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Interaction of alveolar macrophages and respiratory syncytial virus
G Franke1, J Freihorst, C Steinmüller
1Fraunhofer Institute of Toxicology, Department of Immunology, Hannover, Germany.
Abstract:
Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract illness in infants. However, the mechanisms leading to resolution of RSV infections are poorly understood. Since alveolar macrophages play an important role in defending the respiratory tract against infectious agents we investigated the interactions of RSV with these cells. Murine alveolar macrophages were challenged in vitro with RSV at different multiplicities of infection. The percentage of macrophages expressing viral antigen was determined by staining with monoclonal anti-RSV antibodies and evaluation by fluorescence microscopy or FACS analysis. The ability of macrophages to support virus replication was measured by a plaque forming assay on HEp-2 cells. Cell lysates of macrophages contained only small amounts of viable RSV in comparison to disrupted HEp-2 cells. The amount of viable RSV as well as the percentage of macrophages expressing viral antigen decreased rapidly over time. Activated macrophages had a reduced virus load in comparison to resting macrophages. RSV infected macrophages released biologically active tumor necrosis factor (TNF) in a virus dose dependent manner. In contrast, a high virus inoculum resulted in reduced microbicidal activity and oxygen radical production. Our results suggest that RSV infection influences different functions of alveolar macrophages in various ways. Since TNF is thought to restrict viral replication in several cell types it may play a role in limiting virus replication.
Insights
Respiratory syncytial virus (RSV) infection impacts alveolar macrophages, key immune cells in the respiratory tract. While macrophages limit RSV replication, high viral loads impair their protective functions.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Respiratory syncytial virus (RSV) is a primary cause of infant respiratory illness.
- Mechanisms of RSV infection resolution remain unclear.
- Alveolar macrophages are crucial for respiratory tract defense.
Purpose of the Study:
- To investigate the interaction between RSV and murine alveolar macrophages.
- To understand how RSV influences macrophage functions.
Main Methods:
- In vitro challenge of murine alveolar macrophages with RSV.
- Quantification of viral antigen expression using microscopy and FACS.
- Assessment of virus replication via plaque assays.
- Measurement of tumor necrosis factor (TNF) release and microbicidal activity.
Main Results:
- Macrophages supported limited RSV replication compared to HEp-2 cells.
- Viral antigen expression and viable virus decreased over time in macrophages.
- Activated macrophages showed reduced RSV load compared to resting macrophages.
- RSV-infected macrophages released TNF in a dose-dependent manner.
- High RSV inoculum reduced macrophage microbicidal activity and oxygen radical production.
Conclusions:
- RSV infection differentially affects alveolar macrophage functions.
- TNF release by macrophages may play a role in limiting RSV replication.
- Understanding these interactions is key to resolving RSV infections.