Human dendritic cells genetically engineered to express a melanoma polyepitope DNA vaccine induce multiple cytotoxic T-cell responses.
OBJECTIVE
To assess the therapeutic potential of a melanoma polyepitope vaccine in human cells. Polyepitope DNA vaccines encoding T-cell epitopes have been demonstrated in murine systems to generate multiple cytotoxic T-cell responses to different antigens. Here, for the first time we demonstrate the ability of a melanoma polyepitope to stimulate lymphocytes from normal human donors to simultaneously generate multiple antigen-specific responses.


METHODS
Human dendritic cells (DC), transduced with a melanoma-polyepitope cDNA, were used to activate autologous lymphocytes from naïve donors as an in vitro model of DNA vaccination. Lymphocytes were primed with polyepitope or mock-transduced DC, boosted with peptide, then measured for antigen-specific cytotoxicity.


RESULTS
Lymphocytes primed with polyepitope-transduced DC and boosted with peptide generated multiple cytotoxic responses. By contrast lymphocytes primed with mock-transfected DCs and boosted with peptide gave no specific cytotoxicity. However, when lymphocytes were repeatedly stimulated with polyepitope-transduced DCs immunodominance was seen with CTLs being generated to only one epitope, MART(27-35).


CONCLUSIONS
We show in a human system that a melanoma polyepitope primes CTL to multiple epitopes. However, repeated stimulation by the polyepitope restricts the response to only the MART1 epitope. Thus, although polyepitope vaccines are an effective way of priming multiple naïve T-cell responses, continual boosting with polyepitope vaccines may, as a result of immunodominance, restrict the CTL. These findings have important implications for the use of DNA polyepitope vaccines in cancer immunotherapy.
Smith
S G
SG
Applied Immunology Group, Imperial Cancer Research Fund, Cancer Medicine Research Unit, St. James's University Hospital, Leeds, LS9 7TF, United Kingdom.
Patel
P M
PM
Porte
J
J
Selby
P J
PJ
Jackson
A M
AM
D000818:Animals; D019556:COS Cells; D019496:Cancer Vaccines / Q000276:immunology*; D002522:Chlorocebus aethiops; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D019084:Fluorescent Antibody Technique, Indirect; D005818:Genetic Engineering / Q000379:methods; D006801:Humans; D008545:Melanoma / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology; D014162:Transfection; D017778:Vaccines, Combined
D019496:Cancer Vaccines; D000939:Epitopes; D011994:Recombinant Proteins; D017778:Vaccines, Combined; C094534:polyvalent melanoma cell vaccine