Detection and Preliminary Characterization of Taenia solium Metacestode Proteases

Abstract

The metacestode of Taenia solium persists for years in the human central nervous system. As proteolytic enzymes play an important role in the survival of tissues helminths, we examined extracts of T. solium metacestodes for proteolytic activity using 9 synthetic peptide substrates and 3 proteins (hemoglobin, albumin, and immunoglobulin G). The proteolytic enzymes were classified based on their inhibitor profiles. At neutral pH, aminopeptidase(arginine-7-amino-4-trifluoromethylcoumarin) and endopeptidase(benzyloxy-carbonyl-glycine-glycine-arginine-7-amino-4- trifluoromethylcoumarin) substrates were cleaved. Hydrolysis of both substrates was inhibited by chelating agents, which inhibit metalloproteases. Peak activity with both substrates eluted in gel filtration fractions corresponding to a molecular weight of about 104 kDa. Cysteine protease activity was identified, which cleaved benzyloxy-carbonyl-phenylalanine-arginine-7-amino- 4-trifluoromethylcoumarin (Z-Phe-Arg-AFC) and hemoglobin. Cleavage of Z-Phe-Arg-AFC was maximal at acid pH, was stimulated by thiols, and was inhibited by leupeptin and Ep459. Peak cysteine protease activity eluted in gel filtration fractions corresponding to a molecular weight of 32 kDa. Aspartic protease activity was identified by specific inhibition with pepstatin of acid digestion of hemoglobin and immunoglobulin G. Immunoglobulin digestion occurred at acid pH, with preferential degradation of the heavy chain. Upon gel filtration chromatography, the aspartic protease activity eluted as a broad peak with maximal activity at about 90 kDa. No serine protease activity was detected. None of the parasite enzymes digested albumin. Proteolytic enzymes of T. solium may be important for parasite survival in the intermediate host, by providing nutrients and digesting host immune molecules.

The implantation of Taenia solium metacestodes in mice induces down-modulation of T-cell proliferation and cytokine production

“…The depletion of T cells, particularly the CD4 + population Molinari et al 1987), and the suppression of T-cell proliferative responses (Molinari et al 1993a), have been described in cysticercotic pigs. The present results suggest that implanted metacestodes release the suppressive MF in vivo, which may be responsible, along with other molecules such as paramyosin (Laclette et al 1992) and cysteine proteases (White et al 1992;Molinari et al 2000;Tato et al 2004), for suppressing the host immune system. As far as we are aware, the down-modulation induced by F1 is not caused by the stimulation of a particular subset of cells (Th1 or Th2 for instance), but is due to the interaction of this molecule with different cells inducing the inhibition of cytokine production in a non-specific manner.…”

A cysteine protease from Taenia solium metacestodes induce apoptosis in human CD4+ T-cells

“…Cysteine proteases released by parasites including T. solium are involved in immune evasion, since they cleave human immunoglobulins (Auriault et al 1980;Tamashiro et al 1987;White et al 1992;Carmona et al 1993;Kong et al 1994;Shin et al 2001). Cysteine and metallo-protease activities have been characterized by using specific inhibitors in T. solium metacestode E/S products.…”

Discrimination between active and inactive neurocysticercosis by metacestode excretory/secretory antigens of Taenia solium in an enzyme-linked immunosorbent assay.

“…25 Cysteine, aspartic, and metalloprotease activities have been characterized in excretory/secretory (E/S) antigens from T. solium metacestodes. 26,27 Live metacestodes may release such proteases for parasite nutrition, and they may also induce a humoral immune response in the host. The linkage between live metacestodes and the induced humoral response prompted us to test for IgG antibodies against metacestode E/S antigens of T.…”