PMID- 25078697 OWN - NLM STAT- MEDLINE DCOM- 20141125 LR - 20211021 IS - 1098-5514 (Electronic) IS - 0022-538X (Print) IS - 0022-538X (Linking) VI - 88 IP - 20 DP - 2014 Oct TI - Toll-like receptor 9-mediated protection of enterovirus 71 infection in mice is due to the release of danger-associated molecular patterns. PG - 11658-70 LID - 10.1128/JVI.00867-14 [doi] AB - Enterovirus 71 (EV71), a positive-stranded RNA virus, is the major cause of hand, foot, and mouth disease (HFMD) with severe neurological symptoms. Antiviral type I interferon (alpha/beta interferon [IFN-alpha/beta]) responses initiated from innate receptor signaling are inhibited by EV71-encoded proteases. It is less well understood whether EV71-induced apoptosis provides a signal to activate type I interferon responses as a host defensive mechanism. In this report, we found that EV71 alone cannot activate Toll-like receptor 9 (TLR9) signaling, but supernatant from EV71-infected cells is capable of activating TLR9. We hypothesized that TLR9-activating signaling from plasmacytoid dendritic cells (pDCs) may contribute to host defense mechanisms. To test our hypothesis, Flt3 ligand-cultured DCs (Flt3L-DCs) from both wild-type (WT) and TLR9 knockout (TLR9KO) mice were infected with EV71. More viral particles were produced in TLR9KO mice than by WT mice. In contrast, alpha interferon (IFN-alpha), monocyte chemotactic protein 1 (MCP-1), tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, interleukin 6 (IL-6), and IL-10 levels were increased in Flt3L-DCs from WT mice infected with EV71 compared with TLR9KO mice. Seven-day-old TLR9KO mice infected with a non-mouse-adapted EV71 strain developed neurological lesion-related symptoms, including hind-limb paralysis, slowness, ataxia, and lethargy, but WT mice did not present with these symptoms. Lung, brain, small intestine, forelimb, and hind-limb tissues collected from TLR9KO mice exhibited significantly higher viral loads than equivalent tissues collected from WT mice. Histopathologic damage was observed in brain, small intestine, forelimb, and hind-limb tissues collected from TLR9KO mice infected with EV71. Our findings demonstrate that TLR9 is an important host defense molecule during EV71 infection. Importance: The host innate immune system is equipped with pattern recognition receptors (PRRs), which are useful for defending the host against invading pathogens. During enterovirus 71 (EV71) infection, the innate immune system is activated by pathogen-associated molecular patterns (PAMPs), which include viral RNA or DNA, and these PAMPs are recognized by PRRs. Toll-like receptor 3 (TLR3) and TLR7/8 recognize viral nucleic acids, and TLR9 senses unmethylated CpG DNA or pathogen-derived DNA. These PRRs stimulate the production of type I interferons (IFNs) to counteract viral infection, and they are the major source of antiviral alpha interferon (IFN-alpha) production in pDCs, which can produce 200- to 1,000-fold more IFN-alpha than any other immune cell type. In addition to PAMPs, danger-associated molecular patterns (DAMPs) are known to be potent activators of innate immune signaling, including TLR9. We found that EV71 induces cellular apoptosis, resulting in tissue damage; the endogenous DNA from dead cells may activate the innate immune system through TLR9. Therefore, our study provides new insights into EV71-induced apoptosis, which stimulates TLR9 in EV71-associated infections. CI - Copyright (c) 2014, American Society for Microbiology. All Rights Reserved. FAU - Hsiao, Hung-Bo AU - Hsiao HB AD - National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Miaoli, Taiwan. FAU - Chou, Ai-Hsiang AU - Chou AH AD - National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Miaoli, Taiwan. FAU - Lin, Su-I AU - Lin SI AD - National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Miaoli, Taiwan. FAU - Chen, I-Hua AU - Chen IH AD - National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Miaoli, Taiwan. FAU - Lien, Shu-Pei AU - Lien SP AD - National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Miaoli, Taiwan. FAU - Liu, Chia-Chyi AU - Liu CC AD - National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Miaoli, Taiwan. FAU - Chong, Pele AU - Chong P AD - National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Miaoli, Taiwan Graduate Institute of Immunology, China Medical University, Taichung, Taiwan. FAU - Liu, Shih-Jen AU - Liu SJ AD - National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Miaoli, Taiwan Graduate Institute of Immunology, China Medical University, Taichung, Taiwan levent@nhri.org.tw. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20140730 PL - United States TA - J Virol JT - Journal of virology JID - 0113724 RN - 0 (Cytokines) RN - 0 (DNA Primers) RN - 0 (Interferon Type I) RN - 0 (NF-kappa B) RN - 0 (Tlr9 protein, mouse) RN - 0 (Toll-Like Receptor 9) SB - IM MH - Animals MH - Base Sequence MH - Cells, Cultured MH - Cytokines/metabolism MH - DNA Primers MH - Enterovirus A, Human/*isolation & purification/physiology MH - Enterovirus Infections/*prevention & control MH - Enzyme-Linked Immunosorbent Assay MH - Interferon Type I/biosynthesis MH - Mice MH - Mice, Knockout MH - NF-kappa B/metabolism MH - Real-Time Polymerase Chain Reaction MH - Toll-Like Receptor 9/genetics/*physiology MH - Virus Replication PMC - PMC4178751 EDAT- 2014/08/01 06:00 MHDA- 2014/12/15 06:00 PMCR- 2015/04/01 CRDT- 2014/08/01 06:00 PHST- 2014/08/01 06:00 [entrez] PHST- 2014/08/01 06:00 [pubmed] PHST- 2014/12/15 06:00 [medline] PHST- 2015/04/01 00:00 [pmc-release] AID - JVI.00867-14 [pii] AID - 00867-14 [pii] AID - 10.1128/JVI.00867-14 [doi] PST - ppublish SO - J Virol. 2014 Oct;88(20):11658-70. doi: 10.1128/JVI.00867-14. Epub 2014 Jul 30.