Researchers have identified three antibodies that could lead to better treatments and vaccines to fight the flu, which sickens millions in the U.S. each year.
By isolating antibodies from flu patients, the researchers discovered they provided protection against several influenza strains when tested in mice and in vitro.
The antibodies bound to the neuraminidase enzyme, which breaks down sugar, on the surface of the flu virus.
“The target of these antibodies is something the virus cannot change easily because it’s an enzyme active site,” said Ali Ellebedy, one of the researchers and an assistant professor of pathology and immunology at the Washington University School of Medicine. “Now we have these antibodies as potential therapeutics to treat influenza virus infected patients.”
In their study, which was published last week in the journal Science, the researchers used three human cloned antibodies that bind to various influenza neuraminidases. They tested the antibodies in mice infected with human, avian and swine flu strains — most of them lethal to the laboratory rodents — and found the antibodies prevented death and weight loss.
“They showed remarkable activity and remarkable potency in protecting mice from the challenges with lethal influenza virus infections,” Mr. Ellebedy said, adding that the researchers learned about another point of weakness in the flu virus that they can target.
Dr. William Schaffner, medical director for the National Foundation for Infectious Diseases and who was not involved in the study, called the researchers’ work another attempt to develop a “universal flu vaccine” that would cover a wide variety of viral strains.
“The main reason we have to vaccinate ourselves annually is because the virus itself mutates and changes, and it changes principally the hemagglutinin [a protein on the surface of the virus],” Dr. Schaffner said. “The neuraminidase, which is the subject of this investigation, is more stable. And if we could develop a vaccine that could work effectively against the neuraminidase, that would cover many, many more strains.”
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said many researchers study hemagglutinin, but there are other proteins on the flu virus that do not get as much attention, including neuraminidase.
“Now, for the first time, we have some pretty solid proof that antibodies against neuraminidase can really be very broadly protective against multiple, diverse strains of influenza,” Dr. Fauci said. “It [has] now provided for us yet another credible target to which direct our efforts to developing an antibody.”
The stem of the hemagglutinin doesn’t mutate that much, but the head of the protein does. A standard strategy to develop better flu vaccines is to induce a response from the stem of the hemagglutinin.
The Centers for Disease Control and Prevention estimate the flu has caused between 9.3 million and 49 million illnesses, between 140,000 and 960,000 hospitalizations, and between 12,000 and 79,000 deaths each year since 2010.
Last season, there were between 37 million to 42.9 million illnesses, 531,000 to 647,000 hospitalizations and 36,400 to 61,200 deaths in the U.S.
Health professionals recommend everyone 6 months old and older get vaccinated before the end of the month.
Dr. Fauci said he thinks many people don’t take the flu seriously since it happens every year and because people often confuse minor respiratory symptoms as the flu when it’s not.
He stressed that while many are able to recover from the flu on their own, there are others such as infants, the elderly, pregnant women and people with underlying medical conditions who are likely to develop complications.
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