Summary
Infection by Streptococcus pneumoniae, which can result in development of pneumonia, meningitis, sepsis and bacteraemia, is a leading cause of ill-health and death in children, elderly and immunocompromised worldwide. The high prevalence of antimicrobial resistant pneumococci has prompted further emphasis on the importance of pneumococcal vaccines. There are over 95 serotypes, and current licenced vaccines, based on capsular components, only protect against 13. These vaccines are expensive to produce which limits the affordability and availability, especially in low and middle-income countries where the burden of the disease is the highest. In addition, there is potential for serotype replacement, which can hinder efforts to control colonisation and the disease.
To address these limitations, we propose a spray dried nanoparticle (NP) vaccine, which incorporates multiple pneumococcal protein antigens, to ensure coverage against multiple strains. The formulation will be administered through the mucosal route in order to induce mucosal immune responses. A mucosally administered pneumococcal vaccine which has complete coverage of serotypes, would not only provide a single vaccine which could be used all over the world, but also offers a needle-free means of administration to promote use. Additionally, the formulation of the vaccine will be prepared using readily available scale-up production methods, addressing a large hurdle in pre-clinical translation and further reducing costs. The dry powder form of the vaccine also addresses accessibility through and negation of cold chain requirements. The project seeks to produce and evaluate spray dried NPs, incorporating pneumococcal protein antigens, as a mucosal vaccine against all pneumococcal serotypes.
Project Outcomes
Our aim was to produce a dry-powder NPs vaccine formulation incorporating pneumococcal protein antigens for lung delivery. In order to induce optimal cellular and protective immunity, recombinant pneumococcal proteins will be used as the antigenic component of the vaccine. The pneumococcal proteins are found in virtually all pneumococcal strains, unlike, polysaccharides found in current pneumococcal vaccines, which are specific for 13-serotypes. We have successfully produced and purified multiple pneumococcal protein antigens, without the use of polyhistidine-tagging, and with the minimal number of purification steps, which both simplify and reduce the cost for large scale production. The proteins were produced with very high purity (> 94% after multimodal chromatography).
The protein antigens were successfully incorporated within nanoparticles (NPs) produced using an optimised microfluidic mixing method. The NPs were produced from combining two polymers (core and coating). Experiments were carried out to ensure the suitability of the mixing ratio, reproducibility of results, and reliability of the method for NPs formulations and antigen incorporation. The optimum NPs using combination polymers demonstrated in vitro compatibility and adjuvant immunogenicity with upregulation of cell surface markers CD40 and CD86 compared. Furthermore, the protein antigens were successfully incorporated achieving, size <400 nm, PDI <0.3 and positively charged. Moreover, the NPs and protein antigens were stable, and the protein integrity maintained following nebulisation as determined by SDS-PAGE and lactoferrin-binding western blot assays.
We have successfully produced a spray dried nanocomposite microcarrier system incorporating NPs-antigens with high yield and low moisture content and NPs characteristics following dispersion achieving similar physicochemical characteristics to NPs prior to spray drying. The spray dried formulation generated upregulation of cell surface markers which was higher than NPs alone. Furthermore, the protein stability and integrity were maintained following spray drying and nebulisation as indicated by SDS-PAGE and lactoferrin-binding western blot assays. The results were maintained following 3 weeks of storage as a dry powder at room temperature.