Taenia solium: A cysteine protease secreted by metacestodes depletes humanCD4 lymphocytes in vitro

Taenia solium: A cysteine protease secreted by metacestodes depletes human CD4 Lymphocytes in Vitro. Experimental Parasitology 94, 133-142. Excreted/s ecreted products from Taenia solium metacestodes cultured in vitro were ana lyzed for peptidase activity using peptide substrates Z-Phe-Arg-AFC, Arg-AF C, and Z-Gly-Gly-Arg-AFC and zymography studies. Specific inhibitor profile s revealed mainly cysteine and metalloprotease activities. Hydrolysis of su bstrate Z-Phe-Arg-AFC was augmented by the addition of L-cysteine and acid pH, consistent with cysteine protease activity. Cysteine protease activity was more prominent in supernatants from living metacestodes cultured in PBS than in either RPMI or RPMI plus fetal calf serum and was proportional to the number of metacestodes. Flow cytometry analysis showed depletion of hum an T lymphocytes cultured with living II: solium metacestodes. CD4(+) expre ssion was significantly decreased when metacestode E/S products and L-cyste ine were added to lymphocyte cultures (P = 0.027). This peptidase activity was inhibited by E-64 indicating that the depletion of CD4+ cells was due t o cysteine protease activity. Thus, T. solium metacestodes produce excretor y/secretory proteases. These enzymes may cleave molecules critical for the host immune response allowing the parasites to survive in the host tissues. (C) 2000 Academic Press.