Screening of horse polyclonal antibodies with a random peptide library displayed on phage: identification of ligands used as antigens in an ELISA test to detect the presence of antibodies to equine arteritis virus.

This research study utilized a random hexapeptide fusion-phage library to identify peptide sequences that can act as antigens in a diagnostic enzyme-linked immunosorbent assay (ELISA) for equine arteritis virus (EAV). The study reported that the technique effectively improved virus detection compared to the standard EAV neutralisation test.

Overview of Study and Methodology

• The study opened by explaining their approach of screening a random hexapeptide fusion-phage library. These libraries hold complex mixtures of phages that are useful for finding peptides that interact with target molecules, in this case, antibodies for equine arteritis virus (EAV).
• The screening process aimed at isolating phages that were capable of binding to antibodies found in the horse serum, which tested positive for EAV.
• To enhance the effectiveness of their methodology, the researchers analyzed the peptide sequences displayed by the isolated phages. This work resulted in the identification of seven groups of peptide sequences.

Use of Isolated Phages in ELISA

• 25% of the isolated phages were then used as antigens in an ELISA test. When subject to the test serum pool, these phages were specifically recognised by the serum that tested positive for EAV in virus neutralisation tests.
• Furthermore, five of the identified peptide sequences were able to detect greater than 50% of sera containing antibodies to EAV. This detection rate was when the samples were subject to a virus neutralisation test.
• By pooling these five effective phages and using them as a collective antigen in the ELISA, the detection rate of antibodies to EAV considerably improved.

Outcome and Implications

• The newly developed ELISA test demonstrated a sensitivity and specificity of 99% and 71% respectively, as compared to the standard EAV neutralisation test.
• This success insinuates a significant potential that phage display libraries hold. Such libraries could identify specific peptide sequences that can work as antigens in diagnostic ELISAs, potentially increasing the efficiency and accuracy of such diagnostic tests.