Immunokinetics of equine herpesvirus 1 in donkey mares: suppression of secondary cell-mediated response.

This research investigates the immune response in donkey mares to equine herpesvirus 1 (EHV1), and finds that secondary cell-mediated immune responses are weaker than initial responses, which may explain why immunised mares still suffer from EHV1-related illnesses.

Research Context

• The study is focused on understanding the immunokinetics, or the immune response over a period of time, of equine herpesvirus 1 (EHV1) in donkey mares.
• EHV1 is a common virus in equine species that can result in respiratory disease, abortion, and neurological disorders.
• This virus is of significant concern in the equine industry, therefore understanding how to more effectively vaccinate against it is crucial.

Methods

• For the study, donkey mares were either immunised with a lab strain of EHV1 or with recommended doses of Pneumabort-K vaccine, which contains a formalin-inactivated strain of EHV1 with an oil adjuvant.
• A booster dose was provided after three months.
• To measure humoral immune response, or the component of the immune response involving antibodies and immune cells in bodily fluids, a virus neutralisation (VN) test was used.
• The cellular immune response, which involves T cells and is responsible for addressing pathogens within cells, was measured by a leucocyte migration inhibition test (LMIT).

Results

• The VN antibody titre, or amount of antibodies capable of neutralising the virus, reached levels of 1:64 or 1:128 after the first immunisation. There was a slight increase to 1:256 after the booster dose.
• Cellular response increased progressively after the initial immunisation, being maintained for up to three months.
• However, upon secondary or booster immunisation, the cell-mediated immune response was both short-lived and weaker compared to the initial response.

Conclusions and Implications

• This weaker secondary response could explain why mares that have been immunised can still suffer from EHV1-associated diseases, namely abortion.
• The lack of a sustained and robust secondary cell-mediated immune response might be contributing to the breakdown in anti-EHV1 immunity, thus limiting the effectiveness of the existing vaccination.
• This provides a new avenue for research into improving EHV1 vaccine strategies.