Body's own T cells identified as potential source of universal flu
23 September 2013
A virus-killing immune cell, called CD8 T, is more numerous in
the body of people who avoid more serious bouts of flu, according to
research at Imperial College London, and could be the source of a
new type of vaccine.
As the cell can attack all strains of the virus, finding a way to
triggering the body to produce more of these cells could be a way to
prevent symptoms of flu.
Researchers at Imperial College asked volunteers to donate blood
samples just as the 2009 swine flu pandemic was getting underway and
report any symptoms they experienced over the next two flu seasons.
They found that those who avoided severe illness had more CD8 T
cells, a type of virus-killing immune cell, in their blood at the
start of the pandemic.
They believe a vaccine that stimulates the body to produce more
of these cells could be effective at preventing flu viruses,
including new strains that cross into humans from birds and pigs,
from causing serious disease.
Professor Ajit Lalvani from the National Heart and Lung Institute
at Imperial College London, who led the study, said: “New strains of
flu are continuously emerging, some of which are deadly, and so the
Holy Grail is to create a universal vaccine that would be effective
against all strains of flu.”
Today’s flu vaccines make the immune system produce antibodies
that recognise structures on the surface of the virus that are
specific to each strain, which means health authorities have to
guess which strains will outbreak each year. But they are usually
one step behind as they have to be changed each year as new viruses
with different surface structures evolve.
Previously, experimental models had suggested that T cells may
protect against flu symptoms but until now this idea has not been
tested in humans during a pandemic.
Professor Lalvani’s team rapidly recruited 342 staff and students
at Imperial to take part in their study in autumn 2009. The
volunteers donated blood samples and were given nasal swabs. They
were sent emails every three weeks asking them to fill in a survey
about their health. If they experienced flu symptoms, they took a
nasal swab and sent it back to the lab.
They found that those who fell more severely ill with flu had
fewer CD8 T cells in their blood, and those who caught flu but had
no symptoms or only mild symptoms had more of these cells.
Professor Lalvani said, “The immune system produces these CD8 T
cells in response to usual seasonal flu. Unlike antibodies, they
target the core of the virus, which doesn’t change, even in new
pandemic strains. 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.
“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. This provides the blueprint for developing a
universal flu vaccine.
“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.”
S Sridhar et al. Cellular immune correlates of
protection against symptomatic pandemic influenza. Nature