Both TRIF and IPS-1 Adaptor Proteins Contribute to the Cerebral Innate Immune Response against Herpes Simplex Virus

Toll-like receptors (TLRs) and RNA helicases (RLHs) are important cell sensors involved in the immunological control of viral infections through production of type I interferon (IFN). The impact of a deficiency in the TRIF and IPS-1 adaptor proteins, re-spectively, implicated in TLR3 and RLH signaling pathways, was investigated during herpes simplex virus 1 (HSV-1) encephali-tis. TRIF/, IPS-1/, and C57BL/6 wild-type (WT)mice were infected intranasally with 7.5 105 PFU of HSV-1. Mice were monitored for neurological signs and survival over 20 days. Groups of mice were sacrificed on days 3, 5, 7, 9, and 11 postinfection for determination of brain viral replication by quantitative PCR (qPCR), plaque assay, and immunohistochemistry and for al-pha/beta interferon (IFN-/) levels and phosphorylation of interferon regulatory factors 3 and 7 (IRF-3 and-7) in brain ho-mogenates by enzyme-linked immunosorbent assay (ELISA) andWestern blotting, respectively. TRIF/ and IPS-1/mice had higher mortality rates thanWTmice (P 0.02 and P 0.09, respectively). Viral antigens were more disseminated throughout the brain, correlating with a significant increase in brain viral load for TRIF/ (days 5 to 9) and IPS-1/ (days 7 and 9) mice compared to results for theWT. IFN- production was reduced in brain homogenates of TRIF/ and IPS-1/mice on day 5 compared to results for theWT, whereas IFN- levels were increased on day 7 in TRIF/mice. Phosphorylation levels of IRF-3 and IRF-7 were decreased in TRIF/ and IPS-1/mice, respectively. These data suggest that both the TRIF and IPS-1 signaling pathways are important for the control of HSV replication in the brain and survival through IFN- production. Herpes simplex virus 1 (HSV-1) is a frequent human pathogen,most commonly associatedwith orolabial, genital, and ocula