Improved immunogenicity of an immunodominant epitope of the HER-2/neu protooncogene by alterations of MHC contact residues.
The HER-2/neu (HER-2) oncogene is expressed in normal epithelial surfaces at low levels and overexpressed in several types of tumors. The low immunogenicity against this self tumor Ag can be improved by developing epitopes with amino acid replacements in their sequences. In this study, three HER-2/neu.369 (HER-2.369) analogue peptides, produced by modifying both anchor positions by introducing L, V, or T at position 2 and V at the C terminus, were analyzed for their capacity to induce CTLs in vitro from human PBMC and in vivo in HLA-A2.1/Kb transgenic mice. One of the analogues (HER-2.369 V2V9) sensitized target cells for HER-2-specific recognition by human CTLs and induced specific CTLs in vitro at 100-fold lower concentrations than the HER-2.369 wild-type epitope. These CTLs were also able to recognize the wild-type epitope and HER-2-expressing tumors in an MHC-restricted manner. Furthermore, a 100-fold lower amount of the HER-2.369 V2V9 analogue compared with the wild-type epitope was required to induce CTLs in HLA-A2.1/Kb transgenic mice. However, the V2V9 analogue demonstrated only marginally better binding to the MHC class I A2 allele compared with wild type. To establish thermodynamic parameters, we developed radiolabeled F3*Y analogues from both the HER-2.369 epitope and the V2V9 analogue. Our results indicate that the high biological activity of the HER-2.369 V2V9 epitope is associated with a slower dissociation kinetic profile, resulting in an epitope with greater HLA-A2 stability.
Cancer Center Karolinska, Karolinska Hospital, Stockholm, Sweden.
Simona
S
Vertuani
Alessandro
A
Sette
John
J
Sidney
Scott
S
Southwood
John
J
Fikes
Elissa
E
Keogh
Jan Alvar
JA
Lindencrona
Glenn
G
Ishioka
Jelena
J
Levitskaya
Rolf
R
Kiessling
D019943:Amino Acid Substitution / Q000235:genetics / Q000276:immunology*; D000818:Animals; D017951:Antigen Presentation / Q000235:genetics; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic / Q000235:genetics; D018984:Epitopes, T-Lymphocyte / Q000276:immunology / Q000378:metabolism; D006183:H-2 Antigens / Q000235:genetics; D015789:HLA-A2 Antigen / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D016056:Immunodominant Epitopes / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis / Q000276:immunology* / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism; D013816:Thermodynamics
D018984:Epitopes, T-Lymphocyte; D006183:H-2 Antigens; D015789:HLA-A2 Antigen; D016056:Immunodominant Epitopes; D010446:Peptide Fragments; D018719:Erb-b2 Receptor Tyrosine Kinases; C032876:H-2Kb protein, mouse