Interação do scFv do anticorpo Alemtuzumab com o receptor de membrana CD52: um estudo via dinâmica molecular

Abstract

The Alemtuzumab antibody recognizes the CD52 molecule overexpressed on lymphoma’s and on B and T lymphocytes’ cells membrane. The understanding of the interaction between the CD52 and Alemtuzumab is crucial to propose mutations and engineer biobetters with greater affinity and specificity. A strategy for antibody engineering is working with the antibody’s fragments, involving the variable domains (VH and VL) that are responsible for antigen recognition. Mutations that result in greater affinity and specificity can be suggested by monitoring the interactions between residues of the Alemtuzumab’s complementarity determining regions (CDRs) and CD52. This work aimed to study, through Molecular Dynamics (MD) simulation, the structural and energetic determinants involved in the formation of the interface between the Alemtuzumab’s single chain variable fragment (scFv) and the CD52. Two systems with different cell membrane models, DMPC bilayer and nhexane were analysed. The scFv was submitted to the DM in electrically neutral simulation systems, with addition of Cl- ions. The systems were composed of water molecules (SPC model), CD52, scFv and DMPC or n-xexane. The CD52, comprised of a peptide with 12 amino acids and a GPI anchor, was inserted into a DMPC bilayer or into n-hexane. The molecules structural stability was determined by the root mean square deviation (RMSD). The intermolecular interaction potential (IIP) between scFv residues and the CD52’s peptide and between the scFv and the GPI were measured along the simulation, using in-house program. There is a relative position change between the scFv VH-VL in water, with the VH and VL maintenance. The CD52 structure stabilizes in the DM simulations. The scFv residues that feature attractive IIP for the peptide residues are positively charged, located in the CDR H2, L1 and L3 in both systems. The ones interacting attractively with the GPI are from the CDR H2, in both systems, and also of L1 in the system with n-hexane. The n-hexane/water interface enhanced scFv interaction with the GPI. This made it possible to identify CDR L1 residues interacting with the GPI which had not been observed in the system with the DMPC. The analysis of scFv-CD52 interaction enabled the site-directed mutations suggestions to enhance Alemtuzumab’s affinity and specificity.