Outbreak H5N2 viruses from 2015 show increased adaptation to chickens
The highly pathogenic H5N2 avian flu virus strain that caused outbreaks in poultry flocks across the United States is better adapted to chickens than a precursor H5N2 virus and is highly adapted to wild ducks, according to a new study by US Department of Agriculture (USDA) scientists published in Virology.
The researchers inoculated chickens and mallard ducks with one of 4 outbreak H5N2 viruses, 3 from affected turkey farms in Minnesota, South Dakota, and Arkansas, and 1 from a chicken outbreak in Iowa. They found that 3 of the viruses were better adapted to chickens compared with a wild-type H5N2 strain isolated from a norther pintail duck in Oregon in 2014.
But they also found that transmission of these four poultry isolates was not increased compared with the wild-type strain except in the case of the Minnesota isolate, which is at odds with what happened in the 2015 outbreaks: fairly rapid farm-to-farm spread of the disease. The USDA authors say a number of factors could be at play in this discrepancy, such as environmental factors, secondary infections, and the physiological stress of egg-laying.
"So although we see indications of increased adaptation to chickens," the authors wrote, "the viruses are still in transition to being fully chicken-adapted viruses."
In the mallard experiments, the team found the poultry viruses highly adapted. Also, two of the poultry isolates had a similar high infectivity as the pintail H5N2 virus, while the other two had a lower rate. The investigators also found that the H5N2 poultry isolate from Minnesota occasionally caused deaths in the ducks at high doses.
"This increased virulence in mallards was unexpected since this virus showed increased adaptation to chickens," the researchers wrote. "However, previous experiments have shown great variability in virulence in ducks."
Sep 12 Virology study
Protein Sciences awarded BARDA grant for pandemic vaccine
Protein Sciences announced that it has received a contract from the Biomedical Advanced Research and Development Authority (BARDA) to enlist the company's proprietary cell-based flu vaccine platform in making pandemic vaccine, according to a Sep 7 press release.
The company, of Meriden, Conn., said the contract will cover preparation of the starting materials to prepare for multiple potential pandemics. The preparations could shave a month or more off the time when Protein Sciences would have a vaccine available, the company said. It added that the contract is worth up to $610 million through 2021 if BARDA, part of the US Department of Health and Human Services (HHS), exercises all its options.
Manon Cox, PhD, MBA, Protein Sciences president and chief executive officer, said in the statement, "We are very pleased to extend our relationship with BARDA and support them in their mission to provide 'More, Faster, Better' vaccines in the face of a pandemic."
Protein Sciences' recombinant protein-based cell-culture flu vaccine platform , already used to make the seasonal flu vaccine Flublok, is the only vaccine made without using egg-based technology. It doesn't require infectious flu virus, antibiotics, preservatives, or adjuvants. In 2009 the company won a BARDA contract for late-stage development.
A 2012 analysis of the flu vaccine landscape found that alternative platforms such as cell culture likely shorten production time and are less vulnerable to contamination, but added that flu vaccines that continue to target the hemagglutinin head of the virus have limited capacity to boost effectiveness or provide broad durable protection against a range of flu viruses.
Sep 7 Protein Sciences press release
Oct 2012 flu vaccine analysis "The Compelling Need for Game-Changing Influenza Vaccines"