See­ing be­yond an­ti­bod­ies in im­mu­nity hunt

Kuwait Times - - Front Page -

PARIS: 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 COVID19 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.

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.

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 em­pha­size 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. — AFP

— AFP

HANOI: A health worker wear­ing pro­tec­tive cloth­ing con­ducts a swab test on a woman at a test­ing cen­ter for COVID-19 yes­ter­day.

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