Development of 111In-labeled tumor-associated antigen peptides for monitoring dendritic-cell-based vaccination.
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.


CONCLUSIONS
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.
Laverman
Peter
P
Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands. p.laverman@nucmed.umcn.nl
de Vries
I Jolanda M
IJ
Scharenborg
Nicole M
NM
de Boer
Annemiek
A
Broekema
Matthias
M
Oyen
Wim J G
WJ
Figdor
Carl G
CG
Adema
Gosse J
GJ
Boerman
Otto C
OC
D000970:Antineoplastic Agents / Q000276:immunology / Q000627:therapeutic use; D001665:Binding Sites; D019496:Cancer Vaccines / Q000276:immunology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D003713:Dendritic Cells / Q000000981:diagnostic imaging / Q000276:immunology / Q000637:transplantation*; D015789:HLA-A2 Antigen / Q000276:immunology*; D006801:Humans; D007205:Indium Radioisotopes / Q000276:immunology; D010455:Peptides / Q000276:immunology*; D011485:Protein Binding; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000276:immunology
D000970:Antineoplastic Agents; D019496:Cancer Vaccines; D015789:HLA-A2 Antigen; D007205:Indium Radioisotopes; D010455:Peptides; D019275:Radiopharmaceuticals