BFF-51, 52 Scientists look beyond antibodies in virus immunity hunt

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Scientists look beyond antibodies in virus immunity hunt

PARIS, Aug 7, 2020 (BSS/AFP) – Could the ghosts of your previous
colds help protect you from COVID-19, even if you have never been
infected by the new coronavirus spreading across the planet?

Scientists are investigating a poorly-understood immune mechanism in
the body that they hope could help efforts to curb the pandemic.

At the moment, people who think they have had the virus might get a
serological test to check for antibodies.

These proteins help fight off infection and may prevent them from
getting the disease again in the future — but there are signs that
with COVID-19 they could fade away within weeks.

This leaves the other instrument in the body’s toolkit — T
lymphocytes — a type of white blood cell responsible for the second
part of the immune response.

With little yet known about how they operate against COVID-19,
scientists are racing to fill in the gaps in our knowledge.

One hypothesis is that these T cells might help give people a level
of cross-immunity protection from COVID-19 because they “remember”
previous infections by other viruses in the same family, four of which
cause common colds.

“The immune system is complex,” said Andreas Thiel, who co-authored
a study that looked at the presence of T cells able to react to the
new coronavirus, both among those with confirmed infections and
healthy people.

The research, published last week in the journal Nature, found that
at least a third of adults that had never had COVID-19 have these T
cells.

“These most likely originate from previous infections with endemic
coronaviruses,” Thiel, a professor at Berlin-Brandenburg Center for
Regenerative Therapies, told AFP.

But he cautioned that much more research was needed to find out
whether their presence would necessarily mean immunity.

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– Virus family –

The research followed a study by a team in Singapore published in
Nature earlier in July that reached a similar conclusion.

Another study from the United States, published Tuesday in the
journal Science, found a number of T cells that reacted both to the
new virus, SARS-CoV-2, as well as to the coronaviruses that cause
colds.

“This could help explain why some people show milder symptoms of
disease while others get severely sick,” said co-author Daniela
Weiskopf, of La Jolla Institute for Immunology, in a statement.

This study builds on research, published in the journal Cell in May
by the same team, which detected these SARS-CoV-2 reacting T cells in
40 to 60 percent of people who had never had COVID-19.

– Lasting immunity? –

The vaccines currently in development for the new coronavirus seek
to trigger both types of immune response.

Previously attention, however, has largely focused on the immunity
conferred by antibodies.

“But we must not think that nothing else exists,” Yonathan Freund,
professor of emergency medicine at the Paris Pitie-Salpetriere
hospital, told AFP.

Studies have shown that the level of antibodies for patients who
have had COVID-19 drops rapidly, perhaps within a few weeks.

“That could mean two things: One, which would be catastrophic, is
that immunity to COVID does not last,” said Freund, adding that he
doubts this is the case.

The second possibility, he said, is that potential immunity exists
but “cannot be detected” by the serology tests for antibodies.

That would mean our calculations on the percentage of the population
who are potentially immune to the coronavirus, which are based on the
detection of antibodies, could be underestimated across the world.

A recent study at Sweden’s Karolinska University Hospital showed
that many people with mild or asymptomatic COVID-19 demonstrated a T
cell immune response to the virus, even if their antibody test was
negative.

But Freund stressed that discussions around T cells were mostly just
“hypotheses” for now.

And scientists are keen to emphasise that thorough, large-scale
research is needed before there would be any implications for tackling
the pandemic.

“Pet theories (are) fine in academic debates, but dangerous when
advising for policy,” Devi Sridhar, a professor of global public
health at the University of Edinburgh, said on Twitter this week.

She added that if there was clear evidence of wider public immunity
or that the virus was weakening she would be “delighted”.

“That is what we are all hoping for. But have to plan & prepare
according to current evidence & observational studies from around the
world,” she said.

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