Serological signatures of SARS-CoV-2 infection: Implications for antibody-based diagnostics

Abstract

BackgroundThe antibody response generated following infection with SARS-CoV-2 is expected to decline over time. This may cause individuals with confirmed SARS-CoV-2 infection to test negative according to serological diagnostic tests in the months and years following symptom onset. MethodsA multiplex serological assay was developed to measure IgG and IgM antibody responses to four SARS-CoV-2 Spike (S) antigens: spike trimeric ectodomain (S tri ), its receptor-binding domain (RBD), spike subunit 1 (S1), and spike subunit 2 (S2).Antibody responses were measured in serum samples from patients in French hospitals with RT-qPCR confirmed infection (n = 259), and negative control serum samples collected before the start of the SARS-CoV-2 epidemic in 2019 (n = 335).The multiplex antibody data was used to train a random forests algorithm for classifying individuals with previous SARS-CoV-2 infection. A mathematical model of antibody kinetics informed by prior information from other coronaviruses was used to estimate time-varying antibody responses and assess the potential sensitivity and classification performance of serological diagnostics during the first year following symptom onset. ResultsIgG antibody responses to one S antigen identified individuals with previous RT-qPCR confirmed SARS-CoV-2 infection with 90.3% sensitivity (95% confidence interval (CI); 86.1%, 93.4%) and 99.1% specificity (95% CI; 97.4%, 99.7%). Using a serological signature of IgG to four antigens, it was possible to identify infected individuals with 96.1% sensitivity (95% CI; 93.0%, 97.9%) and 99.1% specificity (95% CI; 97.4%, 99.7%). Antibody responses to SARS-CoV-2 increase rapidly 1-2 weeks after symptom onset, with antibody responses predicted to peak within 2-4 weeks. Informed by prior data from other coronaviruses, one year following symptom onset antibody responses are predicted to decay by approximately 60% from the peak response. Depending on the selection of sero-positivity cutoff, we estimate that the sensitivity of serological diagnostics may reduce to 56% -97% after six months, and to 49% -93% after one year. ConclusionSerological signatures based on antibody responses to multiple antigens can provide more accurate and robust serological classification of individuals with previous SARS-CoV-2 infection. Changes in antibody levels over time may cause reductions in the sensitivity of serological diagnostics leading to an underestimation of sero-prevalence. It is essential that data continue to be collected to evaluate this potential risk.

Evaluating SARS-CoV-2 spike and nucleocapsid proteins as targets for IgG antibody detection in severe and mild COVID-19 cases using a Luminex bead-based assay

“…Nevertheless, many commercial ELISAs became rapidly CE-labelled and are currently used for serosurveillance studies 7 . Since ELISAs as well as VNTs have important limitations for large-scale serosurveillance, microsphere bead-based assays using the Xmap Luminex technology have been increasingly developped [12][13][14] . This high-throughput platform allows the simultaneous detection of antibodies against different antigens from SARS-CoV-2, which can significantly increase the specificity of serological testing, in contrast to ELISA that usually includes only one antigen.…”

<strong>Two SARS-CoV-2 IgG Immunoassays Comparison and Time-Course Profile of Antibodies Response</strong>

“…Concentrations of IgG were found to decline after few months from the onset of symptoms, although the positivity rate remained relatively stable over a longer period [14,15]. A model of antibodies kinetics [16] mainly based on previous experience from other coronaviruses predicted a peak around 2-4 weeks and a subsequent slow decrease of antibody titer, with the hypothesis that about 50% of cases will be negative one year after the infection.…”

A comparison of non-magnetic and magnetic beads for measuring IgG antibodies againstP. vivaxantigens in a multiplexed bead-based assay using Luminex®technology (Bio-Plex®200 or MAGPIX®)

“…Non-magnetic beads: A$640/ml/1.25x10 7 beads 20% less than magnetic beads Up to 100 beads available Magnetic beads: ~A$800/ml/1.25x10 7 beads Up to 50 beads available Better beads retention Whilst these results were obtained in the context of P. vivax-specific IgG responses in individuals from malaria-endemic areas, the large panel of proteins used and consistent results obtained for all proteins suggest these results can be applied to guide studies in other fields. Luminex xMAP ® technology has been used to measure antibody responses against other infectious pathogens, such as HIV and influenza [17,18], to a variety of vaccine antigens such as tetanus toxoid [19], and more recently to SARS-CoV-2 [6][7][8]. was not tested in this experiment.…”

“…This study used a panel of 19 different P. vivax proteins and plasma samples from P. vivax-endemic areas to detect P. vivax-specific IgG responses, however the large number of proteins assessed and consistent results obtained, suggest these findings should be generalizable for optimization of the multiplexed bead-based assay for other pathogens. This is important in the context of the ongoing SARS-CoV-2 pandemic, as multiple laboratory assays based on Luminex technology are under development [6][7][8].…”