Антитела IgG- и IgM-класса были исследованы в венозной крови 76 пациентов с подтвержденным по ПЦР и/или КТ наличием вируса SARS-CoV-2, в том числе 61 больной обследовались в динамике. Определение антител к SARS-CoV-2 проводилось методом ИФА с использованием отечественных диагностических тест-систем с сорбированными в лунках планшета как цельновирионными частицами SARS-CoV-2, так и рекомбинантными белками вируса. Результаты исследований выражались в виде коэффициента позитивности. Сероконверсия как IgM- так и IgG-антител наблюдалась к первой неделе заболевания, что было зафиксировано при использовании всех 6 иммуноферментных тест-систем. Была отмечена различная динамика выработки IgG- и IgM-антител к N-белку нуклеокапсида и к RBD – основному домену S-белка. Характерная динамика уровня IgG-антител, измеренная с помощью тест-системы с сорбированными цельным вирионом или рекомбинантными S-белком или RBD (но не с N-белком), позволяет судить о продолжительности заболевания (то есть сроке от момента инфицирования), что может иметь диагностическое значение.
The presence of IgG and IgM antibodies in the venous blood of 76 patients with confirmed COVID-19 infection was determined by ELISA using Russian test systems. Different levels of IgM antibodies to N-protein and receptor binding domain of the Spike protein (RBD) were revealed. The dynamics of IgG antibodies to the whole virion antigen and recombinant antigens showed high values on weeks 4-5 of the disease. The level of IgG antibodies to Nprotein remained low throughout the observation period. The characteristic dynamics of IgG measured using test systems with sorbed whole virion or recombinant spike proteins reflects the duration of the disease.
IgM and IgG antibodies to the SARS-CoV-2 virus are detected in subjects who have recovered from COVID-19; IgM antibodies persist in a 1/3 of infected subjects up to 12 months from the moment of the disease, while IgG antibodies are present in the vast majority of cases (97%; medium and high levels antibodies were registered in 85% of cases). By the 12th month, 40% of those who recovered still have a very high level of IgG antibodies to the S-protein (>500 BAU/ml). In the feces, urine, and blood serum of patients with long-term persistent IgM antibodies, no coronavirus antigens were detected. After vaccination with the Gam-COVID-Vac vaccine, IgG antibodies to the S-protein are detected in 100% of cases and remain at a high level for 4 months, by the 5-6th month, the level of antibodies decreases. During revaccination, the level of IgG antibodies to S-protein reaches high values earlier than during primary vaccination, and remains high for 4 months (observation period). The blood sera of recovered and vaccinated patients have a high virus-neutralizing activity (at least 1:80), while its level is somewhat higher in recovered patients.
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