TLR3 Increases Disease Morbidity and Mortality from Vaccinia Infection

Graduate Program in Immunology, Department of Radiology, Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor 48109-2200, USA.
The Journal of Immunology (Impact Factor: 4.92). 02/2008; 180(1):483-91. DOI: 10.4049/jimmunol.180.1.483
Source: PubMed


Innate immunity is required for effective control of poxvirus infections, but cellular receptors that initiate the host response to these DNA viruses remain poorly defined. Given this information and the fact that functions of TLRs in immunity to DNA viruses remain controversial, we investigated effects of TLR3 on pathogenesis of vaccinia virus, a prototype poxvirus. We used a recombinant strain Western Reserve vaccinia virus that expresses firefly luciferase to infect wild-type C57BL/6 and TLR3-/- mice through intranasal inoculation. Bioluminescence imaging showed that TLR3-/- mice had substantially lower viral replication in the respiratory tract and diminished dissemination of virus to abdominal organs. Mice lacking TLR3 had reduced disease morbidity, as measured by decreased weight loss and hypothermia after infection. Importantly, TLR3-/- mice also had improved survival relative to wild-type mice. Infected TLR3-/- mice had significantly reduced lung inflammation and recruitment of leukocytes to the lung. Mice lacking TLR3 also had lower levels of inflammatory cytokines, including IL-6, MCP-1, and TNF-alpha in serum and/or bronchoalveolar lavage fluid, but levels of IFN-beta did not differ between genotypes of mice. To our knowledge, our findings show for the first time that interactions between TLR3 and vaccinia increase viral replication and contribute to detrimental effects of the host immune response to poxviruses.

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Available from: Gary D Luker, Oct 14, 2015
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    • "TLR3 has been shown experimentally to be essential for optimal protection against some but not all viruses, even those with a dsRNA genome [17]. Moreover, under some circumstances TLR3 may be responsible for exaggerated inflammation [65], and anti-TLR3 blocking antibody is being developed for therapeutic use [66]. Importantly, TLR3 is a receptor not only for microbial dsRNA, but also for dsRNA from necrotic host cells [67], an example of an endogenous danger-associated molecular pattern. "
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    ABSTRACT: Cigarette smoking is associated with increased frequency and duration of viral respiratory infections, but the underlying mechanisms are incompletely defined. We investigated whether smoking reduces expression by human lung macrophages (Mø) of receptors for viral nucleic acids and, if so, the effect on CXCL10 production. We collected alveolar macrophages (AMø) by bronchoalveolar lavage of radiographically-normal lungs of subjects undergoing bronchoscopies for solitary nodules (n = 16) and of volunteers who were current or former smokers (n = 7) or never-smokers (n = 13). We measured expression of mRNA transcripts for viral nucleic acid receptors by real-time PCR in those AMø and in the human Mø cell line THP-1 following phorbol myristate acetate/vitamin D3 differentiation and exposure to cigarette smoke extract, and determined TLR3 protein expression using flow cytometry and immunohistochemistry. We also used flow cytometry to examine TLR3 expression in total lung Mø from subjects undergoing clinically-indicated lung resections (n = 25). Of these, seven had normal FEV1 and FEV1/FVC ratio (three former smokers, four current smokers); the remaining 18 subjects (14 former smokers; four current smokers) had COPD of GOLD stages I-IV. We measured AMø production of CXCL10 in response to stimulation with the dsRNA analogue poly(I:C) using Luminex assay. Relative to AMø of never-smokers, AMø of smokers demonstrated reduced protein expression of TLR3 and decreased mRNA for TLR3 but not TLR7, TLR8, TLR9, RIG-I, MDA-5 or PKR. Identical changes in TLR3 gene expression were induced in differentiated THP-1 cells exposed to cigarette smoke-extract in vitro for 4 hours. Among total lung Mø, the percentage of TLR3-positive cells correlated inversely with active smoking but not with COPD diagnosis, FEV1% predicted, sex, age or pack-years. Compared to AMø of never-smokers, poly(I:C)-stimulated production of CXCL10 was significantly reduced in AMø of smokers. Active smoking, independent of COPD stage or smoking duration, reduces both the percent of human lung Mø expressing TLR3, and dsRNA-induced CXCL10 production, without altering other endosomal or cytoplasmic receptors for microbial nucleic acids. This effect provides one possible mechanism for increased frequency and duration of viral lower respiratory tract infections in smokers. NCT00281190, NCT00281203 and NCT00281229.
    Respiratory research 03/2013; 14(1):33. DOI:10.1186/1465-9921-14-33 · 3.09 Impact Factor
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    • "TLR3-deficient mice are susceptible to some viruses (Edelmann et al., 2004; Tabeta et al., 2004; Rudd et al., 2006; Hardarson et al., 2007; Negishi et al., 2008; Richer et al., 2009) but normally resistant or more resistant to others (Table S3; Edelmann et al., 2004; Wang et al., 2004; Gowen et al., 2006; Le Goffic et al., 2006; Hutchens et al., 2008). TLR3-deficient mice are susceptible to EMCV (Hardarson et al., 2007), mouse CMV (Tabeta et al., 2004, Edelmann et al., 2004), respiratory syncytial virus (Rudd et al., 2006), CVB3 (Negishi et al., 2008), and CVB4 (Richer et al., 2009) but have normal resistance to lymphocytic choriomeningitis virus, VSV, and reovirus (Edelmann et al., 2004), and enhanced resistance to Punta Toro virus (Gowen et al., 2006), influenza virus (Le Goffic et al., 2006), West Nile virus (Wang et al., 2004), and vaccinia virus (Hutchens et al., 2008) infections, taking TLR3 WT mice as "
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    ABSTRACT: Autosomal dominant TLR3 deficiency has been identified as a genetic etiology of childhood herpes simplex virus 1 (HSV-1) encephalitis (HSE). This defect is partial, as it results in impaired, but not abolished induction of IFN-β and -λ in fibroblasts in response to TLR3 stimulation. The apparently normal resistance of these patients to other infections, viral illnesses in particular, may thus result from residual TLR3 responses. We report here an autosomal recessive form of complete TLR3 deficiency in a young man who developed HSE in childhood but remained normally resistant to other infections. This patient is compound heterozygous for two loss-of-function TLR3 alleles, resulting in an absence of response to TLR3 activation by polyinosinic-polycytidylic acid (poly(I:C)) and related agonists in his fibroblasts. Moreover, upon infection of the patient's fibroblasts with HSV-1, the impairment of IFN-β and -λ production resulted in high levels of viral replication and cell death. In contrast, the patient's peripheral blood mononuclear cells responded normally to poly(I:C) and to all viruses tested, including HSV-1. Consistently, various TLR3-deficient leukocytes from the patient, including CD14(+) and/or CD16(+) monocytes, plasmacytoid dendritic cells, and in vitro derived monocyte-derived macrophages, responded normally to both poly(I:C) and HSV-1, with the induction of antiviral IFN production. These findings identify a new genetic etiology for childhood HSE, indicating that TLR3-mediated immunity is essential for protective immunity to HSV-1 in the central nervous system (CNS) during primary infection in childhood, in at least some patients. They also indicate that human TLR3 is largely redundant for responses to double-stranded RNA and HSV-1 in various leukocytes, probably accounting for the redundancy of TLR3 for host defense against viruses, including HSV-1, outside the CNS.
    Journal of Experimental Medicine 09/2011; 208(10):2083-98. DOI:10.1084/jem.20101568 · 12.52 Impact Factor
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    ABSTRACT: Protection against West Nile virus (WNV) infection requires rapid viral sensing and the generation of an interferon (IFN) response. Mice lacking IFN regulatory factor 3 (IRF-3) show increased vulnerability to WNV infection with enhanced viral replication and blunted IFN-stimulated gene (ISG) responses. IRF-3 functions downstream of several viral sensors, including Toll-like receptor 3 (TLR3), RIG-I, and MDA5. Cell culture studies suggest that host recognizes WNV in part, through the cytoplasmic helicase RIG-I and to a lesser extent, MDA5, both of which activate ISG expression through IRF-3. However, the role of TLR3 in vivo in recognizing viral RNA and activating antiviral defense pathways has remained controversial. We show here that an absence of TLR3 enhances WNV mortality in mice and increases viral burden in the brain. Compared to congenic wild-type controls, TLR3−/− mice showed relatively modest changes in peripheral viral loads. Consistent with this, little difference in multistep viral growth kinetics or IFN-α/β induction was observed between wild-type and TLR3−/− fibroblasts, macrophages, and dendritic cells. In contrast, a deficiency of TLR3 was associated with enhanced viral replication in primary cortical neuron cultures and greater WNV infection in central nervous system neurons after intracranial inoculation. Taken together, our data suggest that TLR3 serves a protective role against WNV in part, by restricting replication in neurons.
    Journal of Virology 09/2008; 82(21):10349-58. DOI:10.1128/JVI.00935-08 · 4.44 Impact Factor
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