title: Reconstructed adeno-associated virus with the extracellular domain of murine PD-1 induces antitumor immunity.
abstract: BACKGROUND
  The negative signaling provided by interactions of the co-inhibitory molecule, programmed death-1 (PD-1), and its ligands, B7-H1 (PD-L1) and B7-DC (PD-L2), is a critical mechanism contributing to tumor evasion; blockade of this pathway has been proven to enhance cytotoxic activity and mediate antitumor therapy. Here we evaluated the anti-tumor efficacy of AAV-mediated delivery of the extracellular domain of murine PD-1 (sPD-1) to a tumor site.
  
  
  METHODS
  An rAAV vector was constructed in which the expression of sPD-1, a known negative regulator of TCR signals, is driven by human cytomegalovirus immediate early promoter (CMV-P), using a triple plasmid transfection system. Tumor-bearing mice were then treated with the AAV/sPD1 construct and expression of sPD-1 in tumor tissues was determined by semi quantitative RT-PCR, and tumor weights and cytotoxic activity of splenocytes were measured.
  
  
  RESULTS
  Analysis of tumor homogenates revealed sPD-1 mRNA to be significantly overexpressed in rAAV/sPD-1 treated mice as compared with control levels. Its use for local gene therapy at the inoculation site of H22 hepatoma cells could inhibit tumor growth, also enhancing lysis of tumor cells by lymphocytes stimulated specifically with an antigen. In addition, PD-1 was also found expressed on the surfaces of activated CD8+ T cells.
  
  
  CONCLUSIONS
  This study confirmed that expression of the soluble extracellular domain of PD-1 molecule could reduce tumor microenvironment inhibitory effects on T cells and enhance cytotoxicity. This suggests that it might be a potential target for development of therapies to augment T-cell responses in patients with malignancies.
authors.affiliation: Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Hubei, China.
authors.forename: Osama A O
authors.initials: OA
authors.lastname: Elhag
authors.forename: Xiao-Jing
authors.initials: XJ
authors.lastname: Hu
authors.forename: Zhang
authors.initials: Z
authors.lastname: Wen-Ying
authors.forename: Xiong
authors.initials: X
authors.lastname: Li
authors.forename: Yong-Ze
authors.initials: YZ
authors.lastname: Yuan
authors.forename: Ling-Feng
authors.initials: LF
authors.lastname: Deng
authors.forename: De-Li
authors.initials: DL
authors.lastname: Liu
authors.forename: Ying-Le
authors.initials: YL
authors.lastname: Liu
authors.forename: Geng
authors.initials: G
authors.lastname: Hui
mesh_terms: D000818:Animals; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000276:immunology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D000229:Dependovirus / Q000235:genetics*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D061026:Programmed Cell Death 1 Receptor / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000276:immunology / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: C491383:Pdcd1 protein, mouse; D010446:Peptide Fragments; D061026:Programmed Cell Death 1 Receptor; D012333:RNA, Messenger