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Updated: May 16, 2026
High-Resolution 3D Imaging of Rabies Virus Infection in Solvent-Cleared Brain Tissue
Published on: April 30, 2019
Infectivity of rabies virus-exposed macrophages
Florence Nazé1, Vanessa Suin, Sophie Lamoral
1National Reference Laboratory of Rabies, Viral Diseases, Communicable and Infectious Diseases, Scientific Institute of Public Health, Engeland St. 642, B-1180 Brussels, Belgium.
Abstract:
Rabies virus distributes widely in infected mice, including lymphoid tissues and spleen macrophages. The infection characteristics in murine macrophages and the infectivity of virus-exposed macrophages were examined upon inoculation in mice. In vitro, Mf4/4 spleen macrophages supported mild virus production (10(4)-fold less than neuroblastoma), with formation of typical virions. Bone marrow-derived macrophages (BMM) were most efficient to capture virus, but new virus production was not detected. Virus-induced cell death was significantly stronger in BMM, which might have eliminated BMM with productive infection. Still, viral RNA remained detectable in the remaining BMM for at least 4 weeks. Injection of in vitro-infected Mf4/4 in the nose or brain proved efficient to propagate infection in mice, even when cells were pre-incubated with neutralizing antibodies. Surprisingly, injection of ex-vivo-infected BMM in the brain also led to lethal infection in 8 out of 12 mice. Injection of infected Mf4/4 in the muscle mostly favoured a protective antibody response. Despite that macrophages are less fit to support virus production, they can still act as a source of infectious virus upon transfer in mice. This may be relevant for screening donor organs/cells, for which RT-PCR should be preferred over the traditional antigen or virus isolation assays.
Insights
Macrophages can harbor and transmit rabies virus, even when they produce little infectious virus. This highlights the importance of sensitive detection methods like RT-PCR for screening cells and organs to prevent rabies spread.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Rabies virus disseminates throughout infected hosts, targeting lymphoid tissues and macrophages.
- Understanding macrophage roles in rabies pathogenesis is crucial for disease control.
Purpose of the Study:
- To investigate rabies virus infection characteristics in murine macrophages.
- To assess the infectivity of virus-exposed macrophages upon inoculation in mice.
Main Methods:
- In vitro culture of Mf4/4 spleen macrophages and bone marrow-derived macrophages (BMM).
- Assessment of viral production and cell death in infected macrophages.
- Inoculation of infected macrophages into mice via nasal, brain, or muscle routes.
- Detection of viral RNA using RT-PCR and traditional antigen/virus isolation assays.
Main Results:
- Mf4/4 macrophages supported limited virus production, while BMM efficiently captured but did not produce detectable new virus.
- BMM exhibited higher virus-induced cell death, potentially eliminating productively infected cells.
- Viral RNA remained detectable in BMM for at least 4 weeks.
- Inoculation of infected Mf4/4 cells (nasal/brain) efficiently propagated rabies in mice, even after antibody incubation.
- Ex-vivo-infected BMM injected into the brain caused lethal infections in a majority of mice.
- Muscle inoculation of infected Mf4/4 cells primarily induced antibody responses.
Conclusions:
- Macrophages, despite limited viral replication, can serve as a source of infectious rabies virus upon transfer.
- RT-PCR is a more sensitive method than antigen or virus isolation for detecting rabies in potential donor organs/cells.
