Original Article: https://doi.org/10.1371/journal.pone.0241104
- To accurately interpret COVID-19 surveys related to positive results, it is important to learn the knowledge of serum-IgG responses to COVID-19 virus with a better understanding of patients who do not develop antibody.
- The research aimed to describe serum-IgG responses to COVID-19 virus in a group of patients with both severe and mild cases of COVID-19.
- The research includes extended analyses of patients who do not develop specific antibodies for more than 90 days after symptoms begun.
- SARS-CoV-2-specific IgG antibody levels were quantified using two clinically validated and widely used commercial serological assays.
- The assays detected antibodies against the spike and nucleocapsid proteins.
- Forty-seven patients with an average age of 49 years were included.
- Of all the patients, 38% are female.
- All patients with severe symptoms and most of the patients with mild symptoms of COVID-19 developed SARS-CoV-2-specific IgG antibodies in serum.
- The time it takes for the antibody to be detected is significantly shorter in patients with severe compared to mild symptoms.
- Three patients without detectable IgG-responses after 90 days were observed and all had detectable virus-neutralizing antibodies.
- From the three patients, two had 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 developed antibody, regardless of the severity of symptoms, still had detectable IgG levels after 75 days after symptoms begun.
- Patients with severe COVID-19 both develop antibody earlier and develop higher concentrations of SARS-CoV-2-specific IgG compared to patients with mild symptoms.
- Patients who not develop detectable IgG antibodies have detectable virus-neutralizing antibodies.
- The results show that not all COVID-19 patients develop detectable IgG antibody, and are vital for the interpretation of COVID-19 seroprevalence surveys.
Marklund E, Leach S, Axelsson H, Nyström K, Norder H, Bemark M, et al. (2020) Serum-IgG responses to SARS-CoV-2 after mild and severe COVID-19 infection and analysis of IgG non-responders. PLoS ONE 15(10): e0241104. https://doi.org/10.1371/journal.pone.0241104