A team of American and Chinese scientists have found a new approach to vaccine development that may effectively prevent the seasonal flu, a new study says.

Scientists from two countries used cutting-edge genomics to identify and eliminate the virus' defense mechanisms, enabling them to develop a vaccine "candidate" that in animals has been proven to be safe and highly effective against influenza, according to the study published in the journal Science on Thursday.

The study shows that the engineered influenza virus induced strong immune responses in animals.

Scientists are hopeful that their approach could lead to a new, more effective vaccine that can be taken as a nasal spray at home, rather than an injection by a health professional.

"Because the variations of seasonal influenza viruses can be unpredictable, current vaccines may not provide effective protection against them," said Ren Sun, a professor of molecular and medical pharmacology at University of California Los Angles and the study's senior author.

The key to the new vaccine is an understanding of the interactions between the virus and interferons, which are proteins that are critical to the body's immune response.

In the study, Sun and his Chinese colleagues defined the function of every amino acid in the influenza virus's entire genome, and deactivated the sequences that prevent interferon induction, so the interferon production would be highly stimulated in organisms infected with the virus.

"By disabling these interferon-evasion functions, the engineered virus is weakened in typical hosts," said Yushen Du of Zhejiang University School of Medicine, the study's first author. "At the same time, however, due to interferon stimulation, the engineered virus generates very strong immune responses."

Although researchers have disabled genetic sequences that block interferon before, the scientists were the first to systematically identify and eliminate multiple interferon-evasion sites at single amino acid resolution on the virus.

"Other researchers have knocked out one anti-interferon sequence, but we knocked out eight locations by changing one amino acid at a time," Du said.

Sun and his colleagues plan to test the vaccine in animals with two strains of influenza before moving to clinical trials with humans. He said the approach could also be applied to developing vaccines against a wide range of other viruses.

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