Researchers at Kansas State Univ., Manhattan, Kan., created the new vaccine development method for H5N1 and H7N9 strains of avian influenza which can be transmitted from poultry to people. The two have led to the culling of millions of commercial chickens and turkeys as well as the death of hundreds of people.
“H5N1 is a zoonotic pathogen, which means that it is transmitted from chickens to humans,” Jürgen Richt, regents distinguished professor of veterinary medicine, said. “So far it has infected more than 700 people worldwide and has killed about 60 percent of them. Unfortunately, it has a pretty high mortality rate.”
Researchers developed a vaccine for H5N1 by transplanting a small section of the H5N1 virus into a cloned vaccine strain of the Newcastle disease virus.
Tests showed that the new recombinant virus vaccinated chickens against both Newcastle disease virus and H5N1.
“We believe this Newcastle disease virus concept works very well for poultry because you kill two birds with one stone, metaphorically speaking," Richt said. “You use only one vector to vaccinate and protect against a selected virus strain of avian influenza.”
The new approach to vaccine development could reduce the number and intensity of large-scale outbreaks at poultry farms as well as curb human transmission, Richt said.
Researchers developed a vaccine for H7N9 using the same method for developing the H5N1 vaccine. A small section of the H7N9 virus was inserted into the Newcastle disease virus vaccine. Chickens given this recombinant vaccine were protected against the Newcastle disease virus and H7N9.
H7N9 is an emerging zoonotic strain that has been circulating in China since 2013. China has reported about 650 cases in humans and Canada has reported two cases in people returning from China. To date, 230 people have died from H7N9.
“In Southeast Asia there are a lot of markets that sell live birds that people can buy and prepare at home,” Richt said. “In contrast to the H5N1 virus that kills the majority of chickens in three to five days, chickens infected with the H7N9 virus do not show clinical signs of sickness. That means you could buy a bird that looks perfectly healthy but could be infected. If an infected bird is prepared for consumption, there is a high chance you could get sick, and about 1 in 3 infected people die.”
Richt added that it may also lead to new influenza vaccines for pigs and novel vaccines for sheep and other livestock. Researchers developed a vaccine to protect pigs against H3 influenza using the recombinant method.
Richt, who also serves as director of the US Department of Homeland Security's Center of Excellence for Emerging and Zoonotic Animal Diseases, conducted the study with Wenjun Ma, Kansas State Univ. assistant professor of diagnostic medicine and pathobiology, Adolfo Garcia-Sastre at the Icahn School of Medicine at Mount Sinai in New York, and several other colleagues.
The researchers published their findings in theJournal of Virology, “Newcastle disease virus-vectored H7 and H5 live vaccines protect chickens from challenge with H7N9 or H5N1 avian influenza viruses.”