Peptides corresponding to proteins VP1, VP2 and VP3 of the capsid of the hepatitis A virion have been synthesized by the Fmoc-polyamide solid phase method, and administered to laboratory animals in three different forms: Free, encapsulated in multilamelar liposomes and coupled to keyhole limpet hemocyanin (KLH) by using glutaraldehyde as a coupling agent. Potential epitopes of HAV were selected by determining the exposed regions on the surface of the virion according to hydrophilicity profiles, calculated by the Hoop and Woods method, and protein iodination. Overall, VP3 peptide appeared to be more immunogenic than VP1 and VP2. The maximum anti-HAV titers were also observed in mice immunized with VP1 and, particularly, VP3 peptides. Neutralization of HAV infectivity was achieved with both of these peptides. Immune responses generated by peptides entrapped into liposomes and coupled to KLH were of higher magnitude than those induced by free peptides. Liposomes, are a safe and promising alternative for the enhancement of the immune response evoked by synthetic peptides.
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