Researchers have discovered a new class of antibodies capable of neutralizing various strains of the flu virus, which could help develop more protective flu vaccines. The breakthrough, which will be published in PLOS Biology, highlights the importance of diversifying influenza vaccine production methods and provides new avenues for vaccine design. The findings could help lead to vaccines that protect against a wider range of influenza viruses.
Researchers led by Holly Simmons of the University of Pittsburgh School of Medicine have discovered a new type of antibody that shows potential in neutralizing various types of influenza viruses. This significant advance, recently published in the journal PLOS Biology, could lead to a more universally effective flu vaccine.
The flu vaccine causes the immune system to produce antibodies that bind to a viral protein called hemagglutinin on the outside of the invading flu virus, preventing it from entering human cells. Different antibodies bind to different parts of the hemagglutinin in different ways, and the hemagglutinin itself changes over time, leading to the emergence of new strains of influenza that are able to evade old antibodies. New flu vaccines are offered every year based on predictions of the most dominant strains.
Extensive research efforts are paving the way to develop flu vaccines that better protect against multiple strains at once. Many scientists are working on antibodies that protect against both influenza subtypes known as H1 and H3.
Simmons and colleagues identified a particular challenge in this work—in some H1 strains, there are subtle changes in the sequence of the building blocks that make up hemagglutinin. Some antibodies that neutralize H3 can also neutralize H1, but cannot neutralize H1 if the hemagglutinin of H1 has this change (i.e., 133a insertion).
Now, through a series of experiments on patient blood samples, researchers have discovered a new class of antibodies that are capable of neutralizing certain H3 strains and certain H1 strains with or without the 133a insertion. Unique molecular features distinguish these antibodies from other antibodies that are able to cross-neutralize H1 and H3 strains through other pathways.
This study expands the list of antibodies that may aid in the development of influenza viruses that achieve broader protection through various molecular mechanisms. Additionally, there is growing evidence that currently the most common method of making flu vaccines is by growing them in eggs, and this study supports moving away from this method.
The authors add: "We need annual influenza virus vaccination to keep up with the ongoing evolution of viruses. Our study shows that the barriers to eliciting broader protective immunity may be surprisingly low. With the right series of influenza virus exposures/vaccination, it is possible for humans to generate robust antibody responses that neutralize different H1N1 and H3N2 viruses, opening new avenues for designing improved vaccines."