Quadrivalent flu vaccines will be on offer this season in the US, but the hunt for a "universal" flu vaccine still continues. Now an Imperial College research team led by Professor Ajit Lalvani says that clues offered by the 2009 UK swine flu outbreak highlight the critical importance of CD8 T cells in universal flu protection. The team also identified the exact characteristics of T cells that were crossreactive.
While previous studies have hinted at the link between T cells and symptomatic protection from influenza, this was study was unique in testing the theory in humans during a pandemic. Unlike antibodies which target the ever-changing surface of the virus, CD8 T cells target the viral core which isn't altered between strains. The pandemic offered an opportunity to test whether the CD8 T cells could limit symptomatic illness in individuals who were encountering a particular strain for the first time.
Reporting in Nature Medicine on Sunday, the researchers explain how they followed 342 adults through the H1N1 pandemic and found a correlation between CD8 T cell levels and the clinical outcomes of H1N1 infection.
Healthy volunteers donated blood samples and were handed nasal swabs for use if they felt any symptoms of the flu. Lalvani's team found that individuals who fell more severely ill with the flu had fewer CD8 T cells in their blood than those who became infected with the flu but had only mild symptoms.
"The 2009 pandemic provided a unique natural experiment to test whether T cells could recognise, and protect us against, new strains that we haven't encountered before and to which we lack antibodies," said Lalvani, who will be speaking at this year’s World Vaccine Congress Europe. "Our findings suggest that by making the body produce more of this specific type of CD8 T cell, you can protect people against symptomatic illness."
Such findings could guide researchers down the right path towards a universal flu vaccine, and the identification of key fragments of the virus' internal core provides researchers with a "blueprint" for the design. "We already know how to stimulate the immune system to make CD8 T cells by vaccination. Now that we know these T cells may protect, we can design a vaccine to prevent people getting symptoms and transmitting infection to others. This could curb seasonal flu annually and protect people against future pandemics," Lalvani added.
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Read the Nature Medicine journal article >
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