNP) scans of the chromosome 21 region to define which of 6 possible candidate genes were associated with cold sore frequency. We obtained the annual HSL frequency for 355 HSV-1 seropositive individuals and determined the individual genotypes by SNPlex for linkage analysis and parental transmission disequilibrium testing (ParenTDT).
Results. Two-point linkage analysis showed positive linkage between cold sore frequency and 2 SNPs within the C21orf91 region, 1 of which is nonsynonymous. ParenTDT analysis revealed a strong association between another C21orf91 SNP, predicted to lie in the 3′ untranslated region, and frequent HSL (P = .0047). C21orf 91 is a predicted open reading frame of unknown function that encodes a cytosolic protein.
Conclusions. We evaluated candidate genes in the cold sore susceptibility region using fine mapping with 45 SNP markers. 2 complementary techniques identified C21orf91 as a gene of interest for susceptibility to HSL. We propose that C21orf91 be designated the Cold Sore Susceptibility Gene-1 (CSSG1).
Antibody-mediated intracellular delivery of therapeutic agents has been considered for treatment of a variety of diseases. These approaches involve targeting cell-surface receptor proteins expressed by tumors or viral proteins expressed on infected cells. We examined the intracellular trafficking of a viral cell-surface-expressed protein, rabies G, with or without binding a specific antibody, ARG1. We found that antibody binding shifts the native intracellular trafficking pathway of rabies G in an Fc-independent manner. Kinetic studies indicate that the ARG1/rabies G complex progressively co-localized with clathrin, early endosomes, late endosomes, and lysosomes after addition to cells. This pathway was different from that taken by rabies G without addition of antibody, which localized with recycling endosomes. Findings were recapitulated using a cellular receptor with a well-defined endogenous recycling pathway. We conclude that antibody binding to cell-surface proteins induces redirection of intracellular trafficking of unbound or ligand bound receptors to a specific degradation pathway. These findings have broad implications for future developments of antibody-based therapeutics.
Endosomes; degradation; antibody; trafficking; internalization
Background. Recent studies demonstrate that long palate, lung, and nasal epithelium clone 1 protein (LPLUNC1) is involved in immune responses to Vibrio cholerae, and that variations in the LPLUNC1 promoter influence susceptibility to severe cholera in humans. However, no functional role for LPLUNC1 has been identified.
Metods. We investigated the role of LPLUNC1 in immune responses to V. cholerae, assessing its affect on bacterial growth and killing and on innate inflammatory responses to bacterial outer membrane components, including purified lipopolysaccharide (LPS) and outer membrane vesicles. We performed immunostaining for LPLUNC1 in duodenal biopsies from cholera patients and uninfected controls.
Results. LPLUNC1 decreased proinflammatory innate immune responses to V. cholerae and Escherichia coli LPS. The effect of LPLUNC1 was dose-dependent and occurred in a TLR4-dependent manner. LPLUNC1 did not affect lipoprotein-mediated TLR2 activation. Immunostaining demonstrated expression of LPLUNC1 in Paneth cells in cholera patients and controls.
Conclusions. Our results demonstrate that LPLUNC1 is expressed in Paneth cells and likely plays a role in modulating host inflammatory responses to V. cholerae infection. Attenuation of innate immune responses to LPS by LPLUNC1 may have implications for the maintenance of immune homeostasis in the intestine.
Hepatitis C virus (HCV) infection is a leading cause of liver transplantation and there is an urgent need to develop therapies to reduce rates of HCV infection of transplanted livers. Approved therapeutics for HCV are poorly tolerated and are of limited efficacy in this patient population. Human monoclonal antibody HCV1 recognizes a highly-conserved linear epitope of the HCV E2 envelope glycoprotein (amino acids 412–423) and neutralizes a broad range of HCV genotypes. In a chimpanzee model, a single dose of 250 mg/kg HCV1 delivered 30 minutes prior to infusion with genotype 1a H77 HCV provided complete protection from HCV infection, whereas a dose of 50 mg/kg HCV1 did not protect. In addition, an acutely-infected chimpanzee given 250 mg/kg HCV1 42 days following exposure to virus had a rapid reduction in viral load to below the limit of detection before rebounding 14 days later. The emergent virus displayed an E2 mutation (N415K/D) conferring resistance to HCV1 neutralization. Finally, three chronically HCV-infected chimpanzees were treated with a single dose of 40 mg/kg HCV1 and viral load was reduced to below the limit of detection for 21 days in one chimpanzee with rebounding virus displaying a resistance mutation (N417S). The other two chimpanzees had 0.5–1.0 log10 reductions in viral load without evidence of viral resistance to HCV1. In vitro testing using HCV pseudovirus (HCVpp) demonstrated that the sera from the poorly-responding chimpanzees inhibited the ability of HCV1 to neutralize HCVpp. Measurement of antibody responses in the chronically-infected chimpanzees implicated endogenous antibody to E2 and interference with HCV1 neutralization although other factors may also be responsible. These data suggest that human monoclonal antibody HCV1 may be an effective therapeutic for the prevention of graft infection in HCV-infected patients undergoing liver transplantation.
The majority of individuals infected with hepatitis C virus (HCV) become chronically infected and many go on to develop liver failure requiring liver transplantation. Unfortunately, the transplanted liver becomes infected with HCV in nearly 100% of transplant patients. Current treatments for HCV are poorly tolerated after liver transplantation and graft health is compromised by infection. We have developed a monoclonal antibody called HCV1 that blocks HCV from infecting liver cells in culture. Using chimpanzees as a model for HCV infection, we demonstrate that HCV1 has the ability to prevent HCV infection. We also show that HCV1 can treat chimpanzees chronically infected with HCV and reduce plasma viral load to below the level of detection for a period of 7 to 21 days. The virus that reemerges in the treated chimpanzees was resistant to HCV1 neutralization demonstrating target engagement. Given the ability of HCV1 to protect chimpanzees from HCV infection, we speculate that HCV1 may be beneficial in HCV- infected patients undergoing liver transplant.
Herpes simplex virus 1 (HSV-1) causes a spectrum of disease, including herpes labialis, herpes keratitis, and herpes encephalitis, which can be lethal. Viral recognition by pattern recognition receptors plays a central role in cytokine production and in the generation of antiviral immunity. The relative contributions of different Toll-like receptors (TLRs) in the innate immune response during central nervous system infection with HSV-1 have not been fully characterized. In this study, we investigate the roles of TLR2, TLR9, UNC93B1, and the type I interferon (IFN) receptor in a murine model of HSV-1 encephalitis. TLR2 is responsible for detrimental inflammatory cytokine production following intracranial infection with HSV-1, and the absence of TLR2 expression leads to increased survival in mice. We prove that inflammatory cytokine production by microglial cells, astrocytes, neutrophils, and monocytes is mediated predominantly by TLR2. We also demonstrate that type I IFNs are absolutely required for survival following intracranial HSV-1 infection, as mice lacking the type I IFN receptor succumb rapidly following infection and have high levels of HSV in the brain. However, the absence of TLR9 does not impact survival, type I IFN levels, or viral replication in the brain following infection. The absence of UNC93B1 leads to a survival disadvantage but does not impact viral replication or type I IFN levels in the brain in HSV-1-infected mice. These results illustrate the complex but important roles that innate immune receptors play in host responses to HSV-1 during infection of the central nervous system.
The toll-like receptors comprise one of the most conserved components of the innate immune system, signaling the presence of molecules of microbial origin. It has been proposed that signaling through TLR4, which requires CD14 to recognize bacterial lipopolysaccharide (LPS), may generate low-grade inflammation and thereby affect insulin sensitivity and glucose metabolism. To examine the long-term influence of partial innate immune signaling disruption on glucose homeostasis, we analyzed knockout mice deficient in CD14 backcrossed into the diabetes-prone C57BL6 background at 6 or 12 months of age. CD14-ko mice, fed either normal or high-fat diets, displayed significant glucose intolerance compared to wild type controls. They also displayed elevated norepinephrine urinary excretion and increased adrenal medullary volume, as well as an enhanced norepinephrine secretory response to insulin-induced hypoglycemia. These results point out a previously unappreciated crosstalk between innate immune- and sympathoadrenal- systems, which exerts a major long-term effect on glucose homeostasis.
Signaling via the adapter protein, MyD88, is important in the host defense against Cryptococcus neoformans infection. While certain Toll-like receptors (TLRs) can enhance the clearance of Cryptococcus, the contributions of MyD88-dependent, TLR-independent pathways have not been fully investigated. We examined the roles of IL-1R and IL-18R in vivo by challenging C57BL/6 mice with a lethal strain of Cryptococcus. We found that the absence of IL-18R, but not IL-1R, causes a shift in the survival curve following pulmonary delivery of a virulent strain of C. neoformans (H99). Specifically, IL-18R-deficient mice have significantly shorter median survival times compared to wild-type mice following infection. Cytokine analysis of lung homogenates revealed that deficiency of IL-IR, IL-18R, or MyD88 is associated with diminished lung levels of IL-1β. In order to compare these findings with those related to TLR-deficiency, we studied the effects of TLR9-deficiency and found that deficiency of TLR9 also affects the survival curve of mice following challenge with C. neoformans. Yet the lungs from infected TLR9-deficient mice have robust levels of IL-1β. In summary, we found that multiple signaling components can contribute the MyD88-dependent host responses to cryptococcal infection in vivo and each drives distinct pulmonary responses.
Blockade of Toll-like receptor (TLR)-mediated inflammatory responses represents a new approach in the development of anti-inflammation therapeutics. In the present study, we have screened for TLR2-mediated inflammation inhibitors from a small molecule compound library using a sensitive cell line stably expressing TLR2, CD14, and an NF-κB-driven-luciferase reporter gene. Lymphocytic choriomeningitis virus (LCMV) was used as a virus model. This arenavirus activates a TLR2/CD14-dependent NF-κB signaling pathway. We have identified 10 potential anti-inflammatory compounds out of 101306 compounds. We further evaluated 1 of these positive compounds, E567. We demonstrated that compound E567 efficiently inhibits both LCMV and Herpes simplex virus 1 (HSV-1) induced cytokine responses in both human and mouse cell cultures. We also demonstrated that E567 inhibits cytokine responses in the mouse. Remarkably, E567 is also capable of inhibiting LCMV replication in mice. This is a new model for developing drugs for use in treating viral illnesses.
Toll-like receptor (TLR); Lymphocytic choriomeningitis virus (LCMV); compound screening
Human respiratory syncytial virus (RSV) is a serious respiratory pathogen in infants and young children as well as elderly and immunocompromised populations. However, no RSV vaccines are available. We have explored the potential of virus-like particles (VLPs) as an RSV vaccine candidate. VLPs composed entirely of RSV proteins were produced at levels inadequate for their preparation as immunogens. However, VLPs composed of the Newcastle disease virus (NDV) nucleocapsid and membrane proteins and chimera proteins containing the ectodomains of RSV F and G proteins fused to the transmembrane and cytoplasmic domains of NDV F and HN proteins, respectively, were quantitatively prepared from avian cells. Immunization of mice with these VLPs, without adjuvant, stimulated robust, anti-RSV F and G protein antibody responses. IgG2a/IgG1 ratios were very high, suggesting predominantly TH1 responses. In contrast to infectious RSV immunization, neutralization antibody titers were robust and stable for 4 months. Immunization with a single dose of VLPs resulted in the complete protection of mice from RSV replication in lungs. Upon RSV intranasal challenge of VLP-immunized mice, no enhanced lung pathology was observed, in contrast to the pathology observed in mice immunized with formalin-inactivated RSV. These results suggest that these VLPs are effective RSV vaccines in mice, in contrast to other nonreplicating RSV vaccine candidates.
Hepatitis C virus (HCV) core and nonstructural 3 (NS3) proteins induce inflammation and immunity through a Toll-like receptor 2 (TLR2)-dependent pathway. Individuals with the R753Q single nucleotide polymorphism (SNP) in the TLR2 gene have increased risk of allograft failure after liver transplantation for chronic hepatitis C.
To test the hypothesis that R753Q SNP impairs TLR2 recognition of HCV proteins, a series of in vitro experiments were performed wherein stable clones of wild-type TLR2-deficient HEK293 cells, and HEK293 cells transfected with wild-type (HEK293-TLR2) or variant TLR2 genes (HEK293-TLR2-R753Q) were stimulated with HCV core and NS3 proteins. Cellular activation was assessed by nuclear factor-kappa B (NFκB)-driven luciferase activity, cytokine secretion, and gene upregulation.
Compared to TLR2-deficient HEK293 cells, HEK293-TLR2 cells had marked NFκB-driven luciferase activity, had modest to marked upregulation in TLR2 signaling-associated genes, and secreted large quantities of interleukin-8 during exposure to HCV core and NS3 proteins. In contrast, HEK293-TLR2-R753Q cells did not respond to stimulation with HCV, and behaved similarly like the TLR2-deficient HEK293 cells.
R753Q SNP impairs TLR2-mediated immune recognition of HCV core and NS3 proteins. This biologic defect may account for the predisposition of patients to develop allograft failure after liver transplantation for chronic hepatitis C.
single nucleotide polymorphism; hepatitis C virus; liver transplantation
The discovery of the Toll-like receptors (TLRs) and their importance in the regulation of host responses to infection raised attention to the complex interplay between viral gene products and the host innate immune responses in determining the outcome of virus infection. Robust inflammatory cytokine responses are observed in herpes simplex virus (HSV)-infected animals and cells. Our studies have demonstrated that Toll-like receptor 2 (TLR2) activation by HSV results in NF-κB activation with concomitant inflammatory cytokine production and that TLR2 activation plays a critical role in HSV-induced pathology and mortality. Here we demonstrate that the HSV-1 immediate-early ICP0 protein reduces the TLR2-mediated inflammatory response to HSV 1 (HSV-1) infection. Expression of ICP0 alone is sufficient to block TLR2-driven responses to both viral and nonviral ligands at or downstream of the MyD88 adaptor and upstream of p65. ICP0 alone can also reduce the levels of MyD88 and Mal (TIRAP). In HSV-infected cells, the E3 ligase function of ICP0 and cellular proteasomal activity are required for the inhibitory activity. Our results argue for a model in which ICP0 promotes the degradation of TLR adaptor molecules and inhibition of the inflammatory response, much as it inhibits the interferon response by sequestration and degradation of interferon regulatory factor 3 (IRF-3).
Type I interferons (IFNs) play a critical role in the host defense against viruses. Lymphocytic choriomeningitis virus (LCMV) infection induces robust type I IFN production in its natural host, the mouse. However, the mechanisms underlying the induction of type I IFNs in response to LCMV infection have not yet been clearly defined. In the present study, we demonstrate that IRF7 is required for both the early phase (day 1 postinfection) and the late phase (day 2 postinfection) of the type I IFN response to LCMV, and melanoma differentiation-associated gene 5 (MDA5)/mitochondrial antiviral signaling protein (MAVS) signaling is crucial for the late phase of the type I IFN response to LCMV. We further demonstrate that LCMV genomic RNA itself (without other LCMV components) is able to induce type I IFN responses in various cell types by activation of the RNA helicases retinoic acid-inducible gene I (RIG-I) and MDA5. We also show that expression of the LCMV nucleoprotein (NP) inhibits the type I IFN response induced by LCMV RNA and other RIG-I/MDA5 ligands. These virus-host interactions may play important roles in the pathogeneses of LCMV and other human arenavirus diseases.
Complement-containing immune complexes can be presented to phagocytes by human erythrocytes bearing complement receptor 1 (CR1). Although this has long been assumed to be a mechanism by which humans are able to protect themselves from “extracellular” bacteria such as pneumococci, there is little direct evidence. In these studies we have investigated this question by comparing results for erythrocytes from transgenic mice expressing human CR1 on their erythrocytes to the results for wild-type mouse erythrocytes that do not express CR1. We demonstrate that human CR1 expression on murine erythrocytes allows immune adherence to beads opsonized with either mouse or human serum as a source of complement. The role of CR1 in immune adherence was supported by studies showing that it was blocked by the addition of antibody to human CR1. Furthermore, human CR1 expression enhances the immune adherence of opsonized pneumococci to erythrocytes in vitro, and the pneumococci attached to erythrocytes via CR1 can be transferred in vitro to live macrophages. Even more importantly, we observed that if complement-opsonized pneumococci are injected intravenously with CR1+ mouse erythrocytes into wild-type mice (after a short in vitro incubation), they are cleared faster than opsonized pneumococci similarly injected with wild-type mouse erythrocytes. Finally, we have shown that the intravenous (i.v.) injection of pneumococci into CR1+ mice also results in more rapid blood clearance than in wild-type mice. These data support that immune adherence via CR1 on erythrocytes likely plays an important role in the clearance of opsonized bacteria from human blood.
Insulin resistance is a major characteristic of type 2 diabetes and is causally associated with obesity. Inflammation plays an important role in obesity-associated insulin resistance, but the underlying mechanism remains unclear. Interleukin (IL)-10 is an anti-inflammatory cytokine with lower circulating levels in obese subjects, and acute treatment with IL-10 prevents lipid-induced insulin resistance. We examined the role of IL-10 in glucose homeostasis using transgenic mice with muscle-specific overexpression of IL-10 (MCK-IL10).
RESEARCH DESIGN AND METHODS
MCK-IL10 and wild-type mice were fed a high-fat diet (HFD) for 3 weeks, and insulin sensitivity was determined using hyperinsulinemic-euglycemic clamps in conscious mice. Biochemical and molecular analyses were performed in muscle to assess glucose metabolism, insulin signaling, and inflammatory responses.
MCK-IL10 mice developed with no obvious anomaly and showed increased whole-body insulin sensitivity. After 3 weeks of HFD, MCK-IL10 mice developed comparable obesity to wild-type littermates but remained insulin sensitive in skeletal muscle. This was mostly due to significant increases in glucose metabolism, insulin receptor substrate-1, and Akt activity in muscle. HFD increased macrophage-specific CD68 and F4/80 levels in wild-type muscle that was associated with marked increases in tumor necrosis factor-α, IL-6, and C-C motif chemokine receptor-2 levels. In contrast, MCK-IL10 mice were protected from diet-induced inflammatory response in muscle.
These results demonstrate that IL-10 increases insulin sensitivity and protects skeletal muscle from obesity-associated macrophage infiltration, increases in inflammatory cytokines, and their deleterious effects on insulin signaling and glucose metabolism. Our findings provide novel insights into the role of anti-inflammatory cytokine in the treatment of type 2 diabetes.
Respiratory syncytial virus (RSV) is the leading cause of serious respiratory infections in children as well as a serious cause of disease in elderly and immunosuppressed populations. There are no licensed vaccines available to prevent RSV disease. We have developed a virus-like particle (VLP) vaccine candidate for protection from RSV. The VLP is composed of the NP and M proteins of Newcastle disease virus (NDV) and a chimeric protein containing the cytoplasmic and transmembrane domains of the NDV HN protein and the ectodomain of the human RSV G protein (H/G). Immunization of mice with 10 or 40 μg total VLP-H/G protein by intraperitoneal or intramuscular inoculation stimulated antibody responses to G protein which were as good as or better than those stimulated by comparable amounts of UV-inactivated RSV. Immunization of mice with two doses or even a single dose of these particles resulted in the complete protection of mice from RSV replication in the lungs. Immunization with these particles induced neutralizing antibodies with modest titers. Upon RSV challenge of VLP-H/G-immunized mice, no enhanced pathology in the lungs was observed, although lungs of mice immunized in parallel with formalin-inactivated RSV (FI-RSV) showed the significant pathology that has previously been documented after immunization with FI-RSV. Thus, the VLP-H/G candidate vaccine was immunogenic in BALB/c mice and prevented replication of RSV in murine lungs, with no evidence of immunopathology. These data support further development of virus-like particle vaccine candidates for protection against RSV.