HER2-specific T-cell immune responses in patients vaccinated with truncated HER2 protein complexed with nanogels of cholesteryl pullulan.

Clinical Cancer Research

PubMedID: 17189412

Kitano S, Kageyama S, Nagata Y, Miyahara Y, Hiasa A, Naota H, Okumura S, Imai H, Shiraishi T, Masuya M, Nishikawa M, Sunamoto J, Akiyoshi K, Kanematsu T, Scott AM, Murphy R, Hoffman EW, Old LJ, Shiku H. HER2-specific T-cell immune responses in patients vaccinated with truncated HER2 protein complexed with nanogels of cholesteryl pullulan. Clin Cancer Res. 2006;12(24):7397-405.
PURPOSE
We developed a complex of tumor antigen protein with a novel nanoparticle antigen delivery system of cholesteryl pullulan (CHP). To target HER2 antigen, we prepared truncated HER2 protein 1-146 (146HER2) complexed with CHP, the CHP-HER2 vaccine. We designed a clinical study to assess the safety of the vaccine and HER2-specific T-cell immune responses measured by the newly developed enzyme-linked immunospot assay with mRNA-transduced phytohemagglutinin-stimulated CD4(+) T cells in HLA-A2402-positive patients with therapy-refractory HER2-expressing cancers.

EXPERIMENTAL DESIGN
Nine patients with various types of solid tumors were enrolled. Each patient was s.c. vaccinated biweekly with 300 microg of CHP-HER2 vaccine for three times followed by booster doses. HER2-specific T-cell responses were evaluated by enzyme-linked immunospot assay by targeting autologous phytohemagglutinin-stimulated CD4(+) T cells transduced with 146HER2-encoding mRNA to cover both identified peptides and unknown epitopes for MHC class I and class II that might exist in the sequence of the vaccine protein.

RESULTS
CHP-HER2 vaccine was well tolerated; the only adverse effect was grade 1 transient skin reaction at the sites of vaccination. HER2-specific CD8(+) and/or CD4(+) T-cell immune responses were detected in five patients who received four to eight vaccinations, among whom both T-cell responses were detected in these patients. In four patients with CD8(+) T-cell responses, two patients reacted to previously identified HER2(63-71) peptide and the other two reacted only to 146HER2 mRNA-transduced cells.

CONCLUSIONS
CHP-HER2 vaccine was safe and induced HER2-specific CD8(+) and/or CD4(+) T-cell immune responses.