Molecular Therapy: Methods & Clinical Development (Jun 2021)

Anti-CD19 CARs displayed at the surface of lentiviral vector particles promote transduction of target-expressing cells

  • Nicole Cordes,
  • Carolin Kolbe,
  • Dominik Lock,
  • Tatjana Holzer,
  • Deborah Althoff,
  • Daniel Schäfer,
  • Franziska Blaeschke,
  • Bettina Kotter,
  • Sandra Karitzky,
  • Claudia Rossig,
  • Toni Cathomen,
  • Tobias Feuchtinger,
  • Iris Bürger,
  • Mario Assenmacher,
  • Thomas Schaser,
  • Andrew D. Kaiser

Journal volume & issue
Vol. 21
pp. 42 – 53

Abstract

Read online

Recently, a rare type of relapse was reported upon treating a B cell acute lymphoblastic leukemia (B-ALL) patient with anti-CD19 chimeric antigen receptor (CAR)-T cells caused by unintentional transduction of residual malignant B cells (CAR-B cells). We show that anti-CD19 and anti-CD20 CARs are presented on the surface of lentiviral vectors (LVs), inducing specific binding to the respective antigen. Binding of anti-CD19 CAR-encoding LVs containing supernatant was reduced by CD19-specific blocking antibodies in a dose-dependent manner, and binding was absent for unspecific LV containing supernatant. This suggests that LVs bind via displayed CAR molecules to CAR antigen-expressing cells. The relevance for CAR-T cell manufacturing was evaluated when PBMCs and B-ALL malignant B cells were mixed and transduced with anti-CD19 or anti-CD20 CAR-displaying LVs in clinically relevant doses to mimic transduction conditions of unpurified patient leukapheresis samples. Malignant B cells were transduced at higher levels with LVs displaying anti-CD19 CARs compared to LVs displaying non-binding control constructs. Stability of gene transfer was confirmed by applying a potent LV inhibitor and long-term cultures for 10 days. Our findings provide a potential explanation for the emergence of CAR-B cells pointing to safer manufacturing procedures with reduced risk of this rare type of relapse in the future.

Keywords