TY - JOUR
T1 - TLR2 and TLR9 synergistically control herpes simplex virus infection in the brain
AU - Sørensen, Louise N
AU - Reinert, Line S
AU - Malmgaard, Lene
AU - Bartholdy, Christina
AU - Thomsen, Allan R
AU - Paludan, Søren R
PY - 2008
Y1 - 2008
N2 - Viruses are recognized by the innate immune system through pattern recognition receptors (PRRs). For instance, HSV virions and genomic DNA are recognized by TLR2 and TLR9, respectively. Although several viruses and viral components have been shown to stimulate cells through TLRs, only very few studies have defined essential roles for single TLRs in innate immune defense in vivo. This could suggest that PRRs act in concert to mount the first line of defense against virus infections. To test this hypothesis we have examined the host response of C57BL/6, TLR2(-/-), TLR9(-/-), and TLR2/9(-/-) mice toward HSV-2 infection. After a systemic infection, the cytokine serum response was markedly reduced in the double knockout mice, but only partly affected in either strain of the single knockout mice. This was supported by in vitro data showing that HSV-induced cytokine expression relayed on TLR2 and TLR9 in a cytokine- and cell type-dependent manner. With respect to the cellular response to infection, we found that recruitment but not activation of NK cells was impaired in TLR2/9(-/-) mice. Importantly, the viral load in the brain, but not liver, was significantly higher in the brain of TLR2/9(-/-) mice whereas the viral loads in organs of single knockout mice were statistically indistinguishable from C57BL/6 mice. In the brain we found that TNF-alpha and the IFN-stimulated gene CXCL9 were expressed during infection and were dependent on either TLR2 or TLR9. Thus, TLR2 and TLR9 synergistically stimulate innate antiviral activities, thereby protecting against HSV infection in the brain.
AB - Viruses are recognized by the innate immune system through pattern recognition receptors (PRRs). For instance, HSV virions and genomic DNA are recognized by TLR2 and TLR9, respectively. Although several viruses and viral components have been shown to stimulate cells through TLRs, only very few studies have defined essential roles for single TLRs in innate immune defense in vivo. This could suggest that PRRs act in concert to mount the first line of defense against virus infections. To test this hypothesis we have examined the host response of C57BL/6, TLR2(-/-), TLR9(-/-), and TLR2/9(-/-) mice toward HSV-2 infection. After a systemic infection, the cytokine serum response was markedly reduced in the double knockout mice, but only partly affected in either strain of the single knockout mice. This was supported by in vitro data showing that HSV-induced cytokine expression relayed on TLR2 and TLR9 in a cytokine- and cell type-dependent manner. With respect to the cellular response to infection, we found that recruitment but not activation of NK cells was impaired in TLR2/9(-/-) mice. Importantly, the viral load in the brain, but not liver, was significantly higher in the brain of TLR2/9(-/-) mice whereas the viral loads in organs of single knockout mice were statistically indistinguishable from C57BL/6 mice. In the brain we found that TNF-alpha and the IFN-stimulated gene CXCL9 were expressed during infection and were dependent on either TLR2 or TLR9. Thus, TLR2 and TLR9 synergistically stimulate innate antiviral activities, thereby protecting against HSV infection in the brain.
M3 - Journal article
C2 - 19050280
SN - 0022-1767
VL - 181
SP - 8604
EP - 8612
JO - Journal of Immunology
JF - Journal of Immunology
IS - 12
ER -