Emergency Response for Evaluating SARS-CoV-2 Immune Status, Seroprevalence and Convalescent Plasma in Argentina

Abstract

We report the emergency development and application of a robust serologic test to evaluate acute and convalescent antibody responses to SARS-CoV-2 in Argentina. The assays, COVIDAR IgG and IgM, which were produced and provided for free to health authorities, private and public health institutions and nursing homes, use a combination of a trimer stabilized spike protein and the receptor binding domain (RBD) in a single enzyme-linked immunosorbent assay (ELISA) plate. Over half million tests have already been distributed to detect and quantify antibodies for multiple purposes, including assessment of immune responses in hospitalized patients and large seroprevalence studies in neighborhoods, slums and health care workers, which resulted in a powerful tool for asymptomatic detection and policy making in the country. Analysis of antibody levels and longitudinal studies of symptomatic and asymptomatic SARS-CoV-2 infections in over one thousand patient samples provided insightful information about IgM and IgG seroconversion time and kinetics, and IgM waning profiles. At least 35% of patients showed seroconversion within 7 days, and 95% within 45 days of symptoms onset, with simultaneous or close sequential IgM and IgG detection. Longitudinal studies of asymptomatic cases showed a wide range of antibody responses with median levels below those observed in symptomatic patients. Regarding convalescent plasma applications, a protocol was standardized for the assessment of end point IgG antibody titers with COVIDAR with more than 500 plasma donors. The protocol showed a positive correlation with neutralizing antibody titers, and was used to assess antibody titers for clinical trials and therapies across the country. Here, we demonstrate the importance of providing a robust and specific serologic assay for generating new information about antibody kinetics in infected individuals and mitigation policies to cope with pandemic needs.

An“In-House”ELISA for SARS-CoV-2 RBD uncovers elevated immune response at higher altitudes

“…Therefore, in order to resolve this shortage and support state-led diagnostic efforts, many research laboratories have repurposed their expertise, skilled labor and equipment by developing and assembling in-house testing kits, among other efforts [4][5][6][7] . SARS-CoV-2 serological tests employ enzyme-linked immunosorbent assay (ELISA) 8,9 , immunofluorescence 10 and lateral flow techniques to detect antibodies directed against the nucleocapsid (N) and/or Spike (S) proteins of the viral proteome 11 .…”

Dynamics of SARS-CoV-2-specific antibodies during and after COVID19: Lessons from a biobank in Argentina

“…In a breakthrough report, Ibarrondo et al described that SARS-CoV-2 IgG antibodies decayed early and rapidly after symptom onset in persons with mild disease [14]. Other studies confirmed that indeed there is a decay in IgG levels but at a slower rate and at later times than that reported by Ibarrondo et al [11, 15-21]. Although our understanding in the antibody dynamics is still incomplete, specific IgG levels appear to be maintained during 4-5 months, or even longer, if we consider our data from plasma non-donors, presented in figure 5A.…”

“…This kit was developed by Argentinean researchers from CONICET, Fundación Instituto Leloir and UNSAM together with Laboratorio Lemos S.R.L. The validation process determined that sensitivity to detect specific IgG raises to 90% after 3 weeks of symptoms onset while specificity is 100% [11]. Briefly, samples were loaded in wells pre-coated with recombinant SARS-CoV-2 Spike protein and RBD.…”

Long-Term Duration of Antibody Response to SARS CoV-2 in One of the Largest Slums of Buenos Aires

“…Performance characteristics of the kit indicate a sensitivity of more than 90% after 21 days and more than 95% after 45 days of symptoms onset. The specificity was set to be 100% (8). None of the funding sources provided economical support for the data collection, statistical analysis, or were used to write the manuscript, or to submit it for publication.…”

“…Most of the neutralizing antibodies are directed against the S protein and more specifically to the receptor binding domain RBD (7). Multiple studies have shown that the majority of SARS-CoV-2-infected individuals produce S-and RBD-specific antibodies during the first 2 weeks of the primary response (8). In addition, monoclonal antibodies against this viral protein neutralize the virus in vitro and in vivo (9)(10)(11).…”