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Updated: Mar 11, 2026
Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae
Published on: January 17, 2014
Systemic immunization with rPotD reduces Streptococcus pneumoniae nasopharyngeal colonization in mice
T R Converso1, C Goulart2, D Rodriguez2
1Centro de Biotecnologia, Instituto Butantan, São Paulo, Brazil; Programa de Pós Graduação Interunidades em Biotecnologia USP-IPT-IB, São Paulo, Brazil.
Abstract:
Streptococcus pneumoniae (pneumococcus) is a human pathogen that can cause otitis media, pneumonia and, in severe cases, meningitis and bacteremia. The pneumococcus expresses PotD, a protein belonging to the polyamines transporter complex called PotABCD. PotD is a membrane-associated protein that binds polyamines and has been shown to be important for virulence. In this work we demonstrate that subcutaneous immunization with rPotD reduces the bacterial load in the nasal tissue of mice, following intranasal challenge with a type 6B pneumococcus. The protective effect correlated with the induction of high levels of antibodies in the immunized group; the antibodies were able to increase bacterial phagocytosis by mouse peritoneal cells. The cellular immune response was characterized by the production of gamma-interferon, IL-2 and IL-17 by splenocytes and nitric oxide by peritoneal cells of immunized mice, upon stimulation with rPotD. Taken together our results suggest that PotD is a promising candidate to be included in a protein based pneumococcal vaccine, able to induce phagocytic antibodies, a Th1 cellular immune response and production of IL-17, reducing nasopharyngeal colonization, the main event responsible for transmission of pneumococci in humans.
Insights
Subcutaneous immunization with the pneumococcal protein PotD reduced bacterial load in mice. This protection was linked to antibody-induced phagocytosis and cellular immune responses, suggesting PotD as a vaccine candidate.
Area of Science:
- Immunology
- Microbiology
- Vaccinology
Background:
- Streptococcus pneumoniae (pneumococcus) causes severe infections like meningitis and pneumonia.
- The pneumococcal protein PotD is part of the PotABCD polyamine transporter complex and is crucial for virulence.
- Developing new protein-based vaccines against pneumococcal colonization is a public health priority.
Purpose of the Study:
- To evaluate the efficacy of subcutaneous immunization with recombinant PotD (rPotD) in a mouse model of pneumococcal colonization.
- To investigate the antibody and cellular immune responses induced by rPotD immunization.
- To assess the potential of PotD as a component of a novel pneumococcal vaccine.
Main Methods:
- Mice were subcutaneously immunized with rPotD.
- Immunized mice were intranasally challenged with type 6B pneumococcus.
- Bacterial load in nasal tissue was quantified.
- Antibody levels, bacterial phagocytosis by peritoneal cells, and cellular immune responses (gamma-interferon, IL-2, IL-17, nitric oxide) were measured.
Main Results:
- Subcutaneous immunization with rPotD significantly reduced pneumococcal bacterial load in mouse nasal tissue.
- rPotD immunization induced high levels of antibodies that enhanced bacterial phagocytosis by peritoneal cells.
- Cellular immune responses included gamma-interferon, IL-2, and IL-17 production by splenocytes and nitric oxide production by peritoneal cells.
Conclusions:
- PotD is a promising candidate for a protein-based pneumococcal vaccine.
- rPotD vaccination induces protective immunity characterized by phagocytic antibodies and a Th1/IL-17 cellular response.
- PotD-based vaccination may reduce nasopharyngeal colonization, a key event in pneumococcal transmission.
