PTI
Washington, November 26
An experimental mRNA-based vaccine against all 20 known subtypes of the flu virus provides broad protection against otherwise deadly flu strains in initial tests, according to a study.
This could one day serve as a general preventive measure against future flu pandemics, said researchers from the University of Pennsylvania, US.
According to the study, tests in animal models showed that the vaccine dramatically reduced signs of illness and prevented death, even when the animals were exposed to flu strains other than those used in the vaccine’s production.
The “multivalent” vaccine, which the researchers described in a paper published in the journal Science, uses the same messenger ribonucleic acid (mRNA) technology used in Pfizer and Moderna’s SARS-CoV-2 vaccines, the study said.
This mRNA technology, which enabled these COVID-19 vaccines, was pioneered at Penn, the study said.
“The idea here is to have a vaccine that will give people a baseline level of immune memory to different flu strains so that there will be much less illness and death when the next flu pandemic occurs,” said lead study author Scott Hensley.
Influenza viruses periodically cause pandemics with massive deaths. The most famous of these is the “Spanish Flu” pandemic of 1918-1919, which killed at least tens of millions of people worldwide.
Influenza viruses can circulate in birds, pigs, and other animals, and pandemics can begin when one of these strains crosses into humans and acquires mutations that make it better adapted to spread among humans.
Current flu vaccines are simply “seasonal” vaccines that protect against recently circulating strains but are not expected to protect against new, pandemic strains.
The strategy used by the Penn researchers was to vaccinate using immunogens — a type of antigen that stimulates immune responses — from all known subtypes of influenza to induce broad protection, the study said.
The vaccine is not expected to provide “sterilizing” immunity that completely prevents viral infections. Instead, the new study showed that the vaccine induces a memory immune response that can be quickly recalled and adapted to new pandemic virus strains, significantly reducing severe illness and death from infections.
“This would be comparable to first-generation SARS-CoV-2 mRNA vaccines that targeted the original Wuhan strain of the coronavirus.
“Contrary to later variants such as Omicron, these original vaccines did not completely block viral infections, but continued to provide lasting protection against severe disease and death,” Hensley said.
The experimental vaccine, when injected and taken up by recipient cells, begins to produce copies of a key influenza virus protein, the hemagglutinin protein, for all twenty influenza hemagglutinin subtypes—H1 through H18 for influenza A viruses and two more for influenza B viruses .
“For a conventional vaccine, immunizing against all these subtypes would be a big challenge, but with mRNA technology, it’s relatively easy,” Hensley said.
In mice, the mRNA vaccine induced high levels of antibodies that remained elevated for at least four months and responded strongly to all 20 influenza subtypes. What’s more, the vaccine appears relatively unaffected by previous exposures to the flu virus, which can skew the immune response to conventional flu vaccines.
The researchers noted that the antibody response in the mice was strong and broad, regardless of whether the animals had been exposed to the flu virus before or not.
Hensley and his colleagues are currently designing human clinical trials, he said. The researchers predict that if these trials are successful, the vaccine could be useful in inducing long-term immune memory against all subtypes of influenza in people of all age groups, including young children.
“We think this vaccine can significantly reduce the chances of you ever getting a severe flu infection,” Hensley said.
In principle, he added, the same multivalent mRNA strategy could be used for other viruses with pandemic potential, including coronaviruses.
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