DRY POWDER INHALATION OF PNEUMOCOCCAL VACCINE USING POLYMERIC NANOPARTICLES AS CARRIERS

Abstract

Streptococcus pneumoniae is the leading bacterial cause of pneumococcal diseases, of which pneumonia is the main cause of death amongst the immunocompromised, elderly over the age of 50 and children under the age of 5. Although vaccines such as pneumococcal polysaccharide vaccine 23, pneumococcal conjugate vaccine 7, 10 and 13 are available, they are expensive to produce and distribute. Moreover, the variation in serotype distribution across geographical locations and rise in dominance of disease due to non-vaccine serotype coverage has led to significant attention towards the development of alternate vaccine candidates such as pneumococcal surface protein A (PspA). A potential dry powder vaccine formulation containing polymeric nanoparticles (NPs) adsorbed with PspA4Pro and formulated into nanocomposite microparticles (NCMPs) using L-leucine (L-leu) to be delivered via inhalation was developed. Poly(glycerol adipate-co-ω-pentadecalactone), PGA-co-PDL, NPs with either anionic or cationic surface charge of optimum size (~200-250 nm) to be effectively taken up by the lung dendritic cells (DCs) were successfully produced. The NPs were then surface adsorbed with PspA4Pro (~20 µg of PspA4Pro per mg of NPs) and spray-dried using L-leu as a microcarrier to produce NCMPs with a product yield of 55.55±6.64% for the PspA4Pro adsorbed anionic NPs/NCMPs and 53.98±2.23% for the PspA4Pro adsorbed cationic NPs/NCMPs. The NCMPs produced had a corrugated and wrinkled surface morphology. The aerosol properties of anionic NPs/NCMPs determined using a Next Generation Impactor displayed a fine particle fraction (FPF) of 74.31±1.32% and mass median aerodynamic diameter (MMAD) of 1.70±0.03 μm indicating that the majority of the dose would be deposited in the respirable airways of the lungs. The anionic and cationic PGA-co-PDL NPs upon incubation with DCs for 1 h showed an effective uptake as visualised using confocal microscopy. Furthermore, the anionic NPs/NCMPs were well tolerated by the A549 cell line with a cell viability of 87.01±14.11% at 1.25 mg/ml concentration, whereas the cationic NPs/NCMPs showed a cell viability of 75.76±03.55% at 156.25 µg/ml concentration upon 24 h exposure. The PspA4Pro released from the optimised formulations largely maintained its structure as determined using SDS-PAGE and circular dichroism, and the relative antigenicity measured using ELISA was 0.97±0.20 and 0.85±0.05 for anionic and cationic formulations, respectively. Overall, the results obtained indicate the use of these NPs as novel carriers for pulmonary vaccine delivery against pneumococcal diseases.