Development of 111In-labeled Tumor-Associated Antigen Peptides for Monitoring Dendritic-Cell-Based Vaccination

Nucl Med Biol. 2006 May;33(4):453-8. doi: 10.1016/j.nucmedbio.2006.02.005. Epub 2006 May 2.

Abstract

Dendritic cells (DC) are professional antigen-presenting cells capable of inducing potent immune responses. In our ongoing clinical trials, human leukocyte antigen (HLA)-A2.1+ melanoma patients are vaccinated with mature DC, presenting tumor-derived peptides in major histocompatibility complexes (MHC) to naive T cells. Previously, we have shown that both intradermally and intranodally injected (111)In-labeled mature DC migrate to draining lymph nodes. However, little is known about the fate of the MHC-peptide complex after injection of these peptide-loaded DC. The aim of the present study was to develop radiolabeled, tumor-derived peptides to monitor their binding to MHC Class I.

Methods: The HLA-A2.1 binding peptide gp100:154-162mod (gp100:154m) was conjugated with diethylenetriamine pentaacetic acid (DTPA) either at the N-terminus (alpha-DTPA-gp100:154m) or at the epsilon amino group of the Lys(154) residue (epsilon-DTPA-gp100:154m) and labeled with (111)In.

Results: The maximum specific activity for both peptides was 13 GBq/micromol. The IC50 of the alpha-[(111)In]DTPA-gp100:154m peptide was >75 microM. The IC50 of the (111)In-labeled epsilon-DTPA-gp100:154m was 3 microM, similar to the unconjugated peptide. MHC binding studies showed specific binding of the epsilon-[(111)In]DTPA-gp100:154m peptide to the JY cells at 4 degrees C. Interestingly, no specific binding was observed for the alpha-[(111)In]DTPA-gp100:154m peptide. In contrast to the alpha-[(111)In]DTPA-gp100:154m peptide, the epsilon-[(111)In]DTPA-gp100:154m peptide was recognized by cytotoxic T cells.

Conclusion: When DTPA was conjugated to the epsilon NH2 group of the Lys(154) residue, MHC binding of the peptide was preserved and could still be recognized by cytotoxic T cells. These studies allow the noninvasive determination of the behavior of MHC-peptide complexes on DC in vivo.

MeSH terms

  • Antineoplastic Agents / immunology
  • Antineoplastic Agents / therapeutic use
  • Binding Sites
  • Cancer Vaccines / immunology*
  • Cancer Vaccines / therapeutic use
  • Cell Line, Tumor
  • Dendritic Cells / diagnostic imaging
  • Dendritic Cells / immunology
  • Dendritic Cells / transplantation*
  • HLA-A2 Antigen / immunology*
  • Humans
  • Indium Radioisotopes* / immunology
  • Peptides / immunology*
  • Protein Binding
  • Radionuclide Imaging
  • Radiopharmaceuticals / immunology

Substances

  • Antineoplastic Agents
  • Cancer Vaccines
  • HLA-A2 Antigen
  • Indium Radioisotopes
  • Peptides
  • Radiopharmaceuticals