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?

This paper unravels how the immune responses of horses contribute to the pathogenesis of the equine herpesvirus-1 (EHV-1) and identifies any immune correlates that might predict a higher risk or provide protection from EHV-1 myeloencephalopathy (EHM), a rare but severe complication of EHV-1.

Study Objective

The main objective of this review article is to bring attention to how the horse’s immunity plays a role in EHM pathogenesis at various sites of EHV-1 infection. It aims to explore the varying features and interdependence of a horse’s immune response to EHV-1 throughout the infection.

Significance of EHV-1

• Equine herpesvirus-1 or EHV-1 is a common infection among horses causing serious health problems including respiratory disease, abortion in pregnant mares, and EHV-1 myeloencephalopathy, that affects the horse’s central nervous system.
• However, clinical EHM is comparatively rare, affecting only about 10% of horses infected with EHV-1.
• EHM is highly detrimental, thus having considerable economic implications due to loss of the horse’s productivity and high treatment costs.

Correlation of Immune System and EHM

• Although the incidence of EHM relates positively to the duration and magnitude of viremia (the presence of viruses in the blood), it is not the sole determinant of whether EHM occurs or not.
• A combination of certain factors, including host (horse) and viral factors, influence the development of EHM.
• Therefore, identifying these factors is crucial, not only for vaccine development but also for predicting which horses are at higher risk of developing EHM.

In conclusion, this review explores the complexities in the immune response to EHV-1 and its potential implications for managing the fraught consequences of this infection. The findings also suggest prospective areas of future research for vaccine development and protective measures in horses.