One way protection between equid herpesvirus 1 and 4 in vivo.

The research investigates the immunity response of ponies to sequential infections of two types of equid herpesvirus (EHV-1 and EHV-4). It was found that while being infected twice with EHV-1 protected the ponies from EHV-4, the reverse was not true.

Experiment Methodology

• In this experiment, two groups of six sibling ponies each were exposed to sequential infections with Equid Herpesvirus 1 or Equid Herpesvirus 4 (EHV-1 or EHV-4) at four or five-month intervals.
• Their reactions, including virus shedding (release of virus particles potentially leading to infection of others) and pyrexia (fever), were monitored and compared across the two groups.

Findings

• The researchers found no significant reduction in virus shedding or pyrexia when the ponies that were twice exposed to EHV-4 were later exposed to EHV-1. This suggests that previous exposure to EHV-4 did not confer significant immunity to EHV-1.
• Contrarily, ponies that had two sequential infections with EHV-1 were found to be completely protected from EHV-4, indicating that exposure to EHV-1 conferred immunity to EHV-4.
• The researchers also monitored the generation of virus-neutralising antibody in each group. They found that it did not increase until 21 days after primary exposure, and its generation was specific to the subtype of herpesvirus to which the ponies were exposed.
• In addition to the virus-neutralising antibody, the complement-fixing antibody, another type of immune response, was observed to rise within seven days after inoculation with EHV-1, and 14 days after inoculation with EHV-4.
• Unlike the virus-neutralising antibody, the complement-fixing antibody resulting from EHV-1 exposure was effective against both EHV-1 and EHV-4, while that resulting from EHV-4 exposure was specific only to EHV-4.

Implication and Future Work

• The results of the research provide insights into how the equine body responds to sequential infections of different types of equine herpesviruses.
• Its findings can be used to better understand the immune responses in horses which may inform future development and improvement of herpesvirus vaccines for equids.