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A Three-Tiered Study of Differences in Murine Intrahost Immune Response to Multiple Pneumococcal Strains
Ericka Mochan-Keef1, David Swigon2, G Bard Ermentrout2
1Joint Carnegie Mellon University-University of Pittsburgh PhD Program in Computational Biology, Pittsburgh, PA, United States of America.
Abstract:
We apply a previously developed 4-variable ordinary differential equation model of in-host immune response to pneumococcal pneumonia to study the variability of the immune response of MF1 mice and to explore bacteria-driven differences in disease progression and outcome. In particular, we study the immune response to D39 strain of bacteria missing portions of the pneumolysin protein controlling either the hemolytic activity or complement-activating activity, the response to D39 bacteria deficient in either neuraminidase A or B, and the differences in the response to D39 (serotype 2), 0100993 (serotype 3), and TIGR4 (serotype 4) bacteria. The model accurately reproduces infection kinetics in all cases and provides information about which mechanisms in the immune response have the greatest effect in each case. Results suggest that differences in the ability of bacteria to defeat immune response are primarily due to the ability of the bacteria to elude nonspecific clearance in the lung tissue as well as the ability to create damage to the lung epithelium.
Insights
This study models the immune response to pneumococcal pneumonia in mice, revealing bacterial evasion of lung clearance and epithelial damage drive disease severity. Understanding these mechanisms is key to combating pneumococcal infections.
Area of Science:
- Immunology
- Microbiology
- Mathematical Biology
Background:
- Pneumococcal pneumonia presents significant public health challenges, with variability in host immune response and bacterial virulence factors influencing disease outcomes.
- Understanding the complex interplay between the host immune system and Streptococcus pneumoniae is crucial for developing effective therapeutic strategies.
Purpose of the Study:
- To investigate the variability of the immune response to pneumococcal pneumonia in MF1 mice using a mathematical model.
- To explore how specific bacterial virulence factors, including pneumolysin, neuraminidase, and different serotypes, impact disease progression and outcome.
- To identify key immune mechanisms contributing to the host's defense against pneumococcal infection.
Main Methods:
- Application of a pre-existing 4-variable ordinary differential equation model simulating in-host immune response to pneumococcal pneumonia.
- Analysis of immune responses to Streptococcus pneumoniae strains with modified virulence factors (pneumolysin, neuraminidase) and different serotypes (D39, 0100993, TIGR4).
- Validation of the model's accuracy in reproducing experimental infection kinetics.
Main Results:
- The mathematical model accurately recapitulated infection dynamics across all tested bacterial strains and conditions.
- Identified that bacterial strategies to evade non-specific lung clearance and damage lung epithelium are primary drivers of immune system defeat.
- Quantified the relative importance of different immune response mechanisms in combating specific bacterial challenges.
Conclusions:
- Bacterial virulence, particularly the ability to evade innate immune defenses and damage host tissues, significantly dictates pneumococcal pneumonia severity.
- Mathematical modeling provides valuable insights into the complex host-pathogen dynamics of pneumococcal pneumonia.
- Targeting bacterial evasion mechanisms and mitigating lung epithelial damage may represent promising therapeutic avenues.
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