Selective acquisition of plasma proteins by Trichomonas vaginalis and human lipoproteins as a growth requirement for this species

Trichomonas vaginalis avidly bound numerous host macromolecules which were not removed by repeated washing in phosphate buffered saline. The use of radioiodinated Cohn plasma fractions in binding studies allowed the identification of plasminogen, fibrinogen, immunoglobulin G, lipoproteins A and B, transferrin, α₁-antitrypsin, and albumin on intact organisms. The binding of immunoglobulin G, albumin, transferrin, and lipoproteins to intact, motile trichomonads was further demonstrated using ¹²⁵I-labeled plasma that was chromatographically depleted of these proteins. Kinetic studies indicated that ¹²⁵I-labeled lipoproteins bind to T. vaginalis in a receptor-ligand-like manner. The surface localization and uptake of bound lipoproteins was shown by treatment of intact organisms with pronase at various times after incubation with lipoproteins. Purified lipoproteins could be substituted for plasma or serum as a growth supplement in a complex medium of trypticase/yeast extract/maltose and supported growth and multiplication rates equal to those in the same medium with plasma.