Utilisation of bacteriophage display libraries to identify peptide sequences recognised by equine herpesvirus type 1 specific equine sera.

This study utilizes bacteriophage display libraries to identify peptide sequences that are recognized by the equine herpesvirus type 1 specific equine sera, suggesting a new method for identifying diagnostic antigens for viral infections.

Background of the Experiments

• The researchers used three bacteriophage (filamentous phages) random peptide display libraries. These are essentially collections of peptides displayed on the coat proteins of bacteriophages, which are viruses that infect bacteria.
• This display library approach allows for high throughput binding assays. By using libraries in what is known as “biopanning” experiments with purified IgG, a type of antibody, from the serum of a foal infected with EHV-1, they could identify peptides that had good binding affinity for the antibodies generated in response to the EHV-1 infection.

Identifying Potential Antibody Binding Regions and Epitopes

• After obtaining a set of peptides with affinity for the EHV-1 specific antibodies, the researchers then aligned the sequences of the amino acids displayed with the protein sequences that are encoded by EHV-1.
• They identified several potential antibody binding regions and epitopes, which are the part of an antigen that is recognized by the immune system, within the proteins encoded by different genes of the virus.
• These proteins, which include DNA helicase/primase complex protein, tegument protein, different types of glycoproteins, and an integral membrane protein, are produced by the EHV-1 virus during infection.

Identifying Type-Specific Epitopes

• The researchers found groups of sequences that seemed to align either with glycoprotein C (gC) or glycoprotein E (gE).
• These identified type-specific epitopes could be used to differentiate between sera (blood serum) from horses infected with either EHV-1 or EHV-4 using an enzyme-linked immunosorbent assay (ELISA) test.

Validation and Conclusion

• A previously identified region in gC had been found to be immunogenic, meaning it could provoke an immune response, through traditional monoclonal antibody screening. This confirmed the validity of their method.
• Meanwhile, an antibody binding region in gE had not been previously identified, showcasing the ability of their method to uncover new information.
• The study demonstrated that screening of phage display peptide libraries with polyclonal sera obtained post-infection is an effective way for identifying diagnostic antigens in virus-like EHV-1.