Anti-SARS-CoV-2 IgG antibody response among Indian COVID-19 patients using β-propiolactone-inactivated, whole virus-based indirect ELISA
- J Virol Methods. 2021 Jan:287:113996. doi: 10.1016/j.jviromet.2020.113996.
- 1. Department of Communicable Diseases, Interactive Research School for Health Affairs (IRSHA), Bharati Vidyapeeth (Deemed to be University), Pune, India.
- 2. Department of Pediatrics, Bharati Vidyapeeth Medical College, Pune, India.
- 3. Department of Communicable Diseases, Interactive Research School for Health Affairs (IRSHA), Bharati Vidyapeeth (Deemed to be University), Pune, India. Electronic address: [email protected].
Background: Coronavirus disease 2019 (COVID-19) pandemic caused by Infection with severe acute respiratory syndrome - coronavirus-2 (SARS-CoV-2) continues to affect many countries and large populations. Serologic assays for antibody detection aid patient diagnosis and seroepidemiologic investigations.
Methods: An indirect IgG ELISA was developed indigenously using β-propiolactone (BPL) inactivated SARS-CoV-2. This assay was used for screening 200 healthy donor sera collected prior to COVID-19 emergence (2017-2019), 185 serum/plasma samples of confirmed COVID-19 patients (n = 137) and 57 samples of viral RNA positive asymptomatic contacts (n = 51). The IgG response was studied in relation to duration and severity of illness.
Results: The ELISA demonstrated 97 % specificity and IgG detection in >50 %, 80 %, 93.8 % and 100 % of the patients respectively during the first, second, third and fourth week of illness. IgG detection rate was higher in patients with severe disease (SD, 90.9 %) than those with mild disease (MD, 68.8 %) during the second week of illness (P = 0.027). IgG seropositivity among asymptomatic contacts was 64.7 %. IgG ELISA absorbance values were higher in SD than MD patients during the first 2 weeks of illness (P < 0.05). No significant difference was observed between the absorbance values of asymptomatic subjects and MD patients (P = 0.94).
Conclusion: The BPL inactivated virus-based ELISA could detect IgG antibodies early and in a significant proportion of COVID-19 patients suggesting its potential utility as a supplement to the currently used viral RNA detection tests in patient diagnosis and contact screening algorithms.