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Influenza viruses and staphylococci in vitro: some interactions with polymorphonuclear leucocytes and epithelial
Abstract:
Bacterial infection contributes substantially to the morbidity and mortality of human influenza. In vitro experiments were performed to test two hypotheses regarding a possible relationship between the virus and bacterial infection. Firstly, maintenance media from tissue and organ cultures infected with influenza virus were tested for the presence of staphylococcal growth-promoting factors; no evidence for these was found. Secondly, we looked for a virus effect on polymorphonuclear leucocyte function. We found that human leucocytes purified from venous blood and exposed to influenza virus responded normally to stimulation of hexose monophosphate shunt activity and chemiluminescence. However, their responses in tests of phagocytic function and of chemotaxis were inhibited. By various criteria this effect was specific to the virus and could be obtained even when only a few virus particles were present per leucocyte. We propose that this is a mechanism by which influenza virus could enhance susceptibility to bacterial infection in the lung.
Insights
Influenza virus impairs key functions of human white blood cells, specifically phagocytosis and chemotaxis. This viral effect may increase susceptibility to secondary bacterial infections in the lungs.
Area of Science:
- Immunology
- Virology
- Microbiology
Background:
- Bacterial infections significantly increase illness and death in human influenza patients.
- Understanding the interplay between influenza virus and bacteria is crucial for effective treatment.
Purpose of the Study:
- To investigate if influenza virus promotes bacterial growth or affects immune cell function.
- To determine the mechanism by which influenza virus might increase susceptibility to bacterial infections.
Main Methods:
- In vitro testing of influenza virus-infected cell culture media for bacterial growth factors.
- Assessing the impact of influenza virus exposure on human polymorphonuclear leucocyte (PMN) functions, including phagocytosis, chemotaxis, hexose monophosphate shunt activity, and chemiluminescence.
Main Results:
- No evidence of staphylococcal growth-promoting factors was found in influenza virus-infected media.
- Influenza virus exposure inhibited PMN phagocytic function and chemotaxis.
- Viral effects on PMN function were specific and detectable even at low virus concentrations.
Conclusions:
- Influenza virus does not promote bacterial growth directly.
- Influenza virus impairs critical human white blood cell functions, suggesting a mechanism for increased bacterial infection risk in the lungs.