Immune response after mild COVID

In a recent study posted on medRxiv* Preprint Server, German researchers evaluated the immunity induced by mild severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Various studies have reported the effects of cases of moderate and severe coronavirus disease 2019 (COVID-19) on hospitalization and associated mortality. However, more research is needed to understand the effect of mild COVID-19 on antibody reactions more than 6 months after infection.

study: Sustained immunity after SARS CoV-2 infection-Conan-Long-term study.. Image Credit: DariaRen / Shutterstock

About research

In this study, researchers evaluated long-term immunity in mild COVID-19-infected individuals up to 1 year after infection.

A total of 626 people participated in the first survey round held in April 2020. Of these, 162 people with a history of SARS-CoV-2 infection and control participants collated based on gender and age were invited. Second and third rounds of study. A total of 146 participants participated in the second visit in October 2020, and 224 participated in the third visit in April 2021. The team determined antibody levels for all participants. In addition, T cell analysis was performed on all individuals with a history of infection. For all three study visits, the team performed a consensus analysis of antibody levels in 40 participants.

At 1.5 months or in the CoNAN1 study, a total of 56 people were found to be anti-SARS-CoV-2 antibody sera positive (AB +), of which 44 and 46 participated in the second and third rounds. Did. Respectively. Another 40 participants who were also tested for the antibody course were considered “infected groups”.

In addition, the team estimated serum antibody levels observed more than a year after SARS-CoV-2 infection. This was achieved by performing tests such as Electronic Data Interchange (EDI), Roche (identifying anti-spikes and anti-nucleocapsid antibodies), Liason and Euroimmune (identifying anti-spikes antibodies), and Magulmi Snibe (identifying anti-spikes and anti-nucleocapsids). it was done. antibody.

The team evaluated SARS-CoV-2T cell-mediated immunity by analysis Spike proteinSpecific CD154 + 4-1BB + cells found in T_H cell. This immunity was determined by collating a cohort of 46 participants in the first and third visits, including 16 controls and 30 infected patients. In addition, spike-reactive T_H Cells were identified by comparing T_H Cells restimulated by covering the N-terminal or C-terminal portion of the SARS-CoV-2 peplomer with T_H Cells that responded only in the presence of dimethyl sulfoxide (DMSO).

result

The study results showed that 161 participants in the third visit of the CoNAN1 study were AB-, 40 of whom became AB +. In addition, nine of the participants tested positive for PCR for COVID-19 between the second and third visits. In addition, 21 participants were not vaccinated. The median age of participants in the infected group was 60.5 years, with 57.43% of males and 42.86 of female participants who were positive for antibodies on their first visit and did not report COVID-19 vaccination or reinfection. %It is included.

Anti-SARS-CoV-2 antibody level over time as assessed by 3 quantitative and 1 semi-quantitative (EU) antibody tests as shown) All participants. B) Hierarchized by Snibe’s age (left panel) and EDI test (right panel). C) Results of the Diasorin Snibe antibody test stratified for PCR status (left panel), asymptomatic and symptomatic diseases (center panel), and gender (right panel). D) Same as C in EDI test. N = Number of individuals per group. Friedman test by Dunns post hoc analysis. * p <0.05; ** p <0.01; *** p <0.001; **** p<0.0001。 略語：AU ..任意単位、ns ..重要ではない（p> 0.05), Snibe: SN .. 2019-nCoV IgG Kit (Snibe Co., Ltd., Shenzhen, China); ED..EDI Severe Acute Respiratory Syndrome SARS-CoV-2 IgGELISA Kit (Epitope Diagnostics Inc., San Diego, USA).

Quantitative tests such as EDI, Liaison, Magrumi Snibe, and Euroimmune showed a significant decrease in serum antibody levels during the one-year observation period. This decrease in antibody concentration was different at different times and between individual tests. Comparing the decrease in antibody concentration between the EDI test and the Euromimmune test for 1.5 to 6 months, it became clear that the decrease in the number of anti-nucleocapsid antibodies was not so important. This effect was found to be consistent even after 12 months.

However, after 12 months, the decrease in antibody concentration was not so pronounced in the Diasorin assay, a test-specific effect. antigen-definite. This also suggested a rapid decrease in serum antibody levels detected in several tests during the first 6 months. In addition, within 1 year of COVID-19 diagnosis, antibody depletion and storage was less pronounced.

The team discovered the presence of SARS-CoV-2 spike-specific CD154 + 4-1BB + T_H Cells 1.5 and 12 months after COVID-19 diagnosis. In addition, there was a slight but significant reduction in spike-specific TH cells among individuals with a history of COVID-19 infection over time.Only 6.7% of patients reported complete disappearance of spike-specific T_H Cellular response 1 year after primary infection. In addition, participants with a history of SARS-CoV-2 infection were found to have a higher rate of SARS-CoV-2 specific compared to SARS-CoV-2 negative individuals. T cells At various points of time tested.

Overall, the findings showed T’s sustainability and robustness._H Cell-mediated immunity induced after mild SARS-CoV-2 infection. Antibody concentration dropped to the minimum detected after 1 year of infection, but certain T_H The cellular response was still detectable.

*Important Notices

medRxiv Publish preliminary scientific reports that should not be considered definitive as they have not been peer-reviewed, guide clinical practice / health-related behaviors, and should not be treated as established information.