Dynamics of the content of immunoglobulin G to severe acute respiratory syndrome-2 in convalescents who have had a new coronavirus infection

The study investigated the dynamics of class G immunoglobulins to severe acute respiratory syndrome-2 coronavirus in the blood serum of convalescents who had a new coronavirus infection for 6 months after the polymerase chain reaction conversion. Among the most common symptoms, 30 (73.8%) convalescents had an increase in body temperature to 38°C, 32 (83.3%) had asthenia, 21 (59.5%) had cough, 29 (73.8%) had perversion or loss of sense of smell, pain, and throat discomfort. The duration of symptoms varied from 3–4 days to 3–4 weeks. Within a month after the end of the acute disease period, 8 (20%) patients had a decrease in working capacity, 13 (33%) had difficulty breathing, 9 (22%) had a cough, and 4 (10%) had pain and sore throat. During severe acute respiratory syndrome 2 infection, the virus activates the innate and adaptive immunity, resulting in the formation of specific class G immunoglobulins to the pathogens. After leveling the clinical manifestations, class G immunoglobulins were detected in the majority of convalescents (79%–90%) during the first 6 months, starting from day 14 from disease onset with a predominantly high (> 10 conl. units) positivity coefficient. Moreover, this pattern occurred in both men and women; however, in some studies, the levels of the positivity coefficient of class G immunoglobulins began to decrease by the fifth month of follow-up and sometimes at an earlier time (2 months). Perhaps, this is due to the different functional activities of the immune system of each convalescent, infecting dose of the pathogen, and peculiarities of its interaction with the macroorganism and its immune system. Nevertheless, the class G immunoglobulins identified in the study do not yet indicate the probability of reinfection of convalescents with the same pathogen. The protective titer of antibodies has yet to be investigated further.