Tragacanth is a commercial gum obtained from Astragalus species plants indigenous t the Middle East. It is GRAS for use in foods and pharmaceuticals. We have growing and are studying seven Astragalus species Tragacantha section plants which produce structurally related tragacanthin polysaccharides. The purified tragacanthins when administered intraperitoneally have shown broad spectrum activity against several different cancers and virus infections in rats and mice. The basis for activity is immunomodulation, involving macrophage stimulation at least. A. echidnaeformis tragacanthin is very active in three different mouse species against murine cytomegalovirus (MCMV), encephalomyocarditis virus (EMCV) and Punta toro virus (PTV). It is significantly active versus a mammary carcinoma induced by a chemical carcinogen in rats, and is active against retrovirus induced splenic lymphomas in mice. The activity of this product and its deproteinated and acylated derivatives will be investigated against fast growing MCMV in mice. Several dose levels, routes of administration and timing regimens will be explored. The use of severe combined immunodeficiency (SCID) mice lacking T and B cells, but with functioning NK cells and macrophage, will help to further define the activated component in the immune system. One or two products found active in mice will be tested in guinea pigs infected with herpes simplex virus type 2 (HSV-2). The products will be prepared as polysaccharides free of all small molecules, and will be characterized by a battery of parameters. A goal is to identify high activity, low toxicity, readily administered tragacanthin immunomodulators that can be developed as antivirals for humans.
Safe immunomodultor drugs for the treatment of human virus infections directly, or as adjuncts with other antiviral drugs.
