The final step of seven steps in the HIV life cycle. During budding, immature (noninfectious) HIV pushes itself out of the host CD4 cell. (Noninfectious HIV can't infect another CD4 cell.) Once outside the CD4 cell, the new HIV releases protease, an HIV enzyme. Protease acts to break up the long protein chains that form the noninfectious virus. The smaller HIV proteins combine to form mature, infectious HIV.