Study of bird flu mutations improves ability to develop vaccines
The results of the study could help scientists to develop more effective live attenuated flu vaccines in a pandemic situation involving bird flu.
"Knowing why bird flu struggles to replicate in the nose and understanding the genetic mutations that would enable it to happen are vital for monitoring viruses circulating in birds and preparing for an outbreak in humans," Wendy Barclay, the leader of the study, said.
The researchers used a laboratory strain of flu with the same proteins on its surface as bird flu, but they engineered the virus so it could not cause serious illness. The team found the mutations of the H5 haemagglutinin helped the protein handle higher levels of acidity and bind to different receptors. The mutation let the virus replicate more efficiently in ferrets and transmit between animals.
The new study supported the conclusions of controversial studies published in 2012 which demonstrated that only a few genetic mutations would allow bird flu to spread between ferrets.
"The studies published last year pointed to a mechanism that restricts replication of H5N1 viruses in the nose," Barclay said. "We've engineered a different mutation with the same effect into one of the virus proteins and achieved a similar outcome. This suggests that there is a common mechanism by which bird flu could evolve to spread between humans, but that a number of different specific mutations might mediate that."
Barclay and her team found that viruses with modified haemagglutinin proteins induced strong antibody responses in ferrets, suggesting that vaccines with similar modifications could be more effective than the typical killed virus vaccines.
"We can't predict how bird flu viruses will evolve in the wild, but the more we understand about the kinds of mutations that will enable them to transmit between humans, the better we can prepare for a possible pandemic," Barclay said.