Subj : Immunological memory provides long-term
To   : All
From : ScienceDaily
Date : Wed Feb 02 2022 21:30:42

 Immunological memory provides long-term protection against coronavirus


  Date:
      February 2, 2022
  Source:
      University of Zurich
  Summary:
      Exposure to SARS-CoV-2 by infection or vaccination generates
      immune cells that provide long-term immunity. These long-lived
      memory T cells play a key role in preventing severe cases of
      COVID-19. Researchers have now discovered how these memory T
      cells form.



FULL STORY
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Exposure to SARS-CoV-2 by infection or vaccination generates immune cells
that provide long-term immunity. These long-lived memory T cells play
a key role in preventing severe cases of Covid-19. Researchers at the
University of Zurich have now discovered how these memory T cells form.


==========================================================================
Many questions about how exposure to SARS-CoV-2 by infection or
immunization might result in long-term protective immunity remain
unanswered. Onur Boyman, head of the Department of Immunology, and his
research team at the University of Zurich and the UniversityHospital
Zurich have now taken a closer look at how this long-lived protection
is formed. Together with researchers from ETH Zurich, they identified
specific signaling pathways that determine when immune cells develop
into so-called memory T cells.

From short-lived killers to long-term memory T cells Virus-specific
antibodies produced by B cells are insufficient to effectively protect
against the novel coronavirus. The cellular immune response to SARS-
CoV-2 is just as important. Here, virus-specific CD8+ T cells play a
crucial role, as they can identify and kill the cells that have been
infected by the virus. These cytotoxic T cells eliminate viruses that
are hidden inside the host cells and help prevent the spread of millions
of newly formed viruses.

"These T cells are usually active for only a short time and disappear
quickly.

When it comes to establishing long-term protective immunity, it is
important to generate long-lived memory T cells that are activated very
quickly upon re- exposure to the virus," explains Onur Boyman. This
latter ability is referred to as immunological memory.

Previous studies have focused on the whole CD8+ T cell population
that formed in response to the virus. Boyman and his team have now
succeeded in tracking individual clones of SARS-CoV-2-specific CD8+
T cells in patients with Covid- 19, from the acute viral infection up
to one year after recovery. The researchers were also able to identify
the signaling pathways responsible for the transition of CD8+ T cells
from short-lived killers to long-lived memory cells -- and they found
a distinct molecular signature.

Immune messengers determine the cell type In their study, the researchers
were able to demonstrate that the signature of long-lived memory CD8+
T cells was already present during acute SARS-CoV- 2 infection, and these
cells could thus be distinguished from their short-lived counterparts at
an early stage. "The distinct signature of memory cells contained signals
of immune messengers, such as interferons, which are an important part of
the immune response against SARS-CoV-2 and also contribute to controlling
viral infections," says Onur Boyman.

Immune response varies from one patient to another The study helps to
unravel the complex way in which immunological memory to SARS-CoV-2 is
-- or is not -- formed and maintained. While some infections result
in robust and long-lasting T cell memory, others fail to do so. The
newly identified signature makes it possible to determine which type
of infection -- e.g. mild or severe, systemic or limited to mucosal
membranes - - gives rise to sustained immunity. The immune response
is also shaped by vaccines, which contain different ingredients and
adjuvants. "While everyone responds differently to the virus or a vaccine,
cellular immunity plays a crucial role in preventing severe cases of
Covid-19 in both vaccinated and recovered people," says Boyman.

Funding The study was supported by the Swiss National Science Foundation
(SNSF), the Clinical Research Priority Program CYTIMM-Z of the University
of Zurich (UZH), an innovation grant from the UniversityHospital Zurich
(USZ), the UZH Pandemic Fund, the Botnar Research Centre for Child Health
(BRCCH), and the Swiss Academy of Medical Sciences (SAMS).

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


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Journal Reference:
   1. Sarah Adamo, Jan Michler, Yves Zurbuchen, Carlo Cervia, Patrick
      Taeschler, Miro E. Raeber, Simona Baghai Sain, Jakob Nilsson,
      Andreas E.

      Moor, Onur Boyman. Signature of long-lived memory CD8+
      T cells in acute SARS-CoV-2 infection. Nature, 2021; DOI:
      10.1038/s41586-021-04280-x
==========================================================================

Link to news story:
https://www.sciencedaily.com/releases/2022/02/220202080322.htm

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