IMMUNIZATION AGAINST ECHIS-OCELLATUS (CARPET VIPER) VENOM USING LIPOSOMES INCORPORATING IMMUNOSTIMULANTS - ROLE OF LIPOPOLYSACCHARIDE IN CONFERRING PROTECTION IN A MOUSE MODEL

Varying doses of whole West African Echis ocellatus venom were incorpo rated, with or without immunostimulants, into membrane-stabilized reve rse phase evaporation (REV) liposomes. Preparations were given either subcutaneously (s.c.) or intravenously (i.v.) to mice and the immune r esponses compared. Addition of lipopolysaccharide (LPS) significantly increased the venom antibody response. Lipid A produced a less pronoun ced and less sustained effect and the addition of muramyl dipeptide an alogues made no significant contribution to the antibody response. The protective ability of circulating venom antibodies was assessed by ch allenging the immunized mice with a minimum lethal dose of whole venom after 175 days. A dose of 250 mug E. ocellatus venom + 300 mug LPS in REVs injected s.c. conferred the highest protection against lethal ve nom effects. Orally administered venom/liposomes incorporated with the mucosal adjuvant avridine primed the antibody response and produced a classic secondary response following a sublethal boost of whole venom . Single injections of venom or venom fraction/liposome preparations w hich produce a high and sustained immune response have potential in co mmercial antivenom production and in active immunization of man in are as of high snakebite incidence and mortality.