Hiding from intracellular pattern recognition receptors, a passive strategy of flavivirus immune evasion.

Tick-borne encephalitis virus (TBEV) is a medically important flavivirus in Europe and Asia, causing meningitis and encephalitis in thousands of people annually. Despite its relevance for public health, the interaction of TBEV with the type I interferon (IFN) system is poorly characterized. Induction of these antiviral cytokines is normally triggered by cytoplasmic recognition of viral signature molecules such as double-stranded (ds) RNA. In a recent paper, we showed that TBEV infection leads to formation of intracellular membrane vesicles which protect the viral dsRNA from cellular recognition. This delays the onset of antiviral IFN production sufficiently enough for an unhindered release of progeny viruses over 24 h. Thus, TBEV has evolved a stealth strategy to outrun the antiviral IFN response.