Year after year, new flu vaccines are formulated based on predictions of what the predominant strains will be. But what if the current approach, which seeks to induce protective antibodies by targeting certain viral proteins, is wrong?
A new National Institute of Allergy and Infectious Diseases study suggests this might be the case. Institute researchers found that inducing antibodies against a different protein from the kind usually targeted produced a better response, and ultimately better protection from flu virus.
"The idea behind this study was to re-evaluate the bar that was previously established for evaluating a person's immune response to influenza vaccines," the study's principal investigator Matthew Memoli, MD, director of the Clinical Studies Unit in NIAID's Laboratory of Infectious Diseases, said in a statement.
The team measured the levels of existing antibodies to a protein called hemagglutinin in 65 healthy patients. Hemagglutinin is the viral protein usually targeted in vaccine development. Those with naturally occurring high and low levels of hemagglutinin were placed into two groups, both of which were dosed with H1N1 virus.
As expected, participants with high levels of hemagglutinin antibodies experienced a lower incidence and somewhat shorter duration of mild flu activity. But they also found that the group with high antibody levels was just as likely to experience certain flu symptoms as those with low levels of the antibody.
However, participants with existing levels of neuraminidase antibody, a different viral protein, were found to be more predictive in determining severity of flu symptoms and likelihood of contracting flu overall.
"We demonstrate that although higher [hemagglutinin antibody] is predictive of some protection, there is stronger evidence to suggest that neuraminidase … is more predictive of protection and reduced disease," the authors concluded. "This is the first time [neuraminidase] has been clearly identified in a controlled trial of this type to be an independent predictor of a reduction in all aspects of influenza."
The findings are published in mBio.