TLR3 and infection: Interestingly, similar patterns of mRNA expression levels of innate immune-associated genes appeared in REV exosome or free virion-mediated viral infections, but the mRNA expression of pattern recognition receptors, including TLR3 and MDA5, and interleukin (IL) like IL-6 and IL-8 of REV exosome-mediated viral infections was significantly higher than that of free virion-mediated infection both in vivo and in vitro.