Structural and functional characterization of a humanized neutralizing antibody targeting the SARS-CoV-2 Receptor Binding Domain (RBD)

SARS-CoV-2, responsible for the ongoing global pandemic, utilizes its spike protein (S protein) to mediate viral entry by interacting with host cell receptors. Since 2020, several variants of the virus have emerged, presenting challenges in neutralization. This study focuses on the functional and structural characterization of a humanized neutralizing antibody (NAb), 9-8F2-B11, which targets the receptor-binding domain (RBD) of the wild-type SARS-CoV-2 and the Alpha, Beta, Gamma, and Delta variants. Leveraging the collaborative expertise of Takis Srl, the Institute of Molecular Biology Pathology of National Research Council (IBPM-CNR) and Sapienza University of Rome, we assessed the antibody’s binding affinity via biolayer interferometry (BLI) and demonstrated its potent neutralization capabilities through a pseudovirus neutralization assay. Furthermore, the cryo-electron microscopy (Cryo-EM) structure of the 9-8F2-B11 Fab bound to the S protein revealed the precise epitope and provided insights into the molecular mechanisms of viral inhibition. This synergistic work enabled the identification of a broadly neutralizing humanized antibody and elucidated the structural basis for its efficacy against multiple SARS-CoV-2 variants, offering potential for therapeutic development.