An article which CBC News referred to today:
SARS-CoV-2-specific T-cell epitope repertoire in convalescent and mRNA-vaccinated individuals:
A comparison of the repertoire of SARS-CoV-2-specific epitopes targeted by T cells induced by vaccination or natural infection reveals that T cells predominantly target non-spike epitopes in convalescent individuals, while there is a broader spike-specific CD8+ T-cell response in vaccinees...
www.nature.com
This morning, I read that paper and came up with a short digest, so non-scientists might understand it better.
ABSTRACT
Continuously emerging variants of concern (VOCs) sustain the SARS-CoV-2 pandemic. The SARS-CoV-2 Omicron/B.1.1.529 VOC harbours multiple mutations in the spike protein associated with high infectivity and efficient evasion from humoral immunity induced by previous infection or vaccination. By performing in-depth comparisons of the SARS-CoV-2-specific T-cell epitope repertoire after infection and messenger RNA vaccination, we demonstrate that spike-derived epitopes were not dominantly targeted in convalescent individuals compared to non-spike epitopes. In vaccinees, however, we detected a broader spike-specific T-cell response compared to convalescent individuals. Booster vaccination increased the breadth of the spike-specific T-cell response in convalescent individuals but not in vaccinees with complete initial vaccination. In convalescent individuals and vaccinees, the targeted T-cell epitopes were broadly conserved between wild-type SARS-CoV-2 variant B and Omicron/B.1.1.529. Hence, our data emphasize the relevance of vaccine-induced spike-specific CD8+ T-cell responses in combating VOCs including Omicron/B.1.1.529 and support the benefit of boosting convalescent individuals with mRNA vaccines.
MAIN
The SARS-CoV-2-specific T-cell epitope repertoire has been studied in some detail
(1,
2,
3,
4,
5,
6 (reviewed in Grifoni et al.
7); however, comparative in-depth studies of the epitope repertoire targeted by infection- versus vaccine-induced T-cell responses are lacking thus far. Thus, precise prediction of the immune escape potential of emerging VOCs including Omicron/B.1.1.529 from the T-cell response in convalescent individuals compared to vaccinees is hardly possible.
In this study, we evaluated SARS-CoV-2-specific T-cell responses in convalescent individuals recovered from SARS-CoV-2 infection (n = 19) as well as individuals after 2 (n = 16) and 3 (n = 7) doses of SARS-CoV-2 vaccination (Pfizer/BioNTech messenger RNA vaccine).
… …
In conclusion:
- Convalescent individuals target a variety of SARS-CoV-2-specific CD8+ T-cell epitopes over the complete SARS-CoV-2 proteome with spike-specific CD8+ T-cell responses being non-dominant.
- In contrast to the CD4+ T-cell response, CD8+ T-cell responses in vaccinees are focused on a broader repertoire of highly conserved spike-specific CD8+ T-cell epitopes leading to an increased cross-recognizing potential.
- Boosting convalescent individuals with mRNA vaccination results in a broader spike-specific CD8+ T-cell response.
- CD8+ and CD4+ T-cell responses in both convalescent individuals and vaccinees target epitopes that are highly conserved between WT SARS-CoV-2 variant B, Omicron/B.1.1.529 and potentially future emerging SARS-CoV-2 variants and thus cross-recognize these variants.
Hence, our data emphasize the relevance of mRNA vaccine-induced spike-specific CD8+ T-cell responses in combating emerging SARS-CoV-2 VOCs including Omicron/B.1.1.529 and support the benefit of also boosting convalescent individuals with mRNA vaccines.
I added a list of vocabulary & abbreviation to help readers understand some scientific jargon used in the paper, as Nature assumes readers have a scientific background. My list is not comprehensive. If other terms baffle you, just ask me, or look them up in Wikipedia.
Vocabulary & Abbreviations
VOC is an abbreviation for variant of concern of an infectious virus.
Proteome is the entire set of proteins expressed by a genome, cell, tissue, or organism. In the case of a virus infection, it's the set of expressed proteins encoded by the virus mRNA.
Epitopes are small fragments of foreign proteins (not made by the host) that become targets of anti-bodies and T-cells. (How these foreign proteins get detected, get partially digested into epitope fragments, and ultimately become the targets of dedicated immune cells is complex and fascinating. I can’t state it simply.)
Humoral immunity is caused by antibody proteins in circulating blood and lymphatic fluid. Antibody proteins are produced by immune system B-cells. Antibodies bind tightly to virus particles circulating inside an infected person, preventing them from entering other cells, and making more virus particles. These antibodies, bound to virus particles, are cleared from the blood, getting destroyed and eliminated in the process.
Cellular immunity is immunity from T-cells. In contrast to antibody proteins, some T-cells detect and kill host cells that have been infected by virus. It stops the manufacture of more virus particles. Unlike antibodies, which can be used once, T-cells work repeatedly.
CD4+ T-cell is a T-cell sub-type, also known as a Helper T-cell. It detects virus-infected cells, and secretes signals to other immune system cells (both B-cells and T-cells). These signals can stimulate the development of immature B- and T-cells, and can alert mature B- and T-cells to become active.
CD8+ T-cell is a T-cell sub-type, also known as a Killer T-cell. It detects virus-infected cells, and directly kills them.
