title: K562-Derived Whole-Cell Vaccine Enhances Antitumor Responses of CAR-Redirected Virus-Specific Cytotoxic T Lymphocytes In Vivo.
abstract: OBJECTIVE
  Adoptive transfer of Epstein-Barr virus (EBV)-specific and cytomegalovirus (CMV)-specific cytotoxic T cells (CTL) genetically modified to express a chimeric antigen receptor (CAR) induces objective tumor responses in clinical trials. In vivo expansion and persistence of these cells are crucial to achieve sustained clinical responses. We aimed to develop an off-the-shelf whole-cell vaccine to boost CAR-redirected virus-specific CTLs in vivo after adoptive transfer. As proof of principle, we validated our vaccine approach by boosting CMV-specific CTLs (CMV-CTLs) engineered with a CAR that targets the GD2 antigen.
  
  
  METHODS
  We generated the whole-cell vaccine by engineering the K562 cell line to express the CMV-pp65 protein and the immune stimulatory molecules CD40L and OX40L. Single-cell-derived clones were used to stimulate CMV-CTLs in vitro and in vivo in a xenograft model. We also assessed whether the in vivo boosting of CAR-redirected CMV-CTLs with the whole-cell vaccine enhances the antitumor responses. Finally, we addressed potential safety concerns by including the inducible safety switch caspase9 (iC9) gene in the whole-cell vaccine.
  
  
  RESULTS
  We found that K562-expressing CMV-pp65, CD40L, and OX40L effectively stimulate CMV-specific responses in vitro by promoting antigen cross-presentation to professional antigen-presenting cells (APCs). Vaccination also enhances antitumor effects of CAR-redirected CMV-CTLs in xenograft tumor models. Activation of the iC9 gene successfully induces growth arrest of engineered K562 implanted in mice.
  
  
  CONCLUSIONS
  Vaccination with a whole-cell vaccine obtained from K562 engineered to express CMV-pp65, CD40L, OX40L and iC9 can safely enhance the antitumor effects of CAR-redirected CMV-CTLs.
authors.affiliation: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston Methodist Hospital and Texas Children's Hospital, Houston, Texas.
authors.forename: Ignazio
authors.initials: I
authors.lastname: Caruana
authors.affiliation: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston Methodist Hospital and Texas Children's Hospital, Houston, Texas.
authors.forename: Gerrit
authors.initials: G
authors.lastname: Weber
authors.affiliation: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston Methodist Hospital and Texas Children's Hospital, Houston, Texas.
authors.forename: Brandon C
authors.initials: BC
authors.lastname: Ballard
authors.affiliation: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston Methodist Hospital and Texas Children's Hospital, Houston, Texas.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Wood
authors.affiliation: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston Methodist Hospital and Texas Children's Hospital, Houston, Texas. Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Barbara
authors.initials: B
authors.lastname: Savoldo
authors.affiliation: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston Methodist Hospital and Texas Children's Hospital, Houston, Texas. Department of Immunology, Baylor College of Medicine, Houston, Texas. Department of Medicine, Baylor College of Medicine, Houston, Texas. gdotti@bcm.edu.
authors.forename: Gianpietro
authors.initials: G
authors.lastname: Dotti
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D023201:CD40 Ligand / Q000378:metabolism; D019496:Cancer Vaccines / Q000276:immunology; D002457:Cell Extracts / Q000276:immunology; D045142:Cross-Priming; D003587:Cytomegalovirus / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D006801:Humans; D020014:K562 Cells; D008213:Lymphocyte Activation; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D053278:OX40 Ligand / Q000378:metabolism; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism*; D047368:Tumor Burden / Q000276:immunology; D014611:Vaccination; D014763:Viral Matrix Proteins / Q000276:immunology / Q000378:metabolism
chemical_list: D019496:Cancer Vaccines; D002457:Cell Extracts; D053278:OX40 Ligand; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; C089251:TNFSF4 protein, human; D014763:Viral Matrix Proteins; C065418:cytomegalovirus matrix protein 65kDa; D023201:CD40 Ligand