The pH-sensitive fusogenic 3-methyl-glutarylated hyperbranched poly(glycidol)-conjugated liposome induces antigen-specific cellular and humoral immunity.

We examined the ability of a novel liposome, surface modified by 3-methyl-glutarylated hyperbranched poly(glycidol) (MGlu-HPG), to enhance antigen-specific immunity in vitro and in vivo and to function as a vaccine carrier. Murine bone marrow-derived dendritic cells took up ovalbumin (OVA) encapsulated in MGlu-HPG-modified liposomes more effectively than free OVA or OVA encapsulated in unmodified liposomes. Immunization of mice with OVA-containing MGlu-HPG-modified liposomes induced antigen-specific splenocyte proliferation and production of gamma interferon (IFN-γ) more strongly than did immunization with free OVA or OVA encapsulated in unmodified liposomes. The immune responses induced by OVA encapsulated in MGlu-HPG-modified liposomes were significantly suppressed by addition of anti-major histocompatibility complex (MHC) class I and class II monoclonal antibodies, indicating the involvement of antigen presentation via MHC class I and II. Furthermore, delayed-type hypersensitivity responses and OVA-specific antibodies were induced more effectively in mice immunized with OVA encapsulated by MGlu-HPG-modified liposomes than with unencapsulated OVA or OVA encapsulated in unmodified liposomes. These results suggested that MGlu-HPG-modified liposomes effectively induced both cell-mediated and humoral immune responses. Collectively, this study is the first to demonstrate the induction of both cell-mediated and humoral immune responses in vivo by MGlu-HPG-modified liposomes.