Abstract
Schistosomiasis japonica is one of the most prevalent parasitic diseases in China. The scarcity of effective diagnostic tools is a major factor that contributes to the high prevalence of schistosomiasis japonica. SjSP-13 is a promising serological diagnostic biomarker of the disease. However, it is unclear whether polymorphisms in SjSP-13 affect its diagnostic efficacy and immunogenicity. Here, we found the SjSP-13 gene was highly polymorphic, and all the alleles of the gene were clustered into two clades, clade A and B. SjSP-13.6 and SjSP-13.25, the representative alleles of clade A and B, were produced in Escherichia coli. The diagnostic value of SjSP-13.6 (AUC = 0.983 ± 0.006), was found to be similar to the SjSP-13.25 (AUC = 0.973 ± 0.009) by receiver operating characteristic (ROC) analysis. SjSP-13.6 and SjSP-13.25 have the same specificity (96.7%), while the sensitivity of SjSP-13.6 (90.4%) is slightly but not significantly higher than SjSP-13.25 (85.2%). The combination use of the two alleles (SjSP-13.6/25) didn’t increase the diagnostic performance of SjSP-13 as the AUC value of SjSP-13.6/25 is 0.977 ± 0.009, lower than individual SjSP-13.6 (AUC = 0.983 ± 0.006). In addition, we found the immunogenicity of clade A alleles is significantly higher than clade B in Schistosoma japonicum naturally infected animals and patients, as the mean antibody levels of SjSP-13.6 was significantly higher than SjSP-13.25. We conclude that polymorphisms of the SjSP-13 gene should not affect its diagnostic efficacy, and it is not necessary to combine the alleles of the two clades for diagnosis of schistosomiasis.
Highlights
Schistosomiasis is a major parasitic disease that affects more than 200 million people in 70 developing countries, and it causes the loss of at least 70 million disability-adjusted life years (Steinmann et al, 2006; Colley et al, 2014)
We identified a novel protein marker, SjSP-13, through genome-wide screening of the proteins secreted by Schistosoma japonicum (Xu et al, 2014)
We obtained a total of 40 allele sequences of the SjSP-13 gene from 20 individual worms derived from a field-isolate of S. japonicum cercariae through cloning and sequencing
Summary
Schistosomiasis is a major parasitic disease that affects more than 200 million people in 70 developing countries, and it causes the loss of at least 70 million disability-adjusted life years (Steinmann et al, 2006; Colley et al, 2014). Schistosomiasis japonica is mainly found in China and to a lesser extent in the Philippines (Rollinson et al, 2013; Xu et al, 2016). In China, about 12 million people were infected in the 1950s. Schistosomiasis has been largely controlled in China through widespread treatment with the anthelmintic drug praziquantel and large-scale environmental campaigns to eradicate snails, which are the intermediate host of the Polymorphisms of Schistosomiasis Biomarker SjSP-13 parasites (Zhou et al, 2005, 2007; Xu et al, 2016). In China, control of schistosomiasis is challenging because of the widespread distribution of the snail hosts and wide range of domestic and wild mammals that act as reservoirs for human infection (Minggang and Zheng, 1999; Gray et al, 2009). Schistosomiasis japonica remains one of the most important public health problems in China
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