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STRUCTURAL BASES OF SPECIFICITY AND AFFINITY IN ANTIGEN-ANTIBODY REACTIONS

Objective

IMPROVED UNDERSTANDING OF THE MOLECULAR BASIS OF ANTIGEN-ANTIBODY INTERACTIONS LEADING TO BASIC INFORMATION ON SIGNAL-GENERATION BY ANTIBODY BINDING AND ON SIGNAL TRANSDUCTION. IMPROVED INTERACTIVE COMPUTER GRAPHICS AND COMPUTER NETWORK COMMUNICATION.

LONG TERM ECONOMIC BENEFITS IN HEALTH CARE AND INDUSTRIAL BIOTECHNOLOGY ARE TO BE EXPECTED.
Research was carried out to determine, by X-ray crystallography, the 3-dimensional structures of:
antigen antibody complexes for which hen eggwhite lysozyme (HEL) was used as the model antigen;
heterologous antigens (other avian lysozymes);
FabNQ10 (from a monoclonal antiphenyloxazolone antibody) and its complexes with specific haptens;
an idiotope antiidiotope complex.

Results obtained in the study of the 3-dimensional structures were:
the determination of those of FabNQ10 free and bound to the phenyloxazolone hapten;
the refinement of the atomic coordinates of the antigen antibody complex FabD1.3-HEL;
the determination and refinement of the structures of the heterologous antigens, turkey and Japanese quail lysozymes;
the determination of the structure of an idiotope antiidiotope complex.

Another major result obtained was that of reshaping human antibodies: the antilysozyme activity of the mouse monoclonal antibody D1.3 was grafted by recombinant deoxyribonucleic acid (DNA) techniques onto a human immunoglobulin, a technique which should facilitate the production of therapeutic human (chimaeric) antibodies. The variable domains of the heavy chains (VH) and light chains (VL) of D1.3 were cloned and expressed in Esherichia coli. It was found that the VH domain binds lysozyme with an affinity constant (Kd = 19 nM) which is only 1 order of magnitude lower than that of the parent antibody (Kd = 2 nM).
THIS IS A JOINT PROJECT TO STUDY THE MOLECULAR BASIS OF ANTIGEN-ANTIBODY INTERACTIONS.

THE AIMS OF THE PART OF THE PROJECT TO BE CARRIED OUT AT LEEDS UNIVERSITY ARE :

1) DETERMINATION OF THE THREE-DIMENSIONAL STRUCTURE AT HIGH RESOLUTION OF THE ANTIGEN-ANTIBODY COMPLEX OF FAB D1.3 WITH HEN EGG WHITE LYSOZYME (IN COLLABORATION WITH INSTITUT PASTEUR).

2) DETAILED ANALYSIS OF THE INTERMOLECULAR INTERACTIONS IN THE COMPLEX USING COMPUTER GRAPHICS AND POTENTIAL ENERGY CALCULATIONS TO ELUCIDATE THE BASIS OF ANTIBODY SPECIFICITY. PREDICTION OF THE RELATIVE IMPORTANCE OF THE CONTRIBUTIONS OF DIFFERENT AMINO-ACID RESIDUES TO THE AFFINITY.

3) DEVELOPMENT OF INTERACTIVE COMPUTER GRAPHICS TECHNIQUES FOR THE REALIZATION OF 1) AND 2), THE PREDICTION OF STRUCTURE AND AFFINITY CHANGES THAT MIGHT BE PRODUCED BY SITE-DIRECTED MUTAGENESIS OF THE ANTIBODY OR ANTIGEN, AND THE MODELLING OF CONFORMATIONALLY RESTRICTED SYNTHETIC MOLECULES THAT COULD MIMIC THE ANTIGEN AND BIND TO THE ANTIBODY.

4) DETERMINATION OF THREE-DIMENSIONAL STRUCTURES OF COMPLEXES INVOLVING MUTATED ANTIGEN OR ANTIBODY (IN COLLABORATION WITH INSTITUT PASTEUR AND MRC)., AND COMPARISON OF THE RESULTS WITH PREDICTIONS FROM COMPUTER GRAPHICS, MOLECULAR DYNAMICS AND CONFORMATIONAL ENERGY REFINEMENT CALCULATIONS.

5) DEVELOPMENT OF THE USE OF COMPUTER NETWORK COMMUNICATION TO ALLOW TRANSFER OF DATA AND COMPUTER SOFTWARE TO THE OTHER THREE LABORATORIES.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

University of Leeds
Address
Woodhouse Lane
LS2 9JT Leeds
United Kingdom

Participants (3)

INSTITUT PASTEUR
France
Address
Rue Du Docteur Roux 25
75724 Paris
Laboratoire pour l'Utilisation du Rayonnement Électromagnetique
France
Address
Université De Paris Xi (Université Paris-sud)
91405 Orsay
MRC MOLECULAR BIOLOGY LABORATORY
United Kingdom
Address

Cambridge