The purpose of the study is to evaluate the usefulness of pH-sensitive fusogenic polymer (succinylated poly(glycidol) (SucPG) and 3-methylglutarylated poly(glycidol) (MGluPG))-modified liposomes as a mucosal vaccine. Immune response in mice immunized with OVA-containing SucPG-modified liposome(OVA-liposome) or in chickens with immunized with Salmonella Enteritidis antigen-containing MGluPG-modified liposome(liposome vaccine) was examined. Mice were immunized with OVA-liposomes intranasally. After immunization, significant antigen-specific antibodies were detected in the serum and intestine. When sera were analyzed for isotype distribution, antigen-specific IgG1 antibody responses were detected in mice immunized with OVA-containing unmodified liposomes, whereas immunization with OVA-liposome resulted in the induction of OVA-specific IgG1, IgG2a and IgG3 antibody responses. In spleen lymphocytes from mice immunized with OVA-liposome, both IFN-γ and IL-4 mRNA were detected. The same result was also obtained in mice imminized with OVA-containing MGluPG-modified liposomes. Furthermore, we examined the induction of immune responses in chickens following intraocular immunization with liposome vaccine, and the protective effect against the challenge with S. Enteritidis. Immunization with liposome vaccine induced significant antibody responses against S. Enteritidis in the serum and intestine. Less fecal excretion of bacteria was observed in chickens imminized with liposome vaccine after challenge. The numbers of bacteria in the caecum were also lower in immunized chickens than in unimmunized controls.