A Long, Naturally Presented Immunodominant Epitope from NY-ESO-1 Tumor Antigen: Implications for Cancer Vaccine Design

Abstract

The tumor antigen NY-ESO-1 is a promising cancer vaccine target. We describe here a novel HLA-B7-restricted NY-ESO-1 epitope, encompassing amino acids 60-72 (APRGPHGGAASGL), which is naturally presented by melanoma cells. The tumor epitope bound to HLA-B7 by bulging outward from the peptide-binding cleft. This bulged epitope was not an impediment to T-cell recognition, however, because four of six HLA-B7 + melanoma patients vaccinated with NY-ESO-1 ISCOMATRIX vaccine generated a potent T-cell response to this determinant. Moreover, the response to this epitope was immunodominant in three of these patients and, unlike the T-cell responses to bulged HLA class I viral epitopes, the responding T cells possessed a remarkably broad TCR repertoire. Interestingly, HLA-B7 + melanoma patients who did not receive the NY-ESO-1 ISCOMATRIX vaccine rarely generated a spontaneous T-cell response to this cryptic epitope, suggesting a lack of priming of such T cells in the natural anti-NY-ESO-1 response, which may be corrected by vaccination. Together, our results reveal several surprising aspects of antitumor immunity and have implications for cancer vaccine design.

Naturally Processed Non-canonical HLA-A*02:01 Presented Peptides

“…Crystallographic studies have reported on seven pHLAs structures involving 12-to 16-mer epitopes (4,7,12,13,31,32). These previous studies were all focused on HLA-B molecules, and here we describe the ability of the HLA-A*02:01 molecule to bind long epitopes too, with 538 12-14-mers being defined.…”

Systematic identification of immunodominant CD8+T-cell responses to influenza A virus in HLA-A2 individuals

“…However, accuracy is known to be low, and the approach does not reproducibly identify immunodominant pMHCI epitopes, despite most prediction programs having integrated scoring systems. In addition, many of the known immunodominant determinants from both viruses and tumors are either unusually long or contain no typical MHC binding motifs (15,16). The broad alternative is to do extensive peptide screens, although this requires a massive effort for outbred, HLA-diverse human populations.…”

“…The IFN-γ ICS assay used a standard protocol (16), whereas for ELISpot analysis, PBMC CD8 + T cells purified (>95%) with MACS beads (Miltenyi Biotec) were added with the respective minimal peptides to 96-well nitrocellulose plates (Millipore) coated with an IFN-γ capture Ab (Mabtech); 18 h later, the wells were washed with PBS containing 0.05% Tween 20. Biotinylated detection Ab (Mabtech), streptavidin-conjugated alkaline phosphatase, and its substrate (Sigma-Aldrich) were used to develop the IFN-γ spots.…”

Processing and cross-presentation of individual HLA-A, -B, or -C epitopes from NY-ESO-1 or an HLA-A epitope for Melan-A differ according to the mode of antigen delivery

“…In contrast, the NY-ESO-1 157-165 /HLA-A2 and NY-ESO-1 92-100 /HLA-Cw3 epitopes were generated in a proteasome-independent manner irrespective of whether NY-ESO-1 and ISCOMATRIX adjuvant were added separately or formulated as an NY-ESO-1/ISCOMATRIX vaccine. Furthermore, the NY-ESO-1 60-72 /HLA-B7 epitope, which is an unusually long (13 amino acid) "bulged" epitope, 45 was dependent on the proteasome for processing irrespective of the mode of delivery (ie, formulated with ISCOMATRIX adjuvant, added separately, or formulated as an IC) because its generation and cross-presentation on HLA-B7 were inhibited by lactacystin in each instance. Thus, different epitopes from the same protein can be processed by different mechanisms; and although the mode of antigen delivery can redirect processing in some instances (eg, NY-ESO-1 on HLA-A2 157-165 and NY-ESO-1 92-100 on HLA-Cw3), this was not the case for NY-ESO-1 60-72 on HLA-B7.…”