Scientists look beyond antibodies in virus immunity hunt

Scientists look beyond antibodies in virus immunity hunt
Could the ghosts of your previous colds help protect you from COVID-19, regardless if you have never been infected by the brand new coronavirus spreading over the planet?

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

At the moment, persons who think they experienced the virus might get a serological test to check for antibodies.

These proteins help fight off infection and could prevent them from obtaining the disease again later on -- 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 portion of the immune response.

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

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

"The disease fighting capability is complex," said Andreas Thiel, who co-authored a report that viewed the occurrence of T cells in a position to react to the new coronavirus, both among people that have 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 really had COVID-19 have these T cells.

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

But he cautioned that a lot more research was needed to determine whether their occurrence would indicate immunity.

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

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

"This could help explain why some people show milder symptoms of disease while some 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 folks who had never really had COVID-19.

Lasting immunity?

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

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

"But we must not feel 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've had COVID-19 drops rapidly, perhaps within a couple weeks.

"That could mean a couple of things: One, which would be catastrophic, is that immunity to COVID will not last," said Freund, adding that he doubts here is the case.

The next possibility, he said, is that potential immunity exists but "can't 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 possibly be underestimated around 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, whether or not their antibody test was negative.

But Freund stressed that discussions around T cells were mostly just "hypotheses" for the present time.

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 proof wider public immunity or that the virus was weakening she'd be "delighted".

"That is what we all have been hoping for. But need to plan & prepare according to current evidence & observational studies from all over the world," she said.
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