Antibodies against original COVID-19 strain may not be effective against variants

The antibodies produced from the original COVID-19 virus strain are not equipped to fight against viral variants, a study suggests. 

The study, published in June, identified two gene sequences commonly found in antibodies against the virus that causes COVID-19.¹ These gene sequences called “clonotypes” are part of the antibodies that bind to the spike protein. 

How do antibodies protect against COVID-19 infection?

The SAR-CoV-2 virus is covered with spike proteins that contain a receptor-binding domain (RBD). This domain or area binds to receptors on human cells to gain entry and cause infection.¹ RBD antibodies bind to the RBD to prevent this interaction from happening. 

Both clonotypes identified by the research team are RBD antibodies that have a high frequency among public COVID-19 infections. 

​​“Antibody response is quite relevant to everything from understanding natural infection and how we recover from infection to vaccine design”, said Dr. Nicholas Wu, professor of biochemistry and co-author of the study. “That means we can design vaccines trying to elicit this kind of antibody response, and that is probably going to improve the responsiveness of more individuals to the vaccine.”²

Antibodies against variant COVID-19 strains differ

The study went on to compare the effectiveness of both clonotypes for the original SARS-CoV-2 strain to variant strains from South Africa and Brazil. These variants decreased the affinity of the clonotypes to the spike protein.¹  

“Even though this antibody response is very common with the original strain, it doesn’t really interact with variants,” Dr. Wu commented.² This finding suggests that new variants could reinfect individuals who have already had COVID-19. 

The varying immune response between strains emphasizes the potential need for a vaccine booster to combat new variant strains. However, more data needs to be collected to determine which immune response is needed to protect the majority of the population from COVID-19 infection.

References

1. Tan, T.J.C. et al. (2021). Sequence signatures of two public antibody clonotypes that bind SARS-CoV-2 receptor binding domain. Nature Communications; 12:3815. Doi: 10.1038/s41467-021-24123-7. 
2. Touchstone, L. (2021). Antibodies from original strain COVID-19 infection don’t bind to variants, study finds. EurekAlert! Accessed Sept 23, 2021. Retrieved from https://www.eurekalert.org/news-releases/928827. 
3. Image by Gerd Altmann from Pixabay