Stepwise PEG Precipitation Coupled with Hydrophobic Interaction Chromatography Enables the Production of Highly Specific Anti-Ag85B IgY for Tuberculosis Immunodiagnostics.

PURPOSE: Reliable antigen detection in tuberculosis (TB) immunoassays requires antibodies with high specificity and minimal background interference. Chicken egg yolk immunoglobulin Y (IgY) is a scalable and cost-effective antibody source; however, crude yolk extracts often show reduced specificity due to non-target proteins. Although antigen 85B (Ag85B) is a well-established Mycobacterium tuberculosis antigen, the generation and purification of Ag85B-specific IgY from egg yolk have not yet been reported. This study established a purification workflow to obtain high-purity Ag85B-specific IgY from chicken egg yolk.

METHODS

Chickens were immunized with recombinant Ag85B, and antibody development was monitored using agar gel precipitation tests (AGPT) with serum collected before and after immunization. Dot blot analysis verified the transfer of anti-Ag85B antibodies from serum to egg yolk prior to IgY extraction. IgY was extracted using either stepwise polyethylene glycol (PEG) precipitation or a NaCl-based water-dilution method, followed by hydrophobic interaction chromatography and centrifugal ultrafiltration.

RESULTS

SDS-PAGE demonstrated progressive IgY enrichment and contaminant removal, with PEG extraction yielding higher purity than NaCl-based extraction. Western blot analysis confirmed a distinct immunoreactive band for Ag85B-His with no cross-reactivity against the non-target M. tuberculosis antigen MPT64. Furthermore, a prototype membrane-based strip assay using purified IgY produced clear signals in both the test and control zones when tested with Ag85B (10 µg/mL), indicating retained antigen-recognition capability in a preliminary membrane-based proof-of-concept format.

CONCLUSION

These findings demonstrate that systematic purification improves IgY specificity and supports the preliminary development of membrane-based proof-of-concept immunodetection systems using Ag85B-specific IgY.