New bird flu studies could help surveillance and vaccine strategies

Two recent studies published on Thursday in Cell identify mutations that would increase infectivity in bird flu viruses and could result in strategies to monitor the emergence of strains capable of infecting humans.

Researchers from the Singapore-MIT Alliance for Research and Technology identified mutations in the H5N1 and H7N9 viruses that would increase infectivity through improved binding to receptors in the human respiratory tract. The findings could help scientists monitor evolving bird flu strains and develop more effective vaccines.

"Avian influenza viruses evolve rapidly, and there are many subtypes of these viruses that we need to be concerned about because, in many cases, humans do not have immunity to these newer strains," Ram Sasisekharan, the senior author of the study, said. "Our findings can be put to use to monitor the evolution of H5N1 and H7N9 viruses in the field as well as in the clinic if and when there is an outbreak."

In the last decade, the H5N1 virus infected close to 600 people, killing approximately 60 percent of infected individuals. The H7N9 virus recently infected at least 131 people in China. While the two viruses do not usually infect humans, they may adapt and spread more easily from person to person.

Sasisekharan and his team found the set of hemagglutinin mutations required to increase the preference of the viruses for human receptors. The researchers identified a single amino acid alteration in the HA sequence needed for the change. The team found that current H7 vaccines would not be effective against the newly emerged virus.

"Right now, there is no vaccine to protect against the H7N9 virus, and our findings could guide efforts to develop effective vaccine strategies," Sasisekharan said.