β-Giardin as an Immunomagnetic Enrichment Target for Multi-Host Detection of Giardia duodenalis Cysts

Giardiasis is a globally prevalent waterborne zoonosis. Rapid enrichment and detection technologies for this disease are essential. Cyst outer wall proteins are ideal targets for the enrichment and detection of cysts in the environment, but there are few available targets with suboptimal effectiveness. In this study, Giardia duodenalis (G. duodenalis) cysts were purified, and outer wall proteins were biotinylated, followed by streptavidin magnetic bead purification and mass spectrometry. Sixty-three novel cyst wall proteins were identified, and their functions were annotated through Gene Ontology (GO) and KEGG analyses. The β-giardin and α-1 giardin were among the newly identified and predicted to be located on the outer wall of G. duodenalis cysts. For the characterization of these two targets, we applied sequence analysis, prokaryotic expression, preparation of polyclonal antibodies, and determination of subcellular localization. Finally, based on β-giardin immunomagnetic beads were prepared using the polyclonal antibodies and tested for their enrichment efficiency. Immunomagnetic beads targeting β-giardin achieved 65% cyst enrichment efficiency in fecal samples, comparable to conventional methods. Clinical evaluation across 163 multi-host fecal samples (ferrets, Siberian tigers, red-crowned cranes) demonstrated concordance with nested PCR, successfully enriching cysts from PCR-positive specimens. The immunomagnetic beads method targeting β-giardin demonstrated effective G. duodenalis cyst enrichment in multi-host fecal samples. These results provide a proteomic framework for the cyst wall proteins of G. duodenalis, expanding the detection targets for G. duodenalis cysts. It also establishes a theoretical foundation for subsequent research on the composition and function of G. duodenalis cysts.