Rapid diagnosis of human paragonimiasis using recombinant Paragonimus westermani cysteine protease 6 antigen-based immunochromatographic devices.

OBJECTIVES: Cysteine proteases, the major components of excretory-secretory substances excreted from adult Paragonimus worms, are known as useful diagnostic antigens for human paragonimiasis. In this study, we develop immunochromatography-based kits to detect specific IgG and IgG4 antibodies against recombinant cysteine protease-6 (rCP-6), and to evaluate their diagnostic performance. METHODS: The rCP-6 was expressed in Escherichia coli, affinity-purified, and evaluated for immunoreactivity. The rCP-6-based immunochromatographic kits were evaluated for detection of IgG and IgG4 using simulated whole-blood and serum samples from paragonimiasis patients, healthy individuals, and patients with other infectious diseases. The diagnostic performance was evaluated. RESULTS: The IgG detection kit exhibited sensitivity of 76.7%, specificity of 90.5%, and accuracy of 87.3% for both simulated whole-blood and serum samples. In comparison, the IgG4 detection kit demonstrated higher performance, with 85.0% sensitivity, 100% specificity, and 96.5% accuracy across both sample types. CONCLUSIONS: Both IgG and IgG4 detection kits were useful for diagnosing paragonimiasis. The IgG4 detection kit showed superior diagnostic performance. These ICT tools possible be applying for diagnosing outpatients in clinical laboratories in paragonimiasis caused by different Paragonimus species (P. heterotremus, P. westermani, and P. skrjabini miyazakii).