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Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) antibody detection and testing are helpful in evaluating the antibody response after infection and vaccination in serum surveillance studies, and distinguishing vaccine-induced and natural SARS-CoV-2 Seropositivity induced by infection.

Research: Antibody response to SARS-CoV-2 for more than one year-the kinetics and persistence of the test mainly depend on the affinity progress and test design. Photo Credit: Kateryna Kon/Shutterstock

However, the interpretation of the SARS-CoV-2 antibody response is still challenging because the results of SARS-CoV-2 antibody tests vary widely and there is considerable heterogeneity among SARS-CoV-2 infected persons. In addition, it is difficult to predict the duration of the antibody response in individuals infected with SARS-CoV-2.

In a review published in the Journal of Clinical Virology, the researchers described the course and duration of the antibody response in a series of symptomatic COVID-19 patients of varying severity over a year. They used 12 anti-SARS-CoV-2 antibody detection methods in this study. These tests include different test designs and antibody (Ab) type tests (total antibodies (TAb), IgG, IgA, IgM) and SARS-CoV-2 target antigens (nucleocapsid protein (N), receptor binding domain (RBD) ), Spike protein (S)). In addition, the researchers tested neutralizing antibodies, assessed test sensitivity, antibody titers, and determined antibody affinity. 

The researchers analyzed the antibody response in samples of 828 patients within 5-430 days after the onset of symptoms (pso). The donor's nucleic acid amplification test (NAT) tested positive and showed symptoms of COVID-19. Their samples were collected and examined for up to 14 months.

In this study, researchers examined two groups to assess the impact of the severity of COVID-19 symptoms-the mild COVID-19 group (1-3 points) and the severe COVID-19 group that requires oxygen (4-7 Points) or ventilation support. Due to the heterogeneity of the mild COVID-19 group, it shows extensive antibody reactivity, which partially overlaps with the severe COVID-19 group, which is consistent with the results of past studies, and there is corresponding variability between different tests. Over time, the results showed unique test-specific patterns, allowing the differences between these tests to be classified.

The duration and sensitivity of antibody detection depend on the development of the test design and high affinity. The sandwich test design of TAb detection and RBD/S-based detection, based on the increase in affinity for S/RBD, leads to higher sensitivity over time. Therefore, these tests show the highest and lasting sensitivity, have stable antibody titers throughout the 14-month observation period, and have no predictable detection endpoints. For up to 300 days of pso, the sensitivity of IgG-S/RBD and IgA-S tests was stable, and then the pso dropped by 10-16% at 430 days, and during this period, the antibody titer decreased moderately.

On the other hand, N-based detection is not as sensitive as the corresponding S-based detection. Therefore, they showed an early decline in antibody titers from the 120th day. Due to its sandwich design, the sensitivity of TAb-N only slightly decreases at 430 days pso. A decrease in antibody titer indicates a further decrease in sensitivity. The IgG-N sensitivity decreased much faster after 120 days, but eventually became insignificant after 240-300 days. 

The sensitivity of the IgM-RBD test indicates that IgM is not suitable for predicting the exact time of infection. Its sensitivity is limited to 30-60 days pso, and then rapidly declines, which is inconsistent because some people continue to show IgM over time.

After 430 days, NAbs targeting RBD showed consistently high or slightly increased base sensitivity of 90-94%, indicating that the duration of neutralization was longer than that shown in past studies. Most patients reach 76% high antibody affinity after 12 months and 94% after 14 months. The affinity for immunogenic S and RBD slowly increased to more than 60% after 120 days, then stabilized, and then further increased after 430 days. In contrast, the affinity for N is low, with only 20-26% of patients showing high affinity.

All in all, the sensitivity to IgG-S, TAb-N, TAb-S/RBD, IgG-N, IgA-S, IgM-RBD and NAb within 30-60 days after surgery was 89.7%, 99.5%, 96.6% , Respectively, 94.3%, 80.9%, 76.9% and 92.8%. During the 430-day pso follow-up, the results showed a slight increase in TAb-S/RBD and a slight decrease in TAb-N. In addition, IgG-S and IgA-S decreased moderately, NAb remained positive, and then decreased slightly after 300 days. IgG-N decreased significantly from day 120, while IgM-RBD decreased after 30-60 days. The test specificity is ≥99%, except for IgA, which has a test sensitivity of 96%. After 430 days, 94.3% of patients observed stable high antibody affinity against S and RBD. Based on the antibody binding efficiency of the test design, these findings are related to continuous antibody detection. 

Research results show that antibody testing shows different patterns, depending on the type of antibody detected, the target antigen, the test design, the level of antibody affinity, and the severity of COVID-19. The duration of the antibody response is mainly driven by the advancement of S/RBD affinity and its utilization through the corresponding test design. The S/RBD-based TAb detection shows high sensitivity and continuous antibody detection for PSOs over 14 months, with consistent antibody titers.

Published in: Medical News | Medical Research News | Disease/Infection News

Tags: Antibody, Antibody, Antigen, Coronavirus, Coronavirus Disease COVID-19, Nucleic Acid, Oxygen, Protein, Receptor, Research, Respiratory, SARS, SARS-CoV-2, Severe Acute Respiratory System, Severe Acute Respiratory Syndrome , Spike protein, syndrome, vaccine, virology

Neha Mathur has a master's degree in biotechnology and extensive experience in digital marketing. She is passionate about reading and music. Outside of work, Neha likes to cook and travel.

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Mathur, Neha. "The kinetics and persistence of the SARS-CoV-2 antibody response". News-Medical. https://www.news-medical.net/news/20211209/Kinetics-and-persistence-of-SARS-CoV-2-antibody-responses.aspx. (Accessed on December 14, 2021).

Mathur, Neha. 2021. The kinetics and persistence of SARS-CoV-2 antibody response. News-Medical, accessed on December 14, 2021, https://www.news-medical.net/news/20211209/Kinetics-and-persistence-of-SARS-CoV-2-antibody-responses.aspx.

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