Toll-like receptors 9 and 3 as essential components of innate immune defense against mouse cytomegalovirus infection

Proc Natl Acad Sci U S A. 2004 Mar 9;101(10):3516-21. doi: 10.1073/pnas.0400525101. Epub 2004 Mar 1.

Abstract

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-oligodeoxynucleotide 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 (Tlr9(CpG1)). Mice homozygous for the Tlr9(CpG1) allele are highly susceptible to mouse cytomegalovirus infection and show impaired infection-induced secretion of IFN-alpha/beta 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 Tlr9(CpG1) 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 Tlr9(CpG1) 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Amino Acid Sequence
  • Animals
  • Antigens, Differentiation / genetics
  • Antigens, Differentiation / metabolism
  • Cytokines / biosynthesis
  • Cytomegalovirus Infections / genetics
  • Cytomegalovirus Infections / immunology*
  • DNA, Complementary / genetics
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Immunity, Innate* / drug effects
  • Immunity, Innate* / genetics
  • Killer Cells, Natural / immunology
  • 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
  • Mutation, Missense
  • Myeloid Differentiation Factor 88
  • Oligodeoxyribonucleotides / genetics
  • Oligodeoxyribonucleotides / pharmacology
  • Phenotype
  • Point Mutation
  • Receptors, Cell Surface / deficiency
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism*
  • Receptors, Immunologic / deficiency
  • Receptors, Immunologic / genetics
  • Receptors, Immunologic / metabolism
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Toll-Like Receptor 3
  • Toll-Like Receptor 9
  • Toll-Like Receptors

Substances

  • Adaptor Proteins, Signal Transducing
  • Antigens, Differentiation
  • CPG-oligonucleotide
  • Cytokines
  • DNA, Complementary
  • DNA-Binding Proteins
  • Membrane Glycoproteins
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • Oligodeoxyribonucleotides
  • Receptors, Cell Surface
  • Receptors, Immunologic
  • Tlr9 protein, mouse
  • Toll-Like Receptor 3
  • Toll-Like Receptor 9
  • Toll-Like Receptors

Associated data

  • GENBANK/AY510704
  • GENBANK/AY510705
  • GENBANK/AY510706