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Experimental analysis of concurrent viral and bacterial infection in the mouse
1Department of Microbiology, School of Medicine, Tokai University, Kanagawa, Japan.
Abstract:
The roles of both microorganisms in combined murine cytomegalovirus (MCMV) and Klebsiella pneumoniae (KP) infection in the mouse, and host response to the infection were investigated. Increased mortality in mixed MCMV and KP infected mice was observed, and this was due to uncontrolled growth of bacteria in the peritoneal cavity, and severe generalized infection. Neutrophil response to growth of KP was defective in MCMV infected mice. While the initial clearance of KP from the blood was more efficient in MCMV-infected mice, it did not protect the mice against KP infection. In the in vitro experiments, the neutrophil chemotaxis of MCMV-infected mice to KP was found to be lowered. Tissue extract and serum of MCMV-infected mice exhibited chemotactic activity for neutrophils, and, at the same time contained some factor(s) which reduced chemotaxis of normal neutrophils to KP.
Insights
Murine cytomegalovirus (MCMV) infection impairs neutrophil response, leading to uncontrolled Klebsiella pneumoniae (KP) growth and increased mortality in mice. This highlights a critical immune deficiency during coinfection.
Area of Science:
- Immunology
- Microbiology
- Virology
Background:
- Coinfections with viruses and bacteria can significantly alter host immune responses.
- Murine cytomegalovirus (MCMV) is a common viral pathogen that can impact the immune system's ability to combat secondary bacterial infections.
Purpose of the Study:
- To investigate the combined effects of MCMV and Klebsiella pneumoniae (KP) infection on host mortality.
- To elucidate the host immune response, particularly neutrophil function, during MCMV and KP coinfection.
Main Methods:
- Mice were infected with MCMV, KP, or both.
- Mortality rates were recorded.
- Bacterial growth in the peritoneal cavity was assessed.
- Neutrophil chemotaxis was evaluated both in vivo and in vitro.
Main Results:
- Combined MCMV and KP infection led to increased mortality compared to single infections.
- Uncontrolled KP growth in the peritoneal cavity and severe generalized infection were observed in coinfected mice.
- Neutrophil response to KP was defective in MCMV-infected mice, with reduced chemotaxis.
- MCMV-infected mouse serum and tissue extracts contained factors that impaired normal neutrophil chemotaxis to KP.
Conclusions:
- MCMV infection compromises the host's ability to control KP infection.
- Defective neutrophil function, including reduced chemotaxis, is a key mechanism underlying increased susceptibility to bacterial coinfection.
- Further research into the factors inhibiting neutrophil function in MCMV-infected hosts is warranted.