Formulation and delivery of polymeric nanoparticle-assisted vaccine against melanoma

Abstract

Poly (lactide-co-glycolide) (PLGA) nanoparticle (NP) is a widely used biodegradable carrier for drug and vaccine delivery. This thesis focused on the formulation, delivery and efficacy of PLGA NP for its potential application in melanoma immunotherapy. To enable reliable PLGA NP formulation for clinical use such as vaccination, lyophilization is the method of choice to manufacture dry NP dosage form. A major risk of the lyophilization product development for NPs is the irreversible NP aggregation due to freezing and drying stress. Based on real-time imaging, freezing stress could be attributed to freeze-concentration of NPs. Cryo-scanning electron microscopy (cryo-SEM) revealed individual NP separately embedded in the freeze-concentrate interstitial space of the sucrose formulation, leading to corroborative support for the "particle isolation" hypothesis of cryo-protection. Various sphere packing models were investigated to guide the rational design of cryo-/lyo-protectant containing NP formulations. To facilitate precise intradermal delivery of NP formulation for vaccination, microneedle array-mediated administration was utilized to deliver large volume of NPs into the skin. The majority of the infused PLGA NPs were retained locally. A PLGA NP vaccine formulation delivered intradermally elicited robust humoral and cellular immunity. Antigen-loaded NP formulation triggered quicker and stronger high affinity antibody responses compared to the soluble antigen formulation. Vemurafenib, a selective inhibitor of BRAF V600E, induces apoptotic melanoma cell death and remarkable tumor burden reduction. However, drug resistance invariably occurs. Novel TLR7/8 agonists were encapsulated in PLGA particulate formulation as immunostimulatory nanoparticles (ISNP) to boost immune response against drug-resistant melanoma. NP-mediated intracellular delivery contributed to enhanced dendritic cell activation in vitro and antigen-specific CD8+ T cell proliferation in vivo. The prophylactic vaccination using NP-assisted whole tumor cell formulation prolonged the survival of mice challenged with melanoma. To take advantage of the clearance of melanoma antigens by immune system in the context of BRAF inhibition, an ISNP-assisted in situ whole tumor cell vaccination strategy was investigated using BRAF V600E positive mouse SM1 melanoma cells. Despite the suppressed tumor growth, no survival benefit was observed in this therapeutic vaccination model.