ABSTRACT
The crystal structure of the antigen-binding fragment of a monoclonal antibody (8F5) that neutralizes human rhinovirus serotype 2 has been determined by X-ray diffraction studies. Antibody 8F5, obtained by immunization with native HRV2 virions, cross-reacts with peptides of the viral capsid protein VP2, which contribute to the neutralizing immunogenic site B in this serotype. The structure was solved by the molecular replacement method and has been refined to an R-factor of 18.9% at 2.8 A resolution. The elbow angle, relating the variable and constant modules of the molecule is 127 degrees, representing the smallest elbow angle observed so far in an Fab fragment. Furthermore, the charged residues of the epitope can be well accommodated in the antigen-binding site. This is the first crystal structure reported for an antibody directed against an icosahedral virus.
Subject(s)
Antibodies, Monoclonal/chemistry , Antibodies, Viral/chemistry , Immunoglobulin Fab Fragments/chemistry , Protein Conformation , Protein Structure, Secondary , Rhinovirus/immunology , Amino Acid Sequence , Antibodies, Monoclonal/genetics , Antibodies, Viral/genetics , Antigens, Viral/immunology , Base Sequence , Capsid/immunology , Cross Reactions , Humans , Immunoglobulin Fab Fragments/genetics , Immunoglobulin Heavy Chains/chemistry , Immunoglobulin Heavy Chains/genetics , Immunoglobulin Light Chains/chemistry , Immunoglobulin Light Chains/genetics , Immunoglobulin Variable Region/chemistry , Immunoglobulin Variable Region/genetics , Models, Molecular , Molecular Sequence Data , Neutralization Tests , Rhinovirus/classification , Serotyping , Virion/immunology , X-Ray DiffractionABSTRACT
We report on the preparation, crystallization, and preliminary x-ray diffraction analysis of the Fab fragment of the monoclonal antibody 8F5 that neutralizes infectivity of human rhinovirus serotype 2 (HRV2). Fab fragments prepared from this antibody by papain digestion were purified to isoelectric homogeneity by ion exchange chromatography and chromatofocusing. Crystals were obtained by the hanging drop vapor diffusion method using ammonium sulfate as precipitant. The crystals belong to the orthorhombic space group P2(1)2(1)2(1) with unit cell dimensions a = 59.9 A, b = 86.3 A, c = 128.2 A and diffract to at least 2.8-A resolution. The cell volume suggests the presence of one molecule per asymmetric unit, and the solvent content is estimated to be 61%.
