After analyzing 639 convalescent participants, 72.9% showed anti-RBD IgG seroconversion with a concentration range in serum between 5 and 55 μg/mL, and no significant correlation with gender, age, and days after symptom offset were observed between groups. In this study, we quantified the abundance of IgG antibodies against the S1-RBD fragment of SARS-CoV-2 in people who recovered from COVID-19 in Santiago, Chile. Antibodies against this segment have been reported as antiviral based on their neutralizing activity in plasma. The SARS-CoV-2 shows two structural proteins as major immunogens, the spike (S) and nucleocapsid (N) proteins, with the RBD domain of the S protein being responsible for the infection of respiratory epithelial cells via interaction with the cell surface receptor angiotensin converting enzyme 2 (ACE2). Īccurate quantitative measurement of anti-SARS-CoV-2 antibody responses is essential for public health interventions and therapeutic applications. The clinical features of COVID-19 vary widely, ranging from asymptomatic to mild or severe forms with multiorgan dysfunction, and most COVID-19 data were derived from hospitalized patients. In patients infected with SARS-CoV-2, immunoglobulin M (IgM) antibodies are detectable around 7 days postinfection and IgG antibodies usually take two weeks to develop. It is widely accepted that IgM provides the first line of defense during viral infections, before generating an adaptive response with a high-affinity IgG production, which is important for long-term immunity and immunological memory. The measurement of serum antibodies has provided crucial data for understanding key aspects of the infection. However, these efforts still do not seem to be enough to control this sanitary emergency. The government and the private sector have implemented several programs to mitigate this pandemic, including PCR and rapid testing across the country, while some institutions have started trials for convalescent plasma. Currently, Chile has reported half a million infected people and more than 16,000 deaths caused by COVID-19. It emerged in December 2019 in Wuhan, China, and was subsequently declared a worldwide pandemic by the World Health Organization (WHO). IntroductionĬoronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The quantification of anti-RBD IgG in convalescent plasma donors is necessary to increase the detection of neutralizing antibodies. We confirmed that the majority of the Chilean patients have developed anti-SARS-CoV-2 antibodies. Neutralizing activity correlated with an increased concentration of anti-RBD IgG ( ) and showed a high variability between donors. Analysis by gender, age, and days after symptom offset did not show significant differences. 72.9% of the convalescent population (468 of 639) showed seroconversion (5-55 μg/mL anti-RBD IgG) and were suitable candidates for plasma donation. ELISA and a luminescent SARS-CoV-2 pseudotype were used for IgG and neutralizing antibody quantification.
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As part of the clinical trial NCT04384588, we quantified IgG against S1-RBD of SARS-CoV-2 (anti-RBD) in recovered people in Santiago and evaluated their suitability as COVID-19 convalescent plasma donors. In Chile, half a million people have been infected and more than 16,000 have died from COVID-19. COVID-19 is a pandemic caused by SARS-CoV-2.