Evaluation of Stearylamine-Modified Liposomes for the Oral Vaccine Adjuvant

Abstract

The usefulness of stearylamine (SA)-modified liposomes for the oral vaccine adjuvant in the induction of immune responses was evaluated. Mice were orally immunized withunmodified liposomes containing ovalbumin (OVA) (group I), OVA-containing monophosphoryl lipid A (MPL)-modified liposomes (group II), OVA-having SA-modified liposomes (group III) or OVA alone (group IV). After immunization, significant OVA-specific antibodies were detected in the serum and intestine from mice of groups I to III, but not in group IV. Especially, intestinal IgG and IgA antibody responses against OVA were significantly higher in mice of group III than in groups I and II. When sera were analyzed for isotype distribution,OVA-specific IgG1 antibody responses were noted in mice of groups I and II, whereas the induction of OVA-specific IgG1 and IgG3 antibody responses was observed in mice of group III. Moreover, substantial production of IFN-γ(Th1-type) and IL-4 (Th2 type) was demonstrated in spleen cells from mice of group III in vitro. These results suggest that the SA-modified liposomes would serve effectively as mucosal vaccine adjuvant for inducing humoral and cell-mediated immune responses.