IgG Study of Blood Sera of Patients with COVID-19.

Elena Kazachinskaia,Valeriya Romanova,Marina Gulyaeva,Daniil Shanshin,Alexander Chepurnov,Dmitry Shcherbakov,Olga Khripko,Teresa Saroyan,Yulia Kononova,Michail Voevoda,Alexander Shestopalov

doi:10.3390/pathogens10111421

Abstract

The COVID-19 pandemic, which began at the end of 2019 in Wuhan, has affected 220 countries and territories to date. In the present study, we studied humoral immunity in samples of the blood sera of COVID-19 convalescents of varying severity and patients who died due to this infection, using native SARS-CoV-2 and its individual recombinant proteins. The cross-reactivity with SARS-CoV (2002) was also assessed. We used infectious and inactivated SARS-CoV-2/human/RUS/Nsk-FRCFTM-1/2020 strain, inactivated SARS-CoV strain (strain Frankfurt 1, 2002), recombinant proteins, and blood sera of patients diagnosed with COVID-19. The blood sera from patients were analyzed by the Virus Neutralization test, Immunoblotting, and ELISA. The median values and mean ± SD of titers of specific and cross-reactive antibodies in blood sera tested in ELISA were mainly distributed in the following descending order: N > trimer S > RBD. ELISA and immunoblotting revealed a high cross-activity of antibodies specific to SARS-CoV-2 with the SARS-CoV antigen (2002), mainly with the N protein. The presence of antibodies specific to RBD corresponds with the data on the neutralizing activity of blood sera. According to the neutralization test in a number of cases, higher levels of antibodies that neutralize SARS-CoV-2 were detected in blood serum taken from patients several days before their death than in convalescents with a ranging disease severity. This high level of neutralizing antibodies specific to SARS-CoV-2 in the blood sera of patients who subsequently died in hospital from COVID-19 requires a thorough study of the role of humoral immunity as well as comorbidity and other factors affecting the humoral response in this disease.

Highlights

According to the WHO, the COVID-19 pandemic, caused by a new pathogen SARSCoV-2 in the human population, which began at the end of 2019 in Wuhan, in China’s Hubei province, has affected 220 countries and territories to date
To study humoral immunity against SARS-CoV-2, a random sample of 54 blood sera received from 26 convalescents (1 asymptomatic case, 13 mild cases, 1 moderate case with hospitalization for pneumonia and 1 without hospitalization, 10 severe cases, and 13 severe cases with a lethal outcome in the hospital) was used
High titers were found in an asymptomatic patient as well as in the case of a patient who recovered after a moderate case of COVID-19—1:6400 (Numbers 1 and 15 on the Appendix A Figure A1)

Summary

Introduction

According to the WHO, the COVID-19 pandemic, caused by a new pathogen SARSCoV-2 in the human population, which began at the end of 2019 in Wuhan, in China’s Hubei province, has affected 220 countries and territories to date. According to the opinion of some researchers, this is a paradox, as such measures leave people without immunity, susceptible to new waves of infection. Healthcare workers, the elderly, and people with medical conditions, such as cardiovascular and cerebrovascular diseases, diabetes, and neoplasms, are at a high risk of infection [2,3]. It is quite possible that the modern world will not return to “pre-pandemic normality” until safe and effective vaccines have been developed and a global vaccination program has been implemented [4]

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