Growth properties and immunogenicity of a virus generated by reverse genetics for an inactivated equine influenza vaccine.
Authors: Ohta Minoru, Bannai Hiroshi, Kambayashi Yoshinori, Tamura Norihisa, Tsujimura Koji, Yamayoshi Seiya, Kawaoka Yoshihiro, Nemoto Manabu
Journal: Equine veterinary journal
Summary
# Editorial Summary Equine influenza vaccine development depends critically on rapid strain updates, and reverse genetics (RG) offers a promising method to accelerate this process by combining modern growth-optimised genetic backbones with current circulating strain surface antigens. Researchers compared wild-type and RG viruses—the latter engineered with haemagglutinin and neuraminidase genes from a 2007 Ibaraki strain but internal genes from a high-growth Puerto Rican strain—evaluating their growth in embryonated chicken eggs and subsequent immune responses in both vaccinated and unvaccinated horses following formalin inactivation. The RG virus demonstrated superior egg growth kinetics, whilst primary vaccination in yearlings showed modest initial responses (particularly with RG vaccine) but robust haemagglutination inhibition titres by the second and third doses, with antibody persistence at 28 weeks; booster vaccination in previously exposed adults maintained pre-booster titres without marked anamnestic responses. These findings support RG viruses as viable vaccine candidates offering both practical manufacturing advantages and adequate immunogenicity, though the absence of challenge studies means efficacy against natural infection remains undemonstrated and field performance should be monitored once vaccines enter practice. The technology's ability to rapidly incorporate emerging strains could substantially improve the timeliness of vaccine updates during epidemiological shifts.
Read the full abstract on PubMed
Practical Takeaways
- •Reverse genetics technology enables rapid updates of equine influenza vaccine strains, allowing faster response to emerging viral variants
- •RG-derived vaccines show adequate immune responses in both primary vaccination series and booster protocols in horses
- •Multiple vaccine doses (3-dose primary series) are recommended for optimal antibody development, particularly in younger horses
Key Findings
- •Reverse genetics virus demonstrated superior growth properties in embryonated chicken eggs compared to wild-type virus
- •Unvaccinated yearlings showed poor response to first vaccination with RG vaccine but mounted better responses to second and third doses, maintaining high HI titres for 28 weeks
- •Vaccinated adult horses showed stable or improved antibody titres 12 weeks after booster vaccination with RG-derived inactivated vaccine
- •RG viruses elicited adequate immunogenicity for vaccine use without virus challenge study validation