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Characterization of caprine microglial cells and in vitro infection with caprine arthritis-encephalitis lentivirus
T V Baszler1, W G Harwood, K L Lester
1Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman.
Background:
Similar to human immunodeficiency virus-1 and simian immunodeficiency virus-1, microglial cells in brain tissue are a major cell target for infection with caprine arthritis-encephalitis lentivirus (CAEV) in vivo. These observations have raised interest in the role of microglial cells in the development of lentivirus-induced neurologic lesions. To initiate in vitro studies into the pathogenesis of encephalomyelitis caused by CAEV, we characterized primary cultures of caprine microglia, determined their susceptibility to virus infection, and examined the effect of virus infection on class I and class II major histocompatibility complex antigen expression.
Experimental Design:
Microglia were examined as adherent cells in purified cultures and as nonadherent cells in mixed glial cell cultures, which also contained astrocytes and oligodendroglia. The cultured cells were investigated with regard to their phenotype, class I and II major histocompatibility complex antigen expression, and susceptibility to infection with CAEV using light and electron microscopy, enzyme and lectin cytochemistry, immunocytochemistry, flow cytometry, and kinetic analysis of virus replication.
Results:
The cultured microglia had a typical macrophage morphology, were actively phagocytic, and expressed macrophage-like markers including non-specific esterase, complement receptor CR3, and Ricinis communis agglutinin-1. Microglia were highly permissive to CAEV infection in vitro as indicated by induction of syncytial cells, formation of lentivirus particles, expression of viral antigens, and release of high titered infectious virus into culture supernatants. CAEV selectively infected microglia in mixed glial cultures but replicated less efficiently than in purified microglial cultures; productive infection of astrocytes or oligodendrocytes was not detected. There was constitutive expression of class I and class II major histocompatibility complex antigens on microglia in purified and mixed cultures that was not altered significantly by CAEV infection alone.
Conclusions:
These observations demonstrated that cultured caprine microglial cells had a macrophage-like phenotype and were highly permissive to productive CAEV infection in vitro. This primary brain culture system is a valuable tool to study lentivirus-microglial interactions in the central nervous system.
Insights
Caprine arthritis-encephalitis lentivirus (CAEV) readily infects caprine microglia in vitro, confirming their role in lentivirus-induced neurological disease. This brain cell culture model aids in studying lentivirus-microglial interactions.
Area of Science:
- Neuroscience
- Virology
- Immunology
Background:
- Microglial cells are a primary target for caprine arthritis-encephalitis lentivirus (CAEV) infection in vivo, similar to HIV-1 and SIV-1.
- This raises interest in microglial cells' role in lentivirus-induced neurological lesions.
- In vitro studies are initiated to understand CAEV encephalomyelitis pathogenesis.
Purpose of the Study:
- Characterize primary caprine microglial cultures.
- Determine their susceptibility to CAEV infection.
- Examine CAEV infection's effect on MHC antigen expression.
Main Methods:
- Cultured microglia (purified and mixed glial cultures) were analyzed for phenotype, MHC antigen expression, and CAEV susceptibility.
- Techniques included microscopy, cytochemistry, immunocytochemistry, flow cytometry, and viral replication kinetics.
Main Results:
- Cultured microglia exhibited macrophage-like morphology and markers, and were highly phagocytic.
- Microglia were highly permissive to CAEV infection in vitro, showing syncytia, viral particles, antigens, and infectious virus release.
- CAEV selectively infected microglia in mixed cultures; astrocytes and oligodendrocytes were not productively infected.
- Class I and II MHC antigen expression on microglia was constitutive and not significantly altered by CAEV infection.
Conclusions:
- Cultured caprine microglia display a macrophage-like phenotype and are highly susceptible to productive CAEV infection in vitro.
- This primary brain cell culture system is valuable for studying lentivirus-microglial interactions in the CNS.