Immunization with synthetic nanoparticles to generate mucosal CD8 T Cell responses

Abstract

Vaccines have benefited global health by controlling or eradicating life threatening diseases. With better understanding of infectious diseases and immunity, more interest has been placed on stimulating mucosal immune responses with vaccines as mucosal surfaces function as a first line of defense against infections. Progress made in nanoparticle research, in particular the successful use of liposomes for drug delivery, has made liposomes an attractive candidate for vaccine delivery. Here, we investigate the efficacy of using a novel nanoparticle system, Interbilayer Crosslinked Multilamellar Vesicles (ICMVs), as a mucosal vaccine to stimulate mucosal and systemic CD8 immunity. We first assessed the ability of ICMVs to elicit mucosal CD8 response, against the model antigen ovalbumin (OVA), by administration of the nanoparticles through the lungs. We explored the use of 2 different Toll-like receptor agonists (TLRa), monophosphoryl lipid A (MPLA) and Polyinosinic:polycytidylic acid (poly (I:C) or pIC) added to ICMVs as adjuvants. Pulmonary administration of ICMV with both adjuvants was found to give the most potent CD8 T cell response in both systemic and mucosal compartments. We looked further into the quality of the immune response and detected the presence of antigenspecific memory CD8 T cells in the system at ~2.5 months after immunization. The majority of these cells were found to be effector memory cells (CD44hiCD62Llo) and expressed markers for long term survival (CD127hiKLRG1lo), suggesting that long term protection against infection can be induced by pulmonary delivery of ICMVs. We also explored using this system to deliver a model HIV peptide epitope, AL 1, and ICMV successfully induced CD8 response against this epitope. Animals immunized against AL 11 were challenged with a live virus expressing the same epitope and protection was seen only in the pulmonary ICMV treatment group. Virus was delivered via the lungs and viral titre was decreased in both the lungs and ovaries. Neither the soluble form of the vaccine or ICMV delivered via parenteral injection conferred protection. Safety of the ICMV system was also assessed and no significant negative effects were observed in body weight and histological analysis on lungs. Finally, mechanism of using nanoparticles as pulmonary vaccines was investigated to gain better understanding in how particulate vaccine and route of immunization improved the efficacy of a vaccine. Overall, this thesis describes a comprehensive study of systemic and mucosal CD8 responses generated by pulmonary delivery of a novel nanoparticle system. This data provides evidence that mucosal delivery of ICMVs can safely and effectively stimulate disseminated mucosal CD8+ T cells at sites relevant for protection against mucosal infection. A better understanding of nanoparticles for pulmonary immunization was also gained.