Comparison of the humoral and cellular immunity in COVID-19 convalescents

Abstract

The SARS-CoV-2 virus that caused the COVID-19 pandemic is related to the SARS-CoV-1 and MERS coronaviruses, which were the cause of epidemics in 2003 and 2012. Antibodies in patients with COVID-19 appear 7-14 days after the onset of symptoms and gradually increase. As the COVID-19 pandemic continues, it is difficult to say how long the immunological memory to the SARS-CoV-2 virus will last. The aim of this study was to study the ratio of humoral and cellular immunity to the S-protein of the SARS-CoV-2 virus in COVID-19 convalescents. The study involved 60 adults with mild to moderate COVID-19 2 to 12 months prior to the examination. The control group consisted of 15 adults who did not have COVID-19 and were not vaccinated against this infection. Specific antibodies to the SARS-CoV-2 virus were determined by ELISA using the SARS-CoV-2-IgG-ELISA-BEST kit. To determine the specific IgG and IgA subclasses, the anti-IgG conjugate from the kit was replaced with a conjugate against the IgG subclasses and IgA. Additional incubation with or without denaturing urea solution was used to determine the avidity of antibodies. Mononuclear cells were isolated from blood by gradient centrifugation, incubated with or without coronavirus S antigen for 20 hours, stained with fluorescently labeled antibodies, and the percentage of CD8highCD107a were counted on a flow cytometer Canto II. In the control group, neither humoral nor cellular immunity to the S-protein of the SARS-CoV-2 was found. In the group of those who had recovered, the level of IgG antibodies to the S-protein of the SARS-CoV-2 virus varies greatly and was not strictly associated with the duration of the disease, 57% of COVID-19 patients had a high level of humoral response, and 43% - low level. The correlation between the levels of specific IgG and IgA was r = 0.43. The avidity of antibodies increased over time after the disease, amounting to 49.9% at a period of 6-12 months. There were no specific IgG subclasses IgG2 and IgG4, and the percentage of IgG1 increased over time and amounted to 100% after 6-12 months after illness. 50% of the examined had high cellular immunity, and the same number - low, no correlations with the level of humoral immunity were found. We identified 4 combinations of humoral and cellular immunity to the S-protein of the SARS-CoV-2: high humoral and cellular, low humoral and cellular, high humoral and low cellular, and vice versa, low humoral and high cellular immunity.

Adaptive post-COVID-19 immune response in female subjects of the Russian arctic region

“…According to (Toptygina et al, 2022), individuals who recovered from COVID-19 exhibited a balanced distribution of high and low levels of cellular immunity in a ratio of 50 to 50%. These results align with analogous findings reported in the works of Dan et al (2021), Stephens and McElrath (2020) and Stephens et al, where the level of specific cellular response in recovering COVID-19 patients was found to vary according to the patients' functional systems and their capability, and to be affected by the severity of the disease.…”