Immune responses and protective efficacy in ponies immunised with an equine influenza ISCOM vaccine containing an ‘American lineage’ H3N8 virus.

The study assessed the protective response of a new vaccine, EQUIP F, which uses immuno-stimulating complex (ISCOM) against equine influenza featuring a new ‘American lineage’ H3N8 virus. The researchers found the vaccine significantly protected horses from clinical signs of infection and virus excretion following an aerosol challenge.

Research Methodology

• The research involved seven ponies in the vaccine group that were given two intramuscular injections of EQUIP F, spaced six weeks apart.
• Four weeks after the booster shot, the ponies were exposed to an aerosol challenge using an A/eq/Newmarket/1/93 reference strain.
• The researchers then monitored the specimens for clinical signs of infection and viral shedding.
• There was a control group of seven influenza-naive animals, which allowed the researchers to compare the effects of the vaccine on the ponies against the effects of the virus on unvaccinated animals.

Key Findings

• The vaccinated ponies were significantly protected from both clinical signs and virus excretion, indicating that the vaccine was effective in safeguarding the horses against the influenza strain.
• The response to the ISCOM vaccine was mainly shown in the IgGa and IgGb sub-isotypes, a pattern researchers noted was similar to that generated by equine influenza virus infection.
• Contrary to the response following infection, virus-specific antibody responses in the nasal washes from the vaccinated group showed the presence of IgG but not IgA antibodies.

Conclusion

• The researchers concluded that the ISCOM-based vaccine containing A/eq/Kentucky/98 offers robust protective immunity against the challenge with an ‘American lineage’ H3N8 reference virus.
• This study significantly adds to the body of knowledge about equine influenza vaccines, and holds promise for better management and control of equine influenza in horses.