A degenerate HLA-DR epitope pool of HER-2/neu reveals a novel in vivo immunodominant epitope, HER-2/neu88-102.
OBJECTIVE
Over the past two decades, there has been significant interest in targeting HER-2/neu in immune-based approaches for the treatment of HER-2/neu+ cancers. For example, peptide vaccination using a CD8 T cell-activating HER-2/neu epitope (amino acids 369-377) is an approach that is being considered in advanced phase clinical trials. Studies have suggested that the persistence of HER-2/neu-specific CD8 T cells could be improved by incorporating human leukocyte antigen (HLA) class II epitopes in the vaccine. Our goal in this study was to identify broad coverage HLA-DR epitopes of HER-2/neu, an antigen that is highly expressed in a variety of carcinomas.


METHODS
A combination of algorithms and HLA-DR-binding assays was used to identify HLA-DR epitopes of HER-2/neu antigen. Evidence of preexistent immunity in cancer patients against the identified epitopes was determined using IFN-gamma enzyme-linked immunosorbent spot (ELIspot) assay.


RESULTS
Eighty-four HLA-DR epitopes of HER-2/neu were predicted, 15 of which had high binding affinity for > or =11 common HLA-DR molecules. A degenerate pool of four HLA-DR-restricted 15-amino acid epitopes (p59, p88, p422, and p885) was identified, against which >58% of breast and ovarian cancer patients had preexistent T-cell immunity. All four epitopes are naturally processed by antigen-presenting cells. Hardy-Weinberg analysis showed that the pool is useful in approximately 84% of population. Lastly, in this degenerate pool, we identified a novel in vivo immunodominant HLA-DR epitope, HER-2/neu(88-102) (p88).


CONCLUSIONS
The broad coverage and natural immunity to this epitope pool suggests potential usefulness in HER-2/neu-targeting, immune-based therapies such as vaccines.
Karyampudi
Lavakumar
L
Department of Immunology, Mayo Clinic, Rochester, Minnesota, USA.
Formicola
Courtney
C
Erskine
Courtney L
CL
Maurer
Matthew J
MJ
Ingle
James N
JN
Krco
Christopher J
CJ
Wettstein
Peter J
PJ
Kalli
Kimberly R
KR
Fikes
John D
JD
Beebe
Melanie
M
Hartmann
Lynn C
LC
Disis
Mary L
ML
Ferrone
Soldano
S
Ishioka
Glenn
G
Knutson
Keith L
KL
D000465:Algorithms; D001943:Breast Neoplasms / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D005260:Female; D006684:HLA-DR Antigens / Q000276:immunology*; D006801:Humans; D016056:Immunodominant Epitopes / Q000032:analysis*; D010051:Ovarian Neoplasms / Q000276:immunology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*
D006684:HLA-DR Antigens; D016056:Immunodominant Epitopes; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human