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Updated: Aug 30, 2026
A Non-invasive and Technically Non-intensive Method for Induction and Phenotyping of Experimental Bacterial Pneumonia in Mice
Published on: September 28, 2016
Cytokine mRNA expression in pneumococcal carriage, pneumonia, and sepsis in young mice
Eduard Ling1, Galia Feldman, Ron Dagan
1Department of Microbiology and Immunology and Pediatric Infectious Disease Unit, Soroka Medical Center, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva, Israel.
Abstract:
We studied cytokine mRNA expression in Streptococcus pneumoniae carriage, pneumonia, and sepsis in 3-week-old, inbred C57BL/6 and BALB/c mice. Mice were inoculated intranasally with S. pneumoniae serotype 6B, 14, or 3. Survival, bacterial load in the nasopharynx (NP) and lungs, and mRNA levels of tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta, interleukin (IL)-10, and IL-12 in the spleen were analyzed. No baseline mRNA expression levels were found, except for TNF-alpha in C57BL/6 mice. Serotype 6B caused NP colonization only, a significant (P<.05) increase in the levels of TNF-alpha, and induction of TGF-beta and IL-12 mRNA. Serotype 14 caused NP and nonlethal lung colonization and induction of TGF-beta, IL-10, and IL-12. Serotype 3 caused NP colonization, pneumonia, 35% mortality, and no alteration in the mRNA expression of tested cytokines. Although activation of the immune system culminated in nonlethal disease, evasion of the immune system was associated with detrimental disease.
Insights
Different Streptococcus pneumoniae serotypes impact mouse immune responses and disease severity. While some serotypes trigger cytokine production leading to mild illness, others evade immune detection, causing severe pneumonia and mortality.
Area of Science:
- Immunology
- Microbiology
- Infectious Diseases
Background:
- Streptococcus pneumoniae causes significant respiratory infections globally.
- Understanding the immune response to different serotypes is crucial for developing effective treatments.
- Cytokine profiles vary depending on the infecting S. pneumoniae serotype.
Purpose of the Study:
- To investigate the impact of S. pneumoniae serotypes 6B, 14, and 3 on cytokine mRNA expression in mice.
- To correlate cytokine mRNA levels with disease outcomes such as carriage, pneumonia, and sepsis.
- To compare the immune response in C57BL/6 and BALB/c mouse strains.
Main Methods:
- Inoculation of 3-week-old C57BL/6 and BALB/c mice with S. pneumoniae serotypes via intranasal route.
- Analysis of survival rates, bacterial load in nasopharynx and lungs.
- Quantification of mRNA levels for TNF-alpha, TGF-beta, IL-10, and IL-12 in spleen tissue.
Main Results:
- Serotype 6B induced TNF-alpha, TGF-beta, and IL-12 mRNA with nasopharyngeal colonization only.
- Serotype 14 led to nasopharyngeal and nonlethal lung colonization, inducing TGF-beta, IL-10, and IL-12 mRNA.
- Serotype 3 caused pneumonia and mortality without altering tested cytokine mRNA levels.
Conclusions:
- Immune system activation correlated with nonlethal disease, while immune evasion was linked to severe outcomes.
- S. pneumoniae serotype dictates the host immune response and subsequent disease pathogenesis.
- Cytokine mRNA expression patterns provide insights into the varying virulence of S. pneumoniae serotypes.
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