Phenotypic characterisation of cell populations in the brains of horses experimentally infected with West Nile virus.
Authors: Delcambre G H, Liu J, Streit W J, Shaw G P J, Vallario K, Herrington J, Wenzlow N, Barr K L, Long M T
Journal: Equine veterinary journal
Summary
# West Nile Virus and the Equine Neuroimmune Response West Nile virus remains one of the most significant causes of viral encephalitis in horses globally, yet detailed understanding of how the equine brain mounts an immune defence during infection remains incomplete. Delcambre and colleagues examined archived brain tissue from experimentally infected horses, using immunohistochemical markers to quantify immune cell populations in the thalamus and hindbrain and compare them against uninfected controls. WNV-infected horses demonstrated significantly elevated microglia (Iba-1+), T lymphocytes (CD3+), and macrophage (MAC387+) staining, with the T cell response comprising both CD4+ and CD8+ populations; astrocytes showed limited activation, whilst B cells and macrophages remained relatively sparse. These findings suggest that early neurological disease in WNV infection involves predominantly a cellular rather than humoral immune response, with mixed T cell recruitment being a hallmark feature. For practitioners managing potentially affected horses, this cellular profile may help inform understanding of disease progression and inflammatory dynamics, though the study's single timepoint collection and reliance on experimental rather than naturally infected animals mean that further investigation across multiple infection stages and clinical cases would strengthen applicability to field practice.
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Practical Takeaways
- •WNV neuroinvasion triggers a predominantly T cell-mediated immune response in the CNS, which may inform understanding of clinical neurologic signs and disease progression
- •The early immune phenotype is dominated by microglia and T lymphocytes rather than antibody-producing B cells, suggesting cell-mediated immunity is critical in early WNV neuropathology
- •Single time-point sampling limits clinical application; naturally infected horses show high variability in sampling timing and tissue quality, making field diagnosis and prognosis challenging
Key Findings
- •WNV-challenged horses showed significantly increased Iba-1+ microglia, CD3+ T lymphocytes, and MAC387+ macrophage staining compared to controls
- •T cell response in WNV-infected horses was mixed, comprising both CD4+ and CD8+ T lymphocyte populations
- •Astrocyte response was limited in WNV-challenged horses, while B cells and MAC387+ macrophages were least abundant immune cell populations
- •Mixed T cell recruitment occurs at the onset of neurologic disease in experimentally infected horses