Among them, cysteine proteases are the most investigated proteolytic enzymes in Leishmania. These enzymes play important roles in Leishmania, such as virulence, viability maintenance, parasite morphology, invasion of the host's mononuclear phagocytic system, and the modulation of its immune response27,28, thus constituting attractive targets for chemotherapy for the treatment of leishmaniasis. The gene discussed is CTSB; the disease is leishmaniasis.