Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 27, 1997
Publication Date: N/A
Interpretive Summary: The stomach worm, Haemonchus contortus is an economically important parasite of grazing animals. The adult parasites are blood feeding and inflict significant pathology on the host. In order to obtain nutrients from ingested red blood cells the parasite requires a mechanism to lyse or break cells to release hemoglobin that could serve as a nutrient source. The present study characterized a hemolytic factor from adult H. contortus. Homogenates of adult parasites have potent lytic activity when incubated with sheep red blood cells (RBCs). The activity was heat stabile and not altered by inhibitors of proteolytic enzymes. Other results suggest that the hemolytic factor functions by forming pores in the RBCs. The hemolytic factor was localized to the intestine and could be solubilized by detergent extraction The results indicate that H. contortus contains a powerful hemolytic factor that functions in the parasites nutrition. Disruption of this mechanism could lead to development of a novel control.
Technical Abstract: Adult Haemonchus contortus contained a factor, predominantly associated with the buffer insoluble fraction, that hemolyzed sheep red blood cells in a time and concentration dependent manner. The hemolytic factor was most active at pH 5.1 and 8.0. The activity was heat stable, unaffected by proteolytic inhibitors, inhibited by coincubation with 20 mM polyethyleneglycol and was extracted from the buffer insoluble fraction with a detergent. The isolated intestine from H. contortus contained hemolytic activity associated with the buffer insoluble fraction. Hemolytic activity was not associated with either the buffer soluble or insoluble fractions from the swine whipworm Trichuris suis. These results suggest that H. contortus contains a factor within its intestine that aids in disruption of red blood cells following the ingestion of blood. Preliminary observations suggest that this hemolytic factor may act as a pore-forming agent.