title: Route of antigen delivery impacts the immunostimulatory activity of dendritic cell-based vaccines for hepatocellular carcinoma.
abstract: BACKGROUND
  Dendritic cells (DC) are uniquely equipped to capture, process, and present antigens from their environment. The context in which an antigen is acquired by DC helps to dictate the subsequent immune response. Cancer vaccination promotes antitumor immunity by directing an immune response to antigens expressed by tumors. We have tested the tumor-associated antigen alpha-fetoprotein (AFP) as an immunotherapy target. The majority of hepatocellular carcinomas (HCC) upregulate and secrete this oncofetal antigen.
  
  
  METHODS
  To develop cancer vaccines for HCC capable of promoting potent tumor-specific T cell responses, we tested adenovirally-encoded synthetic AFP, with or without its signal sequence, as well as protein forms of AFP and compared intracellular routing and subsequent antigen-specific CD8+ and CD4+ T cell responses.
  
  
  RESULTS
  Surprisingly, the secreted form of antigen was superior for both CD4+ and CD8+ T cell activation. We also examined the mechanism through which AFP protein is endocytosed and trafficked in human DC. We identify the mannose receptor (MR/CD206) as the primary uptake pathway for both normal cord blood-derived AFP (nAFP) and tumor-derived AFP (tAFP) proteins. While in healthy donors, nAFP and tAFP were cross-presented to CD8+ T cells similarly and CD4+ T cell responses were dependent upon MR-mediated uptake. In HCC patient cells, tAFP was more immunogenic, and CD4+ T cell responses were not MR-dependent.
  
  
  CONCLUSIONS
  Secreted, cytoplasmically retained, and endocytosed forms of AFP utilize unique uptake and processing pathways, resulting in different immunologic responses from the induced antigen-specific CD4+ and CD8+ T cells and between healthy donors and HCC patients. Collectively, these data elucidate pathways of spontaneous and induced anti-tumor immunity in HCC patients to this secreted antigen.
authors.affiliation: Departments of Medicine, Pittsburgh, PA 15261 USA.
authors.forename: Angela D
authors.initials: AD
authors.lastname: Pardee
authors.affiliation: Departments of Medicine, Pittsburgh, PA 15261 USA.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yano
authors.affiliation: Departments of Medicine, Pittsburgh, PA 15261 USA.
authors.forename: Aliyah M
authors.initials: AM
authors.lastname: Weinstein
authors.affiliation: Departments of Medicine, Pittsburgh, PA 15261 USA.
authors.forename: Aaron A K
authors.initials: AA
authors.lastname: Ponce
authors.affiliation: Departments of Medicine, Pittsburgh, PA 15261 USA.
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Ethridge
authors.affiliation: Departments of Biostatistics, Pittsburgh, PA 15261 USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Normolle
authors.affiliation: Departments of Medicine, Pittsburgh, PA 15261 USA ; Departments of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA.
authors.forename: Lazar
authors.initials: L
authors.lastname: Vujanovic
authors.affiliation: Non-paid Advisor at the Wadsworth Center, New York State Department of Health, Albany, NY 12201 USA.
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Mizejewski
authors.affiliation: Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261 USA.
authors.forename: Simon C
authors.initials: SC
authors.lastname: Watkins
authors.affiliation: Departments of Medicine, Pittsburgh, PA 15261 USA ; Departments of Surgery, Pittsburgh, PA 15261 USA ; Departments of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA ; University of Pittsburgh Cancer Institute, Hillman Cancer Center 5117 Centre Avenue, Suite 1.27, Pittsburgh, PA 15213 USA.
authors.forename: Lisa H
authors.initials: LH
authors.lastname: Butterfield
keywords: Adenovirus; Alpha-fetoprotein; Dendritic cells; Hepatocellular carcinoma