Groundbreaking antibody nasal spray stops flu viruses

When scientists engineer a better way to fight the flu, they often begin with nature’s own defenses. That’s what a new study from researchers at The Ohio State University set out to do. Their goal was to create a more powerful antibody treatment against influenza A, one of the most common and deadly strains of the virus. What they discovered could change how people are protected against future flu pandemics.

The flu virus keeps changing. Its shape-shifting surface proteins allow it to dodge vaccines and weaken antibody treatments. That’s why the seasonal flu shot only works about 30% to 60% of the time. The virus often mutates key parts of its hemagglutinin (HA) protein, which is what most vaccines and treatments target. This constant evolution, called antigenic drift, is one of the biggest challenges in fighting influenza.

Researchers wanted to beat the virus at its own game. They focused on a specific type of antibody called IgG, which binds tightly to one exact spot on the HA protein. These antibodies are highly specific, but they lose strength when the virus mutates that target area. Scientists realized they needed something broader and stronger—something that could still work even after the virus changed.

That’s when they turned to another immune molecule: IgM.

Unlike IgG, which has two arms to bind a virus, IgM antibodies have ten. This pentameric shape gives them multivalency, meaning they can grab onto several parts of a virus at once. Even if one spot mutates, the other arms can still hold on.

Researchers engineered 18 new IgM antibodies by building on existing IgG designs known to work against various versions of influenza A. They tested these antibodies against different H1N1 and H3N2 flu viruses that have circulated over the past 90 years. One engineered molecule stood out. It was called IgM-F045-092 and it targeted the receptor binding site (RBS) of the HA protein.

In lab studies, this new IgM antibody outperformed its original IgG version. It neutralized more virus strains and was effective at extremely low doses. Structural analysis showed that the antibody covered the virus so thoroughly that it could block infection even if the virus mutated.

The real breakthrough came with how the antibody was delivered. Instead of injecting it into the bloodstream, researchers turned it into a nasal spray. This strategy allowed the antibody to stick to the mucus lining of the nose and lungs, where flu viruses usually enter the body.

“The primary purpose is to refuse viruses before they can get into a host cell,” explained Kai Xu, assistant professor of veterinary biosciences and co-lead author of the study. “The mucosal immunity is more efficient than systemic immunity at intercepting, so the initial infection can be reduced or eliminated.”

The antibody stayed in the respiratory tract of mice for a full week. That means in humans, a single spray might last even longer.

“It’s a better platform with a better antibody,” Xu said. “If we can prepare the respiratory environment with this enhanced engineered molecule, it can capture and intercept the virus in an early stage. This would be a therapy that not only can be used for prevention of seasonal flu—it potentially could also be used against pandemic strains in the future.”

To see how well the IgM spray worked, researchers gave mice a single dose of the antibody in their noses. Then, they exposed the animals to lethal doses of H1N1 and H3N2 flu viruses.

The results were promising. None of the mice sprayed with the antibody got sick from H3N2. Most of them also survived the more dangerous H1N1 strain. The control group—those without the spray—had much worse outcomes.

The spray worked not only because of the strong binding power of IgM-F045-092 but also because of how long it stayed in place. Its large size helped it stick to the slippery mucus, forming a protective barrier that caught the virus before it could infect cells.

This new approach mimics the way your body naturally fights off viruses but makes it faster and stronger.

This isn’t the first time scientists have tried enhancing antibodies by switching from IgG to IgM. The research team had already shown success with similar engineered IgM molecules against SARS-CoV-2, the virus that causes COVID-19. Those earlier results laid the foundation for the current study on flu.

Many human antibodies that block the flu virus target the HA protein. Some stop the virus from binding to your cells, while others block it from merging with your cell membrane. But these antibodies often become less effective as the virus mutates. And even when they work in lab settings, they don’t always offer strong protection when given as injections in living organisms.

That’s why the team wanted to try a different route—one that took advantage of both the broad coverage of IgM and the precision of well-designed IgG antibodies.

By combining the two, the new IgM version of F045-092 maintained the original antibody’s sharp aim while adding more gripping power. This helped it overcome the virus’s ability to escape and improved its performance against a wide range of flu strains.

Though this study focused on known strains of influenza A, the researchers believe their approach could work on more dangerous versions, like bird flu or other pandemic threats. Because the method doesn’t rely on identifying a perfect match between the antibody and the virus, it could provide protection even as the virus continues to evolve.

Xu believes this platform could eventually be used for other diseases, even non-viral ones like cancer. “By enhancing the capacity for it to recognize the mutated or differentiated viral surface regions, it can cross-protect against different influenza virus infections and can also work even after mutations occur,” he said.

The study, published in Nature Communications, offers hope for a future where one spray might protect against many strains of flu, even those that haven’t appeared yet.

That kind of early, strong protection could be life-saving—especially for those most at risk, like older adults and people with chronic health problems.

Note: The article above provided above by The Brighter Side of News.

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