Analysis of CD4+ T-Cell Responses to a Novel α-Fetoprotein-Derived Epitope in Hepatocellular Carcinoma Patients

Abstract

Purpose: a-Fetoprotein (AFP) is a tumor-associated antigen in hepatocellular carcinoma and is a target for the development of cancer vaccine. Four immunodominant AFP-derived HLA-A*0201-restricted peptides have been identified and the administration of these peptides with an adjuvant has stimulated AFP-specific CTL responses in hepatocellular carcinoma patients. However, no AFP-derived CD4 T-cell epitope has yet been reported and the status of AFP-specific CD4 + T-cell responses in hepatocellular carcinoma patients is not fully understood. The aim of this study was to analyze naturally occurring CD4 + T-cell responses to AFP. Experimental Design: We analyzed the ability of CD4 + T cells to recognize an HLA-DR-restricted AFP-derived epitope in 41 hepatocellular carcinoma patients and 24 nonhepatocellular carcinoma control patients using intracellular cytokine assays for IFN-g. Results: Here, for the first time, we report the identification of an AFP-derived CD4 + T-cell epitope that is recognized by circulating lymphocytes from hepatocellular carcinoma patients in association with HLA-DR. The absence of detectable responses in healthy donors and patients with chronic liver disease suggests that AFP-specific CD4 + T cells in the responder patients had been previously expanded in vivo in response to the tumor. The anti-AFP CD4 + T-cell response was only detected in hepatocellular carcinoma patients with normal or mildly elevated serum AFP levels who were in the early stage of disease. Conclusion: Our data will be instrumental in the development of cancer vaccine using AFP-derived immunogens.

Unmasking of α-Fetoprotein-Specific CD4+ T Cell Responses in Hepatocellular Carcinoma Patients Undergoing Embolization

“…We have recently reported the first CD4 ϩ epitope (AFP 364 -373 ) in HCC patients (20). In this study we extend this work with the description of two further AFP-derived class II-restricted epitopes.…”

“…We have previously reported the presence of AFP 364 -373 -specific CD4 ϩ T cells in HCC patients that were significantly more likely to be present at an early stage of disease and with a serum AFP of Ͻ1000 ng/ml (20). We therefore first selected 20 HCC patients (Okuda I and Ͻ1000 ng/ml AFP) (Table II) who were theoretically most likely to have an AFP 364 -373 CD4 ϩ T cell response and analyzed CD4 ϩ T cell responses to a panel of 60 AFP-derived peptides (10 pools of 6 peptides; Table I) and AFP 364 -373 .…”

“…CD4 ϩ helper T cells are also important in generating potent anticancer immunity, as they can prime and expand CD8 ϩ memory T cells (17) or induce tumor regression in the absence of CD8 ϩ T cells, including MHC class II-negative or MHC class II-positive tumors (18,19). We have recently reported the presence of CD4 ϩ T cells that recognized an AFP-derived epitope in HCC patients, predominantly in an early stage of the disease (20).…”

“…We first conducted a cross-sectional study of AFP-specific CD4 ϩ T cell responses in the blood of HCC patients (Table II) and controls (Table III). The inclusion criteria for HCC patients in the cross-sectional study were as follows: 1) a diagnosis of HCC made according to the European Association for the Study of Liver disease criteria (9); 2) patients who were most likely to have an AFP 364 -373 -specific CD4 ϩ T cell response (Okuda stage 1 and Ͻ1000 ng/ml serum AFP) (20); and 3) patients who were either treatment naive or had only received TACE/TAE as treatments. The non-HCC liver disease controls are age matched to the HCC group.…”

“…Short-term T cell lines were generated as described previously (20) to study naturally occurring AFP-specific T cell responses (25). In brief, PBMCs were resuspended in AIM-V medium (Invitrogen Life Technologies) with 10% FCS and were …”