Importance of physical association between antigen and liposomes in liposomes adjuvanticity

The importance of a physical association between antigen and liposomes in liposomes adjuvanticity has been evaluated by comparing the anti-BSA secondary humoral response induced by different BSA formulations including free antigen, free antigen + liposomes, or encapsulated antigen. Our results demonstrate that a physical association of antigen with liposomes is required for a potentiation of the humoral response to be observed and that empty liposomes, when used for priming together with free antigen, restrain the induced response, as shown by a slower triggering, a reduced intensity and a more rapid decay rate. Free BSA has an intermediate behavior and, in contrast to what is observed with BSA/liposomes preparations, its effect appears to be dose-dependent. Each of the three BSA formulations also differs in the relative production of IgG and IgM they induced during the response.