Development of nanovaccines against Influenza A and Group A Streptococcus

Abstract

Modern vaccine development has focused on developing effective vaccines without compromisingvaccine safety and tolerability. This has prompted the rational design of modern subunit vaccines,which are safe and well-characterized, by incorporating key immunogenic elements of pathogenproperties to induce tailored responses of appropriate strength, quality and specificity. Based on thisstrategy, Virus-like particles (VLPs) and their subunit capsomeres have been utilized as a platformto present a variety of foreign epitopes from targeted pathogens. Promising vaccine candidatesbased on the modular murine polyomavirus (MPyV) VLP or capsomere platform have beendeveloped to target influenza A and Group A streptococcus (GAS), which are microbially-producedrapidly at low-cost and are easily scalable. However, the understanding of their effectiveness ininducing specific immune response is limited. Building on the previous successful outcomes withthese vaccine candidates, different strategies were investigated to improve their immunogenicityand protective efficacy. This involved the refinement of vaccine at formulation level (e.g.adjuvants) or administration route (e.g. parenteral or non-parenteral). This work utilizes afluorescence optical imaging approach for in vivo tracking of vaccine components afterimmunization to correlate the immune responses with their biodistribution. The main objectives ofthis thesis are: (i) demonstrating the non-carrier adjuvanting efficacy of PLGA and silicananoparticles for modular capsomeres presenting influenza M2e antigen; (ii) visualizing the in vivotrafficking of silica nanoparticle-adjuvanted modular capsomere formulation by fluorescenceimaging to understand their ability to induce effective antibody-biased immune response, eventhough these components are not attached prior to immunization; (iii) determining the potential ofsublingual delivery of modular VLPs presenting GAS J8 antigen; and (iv) evaluating the in vivotrafficking of sublingually-administered modular VLPs to comprehend their ability to raise systemicas well as mucosal response. This work confirms that a simple ‘mix and inject’ formulation ofnanoparticles and modular capsomeres can lead to effective adjuvanting of antigenic modularcapsomeres by nanoparticles, with level of antibody response reliant on physicochemical propertiesof nanoparticles. The non-carrier adjuvanting effect of silica nanoparticles on modular capsomerewas observed despite independent in vivo trafficking of nanoparticles and capsomeres, as visualizedby fluorescence imaging. To the best of my knowledge, this work is the first to demonstrate theefficacy of sublingually-administered modular VLPs-based GAS vaccine and visualize their in vivotrafficking. These sublingually-administered modular VLPs induced high mucosal and systemicresponses, which was aided by the observed draining of VLPs into submandibular lymph nodes and in parallel with rapid absorption into systemic circulation. More importantly, the induced salivaryantibodies opsonized GAS in vitro. This work also reports the potential of a freeze-driedformulation of modular VLPs as a cold-chain free, cost-effective GAS vaccine especially for poorremote regions which are most affected by GAS diseases. The outcomes of this thesis foster thedevelopment of modular VLPs and capsomeres targeting GAS and influenza A, respectively, andhighlights the flexibility of MPyV VP1 based microbial vaccine platform to cater to the need forlow-cost, rapid response and safe and efficacious vaccines.