Study in ferrets shows immunity targeting two flu proteins may significantly reduce airborne transmission of the H1N1 influenza virus.
For years, vaccine researchers have debated an important question: should vaccines mainly focus on stopping a virus from multiplying inside the body, or on preventing it from spreading to other people? New research from scientists at Penn State suggests it may be possible to achieve both goals at the same time. (1✔ ✔Trusted Source
Immunity to hemagglutinin and neuraminidase results in additive reductions in airborne transmission of influenza H1N1 virus in ferrets
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In a study using animal models, published in the journal Science Advances, researchers identified an approach that limits the influenza virus’s ability to pass from one host to another while also suppressing viral replication within the infected individual.
Two Key Viral Proteins Linked to Reduced Flu Spread
The findings indicate that immune responses targeting two key proteins on the virus surface — hemagglutinin (HA) and neuraminidase (NA) — may play an important role in reducing airborne transmission. By generating defenses against both proteins, the body can potentially lower the chances of the virus spreading through the air while still controlling infection inside the host.
“This suggests that intentionally targeting these two proteins together in future vaccines could help curb spread,” said Troy Sutton, who led the study and serves as Huck Early Career Chair in Virology and associate professor of immunology and infectious disease at Penn State. “Critically, transmission was reduced without accelerating viral evolution inside the host, which is a key concern in vaccine design.”
The researchers used ferrets as models to test how different types of immunity (from either vaccination or prior infection) against an influenza H1N1 virus, a strain that causes annual outbreaks in the fall or winter months, affected both viral replication and the likelihood of airborne transmission.
“The virus used in our study is considered representative of seasonal influenza viruses, or viruses that cause outbreaks every fall and winter,” Sutton said.
Seasonal Flu Still Poses a Major Global Health Threat
Infection with an H1N1 influenza virus causes symptoms like fever, cough and fatigue and can lead to severe respiratory illness or even death, particularly in high-risk groups like children, the elderly, and those with weakened immunity.
In fact, the World Health Organization estimates that seasonal influenza viruses, such as the H1N1 virus studied by Sutton’s team, infect up to 1 billion people worldwide each year. As a result, 3 to 5 million people develop severe disease and as many as 650,000 people die from influenza infections each year.
Ferrets, which have remarkably similar respiratory systems to humans, closely mimic how humans become infected with and transmit influenza viruses like H1N1. By pairing infected “donor” ferrets with uninfected “contact” ferrets in shared‑air cages, the team could directly measure how immunity to hemagglutinin, neuraminidase or both influenced viral transmission.
The controlled environment allowed the researchers to track viral shedding, transmission rates and viral evolution to develop an understanding of how specific immune responses shaped influenza transmission.
Across every scenario, animals with immunity to both proteins were consistently less likely to pass the virus on to nearby, uninfected ferrets. Transmission dropped by half, an effect Sutton described not as synergistic but additive, meaning immune responses to both of the HA and NA proteins equally contributed to the overall reduction in transmission.
The team also identified a measurable threshold for effectiveness. When viral levels dipped below a certain point early in infection, the likelihood of spreading the virus fell below 50%.
“That insight could help guide future vaccine design, especially efforts that aim not only to prevent severe illness but to limit viral transmission itself,” Sutton said.
Dual Protein Strategy Shows No Immune Escape in Tests
Critically, he added, the team found no evidence that the virus evolved to evade the body’s immunity to the two proteins. Across dozens of animal models, no consistent escape variants — virus mutations that evolve to evade immune protection — emerged, suggesting that targeting both HA and NA does not appear to drive rapid viral adaptation.
“Our work strengthens the growing consensus among experts that influenza vaccines need to target multiple influenza virus proteins to be maximally effective,” Sutton said. “Vaccines of the future may need to do more than trigger strong antibody responses. They may need to blunt spread at the source and that may mean doubling up on the immune targets the virus relies on most.”
References:
- Immunity to hemagglutinin and neuraminidase results in additive reductions in airborne transmission of influenza H1N1 virus in ferrets – (https://www.science.org/doi/10.1126/sciadv.aea8719)
Source-Eurekalert