title: Insights into the interaction of CD4 with anti-CD4 antibodies.
abstract: Knowledge about the mechanism by which some antibodies can block HIV-1 entry is critical to our understanding of their function and may offer new avenues for controlling the adhesion of HIV-1 to the host cells. While much progress has been made, this mechanism remains unclear. Here, atomic force microscopy, isothermal titration calorimetry (ITC), and circular dichroism spectroscopy were used to measure some biophysical characteristics of the interaction of four-domains (D1-D4) membrane protein CD4 with anti-D3 antibody OKT4 and with HIV-1 entry blocking anti-D1 antibody Leu3a. The results showed that at 37°C they bind with similar binding strength, thermodynamics, and kinetics but with different assembly states. Further analyzing the interactions at different temperatures by ITC showed that binding of CD4 with Leu3a is characteristic for specific hydrophobic binding as well as for protein folding while with OKT4 comes from an extensive additional hydration upon binding and charge-related interactions within the binding site. Comparing these characteristics with those of HIV-1 gp120-CD4 interaction revealed that Leu3a binds to CD4 faster than HIV-1 followed by changing local structure of D1 to which HIV-1 binds leading to a prevention of viral entry.
authors: Center for Innovation Competence, Humoral Immune Reactions in Cardiovascular Diseases, University Medicine Greifswald, 17489 Greifswald, Germany; Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, 17475 Greifswald, Germany.
authors: Van-Chien
authors: VC
authors: Bui
authors: Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, 17475 Greifswald, Germany. Electronic address: nguyent@uni-greifswald.de.
authors: Thi-Huong
authors: TH
authors: Nguyen
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D015704:CD4 Antigens / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D002151:Calorimetry; D002462:Cell Membrane; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D018625:Microscopy, Atomic Force; D011485:Protein Binding / Q000276:immunology; D000072760:Single Molecule Imaging / Q000379:methods; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000911:Antibodies, Monoclonal; D015704:CD4 Antigens
keywords: Assembly states; Binding strength; CD4-antibody interaction; Kinetics; Thermodynamics