Contribution of the immune response to the pathogenesis of equine herpesvirus-1 (EHV-1): Are there immune correlates that predict increased risk or protection from EHV-1 myeloencephalopathy?
Authors: Hussey Gisela Soboll, Giessler Kim S
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: EHV-1 Myeloencephalopathy and Immune Predictors Although equine herpesvirus-1 (EHV-1) infection is common, the severe neurological form—EHV-1 myeloencephalopathy (EHM)—develops in only approximately 10% of affected horses, suggesting that host and viral factors determine clinical outcome. Soboll Hussey and Giessler's 2022 review synthesises current evidence on how immune responses at different sites of infection (viraemia, respiratory tract, nervous system) contribute to EHM pathogenesis, examining both protective and pathogenic immune mechanisms across the infection timeline. The authors identify that whilst prolonged and high-titre viraemia correlates with EHM risk, the interplay between innate immunity, adaptive responses, and viral evasion strategies determines whether infection remains subclinical or progresses to neurological disease. Understanding these immune correlates—including the role of interferon responses, cellular immunity, and tissue-specific inflammation—could enable practitioners to identify at-risk horses and inform vaccine development strategies that enhance protective immunity without exacerbating damaging inflammatory responses. For farriers, veterinarians, and other equine professionals, this review underscores that EHM risk is multifactorial, highlighting the importance of infection management protocols and the potential future application of biomarkers to predict which horses require intensive monitoring during outbreak situations.
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Practical Takeaways
- •Not all horses infected with EHV-1 develop the devastating neurological form of disease; understanding individual immune factors may help identify at-risk horses for targeted management or prophylactic strategies
- •Vaccine development and risk prediction models should focus on characterizing protective versus pathogenic immune responses at multiple infection sites and timepoints rather than systemic viremia alone
- •Practitioners should recognize that EHV-1 myeloencephalopathy results from complex host-pathogen interactions beyond viral load, supporting individualized clinical assessment of infected horses
Key Findings
- •Clinical EHM occurs in approximately 10% of EHV-1 infected horses despite positive correlation between viremia duration/magnitude and EHM incidence
- •Both host and viral factors determine whether EHM develops in infected horses
- •Host immune response contributions to EHM pathogenesis vary across different sites of EHV-1 infection and throughout the infection timeline
- •Identification of immune correlates predicting increased risk or protection from EHM remains a topic of significant research interest for vaccine development