Expression and characterization of the reactivity of recombinant monoclonal antibodies from B lymphocytes from COVID-19 convalescent patients to SARS-CoV-2 variants

• Grant number: 22/08207-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2022
• End date: August 31, 2023
• Field of knowledge: Biological Sciences - Immunology - Applied Immunology
• Principal Investigator: Silvia Beatriz Boscardin
• Grantee: Catarina Harumi Oda Ibrahim
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Coronavirus Disease 2019 (COVID-19) is caused by SARS-CoV-2 virus and has achieved pandemic character at the beginning of 2020. Virus entry in host cells is mediated by spike (S) proteins, which are densely glycosylated proteins present in SARS-CoV-2 envelope, by binding its structure to Angiotensin-Converting Enzyme 2 receptor (ACE-2). Previous studies have shown that this interaction is promoted by the Receptor Binding Domain (RBD) of S protein. RBD specific antibodies have neutralizing activity and serum neutralizing capacity is highly correlated against disease severity. Several monoclonal antibodies (mAbs) which were obtained directly from previously infected or vaccinated people appear to have highly neutralizing activity and were approved for clinical use to patients who have higher risk of developing severe cases of the disease. This project aims to express anti-RBD mAbs in human cell cultures by using variable regions sequences that were previously obtained from memory B cells from COVID-19 convalescent individuals' blood. In order to do so, plasmids containing variable regions of the antibody fused with IgG1 constant regions will be transfected to Expi293 cells and synthesized mAbs will be purified by affinity chromatography. Afterwards, these mAbs will go through Enzyme Linked Immunosorbent Assay (ELISA) with the following recombinant proteins: wild type and beta, gamma, delta and omicron variants of RBD and S protein. By doing so, it is expected to evaluate each mAb's reactivity towards different variants of the virus, in order to select the ones that may be used for new immunotherapies development.