Cysteine protease that plays an essential role in host liquefaction to facilitate horizontal transmission of the virus. Accumulates within infected cells as an inactive proenzyme (proV-CATH), which is activated by proteolytic cleavage upon cell death. Endopeptidase of broad specificity, hydrolyzing substrates of both cathepsin L and cathepsin B. Optimum pH is 5.0-5.5. Interacts with chitinase/CHIA; this interaction maintains VCATH in the host reticulum endoplasmic. Retained in the host reticulum by its interaction with chitinase/CHIA. Synthesized as an inactive proenzyme and activated by proteolytic removal of the inhibitory propeptide. Belongs to the peptidase C1 family.