Flaviviruses have evolved complex mechanisms to evade the mammalian host immune systems including the RIG-I (retinoic acid-inducible gene I) like receptor (RLR) signaling. Zika virus (ZIKV) is a re-emerging flavivirus that is associated with severe neonatal microcephaly and adult Guillain-Barre syndrome. However, the molecular mechanisms underlying ZIKV pathogenesis remain poorly defined. Here we report that ZIKV non-structural protein 4A (NS4A) impairs the RLR-mitochondrial antiviral-signaling protein (MAVS) interaction and subsequent induction of antiviral immune responses. In human trophoblasts, both RIG-I and melanoma differentiation-associated protein 5 (MDA5) contribute to type I interferon (IFN) induction and control ZIKV replication. Type I IFN induction by ZIKV is almost completely abolished in MAVS-/- cells. NS4A represses RLR-, but not Toll-like receptor-mediated immune responses. NS4A specifically binds the N-terminal caspase activation and recruitment domain (CARD) of MAVS and thus blocks its accessibility by RLRs. Our study provides in-depth understanding of the molecular mechanisms of immune evasion by ZIKV and its pathogenesis.

Objectives Nasopharyngeal carcinoma (NPC) is a rare cancer in the United States. An association between NPC and Epstein-Barr virus (EBV) is well-established for World Health Organization (WHO) types II and III (WHO-II/III) NPC but less well-established for WHO type I (WHO-I) NPC. Given the rise in oropharyngeal tumors positive for high-risk human papillomavirus (HPV) and the unique biology of WHO-I NPC, we examined the relationship between HPV and WHO-I NPC. Study Design Retrospective case-comparison study. Methods A search of a large multidisciplinary cancer center tumor registry identified 183 patients seen from January 1999 to December 2008 with incident NPC and no prior cancer. Available paraffin-embedded tumor specimens (N=30) were analyzed for oncogenic HPV status by in-situ hybridization (ISH) and polymerase chain reaction (PCR) for HPV-16 and HPV-18; EBV status by ISH; and p16 expression by immunohistochemistry. Demographic parameters, including race and smoking, were obtained from the medical records. Results Among the 18 WHO-I NPC patients, 66% (N=12) were smokers and 17% (N=3) Asian; among the 165 WHO-II/III NPC patients, 44% (N=73) were smokers and 24% (N=39) Asian. Eight WHO-I NPC patients had available paraffin blocks; 5 of 6 were HPV-16-positive by PCR and 4 of 8 were HPV-positive by ISH; only 2 of 8 (25%) were EBV-positive. Twenty-two WHO-II/III NPC patients had available paraffin blocks; only 1 was HPV-positive by ISH, and 13 of 22 (60%) were EBV-positive. Conclusions These results suggest that WHO-I NPC is associated with oncogenic HPV, though larger studies are needed to verify these findings.

These results suggest that WHO type I NPC may be associated with oncogenic HPV, though larger studies are needed to verify these findings.