The Study of Humoral Immunity in Healthсare Workers Exposed to COVID-19 Patients

Introduction: Today, the novel coronavirus disease (hereinafter referred to as COVID-19) is spreading very quickly, and the healthcare workers exposed to COVID-19 patients represent the most vulnerable occupational cohort at risk of this contagious disease. Issues of immunological protection and health monitoring in medical personnel are of special interest and importance during the pandemic.

The objective of our study was to assess humoral immunity in healthcare professionals by the presence of class G (IgG) antibodies to the nucleocapsid protein of SARS-CoV-2.

Methods: We selected 345 healthcare workers of different specialties who might have been exposed to COVID-19 patients in hospitals and 72 ageand sex-matched controls (engineers, IT-personnel, and accountants) working elsewhere. Blood immunoglobulins G to the nucleocapsid protein of SARS-CoV-2 were tested by enzyme immunoassay using the commercial test kit produced by the Scientific Center for Applied Microbiology and Biotechnology, Obolensk, Russian Federation. The presence of IgG antibodies was established by the SARS-CoV-2 IgG antibody response index (index of positivity) calculated as the ratio of the optical density of the sample to the cut-off level of the assay.

Results: The average IgG antibody response index value was significantly higher in the healthcare workers compared to the controls (p < 0.05). IgG antibodies to SARS-CoV-2 were more prevalent in nurses than in physicians (42.2 ± 3.6 % vs 31.0 ± 3.7 %, p < 0.05) and controls (42.2 ± 3.6 % vs 27.8 ± 5.3 %, p < 0.05) and their index values were higher than in the comparison group (p < 0.05).

Conclusion: Our findings demonstrate a high prevalence of diagnostically important SARS-CoV-2 IgG antibody response and higher index values in nurses possibly related to prolonged contacts with COVID-19 patients. IgG antibodies found in 37.1 ± 2.6 % of the healthcare workers may be a consequence of both symptomatic and asymptomatic diseases and requires further study. According to the generally accepted opinion about the mechanisms of immune response to viral infections, we could assume the presence of protective immunity against COVID-19, but this issue requires further investigation. In the current epidemic situation, however, detection of IgG antibodies to SARS-CoV-2 can be used for implementation of preventive strategies among healthcare workers.

1. Khegay SV, Dzhaparova AK, Dushenalieva EM, et al. Molecular diagnostics of coronavirus infection in the Kyrgyz Republic. Problemy Osobo Opasnykh Infektsiy. 2020; (2):141–143. (In Russian). https://doi.org/10.21055/0370-1069-2020-2-141-143

2. Rakhmanova DN. [Clinical features of coronavirus infection.] Vestnik Nauki. 2020; 3(7(28)):104–108. (In Russian).

3. Chernyshova LI. Coronavirus disease (lecture). Aktual’naya Infektologiya. 2020; 8(2):6–9. (In Ukrainian). https://doi.org/10.22141/2312-413x.8.2.2020.199729

4. Romanov BK. Coronavirus disease COVID-2019. Bezopasnost’ i Risk Farmakoterapii. 2020; 8(1):3–8. (In Russian). https://doi.org/10.30895/23127821-2020-8-1-3-8

5. Sannikova NR, Teterina AD, Zheleznova AD. Clinical features of coronavirus infection COVID-19. Meditsinskoe Obrazovanie Segodnya. 2020; (3(11)):181–190. (In Russian).

6. Kolodkina EV, Bakulina EA, Bekker ED. Etiology of coronavirus infection. Meditsinskoe Obrazovanie Segodnya. 2020; (3(11)):157–164. (In Russian).

7. Zhai P, Ding Y, Wu X, et al. The epidemiology, diagnosis and treatment of COVID-19. Int J Antimicrob Agents. 2020; 55(5):105955. https://doi.org/10.1016/j.ijantimicag.2020.105955

8. Long QX, Liu BZ, Deng HJ, et al. Antibody responses to SARS-CoV-2 in patients with COVID-19. Nat Med. 2020; 26(6):845–848. https://doi.org/10.1038/s41591-020-0897-1

9. Lee C, Lin R, Renia L, et al. Serological approaches for COVID-19: Epidemiologic perspective on surveillance and control. Front Immunol. 2020; 11:879. https://doi.org/10.3389/fimmu.2020.00879

10. Wang B, Wang L, Kong X, et al. Long-term coexistence of SARS-CoV-2 with antibody response in COVID-19 patients. J Med Virol. 2020; 92(9):1684–1689. https://doi.org/10.1002/jmv.25946

11. Patel R, Babady E, Theel ES, et al. Report from the American Society for Microbiology COVID-19 International Summit, 23 March 2020: Value of Diagnostic Testing for SARS–CoV-2/COVID-19. mBio. 2020; 11(2):e00722-20. https://doi.org/10.1128/mBio.00722-20

12. Kolodkina EV, Latyshko OV. Pathogenesis of coronavirus infection. Meditsinskoe Obrazovanie Segodnya. 2020; (3(11)):165–173. (In Russian).

13. Shen L, Wang C, Zhao J, et al. Delayed specific IgM antibody responses observed among COVID-19 patients with severe progression. Emerg Microbes Infect. 2020; 9(1):1096–1101. DOI: https://doi.org/10.1080/22221751.2020.1766382

14. Nikiforov VV, Suranova TG, Chernobrovkina TYu, et al. New coronavirus infection (Covid-19): Clinical and epidemiological aspects. Arkhiv Vnutrenney Meditsiny. 2020; 10(2):87–93. (In Russian). https://doi.org/10.20514/2226-6704-2020-10-2-87-93

15. Pancrazzi A, Magliocca P, Lorubbio M, et al. Comparison of serologic and molecular SARS-CoV 2 results in a large cohort in Southern Tuscany demonstrates a role for serologic testing to increase diagnostic sensitivity. Clin Biochem. 2020; 84:87–92. https://doi.org/10.1016/j.clinbiochem.2020.07.002

16. Özçürümez MK, Ambrosch A, Frey O, et al. SARSCoV-2 antibody testing – questions to be asked. J Allergy Clin Immunol. 2020; 146(1):35–43. https://doi.org/10.1016/j.jaci.2020.05.020

17. Zhang L, Pang R, Xue X, et al. Anti-SARS-CoV-2 virus antibody levels in convalescent plasma of six donors who have recovered from COVID-19. Aging (Albany NY). 2020; 12(8):6536–6542. https://doi.org/10.18632/aging.103102

18. Mathur G, Mathur S. Antibody testing for COVID-19. Am J Clin Pathol. 2020; 154(1):1–3. https://doi.org/10.1093/ajcp/aqaa082

19. Chowdhury MA, Hossain N, Kashem MA, et al. Immune response in COVID-19: A review. J Infect Public Health. 2020; 13(11):1619–1629. https://doi.org/10.1016/j.jiph.2020.07.001

20. Paces J, Strizova Z, Smrz D, et al. COVID-19 and the immune system. Physiol Res. 2020; 69(3):379–388. https://doi.org/10.33549/physiolres.934492

21. Bevova MR, Netesov SV, Aulchenko YuS. New coronavirus infection COVID-19. Molekulyarnaya Genetika, Mikrobiologiya i Virusologiya. 2020; 38(2):51–58. (In Russian). https://doi.org/10.17116/ molgen20203802151

22. Altmann DM, Douek DC, Boyton RJ. What policy makers need to know about COVID-19 protective immunity. Lancet. 2020; 395(10236):1527–1529. https://doi.org/10.1016/S0140-6736(20)30985-5

23. Randolph HE, Barreiro LB. Herd immunity: Understanding COVID-19. Immunity. 2020; 52(5):737– 741. https://doi.org/10.1016/j.immuni.2020. 04.012

24. Kadkhoda K. COVID-19: an immunopathological view. mSphere. 2020; 5(2):e00344-20. https://doi.org/10.1128/mSphere.00344-20

25. Kang H, Wang Y, Tong Z, et al. Retest positive for SARS-CoV-2 RNA of “recovered” patients with COVID-19: Persistence, sampling issues, or re-infection? J Med Virol. 2020; 92(11):2263–2265. https://doi.org/10.1002/jmv.26114

26. Shi Y, Wang G, Cai XP, et al. An overview of COVID-19. J Zhejiang Univ Sci B. 2020; 21(5):343–360. https://doi.org/10.1631/jzus.B2000083

27. Lotfi M, Hamblin MR, Rezaei N. COVID-19: Transmission, prevention, and potential therapeutic opportunities. Clin Chim Acta. 2020; 508:254–266. https://doi.org/10.1016/j.cca.2020.05.044

28. Asselah T, Durantel D, Pasmant E, et al. COVID-19: Discovery, diagnostics and drug development. J Hepatol. 2021; 74(1):168–184. https://doi.org/10.1016/j.jhep.2020.09.031

29. Rodríguez Y, Novelli L, Rojas M, et al. Autoinflammatory and autoimmune conditions at the crossroad of COVID-19. J Autoimmun. 2020; 114:102506. https://doi.org/10.1016/j.jaut.2020.102506

30. Brüssow H. Immunology of COVID-19. Environ Microbiol. 2020; 22(12):4895–4908. https://doi.org/10.1111/1462-2920.15302