To gain more insight into the nature and quality of the systemic immune response, IgG1 and IgG2a subclasses of b-galactosidase-specific antibodies (Fig. 4a, b) were determined. After i.m. immunizations with liposomal DNA vaccine, there were no detectable levels of IgG1 or IgG2a in the sera of the vaccinated mice. As compared to liposomal protein and protein/DNA vaccines, AnExIL-IN and the AnExIL-ON vaccines showed superior IgG1 (P \ 0.05) and IgG2a (P \ 0.001) responses and those induced by AnExIL-ON was the highest (Fig. 4a, b) . The IgG1 and IgG2a responses of control and tested formulations largely corresponded to the total IgG responses (Fig. 4a, b) . Remarkably, the AnExIL-ON induced significantly higher IgG2a antibody levels (Fig. 4a) and consequently notably higher IgG2a/IgG1 ratios after booster vaccination compared to the other formulations (Fig. 4d) . Sera were collected 14 days after each immunization. Antibody titers are expressed as mean of the responding mice; the bars represent the 95% confidence intervals. The numbers above the columns indicate the number of responders per group. Asterisks indicate titers that are significantly (* P \ 0.05; ** P \ 0.001) higher than those of the group immunized (booster vaccination) with liposomal protein/DNA vaccines. Circles indicate titers that are significantly (°P \ 0.05) higher than those of the group immunized (booster vaccination) with AnExIL-IN