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

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).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.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.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.