Antitumor effect of new HER2 peptide vaccination based on B cell epitope.

Background: While the benefit of passive immunotherapy is commonly accepted, active immunization may have advantages for the patient's quality of life. We identified a new epitope of Mab CH401 against Her-2/neu extracellular domain (N: 167-175), and evaluated the effect of active immunization of the 20mer peptide containing the epitope (CH401 peptide). Materials and Methods: Epitope- mapping was performed using ELISA with Her-2/neu-related multiple antigen peptides (MAP). BALB/c mice were transplanted with Her-2/neu-expressing lymphoma cell line and immunized with the peptides. For monitoring the condition, ELISA and flow cytometry was performed. Results: CH401 peptide induced Her-2/neu-specific IgG antibody. Tumor growth in immunized mice was suppressed and tumor- infiltrating lymphocytes comprised more CD8 + T-cells, which secreted larger amounts of interleukin-2 after the peptide re- stimulation. Conclusion: The new Her-2/neu peptide contained epitopes for CD4 + and CD8 + T-cells, which contributes to the suppressive effect on Her-2/neu-expressing tumor cell growth.