. Emergency response for evaluating SARS-CoV-2 immune status, seroprevalence and convalescent plasma in Argentina

DIEGO OJEDA; MARIA GONZALEZ; HPRACIO PLALLARES; GUADALUPE COSTA; LAUTARO SANCHEZ; BEATRIZ PERAZZI; SERGIO VILLORDO; DIEGO ALVAREZ; SNDREA GAMARNIK

Plos Pathogens

Michael S Diamon

Lugar: San Francisco; Año: 2021 vol. 17

1553-7374

We report the emergency development and application of a robust serologic test to evaluateacute 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, privateand public health institutions and nursing homes, use a combination of a trimer stabilizedspike protein and the receptor binding domain (RBD) in a single enzyme-linkedimmunosorbent assay (ELISA) plate. Over half million tests have already been distributed todetect and quantify antibodies for multiple purposes, including assessment of immuneresponses in hospitalized patients and large seroprevalence studies in neighborhoods,slums and health care workers, which resulted in a powerful tool for asymptomatic detectionand policy making in the country. Analysis of antibody levels and longitudinal studies ofsymptomatic and asymptomatic SARS-CoV-2 infections in over one thousand patient samplesprovided insightful information about IgM and IgG seroconversion time and kinetics,and IgM waning profiles. At least 35% of patients showed seroconversion within 7 days, and95% within 45 days of symptoms onset, with simultaneous or close sequential IgM and IgGdetection. Longitudinal studies of asymptomatic cases showed a wide range of antibodyresponses with median levels below those observed in symptomatic patients. Regardingconvalescent plasma applications, a protocol was standardized for the assessment of endpoint IgG antibody titers with COVIDAR with more than 500 plasma donors. The protocolshowed a positive correlation with neutralizing antibody titers, and was used for clinical trialsand therapies across the country. Using this protocol, about 80% of convalescent donor plasmas were potentially suitable for therapies. Here, we demonstrate the importance ofproviding a robust and specific serologic assay for generating new information about antibodykinetics in infected individuals and mitigation policies to cope with pandemic needs.