Each year, seasonal flu attacks up to 10% of the global adult population, and between 20-30% of children, resulting in hundreds of thousands of deaths, mostly within high risk groups such as babies or the elderly. Although vaccines are brought out annually, they rely on predictions of the virus strains that will circulate months in advance of flu season to allow time for manufacture.
Unfortunately, as is the case this year, mismatches often occur, and even when scientists manage to accurately predict the strain, the vaccines are often not very effective. These problems could be solved with the advent of one size fits all “universal” vaccines that protect against a number of flu strains, but so far this has eluded scientists. Now, however, new research suggests that scientists could be tantalizingly close to achieving this, with the discovery of a class of antibodies that are capable of neutralizing a broad range of influenza A viruses.
“Unlike seasonal vaccines, which must be given annually, this type of vaccine would only be given once, and would have the ability to protect against all strains of flu, even when the virus mutates,” lead scientist Matthew Miller said in a news release. “This would prevent the occurrence of flu pandemics and poor vaccine efficiency in the case of mismatches.”
There are two main types of influenza virus: A and B. They routinely spread between people and are responsible for seasonal flu epidemics each year. These viruses possess two surface proteins, hemagglutinin (HA) and neuraminidase, which can be recognized by neutralizing antibodies, although HA is the main target. The reason that flu vaccines need to be changed every year is because the virus is constantly mutating, resulting in altered surface proteins that our immune system may no longer recognize.
To overcome this, scientists are attempting to produce vaccines that contain antibodies which recognize part of the virus that doesn’t change—the stalk of HA. HA looks a bit like a lollipop stuck into a ball, and the stalk is the stick of the lolly.
For the study, scientists from McMaster University and the Icahn School of Medicine compared the neutralization potency of a strain-specific antibody that targets the head of HA, which is the type used in current vaccines, with a broadly-neutralizing antibody that targets the stalk.
As described in the Journal of Virology, they found that the stalk-binding antibodies were vastly inferior in terms of neutralization potency. However, when the stalk-binding antibodies were isolated in their natural setting from human blood, their potencies were significantly enhanced and the antibodies were comparable in terms of neutralization efficiencies. The former also had the added bonus of neutralizing a range of influenza A viruses.
Although this doesn’t prove that the “universal” vaccine will work in humans, the results are encouraging and help inform us of the biological activity of these antibodies in natural contexts. According to ABC News, a clinical trial is due to begin later this year to test out the efficiency of these antibodies in humans. Of course, this is not a true universal vaccine because it does not include influenza B, but that would be much more difficult to achieve.
[Via Journal of Virology, McMaster University and ABC News]