Researchers in China have reported on a promising new vaccine against West Nile Virus which triggered strong immune responses in key species, including horses. Crucially, it elicited an immune response in domestic bird species when given either orally or nasally.
The first recorded case of West Nile fever was reported in Uganda in 1937. The flavivirus is now extensively distributed worldwide throughout Africa, Europe, Asia and North America.
The virus has a range of hosts comprising several species of birds (including poultry), mammals, amphibians and reptiles. Culex mosquitoes play a central role in spreading the virus around the globe, and are responsible for the incidental infection of humans and horses, which are considered dead-end hosts.
Researchers Zhiyuan Wen and Zhigao Bu, from the Chinese Academy of Agricultural Sciences, writing in the Virology Journal, said a versatile vaccine suitable for different species that can be delivered via flexible routes remained an essential unmet medical need.
Effective vaccination in susceptible hosts, especially those abundant in number and closely associated with humans, such as horses, poultry and other bird species, should protect against West Nile infection and significantly reduce viral transmission between animals and from animals to humans, they said.
The pair, joined by other scientists, developed a recombinant avirulent vaccine against West Nile based on the Newcastle disease virus LaSota strain, and then evaluated its performance in mice, horses, chickens, ducks and geese.
They found that the vaccine delivered significant levels of West-Nile-neutralizing antibodies and T-cell responses in mice. It also elicited significant levels of West-Nile-specific immunoglobulins in horses when the vaccine was injected into the muscle. A similar response were obtained in chickens, ducks and geese not only by injection into muscle tissue, but also via the mouth and via the nose.
The researchers said vaccination of sensitive hosts not only protected the animal itself but also prevented transmission from animals to humans.
They noted that several veterinary vaccines for West Nile Virus were currently available, including inactivated whole virus vaccine, DNA vaccines, recombinant canarypox-vectored vaccines, and recombinant Yellow Fever 17D vaccine.
Notably, canarypox-vectored vaccines have been shown to effectively elicit specific neutralizing antibodies and confer protection in horses, geese, cats and dogs against lethal West Nile Virus challenge. But these vaccines required delivery via intramuscular inoculation.
The study team’s research showed that the novel vaccine produced an immunological response in not only mice, horses and poultry when injected into muscle, but also in poultry when given by mouth or through the nose.
They said it was a promising veterinary candidate vaccine for multiple mammalian and bird species that can be delivered via flexible inoculation routes.
Wen and Bu were joined in the study by Jinliang Wang, Jie Yang, Jinying Ge, Ronghong Hua, Renqiang Liu, Xiaofeng Li, Xijun Wang, Yu Shao, Encheng Sun, Donglai Wu, and Chengfeng Qin.
Newcastle disease virus-vectored West Nile fever vaccine is immunogenic in mammals and poultry
Jinliang Wang, Jie Yang, Jinying Ge, Ronghong Hua, Renqiang Liu, Xiaofeng Li, Xijun Wang, Yu Shao, Encheng Sun, Donglai Wu, Chengfeng Qin, Zhiyuan WenEmail author and Zhigao Bu.
Virology Journal 2016 13:109 DOI: 10.1186/s12985-016-0568-5