A Linear Epitope in the N-Terminal Domain of CCR5 and Its Interaction with Antibody

Abstract

The CCR5 receptor plays a role in several key physiological and pathological processes and is an important therapeutic target. Inhibition of the CCR5 axis by passive or active immunisation offers one very selective strategy for intervention. In this study we define a new linear epitope within the extracellular domain of CCR5 recognised by two independently produced monoclonal antibodies. A short peptide encoding the linear epitope can induce antibodies which recognise the intact receptor when administered colinear with a tetanus toxoid helper T cell epitope. The monoclonal antibody RoAb 13 is shown to bind to both cells and peptide with moderate to high affinity (6x10^8 and 1.2x107 M-1 respectively), and binding to the peptide is enhanced by sulfation of tyrosines at positions 10 and 14. RoAb13, which has previously been shown to block HIV infection, also blocks migration of monocytes in response to CCR5 binding chemokines and to inflammatory macrophage conditioned medium. A Fab fragment of RoAb13 has been crystallised and a structure of the antibody is reported to 2.1 angstrom resolution.

The Expanding Therapeutic Perspective of CCR5 Blockade

“…The cell membrane is represented with a green rectangle. Ribbon representation of CCR5 and 5p7-CCL5 three-dimensional structures were generated using PyMOL from PDB entry 5UIW ( 10 ), MVC from PDB entry 4MBS ( 11 ), and the FAB fragment of RoAb13 from PDB entry 4S2S ( 12 ).…”

The Role of Natural Antibodies to CC Chemokine Receptor 5 in HIV Infection

“…Indeed, it has previously demonstrated that immunization with ECL1 domain, in a linear conformation, does not elicit serological Abs responses that bind to the native molecule ( 111 ) and, moreover, in macaques, the immunization with ECL2 in its native conformation induces immune responses with expected properties ( 84 ). Nevertheless, Chain and colleagues have recently defined a new linear epitope of CCR5 within the N-terminus domain recognized by two independently produced mAbs; in particular, they found that RoAb13 Ab is capable to bind to both linear peptide and native form of the epitope and the sulfation of tyrosines at CCR5 N-terminus enhanced its binding to the peptide ( 119 ). RoAb13 has been previously reported to block HIV infection ( 120 ) but also blocks migration of monocytes after the chemokine binding to CCR5 or in the presence of inflammatory macrophage conditioned medium ( 119 ).…”

“…Nevertheless, Chain and colleagues have recently defined a new linear epitope of CCR5 within the N-terminus domain recognized by two independently produced mAbs; in particular, they found that RoAb13 Ab is capable to bind to both linear peptide and native form of the epitope and the sulfation of tyrosines at CCR5 N-terminus enhanced its binding to the peptide ( 119 ). RoAb13 has been previously reported to block HIV infection ( 120 ) but also blocks migration of monocytes after the chemokine binding to CCR5 or in the presence of inflammatory macrophage conditioned medium ( 119 ).…”

“…It is noteworthy that such HIV-1 blocking Abs are present in serum and mucosal fluids from subjects with different genetic backgrounds ( 75 ), thus suggesting that it is possible to elicit these Abs in subjects coming from both developing as well as developed countries. In addition, an individual who received a stem cell transplant from a CCR5-negative donor, for acute myeloid leukemia treatment, is believed to be the only patient to have been cured of HIV ( 119 , 122 ).…”

Exploring Carbon Nanomaterial Diversity for Nucleation of Protein Crystals

“…Four are often used as standards or models for crystallization studies 27 ; they are thaumatin, trypsin, lysozyme and catalase. The fifth was a target protein, antibody RoAb13, the structure of which was recently solved 28 . The ability of each CNM to induce nucleation was assessed by the presence of crystals in the metastable drops.…”