Cleavage of purified bovine complement component C3 in larval Hypoderma lineatum (Diptera: Oestridae) hypodermins

Proteinases isolated from first instars of Hypoderma lineatum (Villers) were assayed for their ability to degrade purified bovine complement component C3. Cleavage products were analyzed by SDS-PAGE followed by immunoblotting. Crude extracts (raw insect homogenate) and purified hypodermin A and B were effective in degrading the alpha chain of C3 at a concentration of 1 microgram/ml. At 10 micrograms/ml, raw insect homogenate caused total degradation of both chains of the molecule, whereas 50 micrograms/ml of hypodermin A was required to obtain similar results. Hypodermin B did not appear to cleave the beta chain of C3. No degradation of the C3 molecule was observed in the absence of added hypodermins. Complement degradation associated with Hypoderma infestations may allow the parasite to escape host defense reactions.