Persistent T cell response to omicron after infection and vaccination


Date:
January 19, 2022
Source:
Karolinska Institutet
Summary:
The omicron variant can partly evade the antibody response
provided by vaccination or infection with previous variants of
SARS-CoV-2. However, T cells still recognise omicron, scientists
report.



FULL STORY ==========================================================================
The omicron variant can partly evade the antibody response provided by vaccination or infection with previous variants of SARS-CoV-2. However,
T cells still recognise omicron, scientists at Karolinska Institutet in
Sweden report in a study published in the journal Nature Medicine.


========================================================================== Omicron has rapidly become the dominant variant of the SARS-CoV-2
virus. New data indicate that omicron is not only more infectious than
previous variants, it can also infect people with previous immunity by
evading what are known as neutralising antibodies.

Serious disease seems, however, to be relatively uncommon in people who
have been vaccinated or infected, suggesting that other components of
the immune system are still able to recognise omicron. A new study by researchers at Karolinska Institutet now shows that so-called memory
T cells formed following previous infection or mRNA vaccination also
respond to the omicron variant.

"Along with viral factors, such as a lower level of viral replication
in the lower airways, and other immune components, these results give
us a clearer picture that may explain why the protection against severe
omicron disease remains good in previously mRNA-vaccinated individuals,"
says principal investigator Marcus Buggert at Karolinska Institutet's
Center for Infectious Medicine.

The study is a collaboration with the Karolinska University Hospital
in Sweden and is based on blood samples from 40 vaccinated individuals,
48 individuals who had had a mild or severe SARS-CoV-2 infection, and 48 individuals who had previously been neither vaccinated nor infected. The samples from the vaccinated group were collected six months after their
second vaccine dose, and from the previously infected group 9 months
after confirmed infection in the spring of 2020, prior to the emergence
of the new viral variants. Other samples were taken from healthy donors
at the end of 2020.

Memory T cells in both the experimental groups displayed a good ability
to recognise the omicron spike protein; the best response, however,
was observed in the vaccinated group.

"These results suggest that booster immunisation may provide benefits
that extend beyond the induction of neutralising antibodies to enhance protection against recurrent episodes of severe COVID-19," says Dr
Buggert.

Even though the memory T-cell response was generally intact against
omicron, some individuals did not respond as well.

"We now want to understand why the response differs from one individual
to the next and if a third vaccine dose can augment the T cell response
to omicron even more," he says.

The study was financed with support from the SciLifeLab/KAW National
COVID-19 Research Program (financed by the Knut and Alice Wallenberg Foundation), the Swedish Research Council, Nordstjernan AB, The
Swedish Cancer Society, the Swedish Childhood Cancer Fund, the AAke
Wiberg Foundation, the Swedish Society of Medicine, Region Stockholm
and Karolinska Institutet. Marcus Buggert is consultant at Oxford
Immunotec. KI researcher and co-author Soo Aleman has received fees
from Gilead, AbbVie, MSD and Biogen and research grants from Gilead and
AbbVie. Co-author Alessandro Sette at La Jolla Institute is a consultant
at Gritstone Bio, Flow Pharma, Arcturus Therapeutics, ImmunoScape,
CellCarta, Avalia, Moderna, Fortress and Repertoire. La Jolla Institute
has applied for a patent relating to different aspects of the T-cell
epitope and vaccine design.

========================================================================== Story Source: Materials provided by Karolinska_Institutet. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Yu Gao, Curtis Cai, Alba Grifoni, Thomas R. Mu"ller, Julia Niessl,
Anna
Olofsson, Marion Humbert, Lotta Hansson, Anders O"sterborg,
Peter Bergman, Puran Chen, Annika Olsson, Johan K. Sandberg,
Daniela Weiskopf, David A. Price, Hans-Gustaf Ljunggren, Annika
C. Karlsson, Alessandro Sette, Soo Aleman, Marcus Buggert. Ancestral
SARS-CoV-2-specific T cells cross-recognize Omicron. Nature
Medicine, 2022; DOI: 10.1038/d41591-022- 00017-z ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220119121348.htm

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