The mucosal humoral immune response of the horse to infective challenge and vaccination with equine herpesvirus-1 antigens.
Authors: Breathnach C C, Yeargan M R, Sheoran A S, Allen G P
Journal: Equine veterinary journal
Summary
# Editorial Summary: Mucosal Immunity and EHV-1 Protection Equine herpesvirus-1 remains a significant respiratory and reproductive pathogen, yet the local antibody defences mounted in the upper airways following infection or vaccination have been poorly characterised. Breathnach and colleagues experimentally infected and vaccinated weanling foals with various EHV-1 regimens before challenging all groups with virulent virus, collecting nasal and serum samples over 13 weeks to quantify specific antibody isotypes using ELISA. Natural infection with virulent EHV-1 generated robust mucosal IgA responses (peaking at 3.1 µg/mg total IgA) that persisted for the study duration, whilst neither intramuscular inactivated nor intranasal attenuated commercial vaccines elicited detectable local antibodies despite triggering systemic responses. Critically, the mucosal antibodies recovered from naturally infected horses demonstrated virus-neutralising capacity in vitro, suggesting they reduce respiratory shedding and may protect against reinfection at the mucosal surface. For practitioners, this work emphasises that current parenteral and intranasal vaccines fail to establish local immunity at the primary site of EHV-1 entry, which may explain incomplete field protection and continued viral circulation among vaccinated populations—pointing toward the need for improved mucosal vaccine formulations.
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Practical Takeaways
- •Current commercial EHV-1 vaccines (inactivated IM and attenuated intranasal formulations) do not elicit protective mucosal immunity in the upper airways, which may explain continued respiratory disease despite vaccination.
- •Natural infection with virulent EHV-1 generates strong local IgA responses that persist for at least 13 weeks and provide some virus-neutralising protection—understanding this may guide future vaccine development strategies.
- •When managing EHV-1 outbreaks, recognition that vaccinated horses lack mucosal immunity should inform biosecurity and isolation protocols, as they remain susceptible to infection and viral shedding.
Key Findings
- •Virus-specific IgA dominated the mucosal antibody response following experimental EHV-1 infection, reaching up to 3.1 μg/mg total IgA at 13 weeks post-challenge.
- •Neither inactivated intramuscular EHV-1 vaccine nor attenuated intranasal vaccine induced detectable mucosal antibodies in weanlings.
- •EHV-1-specific mucosal antibodies demonstrated virus-neutralising capacity by impeding EHV-1 plaque formation in vitro.
- •Mucosal antibodies likely contribute to reducing respiratory shedding of EHV-1 from infected horses.