Abstract
Schistosomiasis remains a serious public health problem with an estimated 200 million people infected in 76 countries. Here we isolated ~ 8,400 potential protein-encoding cDNA contigs from Schistosoma japonicum after sequencing circa 84,000 expressed sequence tags. In tandem, we undertook a high-throughput proteomics approach to characterize the protein expression profiles of a number of developmental stages (cercariae, hepatic schistosomula, female and male adults, eggs, and miracidia) and tissues at the host-parasite interface (eggshell and tegument) by interrogating the protein database deduced from the contigs. Comparative analysis of these transcriptomic and proteomic data, the latter including 3,260 proteins with putative identities, revealed differential expression of genes among the various developmental stages and sexes of S. japonicum and localization of putative secretory and membrane antigens, enzymes, and other gene products on the adult tegument and eggshell, many of which displayed genetic polymorphisms. Numerous S. japonicum genes exhibited high levels of identity with those of their mammalian hosts, whereas many others appeared to be conserved only across the genus Schistosoma or Phylum Platyhelminthes. These findings are expected to provide new insights into the pathophysiology of schistosomiasis and for the development of improved interventions for disease control and will facilitate a more fundamental understanding of schistosome biology, evolution, and the host-parasite interplay.
Highlights
Schistosomiasis remains one of the most prevalent and serious of the parasitic diseases, with an estimated 200 million people infected in 76 countries and territories, located predominantly in tropical and subtropical regions
The Transcriptome of S. japonicum Previously, we reported an initial analysis of the transcriptomes of adult and egg stages of S. japonicum from 43,707 59 expressed sequence tag (EST) that we assigned to 13,131 gene clusters, of which 2,706 clusters were similar to known proteins deposited in GenBank (BLASTP cutoff of E value 10À20), and of which 611 genes containing complete coding sequence (CDS) were isolated [7]
A total of 98,770 raw ESTs derived from 79,639 clones, which were composed of 55,063 new ESTs and the 43,707 ESTs reported previously [7], were quality-trimmed using Phred 20 after removing repetitive, mitochondrial, ambiguous, and vector sequences (Table S1)
Summary
Schistosomiasis remains one of the most prevalent and serious of the parasitic diseases, with an estimated 200 million people infected in 76 countries and territories, located predominantly in tropical and subtropical regions. The disease is caused by three major schistosome species, Schistosoma japonicum, Schistosoma mansoni, and Schistosoma haematobium [1]. Schistosomes have a complex life cycle with specific, differential gene expression for adaptation to their intermediate, snail, and definitive mammalian host environments. The highly adapted relationship between schistosomes and their mammalian hosts appears to involve parasite exploitation of host endocrine and immune signals [2,3,4]. Evasion strategies that underpin avoidance of the host immune system, allowing schistosomes to survive for years despite strong host immunological responses, have long confounded and intrigued investigators intent on controlling these parasites through development of an effective vaccine. A comprehensive deciphering of the schistosome genome, transcriptome, and proteome has become increasingly central for understanding the complex parasite-host interplay and for delivering candidate drug and vaccine targets [5,6]. Genome-scale collections of the full-length cDNAs with potential coding sequences (CDSs) of expressed genes have become important
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