An enzyme-release assay for the assessment of the lytic activities of complement or antimicrobial peptides on extracellular Toxoplasma gondii

A method is described which allows the evaluation of the membrane lytic act ivity of either complement or antimicrobial peptides against the extracellu lar stage of the human protozoan parasite Toxoplasma gondii. The assay is b ased on lacZ transgenic parasites, determining the activity of released cyt oplasmic beta-galactosidase into the culture supernatant upon membrane disi ntegration. This method was used to evaluate the lyric activities of (i) co mplement which is a natural defense mechanism in infected hosts against ext racellular parasites, and (ii) antimicrobial peptides which have not been e valuated against T. gondii before. The results show that the assay provides a simple and convenient way to assess the membrane lytic activity of such compounds and that T. gondii, like other protozoan parasites, is vulnerable to the membrane-lyric effect of antimicrobial peptides. (C) 2000 Published by Elsevier Science B.V. All rights reserved.