Stealth transgenes enable CAR-T cells to evade host immune responses

Area of Science:

• Immunology
• Cell Therapy
• Cancer Research

Background:

• Adoptive cell therapy, including chimeric antigen receptor (CAR)-T cell therapy, has shown promise in treating hematological malignancies.
• Current CAR-T therapies often face immune rejection due to non-self CAR components, limiting treatment effectiveness and repeated dosing.
• The FMC63-based αCD19 single-chain variable fragment is a common binding domain in FDA-approved CAR-T products.

Purpose of the Study:

• To develop a method to prevent the rejection of engineered T cells in adoptive cell therapy.
• To reduce the immunogenicity of both autologous and allogeneic CAR-T cells.
• To enhance the persistence and efficacy of CAR-T cell treatments.

Main Methods:

• Implemented a one-shot approach combining viral inhibitors of transporter associated with antigen processing (TAPi) and shRNA targeting the class II MHC transactivator (CIITA).
• Reduced antigen presentation and major histocompatibility complex (MHC) classes I and II surface expression on CAR-T cells.
• Validated the approach in vitro using flow cytometry and mixed lymphocyte reaction assays, and in vivo using mouse models of leukemia and lymphoma.

Main Results:

• The combination of Epstein-Barr virus TAPi and CIITA-targeting shRNA effectively reduced MHC classes I and II on αCD19 CAR-T cells, creating 'stealth' CAR-T cells.
• Stealth CAR-T cells retained antitumor functionality in vitro and in vivo.
• Patient T cells demonstrated that stealth CAR-T cells evaded autologous and allogeneic anti-CAR immune responses, particularly in patients who received multiple CAR-T infusions.

Conclusions:

• The developed stealth transgenes show potential in reducing the immunogenicity of both autologous and allogeneic cellular therapeutics.
• Patient data suggest that repeated dosing of conventional CAR-T cells can significantly increase anti-CAR T cell responses.
• This strategy may overcome a key limitation in CAR-T cell therapy, paving the way for more effective and durable treatments.