Related Experiment Video
Updated: May 15, 2026
In Vivo Imaging Systems (IVIS) Detection of a Neuro-Invasive Encephalitic Virus
Published on: December 2, 2012
Bioluminescent imaging and histopathologic characterization of WEEV neuroinvasion in outbred CD-1 mice
Aaron T Phillips1, Charles B Stauft, Tawfik A Aboellail
1Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, United States of America. aaron.phillips@colostate.edu
Abstract:
Western equine encephalitis virus (WEEV; Alphavirus) is a mosquito-borne virus that can cause severe encephalitis in humans and equids. Previous studies have shown that intranasal infection of outbred CD-1 mice with the WEEV McMillan (McM) strain result in high mortality within 4 days of infection. Here in vivo and ex vivo bioluminescence (BLM) imaging was applied on mice intranasally infected with a recombinant McM virus expressing firefly luciferase (FLUC) to track viral neuroinvasion by FLUC detection and determine any correlation between BLM and viral titer. Immunological markers of disease (MCP-1 and IP-10) were measured and compared to wild type virus infection. Histopathology was guided by corresponding BLM images, and showed that neuroinvasion occurred primarily through cranial nerves, mainly in the olfactory tract. Olfactory bulb neurons were initially infected with subsequent spread of the infection into different regions of the brain. WEEV distribution was confirmed by immunohistochemistry as having marked neuronal infection but very few infected glial cells. Axons displayed infection patterns consistent with viral dissemination along the neuronal axis. The trigeminal nerve served as an additional route of neuroinvasion showing significant FLUC expression within the brainstem. The recombinant virus WEEV.McM.FLUC had attenuated replication kinetics and induced a weaker immunological response than WEEV.McM but produced comparable pathologies. Immunohistochemistry staining for FLUC and WEEV antigen showed that transgene expression was present in all areas of the CNS where virus was observed. BLM provides a quantifiable measure of alphaviral neural disease progression and a method for evaluating antiviral strategies.
Insights
Western equine encephalitis virus (WEEV) causes severe encephalitis. Bioluminescence imaging tracked WEEV neuroinvasion via cranial nerves, revealing initial olfactory bulb infection and spread through the central nervous system.
Area of Science:
- Neuroscience
- Virology
- Immunology
Background:
- Western equine encephalitis virus (WEEV) is a mosquito-borne alphavirus causing severe encephalitis in humans and equids.
- Intranasal infection with WEEV McMillan (McM) strain leads to high mortality in CD-1 mice within 4 days.
Purpose of the Study:
- To track WEEV neuroinvasion using in vivo bioluminescence (BLM) imaging in mice infected with a recombinant WEEV expressing firefly luciferase (FLUC).
- To correlate BLM imaging with viral titer and assess immunological markers (MCP-1, IP-10) compared to wild-type WEEV.
- To elucidate WEEV dissemination routes and neuronal infection patterns within the central nervous system (CNS).
Main Methods:
- Intranasal infection of mice with WEEV.McM.FLUC, a recombinant virus expressing firefly luciferase.
- In vivo and ex vivo bioluminescence (BLM) imaging for tracking viral neuroinvasion.
- Measurement of immunological markers (MCP-1, IP-10) and viral titers.
- Histopathology and immunohistochemistry to confirm viral distribution and neuronal/glial cell infection.
Main Results:
- BLM imaging successfully tracked WEEV neuroinvasion, primarily through cranial nerves, notably the olfactory and trigeminal nerves.
- Initial infection targeted olfactory bulb neurons, spreading to other brain regions; axons showed patterns of dissemination along the neuronal axis.
- WEEV.McM.FLUC exhibited attenuated replication and a weaker immune response compared to wild-type WEEV, yet induced similar pathologies.
- Immunohistochemistry confirmed FLUC transgene expression mirrored WEEV antigen distribution throughout the CNS, with marked neuronal infection and minimal glial cell involvement.
Conclusions:
- BLM imaging is a valuable tool for quantifying alphaviral neuroinvasion and disease progression in vivo.
- Cranial nerves, particularly the olfactory and trigeminal nerves, serve as critical routes for WEEV entry into the CNS.
- Understanding WEEV neuroinvasion pathways is crucial for developing effective antiviral strategies and treatments for encephalitis.
