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Updated: Oct 18, 2026
Following in Real Time the Impact of Pneumococcal Virulence Factors in an Acute Mouse Pneumonia Model Using Bioluminescent Bacteria
Published on: February 23, 2014
Host cellular immune response to pneumococcal lung infection in mice
A Kadioglu1, N A Gingles, K Grattan
1Department of Microbiology & Immunology, University of Leicester, Leicester, United Kingdom.
Abstract:
Although there is substantial evidence that pneumolysin is an important virulence factor in pneumococcal pneumonia, relatively little is known about how it influences cellular infiltration into the lungs. We investigated how the inability of mutant pneumococci to produce pneumolysin altered the pattern of inflammation and cellular infiltration into the lungs. The effect on bacterial growth in the lungs also was assessed. There were three phases of growth of wild-type bacteria in the lungs: a decline followed by a rapid increase and then stasis or decline. The absence of pneumolysin was associated with a more rapid early decline and then a much slower increase in numbers. The pattern of inflammatory-cell accumulation also had distinct stages, and the timing of these stages was influenced by the presence of pneumolysin. Neutrophils began to accumulate about 12 to 16 h after infection with wild-type pneumococci. This accumulation occurred after the early decline in pneumococcal numbers but coincided with the period of rapid growth. Following infection with pneumococci unable to make pneumolysin, neutrophil influx was slower and less intense. Coincident with the third stage of pneumococcal growth was an accumulation of T and B lymphocytes at the sites of inflammation, but the accumulation was not associated with an increase in the total number of lymphocytes in the lungs. Lymphocyte accumulation in the absence of pneumolysin occurred but was delayed.
Insights
Pneumolysin, a key factor in pneumococcal pneumonia, significantly impacts lung inflammation and immune cell infiltration. Its absence alters bacterial growth and delays neutrophil and lymphocyte accumulation in the lungs.
Area of Science:
- Microbiology
- Immunology
- Pathology
Background:
- Pneumolysin is a critical virulence factor in Streptococcus pneumoniae infections.
- Its precise role in modulating host inflammatory responses and cellular infiltration in the lungs remains incompletely understood.
Purpose of the Study:
- To investigate the influence of pneumolysin production by Streptococcus pneumoniae on lung inflammation and cellular infiltration patterns.
- To assess the impact of pneumolysin deficiency on bacterial growth dynamics within the lungs.
Main Methods:
- Comparative analysis of lung inflammation and cellular infiltration in mice infected with wild-type and pneumolysin-deficient pneumococci.
- Monitoring of bacterial growth kinetics and inflammatory cell accumulation over time post-infection.
Main Results:
- Absence of pneumolysin led to a more rapid initial decline in bacterial numbers followed by slower growth.
- Neutrophil infiltration into the lungs was delayed and less intense in infections with pneumolysin-deficient strains.
- Lymphocyte accumulation occurred but was delayed in the absence of pneumolysin, without altering total lung lymphocyte counts.
Conclusions:
- Pneumolysin significantly influences the timing and intensity of inflammatory cell recruitment, particularly neutrophils, during pneumococcal pneumonia.
- The virulence factor plays a role in bacterial growth kinetics within the lung environment.
- Understanding pneumolysin's immunomodulatory effects is crucial for developing targeted therapies against pneumococcal infections.
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