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The memory T cell levels of the immune system corresponded exactly with the severity of SARS-CoV-2 in the first study, and evaluated a wide range of responses, from healthy to severe. The researchers also evaluated the response of exposed families.
Furthermore, T cell responses persist in convalescent COVID-19 patients, suggesting that such responses provide a more accurate measure of potential long-term immune defense compared to antibody assays.
“the most important [take-home message] CoV-2 produces a strong and highly typical memory T cell response to respiratory viral infections in most individuals,” says Marcus Buggert, a research author at the Center for Infectious Diseases at Huddinge School of Medicine, Karolinska Institute. Dr. Stockholm, Sweden Medscape Medical News..
“We speculate that this type of response should provide some type of protection from severe COVID-19 recurrent episodes,” he said.
Research Published online August 14 cell.
Researchers say that measuring memory T cells may help identify people with asymptomatic or mild COVID-19 disease who are “more likely to misbehave as key transmitters” Says.
In addition, many study participants demonstrated strong memory T cell responses for months, even in the absence of circulating antibodies. This finding suggests a longer window for detecting immune responses. In contrast, the ideal time to detect antibodies to SARS-CoV-2 appears to be 3-4 weeks after exposure. Previously reported..
A cross-sectional study of Buggert and colleagues with 206 participants focused specifically on SARS-CoV-2 specific CD4 + and CD8 + T cells.
The study included 17 with acute severe COVID-19 and 11 with acute moderate. The 66 convalescent participants included 26 who recovered from severe COVID-19 and 40 who were mild.
The researchers measured the immune response of 30 families exposed to patients with mild or severe COVID-19. They also evaluated T cells and other immune components from 55 blood donors during the pandemic and 28 other blood donors from 2019.
Measuring resistance to T
The researchers measured T cell responses to three specific SARS-CoV-2 proteins. One is inside, one is virus spike, and the other is cell membrane. The proportion of each cohort of patients who responded to these proteins correlated with clinical severity or viral exposure.
For example, 100% of participants in convalescence after severe COVID-19 showed “robust” T cell responses to any of these proteins and were in convalescence after mild illness. It represented 87% of patients and 67% of exposed families. , And 46% of the healthy people who donated blood during the pandemic.
In addition, 99% of participants who tested positive for antibodies also showed SARS-CoV-2-specific CD4 + and CD8 + T cell responses. Of those without measurable antibodies, 41% showed a T cell response to the virus.
Clinical impact
When asked if he was surprised at the result, Bugart said, “Yes, no. At first glance it was amazing. But antibodies usually weaken over time, and in some people with mild symptoms, [they wane] Fairly quickly to undetectable levels”
“The data makes sense,” he added. Immune cells with memory such as B cells and T cells “can survive for many years after infection.”
Research limitations include its cross-sectional design and limited follow-up. “Thus, it has not yet been determined whether a strong memory T cell response in the absence of detectable circulating antibodies could protect against severe forms of COVID-19,” the researchers say.
“The convalescents in this study, including those with previous mild illness, have never experienced further episodes of COVID-19,” they added.
Answer “Important Questions”
“This study is very well done and is of great interest because it delves into the details of T cell and antibody responses across the spectrum of disease severity,” said Alessandro Sette. Medscape Medical News When asked for a comment.
The finding says, “We’re starting to provide answers to key questions: do individuals with mild or asymptomatic symptoms of COVID-19 generate T cell and antibody responses?”
Interestingly, some participants had a T-cell response in the absence of detectable antibodies, according to Sette. “This study also confirmed that unexposed people have a cross-reactive T cell memory for SARS2, which was previously shown by several studies, including us. .” He May 14, 2020 Survey It also assessed T cell responses in convalescent and non-exposed individuals.
A more extensive and detailed study of the La Jolla Immunology Institute in La Jolla, California, is needed, Sette said.
The goals include the frequency of mounting T cell immune responses without detectable antibody response, how to distinguish those T cells from pre-existing T cells against the common cold coronavirus, and the future that these T cells will provide. If there are protection levels against your infection, include determination of those levels. He said.
Refers to virus protection
“These are excellent and important data showing that COVID-19 is not only recovered but asymptomatic. [people] It can elicit a SARS-CoV-2 T cell response,” said Dr. Antonio Berletti, who is irrelevant to the current study. Medscape Medical News..
“It’s clear at this time that we don’t yet know the levels of antibodies and T cells that can provide protection,” said Bertoletti, head author of the Emerging Infectious Diseases Program at Duke NUS Medical School in Singapore. Recent research SARS-CoV-2–specific T cell immunity.
“It is important to show that all subjects infected with SARS-CoV-2, regardless of their symptoms, can elicit a virus-specific T cell response that can prevent viral spread, even when not protected from reinfection. Infected hosts,” he added.
Buggert, Sette, and Bertoletti do not disclose related financial relationships.
cell. Published online August 14, 2020. Overview
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