A big question on people's minds these days: How long does immunity to SARS-CoV-2 last following infection?

Now a research team from La Jolla Institute for Immunology (LJI), The University of Liverpool and the University of Southampton has uncovered an interesting clue. Their new study suggests that people with severe COVID-19 cases may be left with more of the protective "memory" T cells needed to fight reinfection.

The data from this study suggest people with severe COVID-19 cases may have stronger long-term immunity.

"This study highlights the enormous variability in how human beings react to a viral challenge," adds co-leader Christian H Ottensmeier, M.D., Ph.D., FRCP, a professor at the University of Liverpool and adjunct professor at LJI.

Since early in the COVID-19 pandemic, scientists at LJI have investigated which antibodies and T cells are important for fighting SARS-CoV-2. As experts in genomics, Vijayanand and Ottensmeier have used sequencing tools to uncover which T cell subsets may control disease severity. In October, the team published the first detailed look at how CD4+ T cells respond to the virus.

For the new study, the researchers used a technique called single-cell transcriptomics analysis to study the expression of individual genes of more than 80,000 CD8+ T cells isolated from both COVID-19 patients and non-exposed donors. CD8+ T cells are the cells responsible for destroying virus-infected host cells. "Memory" CD8+ T cells are also important for protecting the body from reinfection against many viruses.

The team studied CD8+ T cells from 39 COVID-19 patients and 10 subjects who had never been exposed to the virus (their blood samples were given before the pandemic). Of the COVID-19 patients, 17 patients had a milder case that did not require hospitalization, 13 had been hospitalized, and nine had needed additional ICU support.

To the researchers' surprise, they saw weaker CD8+ T cell responses in patients with milder COVID-19 cases. The researchers saw the strongest CD8+ T cell responses in the severely ill patients who required hospitalization or ICU support.

"There is an inverse link between how poorly T cells work and how bad the infection is," says Ottensmeier. "I think that was quite unexpected."

One could expect to see a stronger CD8+ T cell response in the mild cases, since these are the cases where the immune system was equipped to fight off a severe infection—but the study showed the opposite. In fact, CD8+ T cells in the milder cases showed the molecular signs of a phenomenon called T cell "exhaustion." In cases of T cell exhaustion, cells receive so much immune system stimulation during a viral attack that they are less effective in doing their jobs.

While more research is needed, Vijayanand and Ottensmeier think it is worth studying whether T cell exhaustion in the mild COVID-19 cases may hinder a person's ability to build long-term immunity.

"People who have severe disease are likely to end up with a good number of memory cells," says Vijayanand. "People with milder disease have memory cells, but they seem exhausted and dysfunctional—so they might not be effective for long enough."

The new study provides a valuable window into CD8+ T cell responses, but it is limited because it relies on the CD8+ T cells found in blood samples. As a next step, the researchers hope to shed light on how T cells in tissues hit hardest by SARS-CoV-2, such as the lungs, react to the virus. This step will be important because the memory T cells that provide long-term immunity need to live in the tissues.

"This study is very much a first step in understanding the spectrum of immune responses against infectious agents," says Ottensmeier. Going forward, the researchers hope to use single-cell sequencing techniques to look at CD8+ T cells in cancer patients with COVID-19 infection.

"This research highlights the power of these new tools to understand human immunology," says Vijayanand.

Journal of Clinical and Cellular Immunology is pleased to inform you that the Journal is planning to launch its upcoming issue for the month of March 2021. We would like to invite you to submit your research work for publication in this international scholarly open-access journal. There are no space limitations or specific topics; journal publishes all manuscripts within the scope of the journal judged to be sound by editors.

Manuscripts submitted to the journal include, but are not limited to:

Journal accepts all kinds of manuscripts like Original Research Articles, Expert Review Articles, Case Reports, Mini Reviews, Brief Reports, Communications, Letter to Editor, Short Commentaries and Editorials.

Journal of Clinical & Cellular Immunology is using Editorial Manager System for quality in review process. Editorial Manager is an online manuscript submission, review and tracking systems used by most of the best open access journals. Review processing is performed by the editorial board members of Journal of Clinical & Cellular Immunology or outside experts; at least two independent reviewers approval followed by editor's approval is required for acceptance of any citable manuscript. An annual review of Immunology Journal is also shared with authors.

JCCI reviews manuscripts within 21 days of submission and publishes accepted manuscripts online in press immediately regardless of issue publication date. 

Authors are requested to submit manuscripts at https://www.longdom.org/submissions/clinical-cellular-immunology.html or send as an e-mail attachment to the Editorial Office at: immunology@eclinicalsci.com (or) immunology@scholarlymed.com

Media Contact:
Mercy Eleanor
Managing Editor
Journal of Clinical and Cellular Immunology
ISSN: 2155-9899 | NLM ID: 101563152
Journal Impact Factor 2.3* (5 Year Journal Impact Factor)
E-mail: immunology@eclinicalsci.com
What’s App: +1-504-608-2390