Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 6, 1998
Publication Date: N/A
Interpretive Summary: The swine round worm, Ascaris suum, is responsible for significant economic losses by reducing production efficiency and causing organ condemnations at slaughter due to pathology produced by larval stages. Development of novel controls can be enhanced by a knowledge of the biochemical mechanism underlying the process of molting, an essential process in the growth and development of all nematodes. The results demonstrate that both an aminopeptidase and a cysteine protease are involved in the development of L3 to L4 stage. Inhibition of these enzymes may interfere with the molting process.
Third-stage larvae (L3) of Ascaris suum develop and undergo the molt to fourth-stage larvae (L4) during in vitro cultivation; greater than 80% of the larvae consistently develop to the L4 stage during 7 days in culture (DIC). To assess the role of proteases in this process, the effect of protease class-specific inhibitors was studied. The presence of either a serine protease inhibitor (AEBSF, 100 æM) or an aspartic protease inhibito (pepstatin A, 100 æM) had no effect on the percentage of L4 after 7 DIC. However, the presence of either a cysteine protease inhibitor (Z-Phe-Ala- FMK, 100 æM) or an aminopeptidase inhibitor (amastatin, 100 æM) resulted in 77 and 34% reductions, respectively, in the percentage of L4 compared to untreated cultures; viability of the larvae was not affected. The effect of Z-Phe-Ala-FMK on molting was time- and dose-dependent. In contrast to Z- Phe-Ala-FMK, E-64, another specific inhibitor of cysteine proteases, had no oeffect on molting. The data support a role for an aminopeptidase and suggest a role for a cysteine protease in the development of the L3 to L4 stage of A. suum.