Computational modeling of mimetics of antigen-binding fragments targeting the conserved ectodomain region of the hRSV G protein

The human Respiratory Syncytial Virus (hRSV) is a pathogen that causes acute respiratory tract infections. It has a high contagion rate, primarily affecting the elderly and children up to 2 years old. The G glycoprotein of hRSV is related to viral adhesion, being responsible for the initial contact with host cells. This membrane protein exhibits a high degree of genetic variability; however, it has a conserved central region in its ectodomain containing a non-glycosylated CX3C chemokine motif involved in recognizing the CX3CR1 cellular receptor on the host cell surface. Studies have reported that this conserved ectodomain region of the hRSV G protein serves as an efficient epitope for generating neutralizing antibodies against the virus/host cell adhesion process. These studies also presented important structural data on the interaction of this antigenic determinant of G with antigen-binding regions (Fab) of the antibodies CB001.5, 3G12, and 2D10. The present work is focused by using these crystal structure data of the Fabs/epitope G complexes to design new antibodies targeting the adhesion G protein of hRSV. To achieve this, molecular dynamics simulations along with binding free energy calculations (MM-GBSA), fast-growth thermodynamic integration, and umbrella sampling have been employed to evaluate the interaction of the conserved G ectodomain region with the antibodies CB001.5, 3G12, and 2D10. This will allow for targeted mutations in Fab region residues to improve the binding affinity to the G epitope. Thus, the implementation of this proposal will provide relevant structural insights through computational tools to contribute to the development of new neutralizing monoclonal antibodies directed at the G protein, potentially preventing the virus/host cell adhesion process of hRSV.