Immunological Cross-Reactivity of Proteins Extracted from the Oomycete Pythium insidiosum and the Fungus Basidiobolus ranarum Compromises the Detection Specificity of Immunodiagnostic Assays for Pythiosis.
Abstract: Pythiosis, a life-threatening disease caused by , has been increasingly diagnosed worldwide. A recently developed immunochromatographic test (ICT) enables the rapid diagnosis of pythiosis. During the 3-year clinical implementation of ICT in Thailand, we collected the laboratory reports of 38 animals with suspected pythiosis and detected ICT false-positive results in three horses and a dog with basidiobolomycosis. and cause infections with indistinguishable clinical and microscopic features. This study investigated cross-reactive antibodies by probing and crude extracts and cell-free synthesized I06 protein (encoded in genome, not other fungi) against a panel of pythiosis, basidiobolomycosis, rabbit anti-I06 peptide, and control sera by Western blot analyses. ICT false-positive results occurred from the cross-reactivity of anti- antibodies to the 15, 50, 60, and 120 kDa proteins of , not double infections caused by both pathogens. Notably, ICT could help to screen pythiosis, and the positive test requires confirmation by culture or molecular method. The detection specificity of ICT requires improvement. The crude extract containing multispecies antigens needs replacement with a refined -specific protein. We proposed that the 55 kDa I06 protein is an excellent candidate for developing a more specific serodiagnostic test for pythiosis.
Publication Date: 2021-06-11 PubMed ID: 34208304PubMed Central: PMC8231275DOI: 10.3390/jof7060474Google Scholar: Lookup
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Summary
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The research investigates the misdiagnosis of pythiosis, a severe disease in animals caused by Pythium insidiosum, due to the cross-reactivity of disease proteins with Basidiobolus ranarum, a different infectious agent. The study proposes that using a refined, species-specific protein may improve the accuracy of detection tests for pythiosis.
Research Background and Motivation
- Pythiosis is an acute, life-threatening disease caused by the oomycete Pythium insidiosum, with increasing cases being reported globally.
- Currently, a rapid diagnostic tool known as immunochromatographic test (ICT) is utilized to diagnose pythiosis. However, during ICT’s application in Thailand over a span of 3 years, researchers noticed some false-positive results in animals suspected of having pythiosis but actually suffering from Basidiobolomycosis, an entirely different disease caused by the fungus Basidiobolus ranarum.
- The researchers realized that these misdiagnoses occurred due to the similarity in clinical and microscopic characteristics between diseases caused by Pythium insidiosum and Basidiobolus ranarum, leading to an urgent need to improve the specificity of the ICT diagnostic tool.
Investigation and Key Findings
- The study essentially probes the cross-reactive antibodies in these distinct pathogens by analyzing the reactions between crude extracts and a specific protein, termed I06, found only in Pythium insidiosum, to various sera in laboratory settings.
- The false-positive results in ICT were found to be resulting from a cross-reactive phenomenon. Here the anti-Pythium insidiosum antibodies cross-reacted with proteins of Basidiobolus ranarum, thus incorrectly indicating an infection with Pythium insidiosum.
- Importantly, it was noted that these misdiagnosis events were not due to co-infections with both pathogens but solely due to the cross-reactive antibodies.
Implications and Proposed Solutions
- Since the ICT diagnostic tool was prone to cross-reactive errors, researchers suggested improvements in test specificity to reduce false diagnosis rates.
- The study proposed removing the crude extract employed in the test, which contained antigens from multiple species, and replacing it with a refined, Pythium insidiosum-specific protein.
- The I06 protein, distinctive to Pythium insidiosum and not present in other fungi, was proposed as an excellent candidate protein for developing a more specific diagnostic test for pythiosis.
Conclusion
- The research illuminates the importance of refining diagnostic materials to increase specificity and reduce false-positives, contributing to better health outcomes for animals suspected of pythiosis.
Cite This Article
APA
Rotchanapreeda T, Sae-Chew P, Lohnoo T, Yingyong W, Rujirawat T, Kumsang Y, Payattikul P, Jaturapaktrarak C, Intaramat A, Pathomsakulwong W, Yurayart C, Krajaejun T.
(2021).
Immunological Cross-Reactivity of Proteins Extracted from the Oomycete Pythium insidiosum and the Fungus Basidiobolus ranarum Compromises the Detection Specificity of Immunodiagnostic Assays for Pythiosis.
J Fungi (Basel), 7(6), 474.
https://doi.org/10.3390/jof7060474 Publication
Researcher Affiliations
- Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
- Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
- Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
- Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
- Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
- Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
- Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
- Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
- Translational Research Unit and Laboratory of Immunology, Chulabhorn Research Institute, Bangkok 10210, Thailand.
- Equine Clinic, Kasetsart University Veterinary Teaching Hospital, Nakhon Pathom 73140, Thailand.
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.
- Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
Grant Funding
- MU-PD_2020_7 / Mahidol University
- RSA6280092 / Thailand Research Fund
- CF_63008 / Mahidol University
- (none) / Kasetsart University
Conflict of Interest Statement
The authors declare no conflict of interest.
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