Purpose: Current antitumor vaccines are limited by the small number of defined tumor-associated antigens (TAAs) for most solid tumors and by poor delivery of soluble antigen to dendritic cells (DCs). Autologous whole-tumor lysates contain the full antigenic repertoire, but soluble lysates are unstable and poorly internalized. Biodegradable PLGA nanoparticles may protect antigens, improve DC uptake, and enhance cross-presentation to cytotoxic T cells.
Hypothesis: If defined TAAs and complex whole-tumor lysates are encapsulated in biodegradable PLGA nanoparticles, then the nanoparticles will efficiently encapsulate and release the antigens, preserve antigenicity, and enhance DC-mediated T-cell cytokine responses and antitumor protection compared with soluble antigen delivery.
Aims: Optimize PLGA nanoparticle formulation for defined proteins (OVA, gp100) and complex tumor lysates. - Characterize nanoparticle size, encapsulation efficiency, release kinetics, and protein integrity. - Verify that encapsulated tumor-associated antigens retain antigenicity after release. - Test in vitro stimulation of antigen-specific CD8+ T cells by DCs loaded with soluble vs nanoparticle-encapsulated antigen. - Evaluate in vivo protection in a murine B16 melanoma vaccination-challenge model.
Delivery system:
Component: Polymer; Details: 50:50 poly(D,L-lactide-co-glycolide) (PLGA)
Component: Molecular weights; Details: 15K, 45K, 80K, 105K (105K with carboxyl end groups)
Component: Nanoparticle type; Details: Polymeric nanoparticles
Component: Fabrication; Details: Water/oil/water (W₂/O/W₁) double emulsion, solvent evaporation
Component: Stabilizer; Details: Poly(vinyl alcohol) (PVA), 0.5% or 5%
Component: Payloads; Details: Ovalbumin (OVA), gp100 melanoma antigen, BSA/OVA/lysozyme mixtures, B16 melanoma freeze-thaw (FT) lysates, octyl β-glucoside (OG) lysates
Component: Targeting ligand; Details: None
Component: Key feature; Details: Encapsulation of defined antigens and whole-tumor lysates for DC-based immunotherapy
Approach: In vitro: Murine bone marrow–derived dendritic cells (BMDCs) loaded with equimolar soluble or nanoparticle-encapsulated antigen; co-cultured with gp100-specific naive CD8+ T cells from pmel transgenic mice; cytokine readout by cytometric bead array (IL-2, IFN-γ). - In vivo: C57BL/6 mice; DCs loaded ex vivo with B16 lysates (soluble or nanoparticle-encapsulated) or controls; two vaccinations 14 days apart; subcutaneous B16 melanoma challenge 10 days after second vaccination; tumor growth and survival monitored. n = 8 per group. - Disease context: Melanoma immunotherapy; no human studies.
Key methods: Nanoparticle characterization: Scanning electron microscopy (SEM), ImageJ sizing. - Protein encapsulation/release: Bicinchoninic acid (BCA) assay, absorbance at 290 nm for defined proteins. - Protein integrity/composition: SDS-PAGE with silver staining; Western blot for OVA and gp100. - Antigenicity: Western blot with anti-OVA and anti-gp100 antibodies. - T-cell stimulation: Cytometric bead array for IL-2 and IFN-γ. - In vivo efficacy: B16 melanoma tumor growth and survival after DC vaccination.
Key results: Encapsulation: Efficiency increased with PLGA molecular weight and decreased with initial protein loading. For OVA at 50 mg/mL loading: 15K = 27%, 45K = 22%, 80K = 55%, 105K = 99%. At 100 mg/mL loading, encapsulation efficiency was lower. - Release: Biphasic release (burst + sustained). Higher MW PLGA (45K, 80K, 105K) sustained release over 14 days; 15K released faster and shorter. - Lysates: B16 FT and OG lysates were encapsulated; proteins were released, though OG lysates showed altered release of lower-molecular-weight proteins. - Antigenicity: OVA and gp100 retained antibody reactivity after encapsulation and release. - In vitro T-cell response: gp100 encapsulated in nanoparticles led to ~10-fold higher IL-2 and ~3-fold higher IFN-γ production compared with soluble gp100. Blank nanoparticles did not stimulate nonspecific cytokine release. - In vivo: Mice vaccinated with DCs loaded with nanoparticle-encapsulated B16 lysate had the smallest tumors and longest tumor-free durations. However, lysate-containing nanoparticles injected without DCs grew faster than PBS controls, suggesting potential tolerization without DC antigen presentation.
Interpretation: The authors claim that PLGA nanoparticles can efficiently encapsulate defined TAAs and complex whole-tumor lysates, preserve antigenicity, and enhance DC-mediated T-cell stimulation and antitumor protection in vivo. This approach may enable personalized immunotherapy for solid tumors lacking defined antigens, using autologous tumor lysates delivered in particulate form.
Limitations: In vivo model only: Murine B16 melanoma; no human or large-animal validation. - Defined and model antigens: OVA and gp100 used; clinical translation to human tumors not demonstrated. - Small sample size: n = 8 mice per group. - Tumor growth, not survival: Endpoint based on tumor volume/distress; limited late-time data. - No targeting ligand: Delivery relies on passive DC uptake. - Potential tolerization: Nanoparticle-lysate without DCs enhanced tumor growth vs PBS, highlighting dependence on DC loading. - No long-term safety, toxicity, or immune memory data. - No standardized potency assay for clinical release. - No comparison with clinical-grade DC vaccines or other adjuvants. - DOI/link not explicitly provided in the supplied file.
