Scientists determine binding affinity of anti-SARS-CoV-2 antibody in response to infection or vaccination

Scientists in Ireland and France recently evaluated the kinetics of the anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody response induced by acute infection or vaccination.

In the study, it was published in the journal virusScientists have measured the amount and binding affinity (avidity) of antibodies against five different viral proteins.

Background

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), causes unprecedented damage to the global medical system and is 500 million worldwide. More than 50 million cases have been identified and more than 6.3 million have died. ..

COVID-19 vaccines produced at record rates to control the pandemic trajectory have been shown to be highly effective in reducing SARS-CoV-2 infection rate, symptomatic COVID-19, hospitalization, and mortality. ..

Regarding the kinetics of the anti-SARS-CoV-2 antibody response, studies have shown that acute viral infection or vaccination takes about 6 to 15 days to elicit the antibody response and then drops sharply within 3 to 6 months. It is shown.

In the current multicenter study, scientists have thoroughly estimated the titers and binding affinities of antibodies targeting five different antibodies. antigen SARS-CoV-2 Spike proteinReceptor binding domain (RBD), nucleocapsid, spike S2 ​​subunit, and membrane-envelope fusion.

Research design

The kinetics of the infection-induced antibody response was determined by analyzing a total of 522 SARS-CoV-2 positive serum samples collected from 174 healthcare professionals during the 9 months following onset of symptoms.

Similarly, the kinetics of antibody response to vaccination was determined by analyzing serum samples collected from 86 residents of a care facility that had been vaccinated twice with the Pfizer / BioNTech-developed mRNA-based COVID-19 vaccine. it was done. Serum samples were collected before vaccination and 5 weeks and 6 months after the second vaccination.

Serum samples were analyzed in a bead-based multiplex assay to estimate the titers and binding affinities of anti-SARS-CoV-2 antibodies targeting five different viral antigens.

Anti-SARS-CoV-2 antibody titer

The kinetics of all IgG antibodies tested showed a sharp increase in serum titers both after infection and after vaccination, followed by a sharp decline in the first 3-6 months. After that, the antibody titer entered the stage of slowly decreasing.

Anti-spikes and anti-RBD antibodies showed similar patterns to IgG antibodies in terms of the kinetics of IgA-specific antibody responses. However, IgA antibodies declined more rapidly than IgG antibodies.

Consistently higher IgG antibodies to peplomer, RBD, and S2 subunits were observed in previously infected vaccinated individuals compared to uninfected vaccinated individuals.

Binding affinity of anti-SARS-CoV-2 antibody

Analysis revealed that the binding affinity of anti-RBD IgG antibodies peaked at 60% in vaccinated individuals 10 weeks after the first vaccination. However, it took 30 weeks for previously infected but unvaccinated individuals to reach the same level.

In previously infected and vaccinated elderly, the binding affinity between anti-spikes and anti-RBD antibodies peaked at 100% 10 weeks after vaccination. However, in previously uninfected elderly people, the binding affinity peaked at 60%.

Analysis of recent infections

Clear dynamics Antibody titer The binding affinity observed in this study underscores the need to estimate the time since previous SARS-CoV-2 infection. It is well documented that antibody binding affinity assays help distinguish between recent and past infections.

Estimates of time since the last infection were made by including antibody binding affinity and antibody titer measurements in the machine learning algorithm. The findings show that antibody binding affinity is an important biomarker for identifying recent infections and can increase estimation accuracy from 62% to 78%.

Significance of research

This study emphasizes the importance of integrating antibody binding affinity measurements into serological assays to improve seromonitoring during the COVID-19 pandemic.

The novel mutations that appear in the SARS-CoV-2 mutant are mainly involved in the decrease in antigen-antibody binding strength and the increase in virus spike host cell receptor (angiotensin converting enzyme 2) binding strength. These two factors collectively enhance the antigenic escape and transmission capabilities of SARS-CoV-2.

Given these facts, scientists believe that studying changes in antibody binding affinities to newly emerging viral variants is valuable in improving pandemic preparedness.