Worm morphology of Schistosoma japonicum using confocal laser scanning microscopy

Praziquantel promotes protection against Schistosoma japonicum infection in mice

Praziquantel (PZQ) is the first line drug for the treatment of schistosomiasis. Several studies have confirmed that PZQ regulates host immunity, and we have recently found that pretreatment with PZQ enhances resistance against Schistosoma japonicum infection in buffaloes. We speculate that PZQ induces physiological changes in mice that prevent S. japonicum infection. To test this hypothesis and provide a practical measure to prevent S. japonicum infection, we determined the effective dose (the minimum dose), protection period and onset time of protection by comparing the worm burden, female worm burden and egg burden in PZQ-pretreated mice and blank control mice. Morphological differences between parasites were observed by measuring the total worm length, oral sucker, ventral sucker and ovary. The levels of cytokines, nitrogen monoxide (NO), 5-hydroxytryptamine (5-HT) and specific antibodies were measured using kits or soluble worm antigens. Hematological indicators on day 0 were analyzed in mice that received PZQ on days -15, -18, -19, -20, -21 and -22. The PZQ concentrations in plasma and blood cells were monitored using high performance liquid chromatography (HPLC). The effective dose was found to be two oral administrations (interval of 24 h) at 300 mg/kg body weight (BW) or one injection at 200 mg/kg BW, and the protection period of PZQ injection was 18 days. The optimal preventive effect was observed at two days post-administration, with a >92% worm reduction rate and significant worm reduction until 21 days after administration. Adult worms from PZQ-pretreated mice were runtish showing a shorter length, smaller organs and fewer eggs in the uteri of females. Detection of cytokines, NO, 5-HT and hematological indicators showed that PZQ induced immune-physiological changes, including higher levels of NO, IFN-γ and IL-2, and a lower level of TGF-β. No significant difference in the anti-S. japonicum specific antibody levels was observed. The PZQ concentrations in plasma and blood cells 8 and 15 days post-administration were lower than the detection limit. Our results confirmed that pretreatment with PZQ promotes the protection of mice against S. japonicum infection within 18 days. Although we observed some immune-physiological changes in the PZQ-pretreated mice, the exact mechanisms involved in the preventive effect require further study.

Differential gene expression, including Sjfs800, in Schistosoma japonicum females at pre-pairing, initial pairing and oviposition

Background

Schistosomiasis is a prevalent but neglected tropical disease caused by parasitic trematodes of the genus Schistosoma, with the primary disease-causing species being S. haematobium, S. mansoni and S. japonicum. Male–female pairing of schistosomes is necessary for sexual maturity and the production of a large number of eggs, which are primarily responsible for schistosomiasis dissemination and pathology.

Methods

Here, we used microarray hybridization, bioinformatics, quantitative PCR, in situ hybridization and gene silencing assays to identify genes that play critical roles in S. japonicum reproduction biology, particularly in vitellarium development, a process that affects male–female pairing, sexual maturation and subsequent egg production.

Results

Microarray hybridization analyses generated a comprehensive set of genes differentially transcribed before and after male–female pairing. Although the transcript profiles of females were similar 16 and 18 days after host infection, marked gene expression changes were observed at 24 days. The 30 most abundantly transcribed genes on day 24 included those associated with vitellarium development. Among these, the gene for female-specific 800 (fs800) was substantially upregulated. Our in situ hybridization results in female S. japonicum indicated that Sjfs800 mRNA was observed only in the vitellarium, localized in mature vitelline cells. Knocking down the Sjfs800 gene in female S. japonicum by approximately 60% reduced the number of mature vitelline cells, decreased rates of pairing and oviposition, and decreased the number of eggs produced in each male–female pairing by about 50%.

Conclusions

These results indicate that Sjfs800 may play a role in vitellarium development and egg production in S. japonicum and suggest that Sjfs800 regulation may provide a novel approach for the prevention or treatment of schistosomiasis.

High resistance of water buffalo against reinfection with Schistosoma japonicum

Schistosomiasis is a zoonotic parasitic disease threatening tens of millions people and farm animals. Water buffalos are a major reservoir for schistosomiasis and a control target. Epidemiological surveys suggest that buffalos can develop resistance against Schistosoma japonicum reinfection. In the present paper, relative to control animals, we report an over 97% worm burden reduction after two rounds of infection with S. japonicum and treatment with Praziquantel (PZQ). Relative to control animals, shorter length of female worms, and lower egg counts (over 87.7% reduction rates) were observed in reinfected buffalos. We also found that the reinfected buffalos had significantly higher levels of IL-4, IL-10, and IFN-γ, 4-9 weeks after the secondary infection, and a significantly higher level of specific IgG antibodies before infection. Our results confirmed that after infection buffalos develop resistance against S. japonicum reinfection, and that this resistance is mainly due to acquired immunity. These findings may aid in the future vaccine design for water buffalos.

MicroRNAs Are Involved in the Regulation of Ovary Development in the Pathogenic Blood Fluke Schistosoma japonicum

Schistosomes, blood flukes, are an important global public health concern. Paired adult female schistosomes produce large numbers of eggs that are primarily responsible for the disease pathology and critical for dissemination. Consequently, understanding schistosome sexual maturation and egg production may open novel perspectives for intervening with these processes to prevent clinical symptoms and to interrupt the life-cycle of these blood-flukes. microRNAs (miRNAs) are key regulators of many biological processes including development, cell proliferation, metabolism, and signal transduction. Here, we report on the identification of Schistosoma japonicum miRNAs using small RNA deep sequencing in the key stages of male-female pairing, gametogenesis, and egg production. We identified 38 miRNAs, including 10 previously unknown miRNAs. Eighteen of the miRNAs were differentially expressed between male and female schistosomes and during different stages of sexual maturation. We identified 30 potential target genes for 16 of the S. japonicum miRNAs using antibody-based pull-down assays and bioinformatic analyses. We further validated some of these target genes using either in vitro luciferase assays or in vivo miRNA suppression experiments. Notably, suppression of the female enriched miRNAs bantam and miR-31 led to morphological alteration of ovaries in female schistosomes. These findings uncover key roles for specific miRNAs in schistosome sexual maturation and egg production.

Intake of Erythrocytes Required for Reproductive Development of Female Schistosoma japonicum

The reproductive development and maturation of female schistosomes are crucial since their released eggs are responsible for the host immunopathology and transmission of schistosomiasis. However, little is known about the nutrients required by female Schistosoma japonicum during its sexual maturation. We evaluated the promoting effect of several nutrients (calf serum, red blood cells (RBCs), ATP and hypoxanthine) on the reproductive development of pre-adult females at 18 days post infection (dpi) from mixed infections and at 50 dpi from unisexual infections of laboratory mice in basic medium RPMI-1640. We found RBCs, rather than other nutrients, promoted the female sexual maturation and egg production with significant morphological changes. In 27% of females (18 dpi) from mixed infections that paired with males in vitro on day 14, vitelline glands could be positively stained by Fast Blue B; and in 35% of females (50 dpi) from unisexual infections on day 21, mature vitelline cells were observed. Infertile eggs were detected among both groups. To analyze which component of mouse RBCs possesses the stimulating effect, RBCs were fractionated and included in media. However, the RBC fractions failed to stimulate development of the female reproductive organs. In addition, bovine hemoglobin hydrolysate, digested by neutral protease, was found to exhibit the promoting activity instead of untreated bovine hemoglobin. The other protein hydrolysate, lactalbumin hydrolysate, exhibited a similar effect with bovine hemoglobin hydrolysate. Using quantitative RT-PCR, we found the expression levels of four reproduction-related genes were significantly stimulated by RBCs. These data indicate that RBCs provide essential nutrients for the sexual maturation of female S. japonicum and that the protein component of RBCs appeared to constitute the key nutrient. These findings would improve laboratory culture of pre-adult schistosomes to adult worms in medium with well-defined components, which is important to investigate the function of genes related to female sexual maturation.

Confocal laser scanning microscopic observation on adult Schistosoma japonicum harbored in mice following treatment with single-dose mefloquine

The aim of the present study is to assess the mefloquine-induced alteration of adult Schistosoma japonicum using confocal laser scanning microscopy (CLSM). Eight out of ten mice infected with 60-80 S. japonicum cercariae for 35 days were treated orally with mefloquine at a single dose of 400 mg/kg. Four groups of two mice were killed at 24 h and 3, 7, and 14 days post-treatment, and schistosomes were collected by perfusion from the liver and mesenteric veins, fixed in 70% alcohol, stained with acid carmine, and examined by CLSM. Worms obtained from untreated mice served as controls. Twenty-four hours post-treatment, focal tegument of adult male and female worms, which composed of fine and short villus-like materials, became thicker and longer, or disorder arrangement, while the musculatures beneath the tegument revealed in focal and irregular swelling with various degrees. In the gut of male and female schistosomes, severe dilatation accompanied by swelling, collapse, and peeling of gut mucosa was universal. In the reproductive organs, no apparent alteration in the testis structure of male worms was seen, while in female worms, slight damage to the ovary included loose arrangement of mature ovary cells accompanied by some of them degenerated and collapsed. As to vitelline glands, severe damage, such as swelling, indistinction, fusion or collapse of vitelline cells, and apparent swelling of parenchymal tissues in vitelline gland lobules, was seen. Meanwhile, abnormal ova emerged in the uterus at this time point. Three to 7 days post-treatment, the damage to the worms aggravated either in extent or in severity along with time. In some focally swollen worm body, the parenchymal tissues revealed in severe swelling. In addition, a large piece of degenerated and necrotic parenchymal tissues emerged closed to the severe destructed oral or ventral sucker. In the gut of male and female worms, the major alterations manifested by focal collapse or peeling of mucosa, and desquamation of gut epithelial cells. As to the reproductive organs, the testes of male worms revealed in reduction of size, decrease in number of germinative cells, and some of them showed degeneration and collapse, or destruction of the capsule around the testis. In female worms, some ovaries only showed degenerated and collapsed cells accompanied with many cell fragments. Meanwhile, almost all of the vitelline cells lost their definition, which revealed in indistinct cell structure, fusion of some cells, and formation of many cell fragments due to their collapse. Fourteen days post-treatment, only some male worms survived the treatment were collected. Their tegument and musculature showed prominent recovery, but severe damage to the gut and testes was still observed. Our results confirm that under the observation by CLSM, mefloquine exhibits destructive effect on adult S. japonicum, particularly the morphological structure of digestive system and reproductive system of the worms.