Next Generation CRISPR Gene-Edited and Off-the-Shelf Virus-Specific T-Cells for the Immunocompromised Patient

Introduction: A number of Clinical trials have demonstrated the feasibility, safety and efficacy of cell and gene therapy for cancer, autoimmune disorders and infectious disease. Strategies that enhance the function and survival of immune cells are critical for the success of immunotherapy. We have developed a strategy for the ex vivo expansion of off-the-shelf viral-specific T cells (VSRs) from healthy donor buffy coat which have been extremely effective in eradicating refractory cytomegalovirus (CMV), polyomavirus and adenovirus infections in immunocompromised patients. Glucocorticoids commonly used to treat graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (HSCT) are a common cause of iatrogenically-induced immunosuppression and contribute the risk of life-threatening viral-infections. To render VSTs resistant to the lymphocytotoxic effect of glucocorticoids, we have developed a novel strategy to silence the expression of the glucocorticoid receptor using RNA-guided endonucleases CRISPR (clustered regularly interspaced short palindromic repeats) and CRISPR-associated (Cas) 9 gene editing..

Methods: The technique involves the expansion from donor blood of CMV, BKV or adenoviral-specific T cells using peptide libraries from the immunodominant viral proteins followed by CRISPR knockout of exon 2 of the GR gene on chromosome 5 of the human NR3C1 gene. Cells are electroporated with the RNP (Cas9 plus guide RNA) complex (IDT pre-designed alt-R crispr Cas9 platform) using Neon electroporation and the Amaxa 4-D nucleofector system.

Results: GR knockout efficiency in ex vivo expanded virus-specific T cells was consistently > 90%. In vitro experiments confirmed the resistance of VSTs to corticosteroid treatment as assessed by annexin V assay. GR KO VSTs maintained potent antiviral activity as assessed by their ability to proliferate and release effector cytokines in response to viral antigens.

Conclusions: CRISPR gene-editing to knock-out the glucocorticoid receptor gene in viral-specific T cells can preserve the activity of VSTs in the presence of corticosteroid-induced immunosuppression. Engineering runs using GMP-compliant Cas9 protein and gRNA are underway in anticipation of a clinical trial.