Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.
Clinical Veterinary Medicine Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.
Equine Vet J. 2022 Jan;54(1):139-144. doi: 10.1111/evj.13431. Epub 2021 Feb 18.
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.
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.
In vitro and in vivo experiments.
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.
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.
No virus challenge study was performed.
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.
更新疫苗株是控制马流感（EI）的关键。通过反向遗传学（RG）产生的病毒可能对于快速更新疫苗株非常有效。
评估 RG 病毒在鸡胚中的生长特性，并评估源自 RG 病毒的福尔马林灭活疫苗在纯种马中的抗体反应。
体内和体外实验。
将野生型（WT）病毒（A/equine/Ibaraki/1/2007）或 RG 病毒（由 A/equine/Ibaraki/1/2007 的血凝素 [HA]和神经氨酸酶基因以及源自高生长 A/Puerto Rico/8/34 的其他六个基因组成）接种到鸡胚中，在接种后每隔 24 小时收获尿囊液。WT 和 RG 病毒用福尔马林灭活用于疫苗接种。十只未接种的一岁马（WT 或 RG 疫苗各五只）在四周内接受了两剂基础免疫接种，然后在 12 周后接受第三剂接种。二十只接种过的成年马（WT 或 RG 疫苗各十只）接受了一剂加强免疫接种。
RG 病毒在鸡胚中具有高生长特性。未接种的一岁马对第一次接种反应不佳，尤其是接受 RG 疫苗的马，但对第二次和第三次接种反应更好，并且在第一次接种后 28 周内仍保持相对较高的血凝抑制（HI）滴度。接种过的成年马对加强免疫接种反应不明显，但即使在接种后 12 周，也没有马的滴度低于其加强前的值。RG 病毒在马中引起了足够的免疫原性，可用于疫苗接种。
未进行病毒挑战研究。
RG 病毒可作为 EI 疫苗株使用，并且可以通过 RG 技术快速更新 EI 疫苗株。
