ABSTRACT
BackgroundIn the fight against SARS-COV-2, the development of serological assays based on different antigenic domains represent a versatile tool to get a comprehensive picture of the immune response or differentiate infection from vaccination beyond simple diagnosis. ObjectivesHere we use a combination of the Nucleoprotein (NP), the Spike 1 (S1) and Spike 2 (S2) subunits, and the receptor binding domain (RBD) and N-terminal domain (NTD) of the Spike antigens from the Syrius-CoViDiag(R) multiplex IgG assay, to follow the immune response to SARS-CoV-2 infection over a long time period and depending on disease severity. ResultsUsing a panel of 209 sera collected from 61 patients up to eight months after infection, we observed that most patients develop an immune response against multiple viral epitope, but anti-S2 antibodies seemed to last longer. For all the tested IgGs, we have found higher titers for hospitalized patients than for non-hospitalized ones. Moreover the combination of the five different IgG titers increased the correlation to the neutralizing antibody titers than if considered individually. ConclusionMultiplex immunoassays have the potential to improve diagnostic performances, especially for ancient infection or mild form of the disease presenting weaker antibody titers. Also the combined detection of anti-NP and anti-Spike-derived domains can be useful to differentiate vaccination from viral infection and accurately assess the antibody potential to neutralize the virus.
ABSTRACT
ObjectiveThe objective of this study was to monitor the anti-SARS-CoV-2 antibody response in infected patients. MethodsIn order to assess the time of seroconversion, we used 151 samples from 30 COVID-19 inpatients and monitored the detection kinetics of anti-S1, anti-S2, anti-RBD and anti-N antibodies with in-house ELISAs. We also monitored the presence of neutralizing antibodies in these samples as well as 25 asymptomatic carrier samples using retroviral particles pseudotyped with the spike of the SARS-CoV-2. ResultsWe observed that specific antibodies were detectable in all inpatients two weeks post-symptom onset. The detection of the SARS-CoV-2 Nucleocapsid and RBD was more sensitive than the detection of the S1 or S2 subunits. Neutralizing antibodies reached a plateau two weeks post-symptom onset and then declined in the majority of inpatients. Furthermore, neutralizing antibodies were undetectable in 56% of asymptomatic carriers. ConclusionsOur results raise questions concerning the role played by neutralizing antibodies in COVID-19 cure and protection against secondary infection. They also suggest that induction of neutralizing antibodies is not the only strategy to adopt for the development of a vaccine. Finally, they imply that anti-SARS-CoV-2 neutralizing antibodies should be titrated to optimize convalescent plasma therapy. HighlightsO_LISpecific antibodies are detectable in 100% COVID-19 inpatients two weeks post-symptom onset. C_LIO_LIThe detection of the SARS-CoV-2 Nucleocapsid and Receptor Binding Domain is more sensitive than the detection of the S1 or S2 subunits. C_LIO_LINeutralizing antibodies reach a plateau two weeks post-symptom onset and then decline in the majority of inpatients. C_LIO_LINeutralizing antibodies are undetectable in the majority of asymptomatic carriers. C_LI
