ABSTRACT
Recombinant protein vaccines and synthetic peptides generally do not induce robust immune responses when administered in the absence of an adjuvant. By delivering these vaccines with appropriate adjuvants and delivery systems, not only can the immune response be significantly improved but also the antigen can be channeled into the major histocompatibility complex (MHC) class I or MHC class II pathways to induce a Th1 or Th2 type of immune response (1,2). In 1974, liposomes were proposed as carriers of antigens to augment antibody responses in vivo (3,4). The use of liposomes as potential carriers of antigens for vaccines in combination with a variety of adjuvants including lipid A, muramyl dipeptide and its derivatives, and several cytokines has been explored (1,2,5). In fact, the first liposomal hepatitis A vaccine has been licensed in Europe (6,7).
