East Montgomery Times

Prior exposure to specific seasonal influenza viruses appears to boost immunity against the H5N1 avian flu virus, according to research from the Perelman School of Medicine at the University of Pennsylvania. The study indicates that older adults who encountered flu strains circulating before 1968 are more likely to have antibodies that react with H5N1. Published in Nature Medicine, the findings suggest younger people and children might gain more from H5N1 vaccines.

Scott Hensley, PhD, a professor of Microbiology and senior author of the study, stated, "We know that early childhood influenza exposures can elicit immune responses that last a lifetime." He added, "Most of these cross-reactive antibodies cannot prevent infections, but they will likely limit disease if we have an H5N1 pandemic."

The research notes that while H5N1 viruses have long circulated in birds, a newer version called clade 2.3.4.4b has recently spread among cattle. This strain doesn't bind well to human upper airway receptors yet but could mutate for easier transmission between humans.

Influenza viruses use proteins called hemagglutinin and neuraminidase for infection. Current vaccines target hemagglutinin proteins to prevent infection. However, while the heads of these proteins evolve quickly, their stalks change less often.

Researchers tested blood samples from over 150 individuals born between 1927 and 2016 for antibodies targeting various influenza virus stalk proteins. They found those born before 1968 had higher levels of antibodies binding to the H5N1 virus's stalks due to early exposure to H1N1 or H2N2 viruses.

To assess vaccine responses across different birth years, another group received a 2004 H5N1 vaccine not fully matching today's clade 2.3.4.4b strain. Results showed older adults had more pre-vaccination antibodies capable of binding to H5 stalks than younger ones; post-vaccination increases were substantial in children.

"In the event of an H5N1 pandemic...the highest disease burden will be in children," said Hensley. "If this is the case, children should be prioritized for H5N1 vaccinations."

The National Institute of Allergy and Infectious Diseases supported this research.

Kelsey Geesler

C: 215-300-1194

kelsey.geesler@pennmedicine.upenn.edu