CC BY
6
DYNAMIC CHANGES IN THE CONCENTRATION OF ANTI-SARS-COV-2 ANTIBODIES WITHIN 12 MONTHS AFTER RECOVERY FROM COVID-19
Mayanskiy NA1 и, Brzhozovskaya EA1, Stoyanova SS1, Frolkov AV1, Lebedin YuS2
1 Pirogov Russian National Research Medical University, Moscow, Russia
2 XEMA LLC, Moscow, Russia
Generation and maintenance of immunity to SARS-CoV-2 is essential for overcoming the pandemic of the novel coronavirus infection COVID-19. The study was aimed to assess the dynamic changes in the levels of IgG antibodies against the SARS-CoV-2 receptor-binding domain (RBD) with the use of the enzyme-linked immunosorbent assay (ELISA) kits, calibrated using the International Standard for anti-SARS-CoV-2 immunoglobulin (IS-SARS-CoV-2). The concentrations of anti-RBD-IgG were measured in the cohort of individuals, who had recovered from COVID-19, with an interval of a month for 6 months, and at a time point of 12 months, using the ELISA kits, calibrated with the use of IS-SARS-CoV-2; the results were expressed in binding antibody units (BAU) per 1 mL. A total of 97 blood serum samples, obtained from 20 individuals with SARS-CoV-2 infection, confirmed by PCR, were collected. The geometric mean titer (GMT) of anti-RBD-IgG was 433 BAU/mL (range 36-25,900 BAU/mL) within a month after the infection. The concentration of anti-RBD-IgG gradually decreased with time and reached the GMT value of 68 BAU/mL by the 12th month; anti-RBD-IgG persisted in 13 individuals (93%) out of 14, examined 12 months after the infection. The standardized quantitative serological data play a vital part in monitoring the immune response and make in easier to compare the studies, providing the basis for seeking the common serological correlate of the protective immunity to SARS-CoV-2.
Keywords: SARS-CoV-2, anti-RBD IgG, dynamic changes, concentration, BAU/mL
Author contribution: Mayansky NA — concept, data processing, manuscript writing; Brzhozovskaya EA — sample collection, ELISA, data processing, making illustrations; Stoyanova SS — sample collection, data processing, making illustrations; Frolkov AV — data processing, manuscript preparation; Lebedin YuS — concept, ELISA, manuscript editing.
Compliance with ethical standards: the study was approved by the Ethics Committee of the Pirogov Russian National Research Medical University (protocol № 197 dated May 21, 2020).
1^1 Correspondence should be addressed: Nikolay A. Mayanskiy
Ostrovitianova, str. 1, Moscow, Russia; mayanskiy.nikolay@gmail.com
Received: 01.02.2022 Accepted: 14.02.2022 Published online: 20.02.2022
DOI: 10.24075/brsmu.2022.007
ДИНАМИКА КОНЦЕНТРАЦИИ АНТИТЕЛ К SARS-COV-2 В ТЕЧЕНИЕ 12 МЕСЯЦЕВ ПОСЛЕ ПЕРЕНЕСЕННОЙ ИНФЕКЦИИ COVID-19
Н. А. Маянский1 Е. А. Бржозовская1, С. С. Стоянова1, А. В. Фролков1, Ю. C. Лебедин2
1 Российский национальный исследовательский медицинский университет имени Н. И. Пирогова, Москва, Россия
2 Общество с ограниченной ответственностью «ХЕМА», Москва, Россия
Формирование и поддержание иммунитета против SARS-CoV-2 является важным условием преодоления пандемии новой коронавирусной инфекции COVID-19. Целью работы было охарактеризовать динамику уровня антител IgG к рецептор-связывающему домену (RBD) SARS-CoV-2 с использованием набора для иммуноферментного анализа (ИФА), откалиброванного при помощи Международного стандарта анти-SARS-CoV-2-иммуноглобулинов (IS-SARS-CoV-2). Концентрацию анти-RBD-IgG измеряли в когорте лиц после выздоровления от COVID-19 с интервалом в месяц в течение 6 месяцев и в точке 12 месяцев с использованием наборов ИФА, откалиброванных IS-SARS-CoV-2; результаты представляли в единицах связывания антител (BAU) на 1 мл. Всего исследовали 97 образцов сыворотки крови от 20 человек с ПЦР-подтвержденной инфекцией SARS-CoV-2. К первому месяцу после заражения средний геометрический титр (GMT) анти-RBD-IgG составил 433 BAU/мл (диапазон 36-25900 BAU/мл). Со временем концентрация IgG против RBD постепенно снижалась, достигая GMT в 68 BAU/мл к 12 месяцу; анти-RBD-IgG сохранялись у 13 из 14 (93%) лиц, обследованных через 12 месяцев после инифицирования. Стандартизированные количественные серологические данные играют важную роль в мониторинге иммунного ответа и облегчают сравнение между исследованиями, создавая основу для поиска общего серологического коррелята иммунной защиты против SARS-CoV-2.
Ключевые слова: SARS-CoV-2, анти-RBD IgG, динамика, концентрация, BAU/мл
Вклад авторов: Н. А. Маянский — концепция, обработка результатов, написание текста; Е. А. Бржозовская — сбор образцов, выполнение ИФА, обработка результатов, подготовка иллюстраций; С. С. Стоянова — сбор образцов, обработка результатов, подготовка иллюстраций; А. В. Фролков — обработка результатов, подготовка рукописи; Ю. С. Лебедин — концепция, выполнение ИФА, редактирование рукописи.
Соблюдение этических стандартов: исследование одобрено этическим комитетом РНИМУ им. Н. И. Пирогова (протокол № 197 от 21 мая 2020 г.).
[><1 Для корреспонденции: Николай Андреевич Маянский
ул. Островитянова, д. 1. г. Москва, Россия; mayanskiy.nikolay@gmail.com
Статья получена: 01.02.2022 Статья принята к печати: 14.02.2022 Опубликована онлайн: 20.02.2022 DOI: 10.24075/vrgmu.2022.007
The natural infection and vaccination against COVID-19 result in the production of antibodies against viral antigens, playing a vital part in the immune response monitoring [1]. Although it is expected that the naturally acquired immunity against SARS-CoV-2 would last long [2-3], serological equivalent of antiviral host defense has not yet been discovered. The lack of a standardized approach to laboratory testing is one of the obstacles to defining such correlates, which probably explains
the conflicting literature data on the serological assessment of SARS-CoV-2 infection. The WHO have recently introduced the International Standard for anti-SARS-CoV-2 immunoglobulin (IS-SARS-CoV-2), which makes it possible to unify the results of measuring the levels of anti-SARS-CoV-2 antibodies using the IS-SARS-CoV-2 units, namely the binding antibody units (BAU) [1]. The study was aimed to measure the concentration of IgG against the SARS-CoV-2 receptor-binding domain
BULLETIN OF RSMU | 1, 2022 | VESTNIKRGMU.RU
11
ОРИГИНАЛЬНОЕ ИССЛЕДОВАНИЕ I ИММУНОЛОГИЯ
(RBD) at different times over the 12-month period in a cohort of healthcare professionals, who have recovered from the SARS-CoV-2 infection, using the enzyme-linked immunosorbent assay (ELISA) kits, calibrated using the IS-SARS-CoV-2.
METHODS
The study, carried out from May 2020 to June 2021, involved the staff members of the Russian Children's Clinical Hospital, Pirogov Russian National Research Medical University. Inclusion criteria: positive PCR test result for COVID-19. There were no exclusion criteria.
In April and May 2020, after returning to work, individuals with positive PCR test results for COVID-19 gave the blood serum samples with an interval of a month for the anti-RBD-IgG measurement. The samples were collected on a monthly basis for 6 months, and the last sample was obtained 12 months after the positive PCR test result; a total of 4-7 samples was obtained from each subject. The samples collected were stored at a temperature of -80 °C.
In July 2021, all the samples were assayed in one batch using the ELISA kit for the anti-RBD-IgG quantification (XEMA; Russia) [4], calibrated using the IS-SARS-CoV-2. The analytical measuring range was 15-240 BAU/mL; samples with the anti-RBD-IgG concentration exceeding 240 BAU/mL were further diluted 10-100 times and measured repeatedly in a separate batch. The samples were considered positive when the level of anti-RBD-IgG was 15 BAU/mL.
Statistical processing was performed using the IBM SPSS Statistics 27.0 software package (IBM Corp.; USA).
А
и <
m
CD
B
и <
100-
88 oo
8
&
CO £
о
I г
=8° <»
1
О «
-1 before
1 1?
1600 1400 1200 1000 800 600 400 200 0
-1 before 1
RESULTS
A total of 97 serum samples were obtained from 20 individuals during the study, including 14 women (70%) with the SARS-CoV-2 infection, confirmed by PCR. The median age was 50 years (Q1-Q3, 40-57 years). All the subjects had mild to moderate COVID-19, there were no severe cases of the disease.
In three individuals, blood serum samples were obtained a month before the SARS-CoV-2 infection; no anti-RBD-IgG were found in these samples. A month after the positive PCR test result for SARS-CoV-2, anti-RBD-IgG were found in all subjects in a concentration exceeding the threshold value of 15 BAU/mL, with the geometric mean titer (GMT) of 433 BAU/mL (95% CI 123-1,527 BAU/mL; range 36-25,900 BAU/mL) (see Figure). At the time point 2 of the month the median GMT was similar, 456 BAU/mL (95% CI 154-1,353 BAU/mL). Later the concentration of anti-RBD-IgG gradually decreased and reached the median GMT value of 68 BAU/mL (95% CI 35-131 BAU/mL) by the 12th month. All samples were anti-RBD-IgG-positive during the period between the first and the sixth months. Among 14 individuals assessed 12 months after the SARS-CoV-2 infection, 13 individuals (93%) were still seropositive for anti-RBD-IgG with the GMT values exceeding 15 BAU/mL. The median concentration of anti-RBD-IgG was 6.7 times lower (95% CI 4.4-10.3 times) after 12 months compared with the highest median GMT value, defined during the second month after the SARS-CoV-2 infection.
DISCUSSION
To date, the data of only a few studies, involving the standardized values of the amount of antibodies against SARS-CoV-2 after the natural infection and/or vaccination, have been reported
Month after positive PCR test
Fig. Concentration of anti-RBD IgG as a function of time after the positive PCR test result for SARS-CoV-2. (A) individual values for 97 samples and (B) geometric mean titers (GMT) of anti-RBD IgG with the 95% CI, expressed in BAU/mL; dotted line in (A) at the level of 15 BAU/mL specifies the positivity threshold
[5-7]. Thus, the live viral neutralization assay showed that anti-RBD-IgG in a concentration of >100 BAU/mL ensured the complete neutralization of three SARS-CoV-2 variants of concern a year after infection, which reduced the risk of reinfection with these virus strains [5]. Another report mentioned that on day 14 after vaccination, the anti-RBD-IgG GMT in individuals, vaccinated with mRNA vaccine, was 7,756 BAU/mL [6]. Thus, quantitative results provide the basis for seeking the common serological correlate of the protective immunity to SARS-CoV-2. Moreover, these data are important for monitoring the natural immunity and facilitate the comparison of immune responses to various vaccines [1]. Significant differences and systematic error in the numerical results, expressed in BAU/mL, associated with the use of different test systems [7], encourage further efforts to unify serological tests for detection of antibodies against SARS-CoV-2.
CONCLUSIONS
The study analyzes dynamic changes in the antibody response to SARS-CoV-2 infection during the natural immunity production. The use of IS-SARS-CoV-2 for calibration of the ELISA test system made in possible to demonstrate a change in the concentration of anti-RBD IgG over a wide range of 36-25, 900 BAU/mL with the widest disparity within two months after the infection. The levels of anti-RBD-IgG gradually decreased with time, however, positive values persisted throughout 12 months of follow-up in the majority of subjects.
12
ВЕСТНИК РГМУ | 1, 2022 | VESTNIKRGMU.RU
References
1. Kristiansen PA, Page M, Bernasconi V, Mattiuzzo G, Dull P, 5. Makar K, et al. WHO International Standard for anti-SARS-CoV-2 immunoglobulin. Lancet. 2021; 397: 1347-8. DOI: 10.1016/ S0140-6736(21)00527-4.
2. Wang Z, Muecksch F, Schaefer-Babajew D, Finkin S, Viant C, 6. Gaebler C, et al. Naturally enhanced neutralizing breadth against SARS-CoV-2 one year after infection. Nature. 2021; 595: 426-31. DOI: 10.1038/s41586-021-03696-9.
3. De Giorgi V, West KA, Henning AN, Chen LN, Holbrook MR, Gross R, et al. Naturally acquired SARS-CoV-2 immunity persists for up to
11 months following infection. J Infect Dis. 2021: jiab295. DOI: 7. 10.1093/infdis/jiab295.
4. SARS-CoV-2-IgG EIA instruction manual. https://xema-medica. com/eng/sets/ifu/Archive/. (kit K153GQIE v2018). (Assessed 20 September 2021).
Gallais F, Gantner P, Bruel T, Velay A, Planas D, Wendling MJ, et al. Evolution of antibody responses up to 13 months after SARS-CoV-2 infection and risk of reinfection. EBioMedicine. 2021; 71: 103561. DOI: 10.1016/j.ebiom.2021.103561. Borobia AM, Carcas AJ, Pérez-Olmeda M, Castaño L, Bertran MJ, García-Pérez J, et al. Immunogenicity and reactogenicity of BNT162b2 booster in ChAdOx1-S-primed participants (CombiVacS): a multicentre, open-label, randomised, controlled, phase 2 trial. Lancet. 2021; 398: 121-30. DOI: 10.1016/S0140-6736(21)01420-3.
Kim Y, Lee JH, Ko GY, Ryu JH, Jang JH, Bae H, et al. Quantitative SARS-CoV-2 Spike Antibody Response in COVID-19 Patients Using Three Fully Automated Immunoassays and a Surrogate Virus Neutralization Test. Diagnostics (Basel). 2021; 11: 1496. DOI: 10.3390/diagnostics11081496.
Литература
1. Kristiansen PA, Page M, Bernasconi V, Mattiuzzo G, Dull P, 5. Makar K, et al. WHO International Standard for anti-SARS-CoV-2 immunoglobulin. Lancet. 2021; 397: 1347-8. DOI: 10.1016/ S0140-6736(21)00527-4.
2. Wang Z, Muecksch F, Schaefer-Babajew D, Finkin S, Viant C, 6. Gaebler C, et al. Naturally enhanced neutralizing breadth against SARS-CoV-2 one year after infection. Nature. 2021; 595: 426-31. DOI: 10.1038/s41586-021-03696-9.
3. De Giorgi V, West KA, Henning AN, Chen LN, Holbrook MR, Gross R, et al. Naturally acquired SARS-CoV-2 immunity persists for up to
11 months following infection. J Infect Dis. 2021: jiab295. DOI: 7. 10.1093/infdis/jiab295.
4. SARS-CoV-2-IgG EIA instruction manual. https://xema-medica. com/eng/sets/ifu/Archive/. (kit K153GQIE v2018). (Assessed 20 September 2021).
Gallais F, Gantner P, Bruel T, Velay A, Planas D, Wendling MJ, et al. Evolution of antibody responses up to 13 months after SARS-CoV-2 infection and risk of reinfection. EBioMedicine. 2021; 71: 103561. DOI: 10.1016/j.ebiom.2021.103561. Borobia AM, Carcas AJ, Pérez-Olmeda M, Castaño L, Bertran MJ, García-Pérez J, et al. Immunogenicity and reactogenicity of BNT162b2 booster in ChAdOx1-S-primed participants (CombiVacS): a multicentre, open-label, randomised, controlled, phase 2 trial. Lancet. 2021; 398: 121-30. DOI: 10.1016/S0140-6736(21)01420-3.
Kim Y, Lee JH, Ko GY, Ryu JH, Jang JH, Bae H, et al. Quantitative SARS-CoV-2 Spike Antibody Response in COVID-19 Patients Using Three Fully Automated Immunoassays and a Surrogate Virus Neutralization Test. Diagnostics (Basel). 2021; 11: 1496. DOI: 10.3390/diagnostics11081496.
BULLETIN OF RSMU | 1, 2022 | VESTNIKRGMU.RU
1З
