Inosine-containing RNA is a novel innate immune recognition element and reduces RSV infection.
During viral infections, single- and double-stranded RNA (ssRNA and dsRNA) are recognized by the host and induce innate immune responses. The cellular enzyme ADAR-1 (adenosine deaminase acting on RNA-1) activation in virally infected cells leads to presence of inosine-containing RNA (Ino-RNA). Here we report that ss-Ino-RNA is a novel viral recognition element. We synthesized unmodified ssRNA and ssRNA that had 6% to16% inosine residues. The results showed that in primary human cells, or in mice, 10% ss-Ino-RNA rapidly and potently induced a significant increase in inflammatory cytokines, such as interferon (IFN)-β (35 fold), tumor necrosis factor (TNF)-α (9.7 fold), and interleukin (IL)-6 (11.3 fold) (p<0.01). Flow cytometry data revealed a corresponding 4-fold increase in influx of neutrophils into the lungs by ss-Ino-RNA treatment. In our in vitro experiments, treatment of epithelial cells with ss-Ino-RNA reduced replication of respiratory syncytial virus (RSV). Interestingly, RNA structural analysis showed that ss-Ino-RNA had increased formation of secondary structures. Our data further revealed that extracellular ss-Ino-RNA was taken up by scavenger receptor class-A (SR-A) which activated downstream MAP Kinase pathways through Toll-like receptor 3 (TLR3) and dsRNA-activated protein kinase (PKR). Our data suggests that ss-Ino-RNA is an as yet undescribed virus-associated innate immune stimulus.
Laboratory of Respiratory Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, North Carolina, United States of America.
Jie-ying
JY
Liao
Sheetal A
SA
Thakur
Zachary B
ZB
Zalinger
Kevin E
KE
Gerrish
Farhad
F
Imani
D000818:Animals; D000998:Antiviral Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D001483:Base Sequence; D002460:Cell Line; D018925:Chemokines / Q000096:biosynthesis / Q000378:metabolism; D004705:Endocytosis; D004847:Epithelial Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism / Q000821:virology; D005110:Extracellular Space / Q000187:drug effects / Q000276:immunology / Q000378:metabolism / Q000821:virology; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects*; D007288:Inosine; D016899:Interferon-beta / Q000096:biosynthesis; D015850:Interleukin-6 / Q000096:biosynthesis; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000276:immunology / Q000378:metabolism / Q000821:virology; D051379:Mice; D009690:Nucleic Acid Conformation; D011494:Protein Kinases / Q000378:metabolism; D012313:RNA / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D012136:Respiratory Syncytial Viruses / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D051117:Scavenger Receptors, Class A / Q000378:metabolism; D051196:Toll-Like Receptor 3 / Q000378:metabolism; D059467:Transcriptome / Q000187:drug effects / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D014779:Virus Replication / Q000187:drug effects / Q000276:immunology
D000998:Antiviral Agents; D018925:Chemokines; D015850:Interleukin-6; D051117:Scavenger Receptors, Class A; C495344:TLR3 protein, human; D051196:Toll-Like Receptor 3; D014409:Tumor Necrosis Factor-alpha; D007288:Inosine; D012313:RNA; D016899:Interferon-beta; D011494:Protein Kinases