Immunopathological Characterization of liposome Adjuvant Coated with Mannan

The adjuvant activity of liposomes coated with mannan-cholesterol was studied in mice. Ovalbumin (OVA) was reconstituted into liposomes as a model antigen. The adjuvant activity was assessed by the following two immunological responses: delayed-type hypersensitivity (DTH) footpad swelling responses and in vitro release of interferon-γ and interleukin-4 by regional lymph node cells. First, we studied dose effects on DTH responses of total lipid, mannan-cholesterol and OVA used for liposomes. The minimal doses per mouse required for the induction of optimal responses were as follows; 1μg of OVA, 10μg of mannan-cholesterol and 336μg of total lipid. Second, immunological and histopathological studies showed the following two points: 1) mannan-coated liposomes induced a tuberculintype DTH response while non-coated liposomes elicited a Jones-Mote reaction, and 2) mannan-coated liposomes induced obvious microabscesses but non-coated liposome did not. Third, the inoculation of mannan-coated liposomes rendered the regional lymph node cells to release a large amount of interferon-γ with little IL-4 against OVA while non-coated lipo-some released neither of the lymphokines. These results indicated that mannan-coated lipo-somes are a potent adjuvant to induce type 1 helper T cells but have a disadvantage to form microabscesses at the inoculation sites