TLR3 controls constitutive IFN-β antiviral immunity in human fibroblasts and cortical neurons
Daxing Gao, … , Jean-Laurent Casanova, Shen-Ying Zhang
Daxing Gao, … , Jean-Laurent Casanova, Shen-Ying Zhang
Published November 18, 2020
Citation Information: J Clin Invest. 2021;131(1):e134529. https://doi.org/10.1172/JCI134529.
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Research Article Immunology Infectious disease

TLR3 controls constitutive IFN-β antiviral immunity in human fibroblasts and cortical neurons

Abstract

Human herpes simplex virus 1 (HSV-1) encephalitis can be caused by inborn errors of the TLR3 pathway, resulting in impairment of CNS cell-intrinsic antiviral immunity. Deficiencies of the TLR3 pathway impair cell-intrinsic immunity to vesicular stomatitis virus (VSV) and HSV-1 in fibroblasts, and to HSV-1 in cortical but not trigeminal neurons. The underlying molecular mechanism is thought to involve impaired IFN-α/β induction by the TLR3 recognition of dsRNA viral intermediates or by-products. However, we show here that human TLR3 controls constitutive levels of IFNB mRNA and secreted bioactive IFN-β protein, and thereby also controls constitutive mRNA levels for IFN-stimulated genes (ISGs) in fibroblasts. Tlr3–/– mouse embryonic fibroblasts also have lower basal ISG levels. Moreover, human TLR3 controls basal levels of IFN-β secretion and ISG mRNA in induced pluripotent stem cell–derived cortical neurons. Consistently, TLR3-deficient human fibroblasts and cortical neurons are vulnerable not only to both VSV and HSV-1, but also to several other families of viruses. The mechanism by which TLR3 restricts viral growth in human fibroblasts and cortical neurons in vitro and, by inference, by which the human CNS prevents infection by HSV-1 in vivo, is therefore based on the control of early viral infection by basal IFN-β immunity.

Authors

Daxing Gao, Michael J. Ciancanelli, Peng Zhang, Oliver Harschnitz, Vincent Bondet, Mary Hasek, Jie Chen, Xin Mu, Yuval Itan, Aurélie Cobat, Vanessa Sancho-Shimizu, Benedetta Bigio, Lazaro Lorenzo, Gabriele Ciceri, Jessica McAlpine, Esperanza Anguiano, Emmanuelle Jouanguy, Damien Chaussabel, Isabelle Meyts, Michael S. Diamond, Laurent Abel, Sun Hur, Gregory A. Smith, Luigi Notarangelo, Darragh Duffy, Lorenz Studer, Jean-Laurent Casanova, Shen-Ying Zhang

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Figure 2

Unrestricted virus growth and cytotoxicity in fibroblasts with TLR3 signaling deficiencies.

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Unrestricted virus growth and cytotoxicity in fibroblasts with TLR3 sign...
VSV-WT (A) and VSV-M51R (B) single-cycle replication curves for fibroblasts from healthy controls (C1 and C2) and patients with UNC-93B or TLR3 deficiency at a MOI of 1 over 24 hours. Control fibroblasts (C1–C4) and TLR3–/–, UNC93B–/–, NEMO–/–, STAT1–/–, and STAT2–/– fibroblasts were infected with VSV-WT (C) and VSV-M51R (D) at a MOI of 0.01 for 16 hours. Viral VSV-G RNA levels were then determined by RT-qPCR and normalized against C1. Cell mortality following infection with VSV-WT (E) and VSV-M51R (F) at a MOI of 1 for C1, UNC-93B–/–, and NEMO–/– fibroblasts, as measured by the release of lactate dehydrogenase (LDH) at the times indicated, in hours postinfection (hpi). Values are expressed relative to those for uninfected cells. Triplicate measurements from 3 independent experiments (A–B, E–F) or representative results from 3 independent experiments (C–D) are shown. The error bars indicate SD of biological triplicates. P values were obtained through log transformation followed by 1-way ANOVA and subsequent Tukey’s multiple comparison tests (A–B) or likelihood ratio tests (C–D), by comparing each patient’s fibroblasts with control fibroblasts, and the respective P value is indicated. *P < 0.05, **P < 0.01, ***P < 0.001.