Serum-IgG responses to SARS-CoV-2 after mild and severe COVID-19 infection and analysis of IgG non-responders
Journal article, 2020

Background To accurately interpret COVID-19 seroprevalence surveys, knowledge of serum-IgG responses to SARS-CoV-2 with a better understanding of patients who do not seroconvert, is imperative. This study aimed to describe serum-IgG responses to SARS-CoV-2 in a cohort of patients with both severe and mild COVID-19, including extended studies of patients who remained seronegative more than 90 days post symptom onset. Methods SARS-CoV-2-specific IgG antibody levels were quantified using two clinically validated and widely used commercial serological assays (Architect, Abbott Laboratories and iFlash 1800, YHLO), detecting antibodies against the spike and nucleocapsid proteins. Results Forty-seven patients (mean age 49 years, 38% female) were included. All (15/15) patients with severe symptoms and 29/32 (90.6%) patients with mild symptoms of COVID-19 developed SARS-CoV-2-specific IgG antibodies in serum. Time to seroconversion was significantly shorter (median 11 vs. 22 days, P= 0.04) in patients with severe compared to mild symptoms. Of the three patients without detectable IgG-responses after >90 days, all had detectable virus-neutralizing antibodies and in two, spike-protein receptor binding domain-specific IgG was detected with an in-house assay. Antibody titers were preserved during follow-up and all patients who seroconverted, irrespective of the severity of symptoms, still had detectable IgG levels >75 days post symptom onset. Conclusions Patients with severe COVID-19 both seroconvert earlier and develop higher concentrations of SARS-CoV-2-specific IgG than patients with mild symptoms. Of those patients who not develop detectable IgG antibodies, all have detectable virus-neutralizing antibodies, suggesting immunity. Our results showing that not all COVID-19 patients develop detectable IgG using two validated commercial clinical methods, even over time, are vital for the interpretation of COVID-19 seroprevalence surveys.

Author

Emelie Marklund

University of Gothenburg

Susannah Leach

Sahlgrenska University Hospital

Hannes Axelsson

Sahlgrenska University Hospital

Kristina Nystrom

University of Gothenburg

Helene Norder

University of Gothenburg

Mats Bemark

Sahlgrenska University Hospital

Davide Angeletti

Sahlgrenska University Hospital

Anna Lundgren

Sahlgrenska University Hospital

Staffan Nilsson

Chalmers, Mathematical Sciences, Applied Mathematics and Statistics

University of Gothenburg

Lars-Magnus Andersson

University of Gothenburg

Aylin Yilmaz

University of Gothenburg

Magnus Lindh

University of Gothenburg

Jan-ake Liljeqvist

University of Gothenburg

Magnus Gisslen

University of Gothenburg

PLoS ONE

1932-6203 (ISSN) 19326203 (eISSN)

Vol. 15 10 e0241104

Subject Categories

Infectious Medicine

Gastroenterology and Hepatology

Rheumatology and Autoimmunity

DOI

10.1371/journal.pone.0241104

PubMed

33085715

More information

Latest update

12/3/2020