| dc.description.abstract | The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the end of 2019 quickly developed into a pandemic. COVID-19, the disease caused by SARS-CoV-2, has led to over 6 million deaths since the end of 2019. To prevent more deaths and to be prepared for next variants appearing, it is important to study the immune response against SARS-CoV-2. Antibodies are a crucial part of the immune response against SARS-CoV-2. They can bind to the outside of the virus, thereby blocking the virus from entry into human cells. Therefore, it is essential to study what qualities influence the binding efficiency of these antibodies to the virus, as well as how the development of these antibodies by the body can be induced with vaccines. Here, rhesus macaques were immunized with purified spike, a protein present on the outside of SARS-CoV-2. This protein is responsible for the entry of the virus into human cells, and is the primary target for blocking antibodies against SARS-CoV-2 infection. After immunizations, B-cells were isolated from the immunized rhesus macaques. Each of these B-cells produces a unique antibody. The RNA coding for an antibody was sequenced from single B-cells. Based on this RNA sequence, the antibodies were produced in the laboratory for further characterization. This way, 56 different antibodies were produced. 44 out of the 56 antibodies were determined to bind to the Spike protein. The specific part of the spike protein binding to the human cells is the receptor binding domain (RBD). It was determined that 16 out of the 44 spike binders could also bind to the RBD. Although the antibodies bind to the virus, it does not necessarily mean that they can also prevent the virus from entering the cells. To find out if the virus can still enter the cells, a neutralization assay must be performed. From this assay, it became clear that 13 antibodies could prevent the virus from entering the cell. These antibodies are very interesting to study, because they might help to find antibody characteristics important for preventing or treating SARS-CoV-2 infection. Therefore, we wanted to see the specific site on the spike protein that the antibodies bound. We determined that there is a high probability that 9 of the antibodies have a similar binding site, whereas there are 2 antibodies that have a completely different binding site. Lastly, the appearance of new viral variants is a worldwide concern, therefore it is essential to find out which properties allow antibodies to bind to different variants. Thus, a neutralization assay was performed again, to determine if these antibodies could also prevent other SARS-CoV-2 variants from entering human cells. The Omicron subvariants BA.1 and BA.2 were still neutralized well by 4 out of the 5 tested antibodies, however Omicron subvariant BA.4/5 was only neutralized by 1 out of the 5 tested antibodies (antibody 23). With this report, the description of several neutralizing antibodies induced by Spike-immunization can contribute to further understanding on what properties provide antibodies with the neutralizing capability. Additionally, this report resulted in the finding of an antibody capable of neutralizing several different variants that will be valuable to study in the future. | |
