The duration and specificity of the humoral immune response to SARS-CoV-2

Abstract

Background. Our assumption that immunity after COVID-19 will persist has been fully confirmed in the researches already conducted. Our work is a continuation of research that demonstrates the results obtained 12 months of determining the humoral response in patients after COVID-19.
 Materials and methods. The research involved 42 individuals. All subjects had a positive PCR test for COVID-19. At certain intervals, from 40 to 240 days, individuals in the group were tested for IgG SARS-CoV-2. The last step was to check the level of IgG to the COVID-19 nucleocapsid and spike protein in the research group for 360 days from the onset of the disease. A private certified laboratory in Kyiv, the “DNA Laboratory”, was involved. Patients were tested for antibodies to COVID-19 by ELISA using serology COVID-19 test systems VitroTest (Ukraine). The immunological laboratory of the Institute of Pediatrics, Obstetrics and Gynecology was used in parallel for interlaboratory quality control. The results of the research coincided.
 Results. The level of class G immunoglobulins to nucleocapsid in the subjects has gradually decreased over 8 months. It is noteworthy that in the period from 40 to 150 days in all 42 patients (100 %) antibodies did not disappear. Decreasing of antibodies occurred between 150 and 240 days. However, the data obtained for 360 days significantly changed the picture. In a certain part of the subjects, who had low or even negative levels of antibodies for 8 months, as of 12 months, the level of immunoglobulin (Ig) class G again rose above the threshold value. Thus, we see that from the group of 42 people 92.8 % have positive antibodies to the nucleocapsid, and 7.2 %.
 Conclusions. The data obtained illustrate that in the study group within 12 months after SARS-CoV-2, the vast majority of individuals remain with specific antibodies to the nucleocapsid and spike-protein.