Antibody responses to liposome-associated antigen.

The humoral antibody response of CAF1 mice to low doses (1-100 micrograms) of egg albumin (EA) encapsulated in or covalently bound to the surface of liposomes was studied for three routes of administration. The liposome immunoadjuvant effect observed was found to depend on the location of the antigen, either on the liposome surface or entrapped inside the liposome, and on the number of immunizations. Following a single immunization, the highest antibody titers were elicited with liposomes having EA conjugated to their surface, regardless of the route of administration. For multiple immunizations given i.v. or i.p. EA conjugated to the surface of liposomes was also superior to either free or liposome-encapsulated EA. However, the antibody response to EA bound to the surface of liposomes was not enhanced as compared to free EA following multiple subcutaneous immunizations.