Phosphorylated alpha-enolase induces autoantibodies in HLA-DR8 pancreatic cancer patients and triggers HLA-DR8 restricted T-cell activation.

Pancreatic ductal adenocarcinoma (PDAC) is the fourth cause of cancer-induced death in the Western World. In PDAC patients, alpha-enolase (ENOA), a glycolytic enzyme that also acts as plasminogen receptor, is up-regulated and elicits the production of autoantibodies. Our previous studies revealed that most PDAC patients specifically produce antibodies to Serine(419)phosphorylated ENOA (Ser(419)P-ENOA) isoforms (ENOA1,2), and that this humoral response correlates with a better clinical outcome. Since autoantibody production can be influenced by HLA polymorphisms, and the ENOA sequence presents multiple peptides predicted to preferentially bind HLA-DR molecules, including the peptide containing Ser(419), we hypothesized that the presence of autoantibodies against ENOA1,2 is associated with specific HLA-DRB1 alleles. Here, we demonstrate that the HLA-DRB1*08 allele is significantly more frequent in PDAC patients with autoantibodies to ENOA1,2 (ENOA1,2(+), 8%) compared to healthy controls (3%, p=0.0112). We observed that a Ser(419)P-ENOA peptide, bioinformatically predicted to bind with high affinity to the HLA-DR8 allele coded by HLA-DRB1*08:01 or *08:04 alleles, was able to activate specific CD4(+) T cell clones derived from a HLA-DRB1*08:01. Thus complexes of the Ser(419)P-ENOA peptide with the HLA that trigger T-cell signaling might be relevant for induction of anti-tumor immune response.