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Equine veterinary journal2021; 54(1); 139-144; doi: 10.1111/evj.13431

Growth properties and immunogenicity of a virus generated by reverse genetics for an inactivated equine influenza vaccine.

Abstract: Keeping vaccine strains up to date is the key to controlling equine influenza (EI). Viruses generated by reverse genetics (RG) are likely to be effective for quickly updating a vaccine strain. Objective: To evaluate the growth properties of an RG virus in embryonated chicken eggs, and to evaluate antibody responses to a formalin-inactivated vaccine derived from the RG virus in Thoroughbred horses. Methods: In vitro and in vivo experiments. Methods: Wild-type (WT) viruses (A/equine/Ibaraki/1/2007) or RG viruses (consisting of haemagglutinin [HA] and neuraminidase genes derived from A/equine/Ibaraki/1/2007 and the six other genes derived from high-growth A/Puerto Rico/8/34) were inoculated into embryonated chicken eggs, and the allantoic fluids were harvested at every 24 hours after inoculation. WT and RG viruses were inactivated by formalin for vaccine use. Ten unvaccinated yearlings (five each for WT or RG vaccine) received the first two doses of a primary vaccination course 4 weeks apart followed by their third dose 12 weeks later. Twenty vaccinated adult horses (10 each for WT or RG vaccine) received a single dose of a booster vaccination. Results: The RG virus had high growth properties in embryonated chicken eggs. Unvaccinated yearlings responded poorly to the first vaccination, especially those that received the RG vaccine, but mounted better responses to the second and the third vaccinations, and maintained relatively high haemagglutination inhibition (HI) titres up to 28 weeks after the first vaccination. Vaccinated adult horses did not respond remarkably to the booster vaccination, but no horses showed titres below their pre-booster values even at 12 weeks after vaccination. The RG virus elicited immunogenicity in horses adequate for vaccine use. Conclusions: No virus challenge study was performed. Conclusions: The RG viruses are useful as an EI vaccine strain, and quick updates of an EI vaccine strain can be achieved by using RG techniques.
© 2021 EVJ Ltd.
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Publication Date: 2021-02-18 PubMed ID: 33527477DOI: 10.1111/evj.13431Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study investigates the effectiveness of viruses produced by reverse genetics for the timely update of equine influenza vaccines. It specifically evaluates the growth properties of a reverse-genetics virus in chicken eggs and the antibody responses likely to be elicited by a vaccine derived from the virus in Thoroughbred horses.

Methods

  • The researchers conducted both in vitro (in a controlled environment) and in vivo (within a living organism) experiments.
  • Wild-type viruses (A/equine/Ibaraki/1/2007) and reverse-genetics viruses, which consisted of haemagglutinin and neuraminidase genes derived from the stated wild-type virus alongside six other genes taken from A/Puerto Rico/8/34—a high-growth virus—were investigated.
  • The researchers inoculated these viruses into embryonated chicken eggs, with the allantoic fluids then harvested at every 24 hours post-inoculation.
  • The wild-type and reverse-genetics viruses were subsequently inactivated through the use of formalin for vaccine use.

Experimentation and Results

  • Ten unvaccinated yearlings (half received the wild-type vaccine, half the reverse-genetics vaccine) were given a primary vaccination course, consisting of two doses four weeks apart and a third dose 12 weeks later.
  • Twenty vaccinated adult horses also received either the wild-type or reverse-genetics vaccine as a one-off booster vaccination.
  • Observations revealed that unvaccinated yearlings were less responsive to the initial vaccination, particularly those that received the reverse-genetics vaccine. However, their responses improved substantially after the second and third doses.
  • The vaccinated adult horses did not showcase a significant response to the booster vaccination, but no horses’ titres fell below their pre-booster values, even after 12 weeks.

Conclusion

  • The reverse-genetics virus demonstrated high growth properties in the chicken eggs.
  • Despite an initial poor response, the reverse-genetics virus elicited continued immunogenicity in horses, suggesting it is suitable for vaccine use.
  • The researchers concluded that reverse-genetics viruses could be effective for updating strains within an equine influenza vaccination, although it is important to note that virus challenge studies (investigations into whether the virus enters, survives and replicates in the host organism, leading to disease) were not carried out as part of this study.

Cite This Article

APA
Ohta M, Bannai H, Kambayashi Y, Tamura N, Tsujimura K, Yamayoshi S, Kawaoka Y, Nemoto M. (2021). Growth properties and immunogenicity of a virus generated by reverse genetics for an inactivated equine influenza vaccine. Equine Vet J, 54(1), 139-144. https://doi.org/10.1111/evj.13431

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 54
Issue: 1
Pages: 139-144

Researcher Affiliations

Ohta, Minoru
  • Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.
Bannai, Hiroshi
  • Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.
Kambayashi, Yoshinori
  • Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.
Tamura, Norihisa
  • Clinical Veterinary Medicine Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.
Tsujimura, Koji
  • Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.
Yamayoshi, Seiya
  • Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Kawaoka, Yoshihiro
  • Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
  • Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA.
Nemoto, Manabu
  • Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.

MeSH Terms

  • Animals
  • Antibodies, Viral
  • Horse Diseases
  • Horses
  • Influenza Vaccines
  • Orthomyxoviridae Infections / veterinary
  • Reverse Genetics / veterinary
  • Vaccination / veterinary
  • Viruses

Grant Funding

  • JP19fm0108006 / the Japan Initiative for Global Research Network on Infectious Diseases (J-GRID)
  • the Japan Racing Association
  • JP20wm0125002 / the Japan Program for Infectious Diseases Research and Infrastructure of the Japan Agency for Medical Research and Development (AMED)

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