Immune system has long-term defenses after mild COVID-19; children may
be key carriers of virus variants
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[May 25, 2021]
By Nancy Lapid
(Reuters) - The following is a roundup of
some of the latest scientific studies on the novel coronavirus and
efforts to find treatments and vaccines for COVID-19, the illness caused
by the virus.
Immune system may never forget mild COVID-19
Months after recovery from mild COVID-19, when antibody levels in the
blood have declined, immune cells in bone marrow remain ready to pump
out new antibodies against the coronavirus, researchers reported on
Monday in Nature. Upon infection, short-lived immune cells are generated
quickly to secrete an early wave of protective antibodies. As the immune
cells die out, antibody levels decline. But a pool of these immune
cells, called long-lived plasma cells, is held in reserve after
infection. Most of them migrate to the bone marrow, explained coauthor
Ali Ellebedy of Washington University School of Medicine in St. Louis.
His team obtained bone marrow samples from 19 patients seven months
after the onset of mild COVID-19. Fifteen had long-lived plasma cells
secreting antibodies against the coronavirus. Five of the 15 had second
bone marrow biopsies 11 months after symptom onset and all still had
long-lived plasma cells secreting antibodies against SARS-CoV-2.
Ellebedy, in a statement, noted that these cells are "just sitting in
the bone marrow and secreting antibodies. They have been doing that ever
since the infection resolved, and they will continue doing that
indefinitely... These cells will live and produce antibodies for the
rest of people's lives." It is not clear yet whether the same results
would be seen in survivors of moderate to severe COVID-19, the authors
said.
Coronavirus variants seen more often in young U.S. children
Young children appear to be significant carriers of more contagious
variants of the new coronavirus, such as the ones identified in the UK
and in California, according to a new U.S. study. From March 2020 to
April 2021, researchers at nine children's hospitals tested a total of
2,119 COVID-19 patients age 18 or younger for so-called variants of
concern, along with key mutations that help the variants become more
contagious or hide from the patient's immune system. "In total, we
identified 560 of these important mutations, and 75% (420/560) ... were
in children less than 12 years of age, the population that is currently
not eligible for COVID-19 vaccines," said Jennifer Dien Bard of
Children's Hospital Los Angeles, lead author of a report posted on
Monday on medRxiv ahead of peer review. The results provide "clear
evidence" of the emergence of variants of concern in pediatric patients
across diverse geographies and socioeconomic populations in the United
States, the researchers said in their paper. They added that the results
highlight the need for ongoing monitoring of pediatric populations "who
will be among the last groups to receive vaccination and who are key to
ending this pandemic."
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A woman holds a small bottle labelled with a "Coronavirus COVID-19
Vaccine" sticker and a medical syringe in this illustration taken
October 30, 2020. REUTERS/Dado Ruvic/File Photo
Dentures may harbor more bacteria during COVID-19
Denture wearers infected with the coronavirus may be more likely to
harbor bacteria that increase their risk for additional infections
on top of COVID-19, a small study suggests. Researchers analyzed
removable dentures from 30 patients with COVID-19 and 30 healthy
individuals. Swabbing the surface of the dentures yielded
Streptococcus species in 93.3% of COVID-19 patients versus 40% of
healthy volunteers, and Klebsiella pneumonia bacteria in 46.7% of
COVID-19 patients versus 13.4% of the other group. All of these
microorganisms are seen as potentially important causes of
additional bacterial infections in hospitalized COVID-19 patients
that could lead to or worsen problems such as respiratory distress
syndrome and pneumonia, the researchers reported on Friday in The
Journal of Prosthetic Dentistry. They recommend that dental
prostheses in COVID-19 patients be tested and that appropriate
medications be used to prevent the invasion of bacteria in
vulnerable individuals.
(Reporting by Nancy Lapid; Editing by Bill Berkrot)
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