Iscom, a delivery system for parenteral and mucosal vaccination.

The iscom is a supramolecular spherical structure, about 40nm in diameter, built up by structure-forming and immunomodulating quillaja triterpenoids, lipids and antigens. Iscoms with a defined quillaja triterpenoid formulation named QH 703 are in human trials. The advantages of using the particulate iscom form of quillaja components are (i) that local reactions at the site of injection can be avoided; a manifold higher dose of quillaja components in iscoms than in free form can be injected without causing side effects; (ii) considerably lower doses of both quillaja components and antigens are required to obtain a certain level of immune response. The iscom particle targets the antigen and adjuvant components to both the endosomal and cytosolic pathways for antigen presentation, resulting in both MHC class I and class II restricted immune responses. Further, iscoms induce APC to produce IL-1, IL-6 and IL-12 and a TH1 type of response with enhanced IL-2 and IFN-gamma production. Iscoms are now constructed to target the mucosal lymphatic systems. Iscoms administered intranasally induce secretory IgA responses in lungs and distant mucosal membranes e.g. in the genital tract.