Development of polymeric nanoparticle vaccines for immunostimulation

Abstract

Vaccines have revolutionized medicine by increasing the life expectancy of children and substantially decreasing the morbidity of multiple infectious diseases worldwide. Over several decades, we have acquired significant gains in the understanding of the underlying mechanisms involved in developing protective immunity, yet vaccine development has progressed comparatively slowly. This thesis serves to explore two polymeric nanoparticle platforms to demonstrate the therapeutic potential of synthetic nanocarriers as vaccines with the aim of 1) providing greater spatiotemporal release of small molecule adjuvant to secondary lymphoid sites and 2) providing a tunable surface for loading B cell antigen epitopes in a specific conformation to drive epitope-specific antibody response. In recent decades, TLR mechanisms have been elucidated and novel agonists have been developed, yet our generation still has not seen paramount progress in the clinical translation of these agonists due to risks of systemic toxicity and off target effects. In the first section, we synthesized 223±18 nm poly(lactic-co-glycolic acid)- poly(ethylene glycol)/ poly(lactic acid)-R848 (PLGA-PEG/PLA-R848) nanoparticle vaccine that is designed to deliver a combination of antigen and control release of a small molecule adjuvant R848 (tl/2= 42 hours) to drive a potent antigen-specific immune response. Using ovalbumin as a model protein, this vaccine is able to enhance antigen presentation and co-stimulatory molecules on dendritic cells and subsequently enhanced proliferation of antigen-specific naive CD8+ cells in vitro. Upon vaccination, our delivery system is able to increase cell-mediated and humoral response in comparison to its soluble form, thereby illustrating the potential to bring novel small molecule adjuvants to the clinics. In the second section, we developed a nanoparticle vaccine platform that allows selective orientation of peptide epitopes to enhance B cell response in an application that has therapeutic potential for treatment for cardiovascular disease (CVD). Utilizing epitopes discovered through in silico modeling for human PCSK9, a plasma protein that plays an important role in LDL cholesterol (LDL-c) levels in the blood, our nanoparticle allows selective orientation through biotin-streptavidin conjugation. Upon vaccination with CPG, selected synthetic epitopes conjugated to polymeric nanoparticles trended to reduce serum LDL-c and serum PCSK9 in murine models. Additionally, antibodies in the serum showed promise to increase LDL-receptor levels in HepG2 cells transfected in with WT-hPCSK9 and GOF-hPCSK9 separately suggesting that this vaccine has the potential to reduce risks of CVD. These studies demonstrate that designing polymeric nanoparticles for applications to stimulate the immune system can help define new, cost-effective treatment options in applications for prophylaxis against infectious diseases that are unresponsive to traditional routes of vaccination or for immunotherapy against cardiovascular disease and cancer.