Characterization of Schistosoma japonicum tetraspanning orphan receptor and its role in binding to complement C2 and immunoprotection against murine schistosomiasis.

BACKGROUND: Schistosomiasis remains an important global public health problem, as millions of people are at risk of acquiring infection. An ideal method for sustainable control of schistosomiasis would be to develop an efficient vaccine. Schistosomes can survive in the host vascular system by immune evasion, regulating the host complement cascade. Schistosoma japonicum tetraspanning orphan receptor (SjTOR) is a complement regulator, which is a tegument membrane protein. To date there is no experimental evidence to explain the function of SjTOR. RESULTS: We cloned the first extracellular domain of the SjTOR (SjTOR-ed1) gene and expressed the gene in Escherichia coli. The expression level of SjTOR in different developmental stages of S. japonicum was assessed by quantitative real-time RT-PCR. Western blotting showed that recombinant SjTOR-ed1 (rSjTOR-ed1) could be recognised by schistosome-infected mouse serum. Immunolocalization indicated that the protein was mainly distributed on the tegument of the parasite. Haemolytic assays and ELISA revealed that rSjTOR-ed1 could inhibit complement hemolysis and bind to complement C2. Purified rSjTOR-ed1 emulsified with ISA206 adjuvant could induce a significant reduction of worm burden from 24.51 to 26.51%, and liver egg numbers from 32.92 to 39.62% in two independent trials in mice. CONCLUSIONS: The results of this study indicated that rSjTOR-ed1 could inhibit complement hemolysis and bind to complement C2, and it is a potential vaccine candidate that protects against S. japonicum infection.

A novel colloidal gold immunochromatography assay strip for the diagnosis of schistosomiasis japonica in domestic animals.

BACKGROUND: Schistosomiasis remains a major public health concern in China and an epidemiological survey has revealed that schistosome-infected bovines and goats are the main transmission sources for the disease. Therefore, development of a sensitive technique for the diagnosis of schistosomiasis in domestic animals is necessary. METHOD: A novel colloidal gold immunochromatography assay (GICA) strip was developed for detecting Schistosoma japonicum in domestic animals. The colloidal gold was conjugated with recombinant streptococcal protein G (rSPG). As the test and control lines, the schistosome soluble egg antigen and rSPG, respectively, were blotted on nitrocellulose membrane. RESULTS: The lowest detectable serum dilution was 1∶640 for schistosome-infected buffaloes. The cross-reaction rate of GICA was 14.29% with Paramphistomum sp. in buffaloes, 16.67% with Haemonchus sp. in goats, and 33.33% with Orientobilharzia sp. in goats. These results were slightly lower and similar to those obtained through ELISA. Moreover, the strips for detecting S. japonicum in mice, rabbits, buffaloes, and goats showed high sensitivity (100.00%, 100.00%, 100.00%, and 100.00%, respectively) and specificity (100.00%, 100.00%, 94.23%, and 88.64%, respectively). And the sensitivity or specificity of the GICA strips did not present any significant differences after storage for 12 months at room temperature. When compared with ELISA, the GICA strips exhibited similar sensitivity and specificity in the diagnosis of schistosomiasis in mice, rabbits, buffaloes, and goats. Besides, only 5 µl of serum are required for the test and the detection can be completed within 5 min. CONCLUSION: This study is the first to develop a GICA strip using gold-rSPG conjugate for the diagnosing of schistosomiasis in domestic animals, and preliminary results showed that the developed strip may be suitable for large-scale screening of schistosomiasis in endemic areas.

Evaluation of recombinant multi-epitope proteins for diagnosis of goat schistosomiasis by enzyme-linked immunosorbent assay.

BACKGROUND: Schistosomiasis is a huge threat to human and animal health. Apart from bovines, goats play an important role in the transmission of schistosomiasis in some endemic areas of China. An accessible, quality-assured goat schistosomiasis diagnostic technique is needed. Recently, our laboratory identified two recombinant diagnostic antigens, SjPGM and SjRAD23 via an immuno-proteomic method. The application of these two recombinant antigens to develop a higher sensitivity and specificity technique for the sheep schistosomiasis diagnosis is urgently needed. METHODS: Epitopes of SjPGM and SjRAD23 were predicted and three polypeptides, two from SjRAD23 and one from SjPGM, were selected. Recombinant plasmids containing two to three DNA sequences encoding predicted polypeptides or large hydrophilic region of Sj23 (LHD-Sj23) were constructed and expressed. Eight recombinant schistosome antigens including four multi-epitope proteins and four recombinant single-molecule antigens as well as SEA, were assessed by ELISA in 91 sera from schistosome-infected goats, 44 sera from non-infected goats, 37 sera from Orientobilharzia-infected goats, and 12 from Haemonchus contortus-infected goats. RESULTS: ELISA tests showed that three multi-epitope proteins had higher sensitivity than the four single-molecule antigens (rSjRAD23, rSjPGM, rBSjRAD23-1, rBSj23) and the multi-epitope protein rBSjPGM-BSjRAD23-1-BSj23 had the highest sensitivity (97.8 %, 89/91) and maintained good specificity (100 %, 44/44) as well as low cross-reactivity with haemonchosis (8.33 %, 3/12) and orientobilharziasis (13.51 %, 5/37) in the diagnosis of goat schistosomiasis. In contrast, when SEA was applied as a diagnosis antigen, it had 100 % (91/91) sensitivity, 75 % (33/44) specificity, 25 and 83.78 % cross-reactivity with haemonchosis (3/12) and orientobilharziasis (31/37), respectively. CONCLUSIONS: The application of recombinant multi-epitope proteins may increase the sensitivity of diagnosis technique and retain high specificity of single-molecule antigens for schistosomiasis, and the recombinant antigen rBSjPGM-BSjRAD23-1-BSj23 has the potential to be used as a diagnosis antigen for goat schistosomiasis.