Optimized Molecular Spacers for High-Efficiency Targeted Lentiviral Vectors

This technology uses an optimized molecular spacer to display targeting proteins on lentiviral vectors, enabling highly efficient and specific gene delivery to human T cells for improved CAR T cell therapies and other targeted cell-based treatments.

Background

The general landscape for lentiviral vectors and chimeric antigen receptor (CAR) T-cell therapies is highly dense and focused on broad therapeutic applications. A major frontier in this space is enabling specific, in vivo gene transfer to generate CAR T cells directly within a patient. However, existing cell-specific delivery vectors that display binding molecules, such as single chain variable fragments (scFvs), on the viral envelope often yield poor transduction efficiencies in primary human T cells, frequently achieving less than 10% efficiency. While pseudotyped lentiviral vectors utilizing mutated fusion proteins can redirect viral tropism, existing technologies lack the optimized binder orientation needed to maximize target epitope access, limiting overall viral entry and clinical viability.

Technology

Seattle Children’s researchers have engineered a highly efficient, targeted lentiviral vector to overcome the limitations of current T-cell targeted vectors. This technology pairs a receptor-blind viral fusion protein, such as a mutated VSVG, with an affinity-based binder engineered for optimal viral surface-display. The core innovation includes a rationally designed “IgG stalk” for binder presentation and target engagement. The systematically optimized spacers provide the ideal length and orientation for the binder on the lentiviral particle surface.

In experimental validations targeting CD7 as a pan-T cell surface antigen, these optimized spacers achieved 46% transduction efficiency in anti-CD3/28 activated primary human peripheral blood mononuclear cells (PBMCs), outperforming the 35% efficiency of benchmark wild-type VSVG-pseudotyped vectors. Furthermore, in non-activated, resting PBMCs, the targeted vector achieved a 11% transduction efficiency compared to 6% for traditional vectors. Applying the optimized stalk to an anti-CD3 scFv yielded up to 50% transduction efficiency in primary human T cells without additional stimulation. By systematically defining the structural engineering of molecular spacers, this technology successfully fills a critical gap in lentiviral display technologies, offering superior targeted gene delivery to specific cell subsets.

Benefits

  • Achieves up to 50% transduction efficiency in primary human T cells without the need for cellular stimulation

  • Improved transduction efficiency in primary human T cells compared to existing lentiviral vectors at comparable physical viral titers

  • Modular platform that can be adapted to target various other cell surface antigens

  • Amenable for use with other targeted gene delivery chassis, including integrase-deficient lentivirus, transposon-based systems, or ribonucleoprotein editors like Cas9.

Applications

  • In-vivo CAR T-cell, NK cell therapy and other T cell based immunotherapies

  • Therapy development for blood cancers, solid tumors, and autoimmune diseases