|GAMBLE H RAY - 1265-40-00
Submitted to: American Society of Parasitologists
Publication Type: Abstract Only
Publication Acceptance Date: 8/13/1994
Publication Date: N/A
Technical Abstract: Nematodes differ by the routes with which they enter the host. Species which penetrate skin or go through a substantial tissue migration phase are dependent on mechanisms whereby they can mechanically and/or enzymatically move through host tissue. In contrast, orally infective nematodes of the gastrointestinal tract face no physical barriers to arrive at their predilection site in the host. Despite these differences, all these groups are dependent on the function of proteases, both during the infection process and in subsequent developmental stages. Several stage-specific and functionally unique proteases have been identified in the orally-infective ruminant trichostrongyle Haemonchus contortus. The exsheathment process of infective larvae is regulated by a zinc metalloprotease released upon exposure of the parasite to elevated CO2. Coincident with the third molt and the initiation of feeding, H. contortus secretes another metalloprotease. While the in vivo functions of this latter enzyme are not yet known, it may include aspects of exsheathment of the 3M cuticle, penetration of abomasal tissue, extracorporeal digestion, and inhibition of blood clotting. Because of the broad specificity of these and other proteases from nematodes with very different life histories, it is possible that these enzymes have some common lineage and have evolved multiple functions even in the same species.