One age group are more likely to have antibodies that bind to the H5N1 avian flu virus, new research has found.
New research has revealed that a certain age group may be more likely to possess antibodies that bind to bird flu.
The study found that prior exposure to specific types of seasonal influenza viruses can result in ‘cross-reactive immunity’ against the H5N1 avian influenza virus.
Researchers from the Perelman School of Medicine at the University of Pennsylvania discovered that older adults who were exposed to seasonal flu viruses before 1968 were more likely to have antibodies that bind to the H5N1 avian flu virus.
The study, published in Nature Medicine, revealed that younger adults and children would benefit more from vaccines against bird flu.
Senior author on the study, Scott Hensley, PhD, a professor of Microbiology said: “We know that early childhood influenza exposures can elicit immune responses that last a lifetime.
“We found that antibody responses that were primed by H1N1 and H3N2 viruses decades ago can cross-react to H5N1 avian viruses circulating today. Most of these cross-reactive antibodies cannot prevent infections, but they will likely limit disease if we have an H5N1 pandemic.”
Bird flu viruses, or H5N1 viruses, have been infecting birds for many years. But a new strain of the virus called clade 2.3.4.4b H5N1 virus emerged more recently, and has since spread among cattle.
Several cat food products in the US have been recalled due to bird flu contamination, and one person in Louisiana died of the disease in January.
This new strain of bird flu does not easily infect humans, but widespread circulation in mammals could lead to the virus mutating enough that it could infect human airway cells and increase transmission. If this were to happen, bird flu could potentially start spreading between people.
Influenza viruses are covered with two lollipop-shaped proteins called hemagglutinin and neuraminidase, which allow the virus to attach to “healthy” cells and infect them.
Current influenza vaccines recognise hemagglutinin proteins, and prevent them from infecting a person’s cells.
The scientists tested blood samples from over 150 people born between 1927 and 2016 for antibodies to H5N1.
Blood samples from older adults born prior to 1968 who were likely first exposed to H1N1 or H2N2 in childhood had higher levels of antibodies that could bind to the H5N1 virus.
An individual’s birth year was found to be linked to the amount of H5N1-fighting antibodies in their blood. Young children who had not yet been exposed to seasonal flu viruses possessed low levels of antibodies that could fight H5N1.
Researchers also obtained blood samples from a separate group of individuals born between 1918 and 2003 before and after they were vaccinated with a 2004 H5N1 vaccine.
It was again found that older adults had higher amounts of antibodies that could bind to H5 before vaccination. Following vaccination, H5 antibodies increased slightly in older adults, but increased substantially in children. These antibodies bound to both the 2004 H5N1 virus and to the clade 2.3.4.4b H5N1 virus that is circulating at the moment.
Hensley said: “In the event of an H5N1 pandemic, all age groups will likely be highly susceptible, but it is possible that the highest disease burden will be in children. If this is the case, children should be prioritised for H5N1 vaccinations.”
