Schistosoma japonicum strains: differentiation by RAPD and SSR-PCR.

Eight geographical isolates of Schistosoma japonicum from Taiwan and mainland China and one isolate of Schistosoma mansoni were studied by RAPD analysis using six arbitrary primers and SSR-PCR analysis using a (CA)8RY primer. The genetic distance was determined by the percentage of unshared bands. The RAPD and SSR-PCR results showed that the genetic distance between S. mansoni and S. japonicum was more than 0.900 and 0.850 respectively; the genetic distance between the eight geographical isolates of S. japonicum was 0.000 to 0.232 and 0.066 to 0.368 respectively. These results demonstrated the usefulness of RAPD and SSR-PCR for showing the differences of inter- and intra-species of Schistosoma. The results also suggest that there is genetic diversity among the different geographical strains of S. japonicum in China.

Gene cloning and amino acid sequence analysis of triose-phosphate isomerase of Schistosoma japonicum Chinese strain.

A pair of primers was synthesized according to the DNA sequence of Schistosoma japonicum Philippine strain, and the mRNA of adult worms of S. japonicum Chinese strain was prepared. The gene of triose-phosphate isomerase of S. japonicum Chinese strain (SjC TPI) was successfully cloned from the mRNA through reverse transcription polymerase chain reaction (RT-PCR) technic with the primers. The DNA sequence of the gene showed that the open reading frame of encoding SjC TPI DNA includes 759bp, which has 84% homology to Sm TPI, 99.7% homology to SjP TPI. The analysis of deduced amino acid sequence of SjC TPI indicates that SjC TPI is 84.9% (214/252) identical with Sm TPI and 99.2% (250/252) with SjP TPI. The peptide-structure analysis presents 7 extra-surface, hydrophilic regions in the molecule of SjC TPI, the molecular weight of SjC TPI is 27,619. The isoelectric point is 7.38.

Clonning and sequence analysis of the 26 kDa glutathiones-transferase gene of Schistosoma mekongi.

The number of genomic DNA or cDNA sequences of Schistosoma mekongi accessible in Genbank or EMBL is very limited up to now. Recently, two reports have appeared on the molecular phylogeny of Schistosoma species inferred from partial sequence data of rRNA genes; no further sequence data of S. mekongi is available yet. Knowledge of the molecular structure of protein coding genes of S. mekongi will provide a better understanding of gene function in the genus Schistosoma. A cDNA library of S. mekongi adult male was constructed and a cDNA encoding the 26 kDa glutathione S-transferase protein of this species was cloned. Sequence analysis of this cDNA confirmed the close phylogenetic relationship of S. mekongi to S. japonicum.

Strain complex of Schistosoma japonicum in the mainland of China.

The present paper deals with studies on the characteristics of Schistosoma japonicum isolated from five localities in the mainland of China. The following items were observed and compared including morphometric data, susceptibility of six mammalian hosts, prepatent period, compatibility between larvae and snail hosts, size of hepatic granuloma produced by eggs, immunoreactions in experimental animals, sensitivity to praziquantel, SDS-PAGE protein pattern and its antigenicity analysis, DNA hybridization and genetic variation and differentiation by analysis with multilocus enzyme electrophoresis. By means of these multidisciplinary methods, from morphological to molecular level, the following conclusions may be drawn from our results. The evidence indicates firstly that S. japonicum in the mainland of China comprises a strain complex with several components of geographically distributed strains. At least four distinct strains exist, ie Yunnan, Guangxi, Sichuan and Anhui-Hubei. Characteristics of each strain are distinct and the results of these studies lead to discussion on the problem of the intraspecific and interstrain differentiation of S. japonicum in the mainland of China.

Compatibility between Oncomelania hupensis and different isolates of Schistosoma japonicum in China.

Oncomelania hupensis from six localities were used for infection with different isolates of Schistosoma japonicum in the mainland of China, ie Anhui in the east, Hubei in the center, Guangxi in the south, Sichuan in the West, Yunnan in the southwest and Fujian in the southeast. Snails from Anhui and Hubei were readily infected with the local isolate of S. japonicum and cross infection also took place readily between the snails and the schistosomes from these two places. Snails from Sichuan and Yunnan were refractory to infection with schistosome isolates from Hubei and Anhui, but the isolates from Sichuan and Yunnan were able to develop in snails from Hubei and Anhui. Though the Guangxi isolate developed readily in both Anhui and Guangxi snails, the average precercarial period in the former was significantly longer than in the latter. None of the other snails from Sichuan, Yunnan and Fujian became infected. On the other hand, snails from Guangxi infected with Anhui parasites also had a longer precercarial period than that in Anhui snails. Snails from Fujian were readily infected with the isolates from Anhui and Yunnan. The present results suggest that there might be different geographic strains of S. japonicum and their Oncomelania snail hosts in the mainland of China.