COVID-19 Immunology: SARS-CoV-2-Specific T Cells Discovered In COVID-19 Patients
: Researchers from University Of California-San Diego, La Jolla Institute for Immunology-California and Eramus University medical College-Netherland report that patients suffering from severe respiratory symptoms as a result of SARS-CoV-2 infection can rapidly generate virus-attacking T cells, and can increase this production over time.
The researchers conducted a study involving T cells from 10 COVID-19 patients under intensive care treatment.
The research findings were published in the medical journal: Science Immunology. https://immunology.sciencemag.org/content/5/48/eabd2071/tab-article-info
The researchers found that in addition, 2 out of 10 healthy individuals without prior exposure to the virus harbored SARS-CoV-2-reactive T cells, possibly indicating that these T cells can cross-react to the novel coronavirus due to past infection with related coronaviruses that cause common cold symptoms.
Cumulatively, these new findings and data address the poorly understood question of whether SARS-CoV-2-specific T cell responses vary in patients over time depending on disease severity, and helps to answer whether patients with more severe symptoms can generate protective virus-specific T cells at all.
The research also provides new clues regarding the cells responsible for excessive immune responses, including life-threatening "cytokine storms," and may also help inform vaccine design.
Dr Daniela Weiskopf and colleagues extracted blood cells from 10 patients at weekly intervals starting soon after they were admitted to the ICU for COVID-19 and exposed these cells to "megapools" of known SARS-CoV-2 epitopes - a technique meant to capture a large fraction of total viral-reactive T cells.
They study found SARS-CoV-2-specific CD4+
helper T cells in all 10 patients and CD8+
"killer" T cells in 8 out of 10 patients, and characterized the cells' production of specific inflammation-triggering cytokines.
The strongest T cell responses were directed to the virus' spike (S) surface glycoprotein, supporting prior work that has pointed to the S protein as a promising target to induce virus-specific T cells. Furthermore, screening all patients at 0, 7, and 14 days after inclusion in the study revealed that SARS-CoV-2-specific T cells were present relatively early during the course of infection and increased in these patients over time.
Utilizing the same T cell stimulation technique in age-matched healthy controls, the researchers found SARS-CoV-2-reactive T cells in 2 out of the 10 individuals.
The research team note promising areas for future work based on their findings, including an investigation of how preexisting SARS-CoV-2-specific T cells in healthy controls correlate to protection against COVID-19 disease, as well as identification of T cell types responsible for cytokine storms.
The study results have other significant implications for vaccine design.
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