Isolation and biological activities of an antineoplastic protein-polysaccharide complex (PS4A) obtained from Mycobacterium vaccae

A mixture of water-soluble protein-polysaccharides (PS4A) was isolated by b oiling intact cells of Mycobacterium vaccae, a fast growing mycobacterium. Sephadex G75 column chromatography of the crude extract separated the biolo gically active high molecular weight (> 50 kDa) fraction (in the void volum e) from the low molecular weight degradation products. Compositional analys is demonstrated that PS4A contained protein and polysaccharide in a ratio o f approximately 1.5 to 1, but no lipids were detected. The antineoplastic a ctivity was tested by in vivo by a S-180 murine sarcoma model using female CFW mice. The immunostimulating activity was tested in vitro using muring p eritoneal macrophages isolated from BALB/C mice. The results demonstrated t hat PS4A significantly decreased tumor incidence in vivo and produced activ ation of murine peritoneal macrophages. However, the antineoplastic activit y was only attributable to the high molecular weight fraction of the protei n-polysaccharide complex. The low molecular weight fraction had no antineop lastic activity in vivo despite stimulation of TNF-alpha production in vitr o. In vitro experiments, also demonstrated that although all PS4A component s significantly increased TNF-alpha production by macrophages, the high mol ecular weight fraction stimulated more IL-1 production, indicating a better immunostimulating activity.