Phage display

Identification of hepatitis A virus mimotopes by phage display, antigenicity and immunogenicity

A phage-displayed peptide approach was used to identify ligands mimicking antigenic determinants of hepatitis A virus (HAV) for the first time. Bacteriophages displaying HAV mimotopes were isolated from a phage-display peptide library by affinity selection on serum antibodies from hepatitis A patients. Selected phage-peptides were screened for reactivity with sera from HAV infected patients and healthy controls. Four cloned peptides with different sequences were identified as mimotopes of HAV; three of them showed similarity in their amino acid sequences with at least one of the VP3 and VP1 antigenic proteins of HAV. One clone was recognised by 92% of the positive sera. The phagotopes competed effectively with HAV for absorption of anti-HAV-specific antibodies in human sera, as determined by ELISA. The four phage clones induced neutralising anti-HAV antibodies in immunised mice. These results demonstrate the potential of this method to elucidate the disease related epitopes of HAV and to use these mimotopes in diagnostic applications or in the development of a mimotope-based hepatitis A vaccine without the necessity of manipulation of the virus.

Protein array technology: the tool to bridge genomics and proteomics

The generation of protein chips requires much more efforts than DNA microchips. While DNA is DNA and a variety of different DNA molecules behave stable in a hybridisation experiment, proteins are much more difficult to produce and to handle. Outside of a narrow range of environmental conditions, proteins will denature, lose their three-dimensional structure and a lot of their specificity and activity. The chapter describes the pitfalls and challenges in Protein Microarray technology to produce native and functional proteins and store them in a native and special environment for every single spot on an array, making applications like antibody profiling and serum screening possible not only on denatured arrays but also on native protein arrays.

Direct selection of EGF mutants displayed on filamentous phage using cells overexpressing EGF receptor

Understanding receptor-ligand interactions, and the signal transduction pathways they activate, is of great interest for the discovery of novel antagonists and agonists. In this report we describe a rapid and efficient procedure to evaluate the importance of several different epidermal growth factor (EGF) residues for the binding and activation of its receptor (EGFR). We constructed an EGF mutant library randomized at positions 13, 15 and 16 and expressed them on filamentous phages. Phage display is a powerful system, allowing rapid isolation of binding mutants. Since many of the most pharmacologically interesting receptors cannot be produced in a soluble form, we developed a technique to rapidly select receptor-binding molecules directly on cells. A luciferase assay, simple to perform, was then used to test their biological transduction activity and to rapidly detect mutants of interest. Analysis of the resulting sequences revealed that the wild-type amino acids at positions 13, 15 and 16 are optimized for binding and activity. EGF mutants with agonist properties were also isolated and tolerated substitutions were identified.