Each year, the public is advised to get the seasonal flu vaccine, a vaccine that’s custom made for the strains of influenza virus — type A and type B — that research has found will be most common during the upcoming season, according to the Centers for Disease Control and Prevention (CDC). But researchers from St. Jude’s Children’s Research Hospital have discovered a way to develop a universal vaccine that could protect against the most common strains just as much as the deadliest pandemic strains.
The study highlights the researchers’ success at using the immunosuppressant drug, rapamycin, to inhibit the protein mTOR from producing antibodies shaped for specific strains of the influenza virus. Current vaccines encourage the production of antibodies that bind tightly to specific regions of hemagglutinin (HA) and neuraminidase (NA) proteins on the virus — the shape of these proteins change almost every year.
Inhibiting mTOR activity delayed the formation of an immune structure known as the germinal center, which aids in shaping antibodies to their target proteins. By doing this, researchers were able to administer a vaccine to mice that produced antibodies able to target proteins shared by most influenza viruses.
“This study has changed our approach to developing a universal flu vaccine,” Maureen McGargill, co-author of the study and an assistant member of the St. Jude Department of Immunology, said in a statement. “Instead of trying to enhance a highly specific, targeted immune response, our results show that a more diverse, less focused response provides a broader repertoire of antibodies that target different flu strains.”
The researchers vaccinated mice against the H3N2 influenza A strain, a strain that causes relatively mild symptoms, such as runny nose and cough. A few weeks later, the mice were exposed to the more dangerous H5N1 and H7N9 strains, also known as bird flu, which cause acute respiratory distress, abdominal pain, pneumonia, altered mental states, seizures, and sometimes death. But they found that the mice didn’t fall ill to the dangerous strains. When they transferred antibody-rich serum from vaccinated mice to unvaccinated mice, they also found that these mice became resistant to infection — the antibodies did indeed protect.
Although death from the flu are relatively rare — only 500 each year, or 0.2 per 100,000 people — getting sick with strains such as the bird flu are extremely dangerous. Nearly 600 cases of bird flu have been reported from 15 countries since 2003, and about 60 percent of people infected by H5N1 died from the illness, according to the U.S. Department of Health & Human Services.
McGargill’s approach to flu vaccination is among other attempts to create a universal vaccination. European researchers also created a vaccine that attacks two proteins, known as M and NP proteins, that don’t change as the rest of the virus mutates. This universal vaccine has already been proven to work in a small human trial of about 100 people. If it proves to be successful in other human trials, it could be available as early as 2018, the researchers said, according to the Daily Mail.
Source: Keating R, Hertz T, McGargill M, et al. The kinase mTOR modulates the antibody response to provide cross-protective immunity to lethal infection with influenza virus. Nature Immunology. 2013.