Evaluation of extracellular vesicles as vaccine against Streptococcus pneumoniae: role of virulence factors and two-component systems

• Grant number: 24/18870-6
• Support Opportunities: Regular Research Grants
• Start date: April 01, 2025
• End date: March 31, 2028
• Field of knowledge: Biological Sciences - Microbiology - Applied Microbiology
• Principal Investigator: Eliane Namie Miyaji
• Grantee: Eliane Namie Miyaji
• Host Institution: Instituto Butantan. Secretaria da Saúde (São Paulo - Estado). São Paulo , SP, Brazil
• Associated researchers: Leo Kei Iwai ; Maria Leonor Sarno de Oliveira ; Natalia Luisa Hiller

Abstract

Streptococcus pneumoniae causes several diseases, such as otitis media, sinusitis, pneumonia, sepsis and meningitis. Polysaccharide conjugate vaccines led to a significant reduction in invasive pneumococcal disease caused by serotypes included in the vaccine formulations, but serotype replacement by non-vaccine serotypes was observed. Moreover, after a period with reduction of pneumococcal disease during non-pharmacological interventions during the COVID-19 pandemic, several countries are now reporting increased number of cases of pneumococcal disease when compared with pre-pandemic levels. New formulations are thus necessary for controlling diseases caused by pneumococci. This project aims at evaluating pneumococcal extracellular vesicles (pEVs) as a vaccine formulation for the induction of serotype-independent protection. Protocols for production and characterization of pEVs are currently being established in our laboratory. pEVs will be produced using the non-encapsulated strain Rx1 and characterized for protein concentration, size, particle concentration, charge and polydispersivity index. pEVs will also be characterized using scanning electron microscopy and proteomic analysis will be performed by mass spectrometry. pEVs will be isolated from the Rx1 wild-type strain and from knockouts for PspA (Pneumococcal surface protein A), PspC (Pneumococcal surface protein C) and Ply (Pneumolysin). These are important virulence factors that have been described as vaccine candidates. The role of these antigens in the protection induced by parenteral and nasal immunization with pEVs will be evaluated using lethal and nasopharyngeal colonization models in mice. pEVs produced by Rx1 strains expressing different PspA and PspC variants will also be isolated. Since those are variable antigens, a formulation containing different pEVs with variants of these antigens can potentially induce broader vaccine coverage against different pneumococcal isolates. Moreover, knockouts for histidine kinase (HK) from 3 pneumococcal two-component systems (TCS) will be obtained, with potential impact in the production of pEVs. Data obtained in this project can bring important information for the development of a low-cost vaccine with broad-coverage against infections caused by S. pneumoniae. (AU)