ABSTRACT
The purified T. lewisi were subjected to hypotonic lysis plus freezing and thawing in acetone dry ice bath. The trypanosome ghosts were obtained after repeated washing and centrifugation. The homogenized ghost suspension was assayed for enzyme Na++K+ ATPase activity to ratify the presence of the trypanosome surface membrane. Membrane solubilized in sodium dodecyl sulfate were fractionated by gel filtration on Sephadex columns equilibrated with the detergent and electrophoresis in polyacrylamide gel. Crude trypanosome surface membrane antigens were tested for their immunogenicity, administered to rats in Fraund's complete adjuvant. The results of these experiments indicated that the protective immunogen is tightly bound to the membrane since the use of strong anionic detergent is necessary in its extraction.