Immune cells against COVID-19 stay high in number six months after vaccination, study shows
Findings also show that vaccine-elicited fighters recognize and help
attack coronavirus delta variant

Date:
November 16, 2021
Source:
Johns Hopkins Medicine
Summary:
A recent study provides evidence that CD4+ T lymphocytes -- immune
system cells also known as helper T cells -- produced by people
who received either of the two available messenger RNA (mRNA)
vaccines for COVID-19 persist six months after vaccination at only
slightly reduced levels from two weeks after vaccination and are
at significantly higher levels than for those who are unvaccinated.



FULL STORY ==========================================================================
A recent study by Johns Hopkins Medicine researchers provides evidence
that CD4+ T lymphocytes -- immune system cells also known as helper T
cells - - produced by people who received either of the two available
messenger RNA (mRNA) vaccines for COVID-19 persist six months after
vaccination at only slightly reduced levels from two weeks after
vaccination and are at significantly higher levels than for those who
are unvaccinated.


==========================================================================
The researchers also found that the T cells they studied recognize and
help protect against the delta variant of SARS-CoV-2, the virus that
causes COVID- 19. According to the U.S. Centers for Disease Control and Prevention, the delta variant -- currently the predominant strain of
SARS-CoV-2 in the United States -- causes more infections and spreads
faster than earlier forms of the virus.

The study findings were first reported online Oct. 25, 2021, in the
journal Clinical Infectious Diseases.

"Previous research has suggested that humoral immune response -- where
the immune system circulates virus-neutralizing antibodies -- can drop
off at six months after vaccination, whereas our study indicates that
cellular immunity - - where the immune system directly attacks infected
cells -- remains strong," says study senior author Joel Blankson, M.D.,
Ph.D., professor of medicine at the Johns Hopkins University School of Medicine. "The persistence of these vaccine-elicited T cells, along with
the fact that they're active against the delta variant, has important implications for guiding COVID vaccine development and determining
the need for COVID boosters in the future." To reach these findings,
Blankson and his colleagues obtained blood from 15 study participants (10
men and five women) at three times: prior to vaccination, between seven
and14 days after their second Pfizer/BioNTech or Moderna vaccine dose,
and six months after vaccination. The median age of the participants
was 41 and none had evidence of prior SARS-CoV-2 infection.

CD4+ T lymphocytes get their nickname of helper T cells because
they assist another type of immune system cell, the B lymphocyte (B
cell), to respond to surface proteins -- antigens -- on viruses such as SARS-CoV-2. Activated by the CD4+ T cells, immature B cells become either plasma cells that produce antibodies to mark infected cells for disposal
from the body or memory cells that "remember" the antigen's biochemical structure for a faster response to future infections. Therefore, a CD4+
T cell response can serve as a measure of how well the immune system
responds to a vaccine and yields humoral immunity.



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In their study, Blankson and colleagues found that the number of helper
T cells recognizing SARS-CoV-2 spike proteins was extremely low prior
to vaccination - - with a median of 2.7 spot-forming units (SFUs, the
level of which is a measure of T cell frequency) per million peripheral
blood mononuclear cells (PBMCs, identified as any blood cell with a round nucleus, including lymphocytes). Between 7 and 14 days after vaccination,
the T cell frequency rose to a median of 237 SFUs per million PBMCs. At
six months after vaccination, the level dropped slightly to a median
of 122 SFUs per million PBMCs -- a T cell frequency still significantly
higher than before vaccination.

The researchers also looked six months after vaccination at the ability
of CD4+ T cells to recognize spike proteins atop the SARS-CoV-2 delta
variant. They discovered the number of T cells recognizing the delta
variant spike protein was not significantly different from that of T
cells attuned to the original virus strain's protein.

Although the study was limited because of the small number of
participants, Blankson feels it pinpoints areas that merit further
research.

"The robust expansion of T cells in response to stimulation with
spike proteins is certainly indicated, supporting the need for more
study to show booster shots do successfully increase the frequency of SARS-CoV-2-specific T cells circulating in the blood," says Blankson. "The added bonus is finding that this response also is likely strong for
the delta variant." Along with Blankson, the members of the study team
from Johns Hopkins Medicine are study lead author Bezawit Woldemeskel
and Caroline Garliss.

This study was supported by the Johns Hopkins COVID-19 Vaccine-related
Research Fund.

The authors do not have financial or conflict of interest disclosures.

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


========================================================================== Journal Reference:
1. Bezawit A Woldemeskel, Caroline C Garliss, Joel N Blankson. mRNA
Vaccine-
Elicited SARS-CoV-2-Specific T cells Persist at 6 Months and
Recognize the Delta Variant. Clinical Infectious Diseases, 2021;
DOI: 10.1093/cid/ ciab915 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211116111404.htm

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