Longitudinal Study of SARS-CoV-2 Antibody Characteristics Using Label-Free Immunoassays

Abstract Introduction/Objective Since the start of the COVID-19 pandemic, much research has focused on the kinetics and magnitude of humoral immune response. With the advantages of monitoring real-time immunoreactions, label-free immunoassay (LFIA) is becoming a powerful tool in serology studies. We have developed LFIAs to measure SARS- CoV-2 antibody avidity and neutralization activity in a cohort of COVID-19 patients and determine if they correlate with antibody concentration. Serial serum samples collected from mild to severe COVID-19 patients were measured out to 8 months post-symptom onset to determine the durability of the neutralizing antibody response. Methods/Case Report Based on thin-film interferometry technology, we established a label-free IgG avidity assay and a label-free surrogate virus neutralization test (LF-sVNT). For measurement, sensing probes pre-coated with receptor-binding domain (RBD) of SARS-CoV-2 spike protein are applied to serum samples containing SARS-CoV-2 antibodies. The label-free IgG avidity assay measures the binding strength between RBD and IgG under urea dissociation. The LF-sVNT analyzes the binding ability of RBD to ACE2 after neutralizing RBD with antibodies. Results (if a Case Study enter NA) IgG avidity indices and neutralizing antibody titers (IC50) were determined from serum samples (n=246) from COVID-19 patients (n=113). IgG concentrations were measured using a fluorescent immunoassay. The neutralizing antibody titers showed a weak correlation with IgG concentrations and no correlation with IgG avidity indices. Over the time course up to 8 months post-symptom onset, IgG concentrations and neutralizing antibody titers presented similar trends: an initial rise, plateau and then in some cases a gradual decline after 40 days. The IgG avidity indices, in the same cases, plateaued after the initial rise. Conclusion The results demonstrated that LFIA could be used an excellent solution in the determination of SARS- CoV-2 antibody characteristics. The study found that IgG concentration and neutralizing antibody titer declined over time, while IgG avidity index remained constant after reaching a plateau. The decline of antibody neutralization activity can be attributed to the reduction in antibody quantity rather than the deterioration of antibody quality, as measured by antibody avidity.

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A SARS-CoV-2 Label-Free Surrogate Virus Neutralization Test and a Longitudinal Study of Antibody Characteristics in COVID-19 Patients

10.1101/2021.01.19.21250137 ◽

2021 ◽

Author(s):

Yiqi Ruben Luo ◽

Cassandra Yun ◽

Indrani Chakraborty ◽

Alan H.B. Wu ◽

Kara L. Lynch

Keyword(s):

Symptom Onset ◽

Neutralization Test ◽

Neutralizing Antibody ◽

Virus Neutralization Test ◽

Virus Neutralization ◽

Label Free ◽

Serum Samples ◽

Initial Rise ◽

Igg Avidity ◽

Antibody Titers

AbstractBackgroundThe laboratory-based methods to measure the SARS-CoV-2 humoral response include virus neutralization tests (VNTs) to determine antibody neutralization potency. For ease of use and universal applicability, surrogate virus neutralization tests (sVNTs) based on antibody-mediated blockage of molecular interactions have been proposed.MethodsA surrogate virus neutralization test established on a label-free immunoassay platform (LF-sVNT). The LF-sVNT analyzes the binding ability of RBD to ACE2 after neutralizing RBD with antibodies in serum.ResultsThe LF-sVNT neutralizing antibody titers (IC50) were determined from serum samples (n=246) from COVID-19 patients (n=113), as well as the IgG concentrations and the IgG avidity indices. Although there is variability in the kinetics of the IgG concentrations and neutralizing antibody titers between individuals, there is an initial rise, plateau and then in some cases a gradual decline at later timepoints after 40 days post-symptom onset. The IgG avidity indices, in the same cases, plateau after the initial rise and did not show a decline.ConclusionsThe LF-sVNT can be a valuable tool in clinical laboratories for the assessment of the presence of neutralizing antibodies to COVID-19. This study is the first to provide longitudinal neutralizing antibody titers beyond 200 days post-symptom onset. Despite the decline of IgG concentration and neutralizing antibody titer, IgG avidity index increases, reaches a plateau and then remains constant up to 8 months post-infection. The decline of antibody neutralization potency can be attributed to the reduction in antibody quantity rather than the deterioration of antibody avidity, a measure of antibody quality.SummaryA surrogate virus neutralization test established on a label-free immunoassay platform (LF-sVNT). Using the LF-sVNT and other assays, 246 serum samples from 113 COVID-19 patients were measured. We observed the time course of antibody characteristics beyond 200 days post-symptom onset.

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A SARS-CoV-2 Label-Free Surrogate Virus Neutralization Test and a Longitudinal Study of Antibody Characteristics in COVID-19 Patients

Journal of Clinical Microbiology ◽

10.1128/jcm.00193-21 ◽

2021 ◽

Author(s):

Yiqi Ruben Luo ◽

Cassandra Yun ◽

Indrani Chakraborty ◽

Alan H.B. Wu ◽

Kara L. Lynch

Keyword(s):

Symptom Onset ◽

Neutralization Test ◽

Neutralizing Antibody ◽

Virus Neutralization Test ◽

Virus Neutralization ◽

Label Free ◽

Neutralization Activity ◽

Initial Rise ◽

Igg Avidity ◽

Antibody Titers

Methods designed to measure SARS-CoV-2 humoral response include virus neutralization tests to determine antibody neutralization activity. For ease of use and universal applicability, surrogate virus neutralization tests (sVNTs) based on antibody-mediated blockage of molecular interactions have been proposed. A surrogate virus neutralization test was established on a label-free immunoassay platform (LF-sVNT). The LF-sVNT analyzes the binding ability of SARS-CoV-2 spike protein receptor-binding domain (RBD) to ACE2 after neutralizing RBD with antibodies in serum. The LF-sVNT neutralizing antibody titers (IC50) were determined from serum samples (n=246) from COVID-19 patients (n=113), as well as the IgG concentrations and the IgG avidity indices. Although there was variability in the kinetics of the IgG concentrations and neutralizing antibody titers between individuals, there was an initial rise, plateau and then in some cases a gradual decline at later timepoints after 40 days post-symptom onset. The IgG avidity indices, in the same cases, plateaued after an initial rise and did not show a decline. The LF-sVNT can be a valuable tool in research and clinical laboratories for the assessment of the presence of neutralizing antibodies to COVID-19. This study is the first to provide longitudinal neutralizing antibody titers beyond 200 days post-symptom onset. Despite the decline of IgG concentration and neutralizing antibody titer, IgG avidity index increases, reaches a plateau and then remains constant up to 8 months post-infection. The decline of antibody neutralization activity can be attributed to the reduction in antibody quantity rather than the deterioration of antibody quality, as measured by antibody avidity.

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Kinetics of SARS-CoV-2 Antibody Avidity Maturation and Association with Disease Severity

10.1101/2020.07.30.20165522 ◽

2020 ◽

Author(s):

Yiqi Ruben Luo ◽

Indrani Chakraborty ◽

Cassandra Yun ◽

Alan H.B. Wu ◽

Kara Lake Lynch

Keyword(s):

Disease Severity ◽

Symptom Onset ◽

Strong Correlation ◽

Label Free ◽

Antibody Avidity ◽

Mild Disease ◽

Avidity Assay ◽

Igg Avidity ◽

Kinetics Of ◽

Avidity Maturation

The kinetics of IgG avidity maturation during SARS-CoV-2 infection was studied. The IgG avidity assay used a novel label-free immunoassay technology. It was found that there was a strong correlation between IgG avidity and days since symptom onset, and peak readings were significantly higher in severe than mild disease cases.

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A comparison of four serological assays for detecting anti–SARS-CoV-2 antibodies in human serum samples from different populations

Science Translational Medicine ◽

10.1126/scitranslmed.abc3103 ◽

2020 ◽

Vol 12 (559) ◽

pp. eabc3103 ◽

Cited By ~ 30

Author(s):

Ludivine Grzelak ◽

Sarah Temmam ◽

Cyril Planchais ◽

Caroline Demeret ◽

Laura Tondeur ◽

...

Keyword(s):

Symptom Onset ◽

Blood Donors ◽

Serum Samples ◽

Neutralization Activity ◽

S Protein ◽

Antibody Assays ◽

Antibody Titers ◽

Different Populations ◽

Carboxyl Terminal ◽

Nucleoprotein N

It is of paramount importance to evaluate the prevalence of both asymptomatic and symptomatic cases of SARS-CoV-2 infection and their differing antibody response profiles. Here, we performed a pilot study of four serological assays to assess the amounts of anti–SARS-CoV-2 antibodies in serum samples obtained from 491 healthy individuals before the SARS-CoV-2 pandemic, 51 individuals hospitalized with COVID-19, 209 suspected cases of COVID-19 with mild symptoms, and 200 healthy blood donors. We used two ELISA assays that recognized the full-length nucleoprotein (N) or trimeric spike (S) protein ectodomain of SARS-CoV-2. In addition, we developed the S-Flow assay that recognized the S protein expressed at the cell surface using flow cytometry, and the luciferase immunoprecipitation system (LIPS) assay that recognized diverse SARS-CoV-2 antigens including the S1 domain and the carboxyl-terminal domain of N by immunoprecipitation. We obtained similar results with the four serological assays. Differences in sensitivity were attributed to the technique and the antigen used. High anti–SARS-CoV-2 antibody titers were associated with neutralization activity, which was assessed using infectious SARS-CoV-2 or lentiviral-S pseudotype virus. In hospitalized patients with COVID-19, seroconversion and virus neutralization occurred between 5 and 14 days after symptom onset, confirming previous studies. Seropositivity was detected in 32% of mildly symptomatic individuals within 15 days of symptom onset and in 3% of healthy blood donors. The four antibody assays that we used enabled a broad evaluation of SARS-CoV-2 seroprevalence and antibody profiling in different subpopulations within one region.

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TOP-Plus is a Versatile Biosensor Platform for Monitoring SARS-CoV-2 Antibody Durability

Clinical Chemistry ◽

10.1093/clinchem/hvab069 ◽

2021 ◽

Author(s):

Sabrina E Racine-Brzostek ◽

Mohsen Karbaschi ◽

Christian Gaebler ◽

P J Klasse ◽

Jim Yee ◽

...

Keyword(s):

Post Infection ◽

Neutralizing Antibody ◽

Antibody Avidity ◽

Avidity Assay ◽

Paired Samples ◽

The Status ◽

Antibody Titers ◽

Antigen Interaction ◽

Antibody Levels

Abstract Background Low initial SARS-CoV-2 antibody titers dropping to undetectable levels within months after infection have raised concerns over long term immunity. Both the antibody levels and avidity of the antibody-antigen interaction should be examined to understand the quality of the antibody response. Methods A testing-on-a-probe “plus” panel (TOP-Plus) was developed, which included a newly developed avidity assay built into the previously described SARS-CoV-2 TOP assays that measured total antibody (TAb), surrogate neutralizing antibody (SNAb), IgM and IgG on a versatile biosensor platform. TAb and SNAb levels were compared with avidity in previously infected individuals at 1.3 and 6.2 months post-infection in paired samples from 80 COVID-19 patients. Sera from SARS-CoV-2 vaccinated individuals were also evaluated for antibody avidity. Results The newly designed avidity assay in this TOP panel correlated well with a reference Bio-Layer Interferometry avidity assay (r=0.88). The imprecision of the TOP avidity assay was less than 10%. Although TAb and neutralization activity (by SNAb) decreased between 1.3 and 6.2 months post-infection, the antibody avidity increased significantly (P < 0.0001). Antibody avidity in 10 SARS-CoV-2 vaccinated individuals (median 28 days post-vaccination) was comparable to the measured antibody avidity in infected individuals (median 26 days post-infection). Conclusion This highly precise and versatile TOP-Plus panel with the ability to measure SARS-CoV-2 TAb, SNAb, IgG and IgM antibody levels and avidity of individual sera on one sensor can become a valuable asset in monitoring not only SARS-CoV-2-infected patients, but also the status of individuals’ COVID-19 vaccination response.

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Neutralization Activity of Patient Sera Collected during the 2008-2009 Chikungunya Outbreak in Thailand

Journal of Clinical Microbiology ◽

10.1128/jcm.02744-14 ◽

2014 ◽

Vol 53 (1) ◽

pp. 184-190 ◽

Cited By ~ 4

Author(s):

Natsuko Kishishita ◽

Mikiko Sasayama ◽

Naokazu Takeda ◽

Areerat Sa-ngasang ◽

Atchareeya Anuegoonpipat ◽

...

Keyword(s):

Joint Pain ◽

Clinical Symptoms ◽

Neutralizing Antibody ◽

Serum Samples ◽

Chikv Infection ◽

Neutralization Activity ◽

Proinflammatory Mediators ◽

Adaptive Immune Cells ◽

Number Of Patients ◽

Antibody Titers

Chikungunya virus (CHIKV) infection typically causes fever, rash, myalgia, and arthralgia and sometimes results in recurrent joint pain or, in severe cases, neurological disorders or death. How CHIKV infection leads to prolonged or severe symptoms is still not well understood. In this study, we examined the neutralization (NT) titer of 98 serum samples collected from patients during the 2008-2009 chikungunya outbreak in Thailand. While all serum samples showed neutralizing activity, virus was detected in 58% of the serum samples. When we analyzed a possible association between virus and antibody titers and the presence of typical symptoms of CHIKV infection, fever and joint pain, there was no significant association except that the number of patients with fever was over three times more than the number of those without fever when CHIKV was detectable in serum. This study indicates that although neutralizing antibody is critical to eliminate CHIKV, it appears not to be the main factor associated with clinical symptoms in some cases, so that other aspects of immune responses, such as those involving proinflammatory mediators and adaptive immune cells, should be considered altogether.

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Kinetics of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Antibody Avidity Maturation and Association with Disease Severity

Clinical Infectious Diseases ◽

10.1093/cid/ciaa1389 ◽

2020 ◽

Author(s):

Yiqi Ruben Luo ◽

Indrani Chakraborty ◽

Cassandra Yun ◽

Alan H B Wu ◽

Kara L Lynch

Keyword(s):

Severe Acute Respiratory Syndrome ◽

Disease Severity ◽

Symptom Onset ◽

Strong Correlation ◽

Label Free ◽

Antibody Avidity ◽

Mild Disease ◽

Igg Avidity ◽

Kinetics Of ◽

Avidity Maturation

Abstract The kinetics of IgG avidity maturation during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was studied. The IgG avidity assay, using a novel label-free immunoassay technology, revealed a strong correlation between IgG avidity and days since symptom onset. Peak readings were significantly higher in severe than mild disease cases.

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Serum Neutralizing Activity against B.1.1.7, B.1.351, and P.1 SARS-CoV-2 Variants of Concern in Hospitalized COVID-19 Patients

Viruses ◽

10.3390/v13071347 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1347

Author(s):

Claudia Maria Trombetta ◽

Serena Marchi ◽

Simonetta Viviani ◽

Alessandro Manenti ◽

Linda Benincasa ◽

...

Keyword(s):

Natural Infection ◽

Neutralizing Antibody ◽

Original Strain ◽

Immune Protection ◽

Serum Samples ◽

Symptomatic Infection ◽

Neutralizing Activity ◽

The United Kingdom ◽

Antibody Titers ◽

Pandemic Wave

The recent spreading of new SARS-CoV-2 variants, carrying several mutations in the spike protein, could impact immune protection elicited by natural infection or conferred by vaccination. In this study, we evaluated the neutralizing activity against the viral variants that emerged in the United Kingdom (B.1.1.7), Brazil (P.1), and South Africa (B.1.351) in human serum samples from hospitalized patients infected by SARS-CoV-2 during the first pandemic wave in Italy in 2020. Of the patients studied, 59.5% showed a decrease (≥2 fold) in neutralizing antibody titer against B.1.1.7, 83.3% against P.1, and 90.5% against B.1.351 with respect to the original strain. The reduction in antibody titers against all analyzed variants, and in particular P.1 and B.1.351, suggests that previous symptomatic infection might be not fully protective against exposure to SARS-CoV-2 variants carrying a set of relevant spike mutations.

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Delayed neutralizing antibody response in the acute phase correlates with severe progression of COVID-19

Scientific Reports ◽

10.1038/s41598-021-96143-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hitoshi Kawasuji ◽

Yoshitomo Morinaga ◽

Hideki Tani ◽

Miyuki Kimura ◽

Hiroshi Yamada ◽

...

Keyword(s):

Severe Acute Respiratory Syndrome ◽

Neutralization Test ◽

Neutralizing Antibody ◽

Pseudotyped Virus ◽

Serum Samples ◽

Neutralization Activity ◽

Neutralizing Activity ◽

Time Points ◽

Moderate Disease ◽

Activity Dynamics

AbstractAdaptive immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) dynamics remain largely unknown. The neutralizing antibody (NAb) levels in patients with coronavirus disease 2019 (COVID-19) are helpful for understanding the pathology. Using SARS-CoV-2 pseudotyped virus, serum sample neutralization values in symptomatic COVID-19 patients were measured using the chemiluminescence reduction neutralization test (CRNT). At least two sequential serum samples collected during hospitalization were analyzed to assess NAbs neutralizing activity dynamics at different time points. Of the 11 patients, four (36.4%), six (54.5%), and one (9.1%) had moderate, severe, and critical disease, respectively. Fifty percent neutralization (N50%-CRNT) was observed upon admission in 90.9% (10/11); all patients acquired neutralizing activity 2–12 days after onset. In patients with moderate disease, neutralization was observed at earliest within two days after symptom onset. In patients with severe-to-critical disease, neutralization activity increased, plateauing 9–16 days after onset. Neutralization activity on admission was significantly higher in patients with moderate disease than in patients with severe-to-critical disease (relative % of infectivity, 6.4% vs. 41.1%; P = .011). Neutralization activity on admission inversely correlated with disease severity. The rapid NAb response may play a crucial role in preventing the progression of COVID-19.

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Varicella-zoster plaque assay and plaque reduction neutralization test by the immunoperoxidase technique

Journal of Clinical Microbiology ◽

10.1128/jcm.4.5.437-442.1976 ◽

1976 ◽

Vol 4 (5) ◽

pp. 437-442

Author(s):

G Gerna ◽

R W Chambers

Keyword(s):

Neutralization Test ◽

Plaque Assay ◽

Neutralizing Antibody ◽

Immunoperoxidase Technique ◽

Serum Samples ◽

Plaque Reduction Neutralization Test ◽

Varicella Zoster ◽

Convalescent Phase ◽

Antibody Titers ◽

Indirect Immunoperoxidase

A new plaque assay for the quantitation of varicella-zoster virus and a plaque reduction neutralization test for the determination of neutralizing antibody titer have been developed using the indirect immunoperoxidase technique. As compared with the classical plaque assay using a solid overlay, the test gives earlier results since plaque counting can be performed on day 3 after the inoculation of cell cultures. In six patients with zoster infection, neutralizing antibody titers ranged from 1:20 to 1:40 before the onset of infection and reached high levels (1:320 to 1:5,120) during the convalescent phase of the disease. Complement-fixing (CF) titers were all negative (less than 1:8) in prezoster serum samples from the same patients and ranged from 1:128 to 1:2,048 in the convalescent-phase sera. In the two cases in which late serum samples were available, neutralizing antibody titers matched the preillness levels, whereas CF titers dropped to undetectable levels. Neither neutralizing nor CF antibody was detected in two sera from individuals with no history of varicella-zoster infection. No differences in virus titers or neutralizing antibody titers were observed between the immunoperoxidase and the classical plaque assays. The appropriate characterization of reagent specificity is required before routine application of the test.

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