CTSB and infection: Interestingly, a decrease in the infectivity of late penetrating RV strains (UK, Wa, WI61, DS-1, and YM), but not of RV RRV or nar3, has been evidenced in cells where cathepsin B and L were inhibited prior to infection pharmacologically (CA-074 targeting cathepsin B, Z-FF-FMK targeting cathepsin L, leupeptin targeting pan-endolysosomal proteases) or by RNAi [81,93] (Figure 2), suggesting late penetrating RVs to require cathepsin activity for cellular entry.