EFFECT OF PROTEASE CLASS-SPECIFIC INHIBITORS ON IN-VITRO DEVELOPMENT OF THE 3RD-STAGE TO 4TH-STAGE LARVAE OF ASCARIS-SUUM

Third-stage larvae (L3) of Ascaris suum develop and molt to fourth-sta ge larvae (L4) during in vitro cultivation; consistently greater than 80% of the larvae develop to L4 during 7 days in culture (DIC). To ass ess the role of proteases in this process, the effect of protease clas s-specific inhibitors was studied. The presence of either a serine pro tease inhibitor (AEBSF, 100 mu M) or an aspartic protease inhibitor (p epstatin A, 100 mu M) had no effect on the percentage of L4 after 7 DI G. However, the presence of either a cysteine protease inhibitor (Z-Ph e-Ala-FMK, 100 mu M) or an aminopeptidase inhibitor (amastatin, 100 mu M) resulted in 77% and 34% reductions, respectively, in the percentag e of L4 compared to untreated cultures; viability of the larvae was no t affected. The effect of Z-Phe-Ala-FMK on molting was time and dose d ependent. In contrast to Z-Phe-Ala-FMK, E-64, another specific inhibit or of cysteine proteases, had no effect on molting. The data support a role for an amino-peptidase and suggest a role for a cysteine proteas e in the development of the L3 to L4 stage of A. suum.