Abstract
Paragonimiasis is a foodborne trematode infection that affects 23 million people, mainly in Asia. Lung fluke infections lead frequently to chronic cough with fever and hemoptysis, and are often confused with lung cancer or tuberculosis. Paragonimiasis can be efficiently treated with praziquantel, but diagnosis is often delayed, and patients are frequently treated for other conditions. To improve diagnosis, we selected five Paragonimus kellicotti proteins based on transcriptional abundance, recognition by patient sera, and conservation among trematodes and expressed them as His-fusion proteins in Escherichia coli. Sequences for these proteins have 76–99% identity with amino acid sequences for orthologs in the genomes of Paragonimus westermani, Paragonimus heterotremus, and Paragonimus miyazakii. Immunohistology studies showed that antibodies raised to four recombinant proteins bound to the tegument of adult P. kellicotti worms, at the parasite host interface. Only a known egg antigen was absent from the tegument but present in developing and mature eggs. We evaluated the diagnostic potential of these antigens by Western blot with sera from patients with paragonimiasis (from MO and the Philippines), fascioliasis, and schistosomiasis, and with sera from healthy North American controls. Two recombinant proteins (a cysteine protease and a myoglobin) showed the highest sensitivity and specificity as diagnostic antigens, and they detected antibodies in sera from paragonimiasis patients with early or mature infections. In contrast, antibodies to egg yolk ferritin appeared to be specific marker for patients with adult fluke infections that produce eggs. Our study has identified and localized antigens that are promising for serodiagnosis of human paragonimiasis.
Highlights
Foodborne trematode (FBT) infections are important neglected tropical diseases (NTDs) that affect about 56 million people and cause significant morbidity (Furst et al 2012)
Expression of immunoreactive proteins cDNAs of five P. kellicotti immunoreactive antigens were chosen for expression: a cysteine proteinase (CP-6), a myglobin (MYO-1), a cystatin (CYS-2), a microbial defense protein (MDP), and an egg yolk ferritin (EYF) (Table 1)
Human paragonimiasis in an important FBT infection, and it was estimated that in 2017, this group of NTDs is responsible for 1,870,700 years lived with disabilities (YLD) (GBD 2017 Disease and Injury Incidence and Prevalence Collaborators 2018)
Summary
Foodborne trematode (FBT) infections are important neglected tropical diseases (NTDs) that affect about 56 million people and cause significant morbidity (Furst et al 2012). Among FBT infections, lung flukes of the genus Paragonimus are arguably the most important group with an estimated 23 million human infections (Keiser and Utzinger 2009). Section Editor: Sabine Specht species are widely distributed in animals in Asia, Africa, and the Americas, but the infection risk for humans depends largely on whether humans ingest raw or undercooked crustaceans that act as intermediate hosts. For Paragonimus westermani, ingestion of raw meat from mammalian paratenic hosts provides an additional route of infection (Blair 2014). Human Paragonimus infection can be efficiently treated with a short course of praziquantel, but diagnosis is challenging, because infected people are often misdiagnosed and treated for pneumonia, tuberculosis, or cancer (Fischer and Weil 2015). In order to improve the serological diagnosis of P. kellicotti infection, we developed a small animal
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