While some antibodies work together to recruit white blood cells, other antibodies block their recruitment.
Image credit: McMaster University
According to the World Health Organization (WHO), the annual flu epidemics are thought to result in between 3-5 million cases of severe illness worldwide and between 250,000-500,000 deaths every year.
McMaster University's Michael G. DeGroote School of Medicine in Canada, the Icahn School of Medicine at Mount Sinai in New York, and the University of Chicago conducted the new research to build upon their earlier study that uncovered a class of antibodies that are capable of neutralizing the most dangerous types of influenza viruses.
The newly discovered antibodies can train the immune system to detect a part of the virus that remains the same each year, which could pave the way toward a universal flu vaccine that requires one injection with lifelong protective effects. Part of the virus is always recognizable - even as the virus changes and mutates - which means that the body can safeguard against flu.
The Centers for Disease Control and Prevention (CDC) recommend that everyone 6 months of age and older should get the flu vaccine every season. The seasonal flu shot protects against three or four influenza viruses that research indicates will be the most common during the upcoming season.
Seasonal flu vaccines work by causing antibodies to develop in the body about 2 weeks after vaccination. These antibodies bind to the virus and prevent it from infecting cells.
Universal vaccines work in the same way, but they also recruit white blood cells to destroy infected cells. While certain antibodies work together to recruit the helpful white blood cells, other antibodies block their recruitment. The researchers found that where the antibodies bind on the virus makes a significant difference.
Antibodies bind to specific locations to 'call in' white blood cells
"Antibodies work in two ways. One way is by binding to the virus and preventing it from infecting cells. Another way is by recruiting other cells of your immune system in to kill infected cells," says senior author Dr. Matthew Miller, Ph.D., assistant professor in the Department of Biochemistry and Biomedical Sciences at McMaster.
"Universal vaccines do the latter, but everybody used to think as long as antibodies were present, these cells would be called in. Our findings show that just having antibodies isn't enough. You have to have antibodies that bind to very specific places on the virus. And so now we know the places where antibodies have to bind to call in these cells, we can modify our vaccines so that we can generate those antibodies in higher numbers," he adds.
The flu shot remains the recommended route to protect against the virus. How well a flu vaccine works each year depends on factors such as the health and age of the person being vaccinated.
However, other factors that affect the outcome of a flu vaccine are the similarity between seasonal vaccine viruses and circulating viruses, and also whether a live or inactivated vaccine is used.
A universal flu vaccine could prevent mismatches between the vaccine and circulating viruses, and it could protect against all flu strains and the occurrence of flu pandemics.
"Using this knowledge, what we can now do is specifically design our universal vaccine to generate the most desirable types of antibodies and avoid antibodies that block the functions that we want. So in doing that we can make sure that the vaccine will work in the most effective way possible."
Dr. Matthew Miller, Ph.D.
In addition to protecting against flu, the findings by Dr. Miller and team - published in the journal Proceedings of the National Academy of Sciences - may assist with improvements to treatments for other diseases that could use antibodies that recruit white blood cells as a therapy, such as cancer and HIV.
Dr. Miller concludes by saying that a universal flu vaccine could become available within the next 5 years.