Universal flu vaccine on the horizon
Many vaccines can provide nearly complete protection against infection for decades. Unfortunately, the flu vaccine is not one of them. Yet. Recent studies suggest that a universal flu vaccine may be on the horizon.
The influenza virus is not a single virus, but rather a group of viruses of multiple types and subtypes. Only a few infect humans, but they mutate constantly, and different strains predominate in different years.
The annual flu vaccine targets the highly variable head of the haemagglutinin (HA) protein, which allows the virus to bind to and infect cells. As a result, vaccine development is essentially an annual guessing game. Scientists predict which strains they expect to predominate in the upcoming flu season and develop a vaccine against the top three expected strains.
The HA stem mutates less frequently than the head, so a vaccine targeting this portion of the protein could allow the body to neutralize a wider variety of flu virus. A single dose might even last for years or decades.
Several recent reports suggest this approach may work well. In the first of these, a group from the Mount Sinai School of Medicine published a May 2010 report in mBio indicating that a vaccine made of headless HA protected mice against lethal levels of virus. Others have reported similar success using different methods.
NIAID uses universal flu vaccine to protect mice, ferrets and monkeys
An NIH News release from July 2010 reports that National Institute of Allergy and Infectious Diseases (NIAID) scientists have successfully protected several animal species from multiple influenza strains with a two-step (prime-boost) vaccination process.
The researchers gave the animals two vaccines derived from Influenza A H1 subtypes. The first was a DNA vaccine of the HA protein. The second was either:
- A dose of the 2006-2007 seasonal vaccine, or
- An adenovirus engineered to contain HA protein
The vaccinated animals developed an immune response to the HA stem and were able to neutralize multiple subtypes from multiple years. In addition, 80 percent of fully vaccinated animals receiving a normally fatal dose of a strain from 1934 survived.
The University of Adelaide's synthetic universal flu vaccine protects mice
In February 2011, Dr. Darren Miller and his colleagues reported a successful trial of a synthetic universal flu vaccine delivered as a nasal spray to mice. This vaccine also targets conserved areas of HA, but is not derived from the influenza virus.
Instead, this vaccine is a manufactured peptide that completely protected mice against an H3N2 virus. It provided partial protection against so-called "bird flu" (H5N1).
A synthetic vaccine has some potential advantages. It would likely be less allergenic than those made from viruses grown in eggs. In addition, if the nasal spray promotes a local immune response, it could provide stronger protection at the virus' point of entry.
Oxford University's universal flu vaccine stimulates T-cell production in humans
In January 2011, researchers at Oxford's Jenner Institute, led by Dr. Sarah Gilbert, reported successful human trials of a vaccine that boosts the body's T-cell immunity against two viral proteins, nucleoprotein and matrix protein 1, that are greater than 90 percent conserved in all influenza A strains.
The team recruited 28 volunteers between 18 and 50 years of age. Each volunteer received one of three vaccinations:
- A low-dose intradermal dose
- A low-dose intramuscular dose
- A high-dose intramuscular dose
Blood samples taken at regular intervals showed a significant T-cell response in all groups. The high-dose group had a greater response, but also a higher incidence of systemic side effects.
In speaking with the Guardian News, Dr. Gilbert posited that the next step might be to try combining this vaccine and the traditional vaccine to provide both active antibodies and active T-cells.
The Jenner group is also testing their vaccine in people over 50 who do not respond particularly well to traditional vaccines, with the hope that it may be more effective in this group.
These reports are exciting, and a universal flu vaccine certainly seems closer than ever, but it will take more time and research to determine the most effective approach.
