Recently, several types of
immunotherapies have been shown to induce encouraging clinical results, though in a restricted number of patients. Consequently, there is a need to identify immune
biomarkers to select patients who will benefit from such
therapies. Such predictive
biomarkers may be also used as surrogates for overall survival (OS). We have recently found correlations between immunologic parameters and clinical outcome in
prostate cancer patients who had been vaccinated with a HER-2/neu hybrid
polypeptide vaccine (AE37) and received one booster 6 months post-primary vaccinations. Herein, we aimed to expand these retrospective analyses by studying the predictive impact of
HLA-A*24 and
HLA-DRB1*11 alleles, which are expressed at high frequencies among responders in our vaccinated patients, for clinical and immunological responses to AE37 vaccination. Our data show an increased OS of patients expressing the
HLA-DRB1*11 or
HLA-A*24 alleles, or both.
Vaccine-induced immunological responses, measured as
interferon γ (IFN-γ) responses in vitro or delayed-type
hypersensitivity reactions in vivo, were also higher in these patients and inversely correlated with suppressor elements. Preexisting (i.e., before vaccinations with AE37) levels of
vaccine-specific IFN-γ immunity and plasma TGF-β, among the
HLA-A*24 and/or
HLA-DRB1*11 positive patients, were strong indicators for immunological responses to AE37 treatment. These data suggest that
HLA-DRB1*11 and
HLA-A*24 are likely to be predictive factors for immunological and clinical responses to vaccination with AE37, though prospective validation in larger cohorts is needed.