Innate immune system activation by viral RNA: How to predict it?

The immune system is able to identify foreign pathogens via different pathways. In the case of viral infection, recognition of the viral RNA is a crucial step, and many efforts have been made to understand which features of viral RNA are detected by the immune system. The biased viral RNA composition, measured as host-virus nucleotidic divergence, or CpG enrichment, has been proposed as salient signal. Peculiar structural features of these RNA could also be related to the immune system activation. Here, we gather multiple datasets and proceed to a meta-analysis to uncover the best predictors of immune system activation by viral RNA. "A" nucleotide content and Minimum Folding Energy are good predictors, and are more easily generalized than more complex indicators suggested previously. As RNA composition and structure are highly correlated, we suggest further experiments on synthetic sequences to identify the viral RNA sensing mechanisms by immune system receptors.