Each year, seasonal influenza affects around 10% of European citizens, causing hundreds of thousands of hospitalisations across the continent. And while vaccines do exist, the highly variable nature of the influenza virus means sensitive groups like children and the elderly have to get vaccinated every year.
Since these vaccines are based on predictions of the evolution of virus strains, mismatches occur quite frequently – which explains why the development of a universal vaccine, capable of tackling all variations of the virus, has been high of researchers’ agendas for years. Most recently in 2015, the strain has changed at last minute, making the vaccine less effective than initially expected.
A new study conducted on mice has just brought researchers at the United States’ National Institute of Allergy and Infectious Diseases (NIAID) one step closer to this achievement. By presenting a cocktail of flu proteins to the immune system, the team found out that they can induce immunity to strains that the animals have never encountered.
‘For a decade or more, it has been a big dream of the influenza community to develop a universal influenza vaccine, one that would provide you protection against multiple current or future strains of influenza, whether they are from humans or animals,’ study researcher Jeff Taubenberger, a pathologist and infectious-disease specialist at NIAID, said. ‘What we have done is design a strategy where you don’t have to think about matching the vaccine antigen to the virus at all.’
To get to this result, the team used a virus-like particle vaccine cocktail that expressed four of the 16 common H proteins (H1, H3, H5 and H7). H1 and H3 have been the major causes of human seasonal flu since 1918, while H5 and H7 have caused flu outbreaks among bird populations which had pandemic potential.
‘What we got was really kind of unexpected and kind of remarkable,’ Taubenberger said. ‘Almost all of the animals that received the novel vaccine survived, including mice infected with the 1918 influenza virus, H5N1 or H7N9 bird influenza viruses, and importantly mice that were challenged with viruses that expressed hemagglutinin subtypes that were not in the vaccine at all, viruses that expressed H2, H6, H10, and H11. You are challenging the mice with viruses that have a completely different protein on its surface that are not in the vaccine, so the mice should theoretically not have immunity to it.’
About 95 percent of the mice administered with the mix were found to be protected against the eight strains of flu tested. This level of protection surpassed the expectations of the team, to the point that they are still unsure how it even works. Unlike in other vaccines, it would seem that the antibody response is not the main reason the new spray works: T cells, a type of white blood cell, might also be playing a role, according to Taubenberger.
The researchers are now investigating how the vaccine works, and they already demonstrated that it was effective for at least 6 months. They’re also testing it in ferrets, which are the animals most often used to mimic how humans catch and resist the flu. If those tests show promising results, human safety trials for the new vaccine could begin next year, with clinical trials for effectiveness starting the year after that, Taubenberger said.