A Universal Flu Vaccine?
Could it be that 21st century vaccine technology might eventually eliminate the need for the seasonal flu shot?
Several presenters at ImVacS: The Immunotherapeutics & Vaccine Summit, which is taking place this week in Cambridge, Massachussets, highlighted progress on the search for a universal influenza vaccine to the 250 scientists and vaccine industry leaders who gathered for the industry-sponsored conference. One project being led by researchers from Oxford University employs a modified vaccinia Ankara (MVA) viral vector-based vaccine candidate that is designed to minimize the severity of influenza symptoms following infection by inducing strong cellular immune responses, primarily CD8+ T-cell responses. While the vaccine is not designed to prevent infection, it could potentially minimize transmission by muting the symptoms that cause people to spread the respiratory illness. The MVA vaccine candidate targets two internal antigens that are highly conserved among influenza strains in diverse populations. The vaccine candidate, which is administered intramuscularly, is now being tested in a Phase IIa trial.
Meanwhile, a research team from the University of Colorado Denver Health Sciences Center is tackling the hemagglutinin (HA) protein, the influenza surface protein that seasonal vaccines target. Because the HA protein's structure is so unstable and prone to near-constant conformational changes, the seasonal vaccine must be updated yearly. The Denver team, however, has designed a vaccine candidate that could potentially protect against H1 and H3 subtypes common in many influenza strains by stabilizing the stem of the HA protein. This candidate is currently being tested in rabbits and mice.
Still, while the notion of a universal influenza vaccine is an attractive one, some remain skeptical. "A lot of people would like to see a silver bullet, but I don't think you will because it so complicated," said Frank Arnold, senior program manager in vaccine advanced development for the influenza division of the Biomedical Advanced Research and Development Authority (BARDA), a division of the US Department of Health and Human Services.
Arnold noted, however, the robust field of influenza candidates. Along with the 27 influenza vaccines now licensed globally, there are now nearly 90 vaccine candidates in the clinical pipeline, including seven in Phase III trials. Those furthest along are seasonal vaccine candidates using conventional methods, but many of the early stage vaccine candidates use platforms and technologies, such as plant-based systems that allow you to make the vaccine in eight weeks compared to the six months it now takes to make the seasonal flu vaccine, which is grown in eggs. These newer technologies could dramatically reduce the time and cost of flu vaccine development.