In situ programming of leukaemia-specific T cells using synthetic DNA nanocarriers

Component: Carrier Matrix; Description: PBAE 447 (poly(β-amino ester)) — biodegradable, half-life 1-7 h in aqueous conditions; functionalized with MTAS-NLS peptide (microtubule-associated sequence + nuclear localization signal) for enhanced nuclear import

Component: Targeting Ligand; Description: Anti-CD3ε F(ab')₂ fragments (anti-mouse CD3e, clone 145-2C11) — conjugated to polyglutamic acid (PGA) and electrostatically adsorbed to particles

Component: Shielding Layer; Description: Polyglutamic acid (PGA) — negatively charged, reduces off-target binding

Component: Genetic Payload; Description: • Transposon plasmid: pPB-EF1α-murine194-1BBz-P2A-GFP (or CBR-luc) — encodes all-murine CD19-specific CAR (194-1BBz) with 4-1BB and CD3ζ signaling domains; GFP or CBR-luc reporter; piggyBac inverted terminal repeats<br>• Transposase plasmid: pRP-EF1α-iPB7 — encodes hyperactive piggyBac transposase (iPB7)

Component: Control CAR; Description: P4-1BBz (PSMA-specific CAR, tumor-irrelevant in mice)

Component: Nanoparticle Properties; Description: • Size: 155 ± 40 nm<br>• Zeta potential: −7.8 ± 2.1 mV<br>• Lyophilizable (stable with sucrose)

Component: Cell Lines; Description: • Eμ-ALL01 (murine B-cell acute lymphoblastic leukemia; CD19⁺, B220⁺)<br>• B16F10 (melanoma, control)<br>• HEK 293T (lentiviral packaging)

Component: Mouse Model; Description: Albino C57BL/6 mice (immunocompetent); Eμ-ALL01-luc systemic leukemia

Parameter: In Vitro Transfection; Details: Mouse splenocytes activated with ConA/IL-7; CD8⁺ T cells isolated; nanoparticles applied via syringe filter (gravity flow); CAR expression assessed at 30 h

Parameter: Nanoparticle Dosing; Details: 3×10¹¹ nanoparticles/dose; 5 sequential daily doses (i.v., tail vein; 20 min infusion via pump)

Parameter: In Vivo Targeting/Biodistribution; Details: Cy5-labeled DNA; IVIS fluorescence imaging; organ harvest at 4 h; flow cytometry (peripheral blood, spleen)

Parameter: In Vivo CAR Programming; Details: Mice bearing Eμ-ALL01-luc (day 0); nanoparticle treatment days 0-5; CAR⁺ T cells tracked by GFP (flow) or CBR-luc (IVIS); T cell proliferation/persistence monitored

Parameter: Therapeutic Efficacy; Details: IVIS bioluminescence imaging (tumor burden); survival (Kaplan-Meier); B cell aplasia (flow cytometry)

Parameter: Adoptive Transfer Control; Details: 5×10⁶ lentivirally transduced 194-1BBz CAR T cells; cyclophosphamide preconditioning (100 mg/kg, day -1)

Parameter: Safety Assessment; Details: CBC, serum chemistry, histopathology (10 organs), cytokine profiling (IFN-γ, IL-12, IL-6)

Parameter: Replicates; Details: n=10 mice/group for efficacy; n=2-5 for biodistribution/toxicity

Parameter: Statistical Tests; Details: Wilcoxon rank-sum test (photon counts); Log-rank test (survival); P < 0.05 significant

Analysis Category: Nanoparticle Characterization; Methods: Nanoparticle Tracking Analysis (NanoSight NS300) — size/concentration; ZetaPALS — zeta potential; TEM (JEOL JEM-1400) — morphology

Analysis Category: T Cell Transfection; Methods: Flow cytometry: GFP as surrogate for CAR expression (CD3⁺ gated); Confocal microscopy (Zeiss LSM 780) — internalization (Cy5-labeled DNA)

Analysis Category: In Vitro Function; Methods: • Cytotoxicity: Annexin V staining (flow cytometry); Eμ-ALL01 targets<br>• Cytokine secretion: ELISA (IL-2, IFN-γ, TNF-α; R&D Systems)

Analysis Category: Southern Blot; Methods: Genomic DNA digestion (NotI/XmaI); probe for 750-bp transposon fragment; confirms integration

Analysis Category: In Vivo Imaging; Methods: IVIS Spectrum; D-luciferin i.p.; Living Image 4.3.1; bioluminescence quantification

Analysis Category: Biodistribution; Methods: IVIS fluorescence (Cy5); spectral unmixing; % ID/g tissue

Analysis Category: Flow Cytometry; Methods: FACSCanto; antibodies: CD3, CD4, CD8, CD44, CD62L, Foxp3, CD25, CD11b, F4/80, B220, Ly6G, NKp46, CD19; GFP for CAR tracking

Analysis Category: Safety; Methods: Complete blood count (Anilytics); serum chemistry; histopathology (H&E, blinded pathologist)

Parameter: Nanoparticle size; Result: 155 ± 40 nm

Parameter: Zeta potential; Result: −7.8 ± 2.1 mV

Parameter: CAR expression (30 h, 3×10³ NPs:T cell); Result: 3.8 ± 0.3%

Parameter: CAR expression (MTAS-NLS vs. without); Result: 3.8% vs. 1.1% (3.4-fold increase; P < 0.0001)

Parameter: CAR persistence (with piggyBac, day 14); Result: Maintained

Parameter: CAR persistence (without piggyBac, day 14); Result: Lost

Parameter: Cytotoxicity vs. Eμ-ALL01; Result: Equivalent to lentiviral CAR T cells

Parameter: Cytotoxicity vs. B16F10; Result: Minimal (antigen-specific)

Parameter: Circulating T cells binding NPs (4 h); Result: 34 ± 5.1%

Parameter: Off-target cell binding; Result: 5.9 ± 2.8% (low)

Parameter: CD4:CD8 ratio of transfected T cells; Result: Physiological ratio (CD4⁺ > CD8⁺)

Parameter: Subtypes transfected; Result: Naive, effector, central memory, effector memory, Tregs (all)

Parameter: Non-targeted NP biodistribution; Result: Highest in liver

Parameter: T cell-targeted NP biodistribution; Result: Highest in spleen, lymph nodes, bone marrow

Parameter: Liver phagocyte transfection (day 6); Result: <1%

Parameter: Spleen phagocyte transfection (day 6); Result: <1%

Group: 194-1BBz + iPB7; Day 6 (% CAR⁺): 5.8 ± 0.9%; Day 12 (% CAR⁺): 7.1 ± 1.7%; Day 24 (% CAR⁺): ~5% (memory phenotype)

Group: 194-1BBz (no iPB7); Day 6 (% CAR⁺): ~3%; Day 12 (% CAR⁺): <1%; Day 24 (% CAR⁺): Undetectable

Group: P4-1BBz (irrelevant CAR); Day 6 (% CAR⁺): ~2%; Day 12 (% CAR⁺): <1%; Day 24 (% CAR⁺): Undetectable

Group: T cell expansion (with iPB7); Day 6 (% CAR⁺): -; Day 12 (% CAR⁺): 5.5-fold (day 12); Day 24 (% CAR⁺): Memory (CD44ʰⁱᵍʰ CD62L⁺)

Group: 194-1BBz + iPB7; Day 3 Signal: Spleen (weak); Day 12 Signal: Systemic (high); Max Fold Increase: 41-fold

Group: 194-1BBz (no iPB7); Day 3 Signal: Weak; Day 12 Signal: Near-background; Max Fold Increase: Minimal

Group: P4-1BBz; Day 3 Signal: Weak; Day 12 Signal: Near-background; Max Fold Increase: Minimal

Group: Untreated; Tumor Eradication: 0/10; Median Survival: 14 days; vs. Untreated: -

Group: P4-1BBz NPs (irrelevant CAR); Tumor Eradication: 0/10; Median Survival: 13 days; vs. Untreated: NS

Group: 194-1BBz NPs (no iPB7); Tumor Eradication: 0/10; Median Survival: 19 days; vs. Untreated: +5 days

Group: 194-1BBz NPs (+iPB7); Tumor Eradication: 7/10; Median Survival: 72 days; vs. Untreated: +58 days

Group: Adoptive CAR T cells (lentiviral); Tumor Eradication: 8/10; Median Survival: 77 days; vs. Untreated: +63 days

Group: Nanoparticle vs. adoptive; Tumor Eradication: 7/10 vs. 8/10; Median Survival: 72 vs. 77 days; vs. Untreated: Not significant

Parameter: B cells/spleen; Result: 7.4 × 10⁴ ± 8.3 × 10⁴ (dramatically reduced)

Parameter: Healthy vs. malignant B cells; Result: Both eliminated (CD19⁺ target)

Parameter: Reversibility; Result: Consistent with clinical CD19 CAR therapy

Parameter: Gross histopathology; Result: No lesions

Parameter: Cell counts; Result: Normal

Parameter: Blood chemistry; Result: Normal

Parameter: Inflammatory cytokines; Result: Modest increases: IFN-γ 1.6× (NS); IL-12 1.3×; IL-6 2.5×

1. Plasmid DNA (not minicircle): The authors acknowledge that "early clinical testing ... will also likely require that nanoparticle-delivered genetic materials be in the form of minicircles," as conventional plasmids contain bacterial origin of replication and antibiotic resistance genes.

2. Modest in vivo transfection efficiency: Only 5.8% of circulating T cells were CAR⁺ at day 6, yet this was sufficient for therapeutic efficacy. However, higher efficiencies may be needed for solid tumors or weaker antigens.

3. Hematological malignancy model: The study uses a leukemia model (CD19⁺, readily accessible, high antigen expression); the authors note that "treating solid tumours using this nanotechnology platform will be more challenging."

4. Off-target uptake by phagocytes: While CAR expression in off-target cells was <1%, a fraction of injected particles (16.2 ± 3.2%) was cleared by liver-resident phagocytes, with potential safety concerns.

5. piggyBac integration safety: While piggyBac is in clinical trials, the long-term safety of transposon-mediated integration in vivo remains to be fully established. The authors note that "early clinical testing" would require further safety evaluation.

6. No head-to-head comparison with Sleeping Beauty: The study uses piggyBac transposase; while similar systems are in clinical trials (Sleeping Beauty), direct comparison was not performed.

7. Constitutive EF-1α promoter: The authors acknowledge that "cell-specific promoters have a weaker transcriptional activity" but would reduce off-target expression risk.

8. Small sample size for some analyses: Biodistribution and toxicity studies used smaller cohorts (n=2-5); larger studies would strengthen conclusions.

9. No evaluation of T cell exhaustion: Long-term persistence and potential exhaustion of nanoparticle-programmed T cells were not fully characterized beyond 24 days.

10. Cyclophosphamide preconditioning only for adoptive transfer: To model clinical protocols, only the adoptive transfer group received preconditioning chemotherapy; nanoparticle groups did not, which may have favored the adoptive transfer group.

11. No evaluation of repeat dosing after initial response: The study did not assess whether additional nanoparticle doses could be given after tumor relapse.

12. In vivo imaging with CBR-luc: While CBR-luc enabled tracking, the signal may not directly correlate with CAR T cell numbers due to variable luciferase expression.

Report prepared based on the published Nature Nanotechnology article. For full experimental details, supplementary figures, and complete references, please refer to the original publication.