Acquisition of alpha 1-Antitrypsin by a pathogenic strain of Trichomonas vaginalis

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Abstract
The interaction of .alpha.1-antitrypsin, the major serine protease inhibitor in plasma, with pathogenic T. vaginalis and the acquisition by trichomonads of this host protein from normal human plasma were investigated. .alpha.1-Antitrypsin acquired by intact parasites could not be removed by repeated washings in phosphate-buffered saline. Saturation kinetics were observed after incubation of glutaraldehyde-fied organisms with 125I-labeled .alpha.1-antitrypsin. Specific parasite membrane sites may be responsible for trichomonal acquisition of .alpha.1-antitrypsin was obtained through competitive binding experiments using purified preparations of homologous vs. heterologous plasma proteins. No evidence of degradation of bound antitrypsin by live parasites was observed. The avid binding of .alpha.1-antitrypsin by pathogenic T. vaginalis after incubation in normal human plasma was demonstrated by using sensitive electrophoretic and immunodetection techniques. Radioimmunoprecipitation of intrinsically labeled, detergent-solubilized extracts of T. vaginalis incubated with monospecific antisera against .alpha.1-antitrypsin and other human plasma proteins revealed the inability of parasites to biosynthesize any substance cross-reactive with host plasma proteins. T. vaginalis organisms pretreated with .alpha.1-antitrypsin inhibited trypsin caseinase activity in an in vitro assay. The implications of these observations are discussed.