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Morphological and functional changes during cytomegalovirus replication in murine macrophages
I van Bruggen1, P Price, T A Robertson
1Department of Pathology, University of Western Australia, Nedlands.
Abstract:
Structural and functional changes were studied in murine peritoneal macrophages infected with murine cytomegalovirus by using centrifugal enhancement to achieve a high-level (greater than 90%) pulsed infection. During 3 d of culture the infected cells became enlarged and rounded with smooth surface contours. Transmission electron microscopy demonstrated various stages of viral maturation in the nucleus and cytoplasm. Intracellular organization was generally retained, apart from the development of large, irregular, intracytoplasmic vacuoles, in which enveloped virions and cell debris accumulated. The infected macrophages lost most surface markers tested (F4/80, Mac-1, FcR, and the receptor for gluteraldehyde-fixed sheep red blood cells), but H-2 expression was increased. Moreover, ingestion of colloidal gold or horseradish peroxidase was depressed, and the levels of acid phosphatase activity, lymphocytostatic activity, and interleukin 1 production were also decreased. The latter may explain the observed loss of accessory cell function.
Insights
Murine cytomegalovirus infection alters macrophages, causing cell enlargement and loss of surface markers. This impairs their immune functions, including reduced phagocytosis and interleukin-1 production.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Murine peritoneal macrophages play a crucial role in immune responses.
- Murine cytomegalovirus (MCMV) is a significant pathogen affecting macrophages.
Purpose of the Study:
- To investigate the structural and functional consequences of MCMV infection in murine peritoneal macrophages.
- To understand the impact of high-level MCMV infection on macrophage characteristics.
Main Methods:
- Centrifugal enhancement for high-level ( >90%) pulsed MCMV infection of macrophages.
- Transmission electron microscopy (TEM) for ultrastructural analysis.
- Flow cytometry and functional assays to assess surface markers, phagocytosis, and cytokine production.
Main Results:
- Infected macrophages enlarged, rounded, and developed intracytoplasmic vacuoles containing virions.
- Significant downregulation of surface markers (F4/80, Mac-1, FcR) and upregulation of H-2 expression.
- Depressed phagocytosis of colloidal gold and horseradish peroxidase.
- Decreased acid phosphatase activity, lymphocytostatic activity, and interleukin-1 (IL-1) production.
Conclusions:
- MCMV infection induces profound structural and functional alterations in macrophages.
- The observed decrease in IL-1 production may underlie the loss of macrophage accessory cell function.
- These changes highlight MCMV's capacity to subvert macrophage immune functions.