Immunostimulatory CpG-DNA and PSA-peptide vaccination elicits profound cytotoxic T cell responses

Urol Oncol. 2013 Oct;31(7):1395-401. doi: 10.1016/j.urolonc.2011.09.002. Epub 2011 Oct 7.

Abstract

Objective: Novel strategies for the treatment of advanced prostate cancer (CaP), including immunotherapy or gene therapy, are currently under evaluation with Sipuleucel-T as first FDA-approved immunotherapeutic. Here, we examine cytosine-phosphorothioate-guanine (CpG)-DNA oligonucleotides (ODN) to boost cytokine responses and costimulatory molecule expression on murine bone marrow-derived dendritic cells (mBMDC). Furthermore, we evaluate the potency of a PSA-peptide based vaccine in combination with CpG-DNA to elicit specific cytotoxic T cell (CTL) responses.

Materials and methods: mBMDC were stimulated with CpG-DNA (1668: 5'-TCCATGACGTTCCTGATGCT-3') or non-stimulatory control-ODN (1720: 5'-TCCATGAGCTTCCTGATGCT-3'). Subsequently, expression of the costimulatory molecules CD40 and CD86 and induction of proinflammatory cytokines (interleukin (IL)-6 and IL-12) were analyzed. For induction of PSA-peptide specific CTL, female C57BL/6 mice were immunized with PSA-peptide 65-73 (HCIRNKSVI) alone or in combination with 1668 or 1720-ODN. In vivo cytotoxicity assay determined PSA-peptide specific cytotoxicity 1 week after vaccination.

Results: Treatment of mBMDC with stimulatory CpG-DNA ODN resulted in pronounced up-regulation of costimulatory molecule expression on mBMDC in a dose-dependent manner. CpG-ODN significantly increased production of IL-6 and IL-12 in mBMDC (P < 0.001). Induction of PSA-peptide specific CTL responses in mice immunized with PSA-peptide and CpG-DNA were significantly greater than those of PSA-peptide and control-ODN immunized mice or PSA-peptide only vaccination.

Conclusions: CpG-DNA acts as potent adjuvant for vaccination therapies and elicits profound PSA-peptide specific CTL responses in combination with an immunodominant PSA-peptide. CpG-ODN mediated immunotherapy represents a potentially inexpensive, safe, easy-to-produce, and easy-to-handle treatment alternative. Therefore, further evaluation of CpG-DNA in immunization therapies against CaP is warranted.

Keywords: CpG; Immunotherapy; PSA; Prostate cancer; Vaccination.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • B7-2 Antigen / immunology
  • B7-2 Antigen / metabolism
  • Bone Marrow Cells / immunology
  • Bone Marrow Cells / metabolism
  • CD40 Antigens / immunology
  • CD40 Antigens / metabolism
  • Cancer Vaccines / administration & dosage
  • Cancer Vaccines / immunology*
  • Cells, Cultured
  • Dendritic Cells / immunology
  • Dendritic Cells / metabolism
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Flow Cytometry
  • Humans
  • Interleukin-12 / immunology
  • Interleukin-12 / metabolism
  • Interleukin-6 / immunology
  • Interleukin-6 / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Oligodeoxyribonucleotides / immunology*
  • Peptide Fragments / immunology*
  • Prostate-Specific Antigen / chemistry
  • Prostate-Specific Antigen / immunology*
  • Prostatic Neoplasms / immunology
  • Prostatic Neoplasms / prevention & control
  • T-Lymphocytes, Cytotoxic / immunology*
  • T-Lymphocytes, Cytotoxic / metabolism
  • Vaccination / methods

Substances

  • B7-2 Antigen
  • CD40 Antigens
  • CPG-oligonucleotide
  • Cancer Vaccines
  • Interleukin-6
  • Oligodeoxyribonucleotides
  • Peptide Fragments
  • Interleukin-12
  • Prostate-Specific Antigen