To investigate the potency of AnExILs as alternatives for conventional protein or DNA vaccines, we compared systemic humoral responses of mice immunized i.m. with AnExIL-IN, AnExIL-ON, pCMV-Lac-Z encapsulated in liposomes (further referred to as liposomal DNA vaccine), b-galactosidase encapsulated in liposomes (further referred to as liposomal protein vaccines) and b-galactosidase coencapsulated with pDNA (pIVEX-Lac-Z) in liposomes (further referred to as liposomal protein/DNA vaccines). The liposomal DNA vaccine was poorly immunogenic and induced very low serum IgG titers in only some of the vaccinated animals after single dose i.m. immunization (Fig. 3a) . In contrast, AnExIL-IN induced high serum antibody responses after i.m. immunization, which were significantly higher than those achieved after i.m. injection of liposomal protein and liposomal protein/DNA vaccines (Fig. 3b) (P \ 0.001). Single i.m. vaccination with AnExIL-ON could elicit substantially higher serum antibody responses than those elicited by other vaccines (Fig. 3a , b) (P \ 0.001). It has been shown that surfacelinked liposomal antigens could enhance presentation of antigens to APCs and induce stronger immune responses (Taneichi et al. 2006a; Naito et al. 1996; Uchida and Taneichi 2008) . Altogether, these results point to strong immunostimulating effects of AnExIL vaccines and robust impact of surface antigen presentation on systemic antibody response. Since there are usually needs for booster vaccinations in order to induce prolonged and strong immune responses, the effect of a booster immunization on the systemic antibody production was studied in mice.