Toll-Like Receptors 9 and 3 As Essential Components of Innate Immune Defense against Mouse Cytomegalovirus Infection

• Published in: Proceedings of the National Academy of Sciences - PNAS 2004-03, Vol.101 (10), p.3516-3521
• Main Authors: Tabeta, Koichi, Georgel, Philippe, Janssen, Edith, Du, Xin, Hoebe, Kasper, Crozat, Karine, Mudd, Suzanne, Shamel, Louis, Sovath, Sosathya, Goode, Jason, Alexopoulou, Lena, Flavell, Richard A., Beutler, Bruce
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Alleles; Amino Acid Sequence; Amino acids; Animals; Antigens, Differentiation - genetics; Antigens, Differentiation - metabolism; Biological Sciences; Cells; Cytokines; Cytokines - biosynthesis; Cytomegalovirus Infections - genetics; Cytomegalovirus Infections - immunology; DNA, Complementary - genetics; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Double stranded RNA; Genes; Genotype & phenotype; Genotypes; Immunity, Innate - drug effects; Immunity, Innate - genetics; Immunology; Infections; Killer Cells, Natural - immunology; Life Sciences; Membrane Glycoproteins - deficiency; Membrane Glycoproteins - genetics; Membrane Glycoproteins - metabolism; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Mice, Mutant Strains; Molecular Sequence Data; Murine cytomegalovirus; Mutation; Mutation, Missense; Myeloid Differentiation Factor 88; Natural killer T cells; Oligodeoxyribonucleotides - genetics; Oligodeoxyribonucleotides - pharmacology; Pathogens; Phenotype; Phenotypes; Point Mutation; Receptors; Receptors, Cell Surface - deficiency; Receptors, Cell Surface - genetics; Receptors, Cell Surface - metabolism; Receptors, Immunologic - deficiency; Receptors, Immunologic - genetics; Receptors, Immunologic - metabolism; Ribonucleic acid; RNA; Sequence Homology, Amino Acid; Signal Transduction; T cell receptors; Toll-Like Receptor 3; Toll-Like Receptor 9; Toll-Like Receptors; Viral infections; Viruses
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0400525101

Several subsets of dendritic cells have been shown to produce type I IFN in response to viral infections, thereby assisting the natural killer cell-dependent response that eliminates the pathogen. Type I IFN production can be induced both by unmethylated CpG-oligode-oxynucleotide and by double-stranded RNA. Here, we describe a codominant CpG-ODN unresponsive phenotype that results from an N-ethyl-N-nitrosourea-induced missense mutation in the Tlr9 gene (Tlr9CpG1). Mice homozygous for the Tlr9CpG1 allele are highly susceptible to mouse cytomegalovirus infection and show impaired infection-induced secretion of IFN-α/β and natural killer cell activation. We also demonstrate that both the Toll-like receptor (TLR) 9 → MyD88 and TLR3 → Trif signaling pathways are activated in vivo on viral inoculation, and that each pathway contributes to innate defense against systemic viral infection. Whereas both pathways lead to type I IFN production, neither pathway offers full protection against mouse cytomegalovirus infection in the absence of the other. The Tlr9CpG1 mutation alters a leucine-rich repeat motif and lies within a receptor domain that is conserved within the evolutionary cluster encompassing TLRs 7, 8, and 9. In other TLRs, including three mouse-specific TLRs described in this paper, the affected region is not represented. The phenotypic effect of the Tlr9CpG1 allele thus points to a critical role for TLR9 in viral sensing and identifies a vulnerable amino acid within the ectodomain of three TLR proteins, essential for a ligand response.