To assess the retention time and biodistribution of nano-particle based vaccines (OMV), an in vivo bioluminescence model was established. For this purpose, pneumococcal model antigens were produced as recombinant nanoluciferase fusion proteins and purified via affinity chromatography. These luciferase fusion antigens were displayed to OMVs via click chemistry. Once intranasally administered, retention and biodistribution of vaccine particles were assessed by intranasal administration of furimazine (nLuc substrate) and bioluminescence was measured by IVIS. The data indicated the retention of vaccine particles in murine nasal cavity upto 48hrs. In addtition, we also observed luminescence in the throat region indicating the inhalation of vaccine particles towards lower respiratory tract.
Another goal of the project was to analyze the changes in the immune repertoire of different host niches post vaccination i.e. how do different host tissues respond to intranasal vaccination of particles-based vaccines. For this purpose, a mulit-dimensional spectral flow cytometry panel was developed. Spectral flow cytometry in combination with un-supervised analysis lead to novel insights about primary response of airways and lymphoid tissues to particle-based vaccination. The data indicated that particle-based vaccination caused influx of myeloid cells i.e. neutrophils, inflammatory monocytes and myeloid derived suppressor cells at the site of administration i.e. nasal cavity. The changes in immune repertoire varied between upper (nasal cavity) and lower (lugs) airways in respinse to vaccination. The inflammation was observed as early as 6hrs post vaccination, peaked at 24hrs and further declined till 72hrs post vaccination. Particle based vaccines not only led to the influx of myeloid derived cells but also led to the expansion and activation of T cells in murine nose.
Ly6Ghi neutrophils and MDSCs were the predominant cells involved in the uptake of vaccine particles in nasal cavity while in lungs, alveolar macrophages and plasmacytoid dendritic cells were the early responders towards vaccine particles. OMVs also induced the upregulation of costimulatory molecules in several cells of the myeloid compartment in the airways.
The results of the poject provided important insights about the mechanism of protection by particle-based vaccines and would serve as a blue print to further understand the interaction of immune cells with vaccine particles during different stages of infection and vaccination. This project would then lead to further studies on exploring the immune activation at different levels of vaccination e.g. post boost and post bacterial challenge with and without vaccination.
The approach of this project has been conveyed to a general audience via host institution's open day in 2022. In addition, researcher will also be presenting her work in an international conference (Europneumo 2025) in the coming months. A manuscript, showcasing the multimodal approach employed in this project to dissect the mechanism of protection by particle based vaccine, is also in preparation and expected to be submitted to a high quality journal.
