Weiwei Aileen Li

Chimeric antigen receptor (CAR) T cells are ineffective against solid tumors with immunosuppressive microenvironments. To overcome suppression, we engineered circuits in which tumor-specific synNotch receptors locally induce production of the cytokine IL-2. These circuits potently enhance CAR T cell infiltration and clearance of immune-excluded tumors, without systemic toxicity. The most effective IL-2 induction circuit acts in an autocrine and T cell receptor (TCR)- or CAR-independent manner, bypassing suppression mechanisms including consumption of IL-2 or inhibition of TCR signaling. These engineered cells establish a foothold in the target tumors, with synthetic Notch–induced IL-2 production enabling initiation of CAR-mediated T cell expansion and cell killing. Thus, it is possible to reconstitute synthetic T cell circuits that activate the outputs ultimately required for an antitumor response, but in a manner that evades key points of tumor suppression.

SynNotch-CAR T cells durably clear glioblastoma xenografts, overcoming dual challenges of antigen heterogeneity and specificity common to solid tumors.

Vaccines have shown significant promise in eliciting protective and therapeutic responses. However, most effective vaccines require several booster shots, and it is challenging to generate responses against synthetic molecules and peptides often used to increase target specificity and improve vaccine stability. As continuous antigen uptake and processing by antigen‐presenting cells and persistent toll‐like receptor priming can amplify humoral immunity, it is explored whether a single injection of a mesoporous silica micro‐rod (MSR) vaccine containing synthetic molecules and peptides can generate potent and durable humoral immunity. A single injection of the vaccine targeting a gonadotropin‐releasing hormone (GnRH) decapeptide elicits high anti‐GnRH titer for over 12 months and generated higher titers than bolus or alum formulations. Targeting a Her2/neu peptide within the Trastuzumab binding domain causes immunoreactivity to Her2 on tumor cells and, MSR vaccines against nicotine generated long‐term anti‐nicotine antibodies. A single MSR injection induced germinal center (GC) activity for more than 3 weeks, generated memory B cells, and 7 days of immunostimulation by the vaccine is required to generate effective antibody responses. The MSR vaccine represents a promising technology to bypass the need for multiple immunizations and enhance long‐term antibody production in the context of reproductive biology, cancer, and chronic addiction.

Ischemic diseases are a leading cause of mortality and can result in autoamputation of lower limbs. We explored the hypothesis that implantation of an antigen-releasing scaffold, in animals previously vaccinated with the same antigen, can concentrate T_H2 T cells and enhance vascularization of ischemic tissue. This approach may be clinically relevant, as all persons receiving childhood vaccines recommended by the Centers for Disease Control and Prevention have vaccines that contain aluminum, a T_H2 adjuvant. To test the hypothesis, mice with hindlimb ischemia, previously vaccinated with ovalbumin (OVA) and aluminum, received OVA-releasing scaffolds. Vaccinated mice receiving OVA-releasing scaffolds locally concentrated antigen-specific T_H2 T cells in the surrounding ischemic tissue. This resulted in local angiogenesis, increased perfusion in ischemic limbs, and reduced necrosis and enhanced regenerating myofibers in the muscle. These findings support the premise that antigen depots may provide a treatment for ischemic diseases in patients previously vaccinated with aluminum-containing adjuvants.

Existing strategies to enhance peptide immunogenicity for cancer vaccination generally require direct peptide alteration, which, beyond practical issues, may impact peptide presentation and result in vaccine variability. Here, we report a simple adsorption approach using polyethyleneimine (PEI) in a mesoporous silica microrod (MSR) vaccine to enhance antigen immunogenicity. The MSR–PEI vaccine significantly enhanced host dendritic cell activation and T-cell response over the existing MSR vaccine and bolus vaccine formulations. Impressively, a single injection of the MSR–PEI vaccine using an E7 peptide completely eradicated large, established TC-1 tumours in about 80% of mice and generated immunological memory. When immunized with a pool of B16F10 or CT26 neoantigens, the MSR–PEI vaccine eradicated established lung metastases, controlled tumour growth and synergized with anti-CTLA4 therapy. Our findings from three independent tumour models suggest that the MSR-PEI vaccine approach may serve as a facile and powerful multi-antigen platform to enable robust personalized cancer vaccination.

A covalently crosslinked methacrylated (MA)‐alginate cryogel vaccine has been previously shown to generate a potent response against murine melanoma, but is not mechanically robust and requires a large 16G needle for delivery. Here, covalent and ionic crosslinking of cryogels are combined with the hypothesis that this will result in a tough MA‐alginate cryogel with improved injectability. All tough cryogels can be injected through a smaller, 18G needle without sustaining any damage, while covalently crosslinked‐only cryogels break after injection. Cytosine‐phosphodiester‐guanine (CpG)‐delivering tough cryogels effectively activate dendritic cells (DCs). Granulocyte macrophage colony‐stimulating factor releasing tough cryogels recruit four times more DCs than blank gels by day 7 in vivo. The tough cryogel vaccine induces strong antigen‐specific cytotoxic T‐lymphocyte and humoral responses. These vaccines prevent tumor formation in 80% of mice inoculated with HER2/neu‐overexpressing DD breast cancer cells. The MA‐alginate tough cryogels provide a promising minimally invasive delivery platform for cancer vaccinations.

DNA nanostructures have evoked great interest as potential therapeutics and diagnostics due to ease and robustness of programming their shapes, site-specific functionalizations and responsive behaviours. However, their utility in biological fluids can be compromised through denaturation induced by physiological salt concentrations and degradation mediated by nucleases. Here we demonstrate that DNA nanostructures coated by oligolysines to 0.5:1 N:P (ratio of nitrogen in lysine to phosphorus in DNA), are stable in low salt and up to tenfold more resistant to DNase I digestion than when uncoated. Higher N:P ratios can lead to aggregation, but this can be circumvented by coating instead with an oligolysine-PEG copolymer, enabling up to a 1,000-fold protection against digestion by serum nucleases. Oligolysine-PEG-stabilized DNA nanostructures survive uptake into endosomal compartments and, in a mouse model, exhibit a modest increase in pharmacokinetic bioavailability. Thus, oligolysine-PEG is a one-step, structure-independent approach that provides low-cost and effective protection of DNA nanostructures for in vivo applications.