Underivatized, aqueous soluble xcex2(1,3)-glucan (also known as PGG-glucan, triple helix-glucan (TH-glucan) or Betafectin(copyright)) is a novel and unique soluble xcex2-glucan manufactured through a proprietary process. The biological activity of this molecule is clearly distinguishable from particulate or other soluble xcex2-glucans. Numerous laboratories have reported direct induction of arachidonic acid metabolites (Czop et al., J. Immunol. 141(9):3170-3176 (1988)), cytokines (Abel and Czop, Intl. J. Immunopharmacol. 14(8):1363-1373 (1992); Doita et al., J. Leuk. Biol. 14(2):173-183 (1991)) and oxidative burst (Cain et al., Complement 4:75-86 (1987); Gallin et al., Int. J. Immunopharmacol. 14(2):173-183 (1992)) by both particulate and soluble forms of xcex2-glucans. In contrast, underivatized, aqueous soluble xcex2(1,3)-glucan does not directly activate leukocyte functions such as oxidative burst activity (Mackin et al., FASEB J. 8:A216 (1994)), cytokine secretion (Putsiaka et al.,Blood 82:3695-3700 (1993)) or proliferation (Wakshull et al., J. Cell. Biochem. suppl. 18A:22 (1994)). Instead, underivatized, aqueous soluble xcex2(1,3)-glucan primes cells for activation by secondary stimuli (Mackin et al. (1994); Brunke-Reese and Mackin, FASEB J. 8:A488 (1994); and Wakshull et al. (1994)).
The biological activity of xcex2-glucans is mediated through specific receptors located on target cells. Several groups of investigators have described receptors which bind to and mediate phagocytosis of particulate xcex2-glucan preparations (e.g., zymosan-like particles; Goldman (Immunology 63(2):319-324 (1988); Exp. Cell. Res. 174(2):481-490 (1988); Engstad and Robertsen, Dev. Comp. Immunol. 18(5):397-408 (1994); Muller et al., Res. Immunol. 145:267-275 (1994)); Czop, Advances in Immunol. 38:361,398 (1986)); and have partially characterized these receptors (Czop and Kay, J. Exp. Med. 173:1511-1520 (1991); Szabo et al., J. Biol. Chem. 270:2145-2151 (1995)). The leukocyte complement receptor 3 (CR3, also known as MAC 1 or CD11b/CD18) has been reported to bind both particulate and some soluble xcex2-glucans, as well as other polysaccharides (Thornton et al., J. Immunol. 156:1235-1246 (1996)). A soluble aminated xcex2-glucan preparation has been shown to bind to murine peritoneal macrophages (Konopski et al., Biochim. Biophys. Acta 1221:61-65 (1994)), and a phosphorylated xcex2-glucan derivative has been reported to bind to monocyte cell lines (Muller et al., J. Immunol. 156:3418-3425 (1996)).
The present invention relates to xcex2-glucan compositions comprising xcex2-glucan molecules having an average molecular weight of at least 1,000,000 daltons, as determined by multi-angle laser light scattering (MALLS), and referred to herein as very high molecular weight glucans (VHMW-glucans). The VHMW-glucans are soluble in aqueous solutions and are underivatized, i.e., the VHMW-glucans have not been substantially modified by substitution with functional groups. The VHMW-glucans of the invention have a high affinity for the TH-glucan receptor on human monocytes, as well as a novel receptor located primarily on rat NR8383 macrophages, particularly alveolar macrophages. The xcex2-glucan compositions of the present invention have been shown to enhance host immune defense mechanisms to infection, but do not induce an inflammatory response. Specifically, VHMW-glucans retain a specific subset of immunological properties common to xcex2-glucans but uniquely do not induce the production of detrimental pro-inflammatory cytokines, such as TNF-xcex1, IL-1xcex2 and IL-6. Further, VHMW-glucans have been shown to accelerate bacterial clearance and increase platelet counts in both rat and mice infection models.
The VHMW-glucans can be formulated into a composition appropriate for parenteral (e.g., intravenous, interparenteral, subcutaneous, intramuscular), topical, oral or internasal administration to humans and animals as an anti-infective to combat infection associated with burns, surgery, chemotherapy, bone marrow disorders and other conditions in which the immune system may be compromised. The VHMW-glucan compositions of the present invention can be used in therapeutic and/or prophylatic treatment regimens of humans and animals to enhance their immune response, without stimulating the production of certain biochemical mediators (e.g., IL-1xcex2, TNF-xcex1 and IL-6) that can cause detrimental side effects, such as fever and inflammation. The VHMW-glucan compositions can be used for therapeutic or prophylactic application, such as immunosuppression, hematopoiesis, wound healing, prevention and treatment of infectious disease, platelet production, peripheral blood precursor cell mobilization, and induction and enhancement of myelopoeisis and thrombopoeisis.