UCLA researchers in the Department of Chemistry & Biochemistry have recently developed a novel approach for engineering CAR T cells in vivo for immunotherapy through a plant virus-derived vector specifically targeted to T cells.
BACKGROUND: Adoptive T cell (ATC) therapy such as chimeric antigen receptor (CAR) or T cell receptor (TCR)-based immunotherapy has transformed treatment for leukemia, lymphoma, and other blood cancers. While largely effective in these cancers, ATC therapy is often considered a last resort due to the lengthy, complex, and costly manufacturing process.
For ATC therapy, T cells are harvested and transduced with a viral vector, followed by multiple rounds of cell expansion. These crucial steps enable T cells to recognize target antigens from cancer cells and ensure sufficient T cell dosage for a robust, therapeutic effect. However, this process also often is undermined by rapid T cell exhaustion, poor persistence, and inefficient expansion upon administration to the patient, leading to reduced therapeutic response. Therefore, despite the promising results of ATC therapy, its labor-intensive manufacturing process restricts its full clinical potential.
Recently, however, in vivo engineering of T cells through viral vectors has emerged as a possible strategy to circumvent these manufacturing constraints. Adeno-associated virus (AAV-mediated delivery) has been previously used to make engineered T cells in vivo, though these are not specifically targeted and can lead to activation of the innate immune response. Therefore, for in vivo engineered T cell generation to be clinically viable, the vector for transient transfection of T cells needs to be specific and biocompatible, meaning it does not induce off-target effects and minimizes innate immune response activation.
INNOVATION: Researchers at UCLA led by Dr. William M. Gelbart have developed a way to deliver mRNA coding for CAR or TCR T cell generation through an in vitro reconstituted virus-like particle (VLP). VLP is composed of a capsid protein derived from plants, purified mRNA, and targeted with an antibody against CD3 epsilon for specific delivery to T cells. The capsid from the cowpea chlorotic mottle virus is capable of spontaneously packaging mRNA and releasing it to mammalian cells and importantly does not induce adverse side effects in humans. With this delivery system in place, T cells can be specifically targeted for transient expression of CAR or TCR genes and used to clear cancer cells more efficiently without the need for T cell harvesting.
POTENTIAL APPLICATIONS:
- In vivo generation of T cells for ATC therapy
- Broaden applicability of ATC therapy to solid tumor cancers via specific targeting of T cells and minimal patient intervention
- Cancer drug/treatment delivery
ADVANTAGES:
- Increased specificity of ATC therapy
- Vector poses no known risk to humans
- Transient expression of CAR or TCR genes
- Reduced patient burden by eliminating need for T cell harvesting
- Reduced time and cost in manufacturing allows for more patient access to ATC therapy as treatment option
- Greater scalability and standardization of manufacturing process
DEVELOPMENT-TO-DATE: VLP has been shown to self-assemble around RNA molecules and able to be targeted with antibodies for T cell specificity in in vitro settings. Furthermore, this delivery method has been successfully used to transduce cytotoxic T cells into CAR T cells in in vitro settings.
Related Papers (from the inventors only):
- Rodriguez N, Hofmann C, Yang OO, Gelbart WM. A New Approach to In Vivo Transformation of Killer T Cells. J Mol Biol. 2025 Nov 15;437(22):169369. doi: 10.1016/j.jmb.2025.169369. Epub 2025 Aug 7. PMID: 40754153.
- Biddlecome A, Habte HH, McGrath KM, Sambanthamoorthy S, Wurm M, Sykora MM, Knobler CM, Lorenz IC, Lasaro M, Elbers K, Gelbart WM. Delivery of self-amplifying RNA vaccines in in vitro reconstituted virus-like particles. PLoS One. 2019 Jun 4;14(6):e0215031. doi: 10.1371/journal.pone.0215031. PMID: 31163034; PMCID: PMC6548422.
Keywords: Viral vector, plant-derived virus vector, VLP, delivery method, delivery system, in vivo, CAR T cells, TCR T cells, adoptive immune therapy, adoptive T cell therapy (ATC), blood cancer, engineering T cells, immunotherapy, oncology