Cell: Patients with asymptomatic or mild COVID-19 recovery produce a strong T-cell immune response.

21, 2020 /--- In a new study, researchers from sweden's Karolinska Institute report that mild COVID-19 triggers a strong memory T-cell response, even in the absence of detectable virus-specific antibody responses.
they say that natural exposure to SARS-CoV-2 or infection with the virus -- a new type of coronavirus that causes COVID-19 disease -- may produce memory T-cell responses that may be an important immune component in preventing recurrent episodes of serious diseases.
study was recently published in the journal Cell under the title "Robust T cell immunity in convalescent individuals with asymptomatic or mild COVID-19".
image from NIAID.
are facing the biggest global health emergency in decades," said Marcus Buggert, author of the paper and author of the paper.
In the absence of a protective vaccine, it is critical to determine whether the exposed or infected person, especially those who may inadvertently be the main spreader of asymptomatic or very mild forms of the disease, will have a strong adaptive immune response to SARS-CoV-2.
" so far, previously recorded evidence of re-infection of SARS-CoV-2 infections is limited.
most of the studies on human anti-SARS-CoV-2 immune protection have focused on induction and antibodies.
but the antibody response tends to weaken and is not detected in all patients, especially those with milder COVID-19 conditions.
studies of mice have shown that vaccine-induced memory T-cell reactions can last for years and protect mice from the associated virus SARS-CoV, even in the absence of detectable antibodies.
until now, it was not clear how SARS-CoV-2-specific T-cell responses were associated with antibody responses or the clinical process of human COVID-19.
to fill this knowledge gap, Buggert and his co-workers evaluated the SARS-CoV-2-specific T-cell response and antibody response of more than 200 people from Sweden throughout the exposure, infection and illness process.
in the acute phase of infection, T-cell response is associated with various clinical markers of the severity of the disease.
recovery from COVID-19, a SARS-CoV-2-specific memory T-cell reaction can be detected.
strongest T-cell response in patients recovering from severe COVID-19.
, a gradual decline in T-cell response was observed in patients recovering from very mild COVID-19 and in family members exposed to the virus.
consistent with expectations, all 23 people recovering from severe COVID-19 experienced SARS-CoV-2 specific antibody reactions and T-cell reactions.
But surprisingly, after several months of infection, SARS-CoV-2-specific memory T-cell reactions were detected in exposed family members and most individuals with a very mild history of COVID-19, sometimes without SARS-CoV-2 specific antibodies.
of the 28 exposed family members, only 17 (more than half) had detectable antibody reactions, while almost all (26/28) had T-cell reactions.
of the 31 people recovering from mild COVID-19, almost all had detectable antibody reactions (27/31) and T-cell reactions (30/31).
Buggert said, "Our results suggest that reliance on antibody responses may underestimate the level of immunity at the population level against SARS-CoV-2."
, the next step is to determine whether a strong memory T-cell response can prevent COVID-19 in the long term without detectable antibodies.
" (bioon.com) Reference: 1.Takuya Sekine et al. Robust T cell immunity in convalescent individuals with asymptomatic or mild COVID-19. Cell, 2020, doi:10.1016/j.cell.2020.08.017.2.Mild COVID-19 cases can produce can strong T cell response.