Clinical signs and humoral immune response in horses following equine herpesvirus type-1 infection and their susceptibility to equine herpesvirus type-4 challenge.

The research article focuses on studying the clinical signs and immune response in horses following an equine herpesvirus type 1 (EHV-1) infection and their susceptibility to a subsequent equine herpesvirus type 4 (EHV-4) infection.

Objective of Research

• The study primarily aimed to understand the immune response of horses to an EHV-1 infection, the presence of virus-specific antibodies, and how it relates to the progression of the disease. Then, it explored their susceptibility to a subsequent EHV-4 infection.

Methodology and Results

• Researchers administered the EHV-1 virus to three horses and observed clinical signs such as a two-phase fever, leucopenia (i.e., a decrease in the number of white blood cells), and viraemia (presence of viruses in the bloodstream), along with the virus being secreted from the horse’s nasopharynx.
• 18 days post the initial EHV-1 infection, the horses were exposed to EHV-1 again. This led to the presence of the virus in the nasopharynx of one horse.
• This group of horses, along with an additional group of three EHV-1 seropositive horses, were then exposed to EHV-4. This resulted in the secretion of the EHV-4 virus from the nasopharynx without any apparent disease or clinical signs.

Humoral Immune Response and Antibodies

• Following the original EHV-1 infection, the horses exhibited an IgM response, with these antibodies detected by day 5 and remaining high until day 18, the day of the second exposure to EHV-1, when levels decreased.
• In contrast, EHV-1-specific IgG antibodies peaked at day 18 and afterward maintained high levels.
• Moreover, by the 10th day of exposure, neutralizing antibodies and antibodies capable of triggering antibody-dependent cellular cytotoxicity, a response of the immune system, were present.

Implications of Findings

• The research provides valuable insights into the humoral immune response of horses to EHV-1 infection, which shows the potential to control the disease and its progression.
• Understanding the horses’ susceptibility to subsequent EHV-4 infection is crucial as it may contribute to creating effective preventive and mitigation strategies against multiple herpesvirus infections in horses.