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Updated: Jun 22, 2026
Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae
Published on: January 17, 2014
Comparison of the pulmonary response against lethal and non-lethal intranasal challenges with two different
Daniela M Ferreira1, Adriana T Moreno, Aurora M Cianciarullo
1Centro de Biotecnologia, Instituto Butantan, São Paulo, SP, Brazil.
Abstract:
The differences between the immune response elicited during a self-limiting and a life-threatening lung infection with Streptococcus pneumoniae was analyzed in a mouse model of intranasal challenge using two different pneumococcal strains. M10, a serotype 11A strain, induced an early response within the first 12h after the challenge, which was characterized by the early local secretion of TNF-alpha and IL-6, followed by a sharp and rapid neutrophil influx. Bacterial loads in the lungs already started to fall at 12h after the challenge and no pneumococci could be recovered after 36h, at the time point when the animals started to show improvement in disease symptoms. ATCC6303, a serotype 3 strain, on the other hand, showed only a late increase in local TNF-alpha and IL-6 levels, when bacterial growth already seems to be out of control. Although cell influx was also observed, neutrophil rise was not as marked as with M10 (type 11A). Pneumococcal loads increased constantly and bacteria started to be recovered from the blood at 30h after the challenge. After this time point, animals showed worsening of symptoms and became lethargic. The resolution of the acute infection could be thus correlated with the early induction of proinflammatory cytokines, which could be due to the presence of a thinner polysaccharide capsule in M10 (type 11A), rendering bacterial components capable of activating the innate immune response more accessible.
Insights
The study reveals that an early immune response, marked by tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) secretion, predicts self-limiting Streptococcus pneumoniae lung infections. Delayed responses correlate with severe, life-threatening outcomes.
Area of Science:
- Immunology
- Microbiology
- Infectious Diseases
Background:
- Streptococcus pneumoniae causes a spectrum of lung infections, from self-limiting to life-threatening.
- Understanding the immune response differences is crucial for developing effective treatments.
Purpose of the Study:
- To analyze the distinct immune responses to self-limiting versus life-threatening Streptococcus pneumoniae lung infections.
- To identify key immune mediators and bacterial factors influencing infection severity.
Main Methods:
- A mouse model of intranasal Streptococcus pneumoniae challenge using two distinct strains (serotype 11A M10 and serotype 3 ATCC6303).
- Monitoring of local cytokine (TNF-alpha, IL-6) levels, neutrophil influx, and bacterial loads in the lungs and blood.
- Correlation of immune response kinetics with disease progression and outcome.
Main Results:
- Serotype 11A strain (M10) induced early TNF-alpha and IL-6, rapid neutrophil influx, and bacterial clearance within 36 hours, leading to self-limiting infection.
- Serotype 3 strain (ATCC6303) showed delayed cytokine increase, less pronounced neutrophil response, uncontrolled bacterial growth, and systemic spread, resulting in severe disease.
- Early pro-inflammatory cytokine induction was linked to a thinner polysaccharide capsule in the M10 strain, enhancing innate immune activation.
Conclusions:
- Early induction of pro-inflammatory cytokines (TNF-alpha, IL-6) is critical for resolving Streptococcus pneumoniae lung infections.
- Bacterial capsule properties significantly influence the host's innate immune response and infection outcome.
- Distinct pneumococcal strains elicit divergent immune responses, dictating infection severity.
