Ancylostoma caninum: metalloprotease release coincides with activation of infective larvae in vitro.

Infective stages of several nematode parasites are known to release proteases in excretory/secretory products. These enzymes are believed to facilitate tissue invasion, although direct evidence is lacking. For these investigations, we employed an assay that uses the resumption of feeding as a marker for early events in the infectious process. When Ancylostoma caninum third-stage infective larvae are stimulated to feed in vitro, they release proteases of approximately 50,000 and 90,000 molecular weight, as determined by substrate gel electrophoresis. The enzymes are inhibited by the zinc chelator 1,10-phenanthroline, but not by the nonchelating isomer 4,7-phenanthroline, indicating that the proteolytic activity is zinc-dependent. Both compounds inhibit in vitro feeding, although inhibition by 1,10-phenanthroline is zinc-dependent, whereas inhibition by 4,7-phenanthroline is zinc-independent. The specific release of proteases associated with the initiation of feeding suggests that the metalloprotease serves an integral function in the transition of the free-living stage to parasitism.