A new modified live equine influenza virus vaccine: phenotypic stability, restricted spread and efficacy against heterologous virus challenge.
Authors: Chambers T M, Holland R E, Tudor L R, Townsend H G, Cook A, Bogdan J, Lunn D P, Hussey S, Whitaker-Dowling P, Youngner J S, Sebring R W, Penner S J, Stiegler G L
Journal: Equine veterinary journal
Summary
# Editorial Summary Flu Avert IN represents a significant advancement in equine influenza control as a live attenuated intranasal vaccine designed to provide protection against both American and Eurasian lineage equine-2 influenza viruses currently circulating globally. Safety and phenotypic stability were evaluated through serial passage experiments in which vaccine virus was administered to successive groups of naïve ponies over four passages; virus isolated from the final group maintained full attenuation with no reversion to wild-type phenotype or clinical disease manifestation. Crucially, when 39 vaccinated horses and ponies were comingled in pasture with 13 unvaccinated animals, spontaneous spread of vaccine virus occurred in only one contact animal, addressing a significant concern regarding live vaccine transmission. In controlled challenge studies using aerosol exposure to Kentucky/98 (American lineage) and Saskatoon/90 (Eurasian lineage) influenza viruses, vaccinated animals were reliably protected from clinical disease whilst all control animals developed clinical signs of influenza. These findings indicate that practitioners can confidently use Flu Avert IN for herd immunisation with minimal risk of unintended vaccine spread to unvaccinated contacts, whilst achieving robust cross-protective immunity against heterologous challenge viruses representative of field strains.
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Practical Takeaways
- •Flu Avert IN is a safe, stable live attenuated vaccine suitable for field use with minimal risk of reversion or unintended spread to unvaccinated horses
- •This vaccine provides cross-protection against diverse equine influenza strains currently circulating globally, reducing the need for frequent vaccine updates
- •Low spontaneous transmissibility makes this vaccine practical for use in mixed vaccinated/unvaccinated populations without concerns about accidental exposure of non-target animals
Key Findings
- •Flu Avert IN vaccine retained full attenuation phenotype through 5 serial passages with no reversion to wild-type virus phenotype
- •Vaccine virus spread spontaneously to only 1 of 13 non-vaccinated horses/ponies when commingled with 39 vaccinates
- •Vaccinated animals were reliably protected from clinical disease when challenged with both American and Eurasian lineage equine-2 influenza viruses
- •Control animals reliably contracted clinical influenza signs following challenge, confirming efficacy of the challenge model