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PubMed1995

Ss40: the zinc endopeptidase secreted by infective larvae of Strongyloides stercoralis.

Infective larvae of a pathogenic nematode of humans, Strongyloides stercoralis, release a potent zinc endopeptidase activity which has a broad substrate specificity for constituents of extracellular dermal matrix, including elastin. Specific inhibitors of zinc endopeptidases prevent the penetration of mammalian skin by S. stercoralis larvae. We now report the molecular size and isoelectric point of the S. stercoralis zinc endopeptidase at 40 kDa, pI 5 by zymogram analysis. The activity was not influenced by incubation with beta-mercaptoethanol at 22 degrees C, but was inactivated by incubation at 100 degrees C for 2 min. The enzyme, which we term Ss40, is immunogenic and stimulates humoral IgG antibodies during infection of humans; the activity was immunoprecipitable from ES with pooled infection sera. In addition, a HPLC-enriched Ss40 preparation stimulated the release of histamine from peripheral blood leukocytes of S. stercoralis-infected persons, suggesting that Ss40 is allergenic in humans.

Animals↗
PubMed1995

Strongyloides stercoralis: protective immunity to third-stage larvae inBALB/cByJ mice.

A murine model system was developed to study the induction and mechanism of protective immunity to L3 of Strongyloides stercoralis. L3 were implanted in BALB/cByJ mice in diffusion chambers constructed with 0.1- or 2.0-microns-pore-size membranes. Parasites survived equally well regardless or membrane type for 7 days, after which larval survival decreased in diffusion chambers constructed with 2.0-microns-pore-size membranes, which allowed host cells to enter. Survival of S. stercoralis L3 in diffusion chambers implanted in mice was assayed after immunization with live, heat-killed, and homogenized L3. Optimal immunization was achieved with 10,000 live L3, whereby immunized mice eliminated 97% of the larvae either contained within diffusion chambers or free within the tissues of the mouse by 24 hr postinfection. Sera from immunized mice had elevated levels of IgG1, IgM, and IgA parasitic-specific antibody; IgM was the only antibody isotype that recognized surface antigens of L3. Larvae were not killed in immunized mice if contact between host cells and the parasites was prevented. In the peripheral blood and diffusion chamber fluid of immunized mice, eosinophil levels were significantly higher when compared to the levels found in control mice. The rodent model developed in the present study has thus demonstrated that virtually complete immunity can be induced to the L3 of S. stercoralis and that larval killing was found to be associated with the presence of both specific antibody and eosinophils.

Animals↗
PubMed1996

Strongyloides stercoralis: eosinophil-dependent immune-mediated killing of third stage larvae in BALB/cByJ mice.

Challenge worm survival was significantly reduced when BALB/cByJ mice were vaccinated against Strongyloides stercoralis infective third stage larvae (L3) regardless of whether the challenge infections consisted of systemically migrating L3 or L3 implanted in diffusion chambers. The only cell type that increased in number in diffusion chambers in immunized mice, 1 week after booster immunizations, was the eosinophil, and maximal levels of eosinophils were coincident with parasite killing. Mice were treated with mAb to eliminate IL-5 or granulocytes to assess the role that eosinophils play in larval killing. Treated animals showed no decrease in immunity when challenge infections consisted of systemically migrating L3 administered 3 weeks after booster immunizations. Eosinophil numbers in immunized mice decreased to control levels when measured 3 weeks post-booster immunization, both in diffusion chambers and in the peripheral blood, whereas they were elevated at 1 week after booster immunizations. Direct contact between host cells and L3 was, however, still required for larval killing in immunized hosts 3 weeks after booster immunizations. Elimination of eosinophils by treatment with mAb to IL-5 or granulocytes significantly reduced protective immunity, when L3 were implanted in diffusion chambers at 1 and 3 weeks post-booster. However, as systemically migrating L3 were still killed in immunized, eosinophil-depleted animals, other cell types may play a role in larval destruction. Two human eosinophil granule products were found to be toxic for host-adapted L3+, but had no effect on infective L3, indicating that host-adapted larvae are possible targets for eosinophil-mediated destruction of third stage larvae. These findings suggest that inactivation of eosinophils by mAb treatment abolishes protective immunity to L3 contained within diffusion chambers and that small numbers of eosinophils are sufficient for immune-mediated killing of S. stercoralis L3.

Animals↗
PubMed1996

Strongyloides stercoralis: role of antibody and complement in immunity to the third stage of larvae in BALB/cByJ mice.

Mice immunized against Strongyloides stercoralis L3 were shown to kill greater than 90% of challenge larvae contained within diffusion chambers. The objective of the present study was to identify the host components responsible for immunity. Serum from unprotected, control mice and protected, immune mice in doses of 25-500 microliters was transferred into naive mice at the same time and location as larval challenge. Transfer of as little as 50 microliters of immune serum was able to confer protective immunity. The serum-transferred immunity was ablated by excluding cells from the larval microenvironment or by depleting granulocytes through monoclonal antibody treatment in the recipient mice. Specific antibody isotypes were isolated using protein G and isotype-specific affinity columns. The resulting transfer experiments identified IgM as the isotype responsible for protective immunity to S. stercoralis L3. Antibody binding studies in vivo were performed and only IgM bound to the surface of infective L3 and host-derived L3 (L3+) in immune animals. Elevated levels of C3 were also found bound to the surface of L3/L3+ in immune mice. Cobra venom factor treatment of immunized mice to deplete complement completely eliminated C3 binding to the surface of L3/L3+ and ablated immunity. Therefore, IgM, complement, and granulocytes are necessary for immune elimination of S. stercoralis L3/L3+. Identification of antigens recognized by IgM may help select possible vaccine candidates.

Animals↗
PubMed1997

Strongyloides venezuelensis: adhesion of adult worms to culture vessels by orally secreted mucosubstances.

Adults worms of Strongyloides venezuelensis were cultured in vitro. After overnight incubation, about 60% of the worms adhered firmly to the bottom of culture vessels by secreting adhesive substances from the mouth. A single worm produced 24.5 +/- 10.1 of the adhesion spots overnight. When they were transferred to new culture vessels, they still produced new spots comparable to those produced for first 24 hr. The adhesion spots were positively stained with Coomassie brilliant blue and also with mucicarmine, periodic acid-Schiff, and alcian blue, pH 2.5, but not with alcian blue, pH 0.3, indicating their glycoprotein nature. The substances were amorphous and did not contain cells or nuclei. Histologic staining with a panel of lectins showed that the adhesive substances were rich in mannose, N-acetyl galactosamine, and N-acetyl glucosamine, but devoid of sialic acid. These characteristics were distinct from those of jejunal goblet cell mucins of rats. Adhesive substances contained antigenic components recognized by sera from infected rats. Thus, the adhesive substances secreted from the mouth of S. venezuelensis were clearly of parasite origin. We consider the production/secretion of the adhesive substances by S. venezuelensis adult worms a key step for the parasites to invade and establish the host epithelial layer.

Adhesiveness↗
PubMed1998

Strongyloides venezuelensis: binding of orally secreted adhesion substances to sulfated carbohydrates.

Adhesion substances produced by adult worms of Strongyloides venezuelensis bound strongly to hepin-Sepharose beads after incubation at 37 degrees C for 1 h. This binding was completely inhibited by highly sulfated carbohydrates such as soluble heparin, dextran surfate, fucoidan, and pentosan polysulfate. Chondroitin sulfate E and chondroitin sulfate A inhibited to a lesser degree and chondroitin sulfate C and dextran did not inhibit significantly. Carbohydrate moieties as well as the number and position of negatively charged sulfate groups of sulfated glycans were important determinants for the interaction between sulfated carbohydrates and adhesion substances. Adhesion substances of S. venezuelensis adult worms also bound to negatively charged rat red blood cells. The binding was significantly inhibited by heparin but not by mono- or disaccharides. Thus the intraction between red cells and adhesion substances was electrostatic in nature, but did not involve lectin-sugar interactions.

Animals↗
PubMed1998

Efficacy of ivermectin against Strongyloides stercoralis infection in jirds (Meriones unguiculatus).

The activity and distribution of ivermectin (IVM), a broad spectrum anthelmintic for various nematodes and arthropods, was tested against Strongyloides stercoralis infection in the jird (Meriones unguiculatus.) The pattern of IVM concentration in the serum of jirds after either low- (200 microg/kg) or high-dose (1000 microg/kg) treatment by intraperitoneal injection showed a typical single-peak profile with the maximum drug levels detected at 1 h followed by a rapid decline to undetectable values by 48 h posttreatment. With equivalent IVM doses, the serum levels in male jirds were significantly higher than those observed in female jirds at 1 and 12 h posttreatment (P < 0.05). Low-dose IVM treatment of either male or female jirds, in comparison with that of the respective control groups, produced no observable effect on the adult worm burden or the parasite fecundity. The curative dose for S. stercoralis in both sexes of animals was achieved when using the high dose of 1000 microg/kg of IVM. The area under the curve calculated from the serum-concentration profiles in males was significantly higher than that for females after the high-dose treatment of IVM (P < 0.05). By low-dose treatment, a significantly lower adult worm burden was observed in males compared with that in females (P < 0.05), and this difference correlated with the higher serum levels of IVM in male animals. The distribution of IVM in the jird after high-dose treatment was characterized by initial appearances at 1 h of maximum levels of the drug in the serum and intestinal content. The maximum level in the feces was reached at 12 h posttreatment and rapidly declined thereafter. The level in the intestinal tissue was comparatively much lower than that in the intestinal content and the feces. The half-life of IVM in the intestinal content (49.5 h) was longer than those in the serum, feces, and intestinal tissue (6.53-13.07 h). Analyses of the relationship between the peak serum IVM occurring at 1 h posttreatment and the adult worm recovery revealed that the minimal serum concentration associated with clearance of the adult worm from the jird was approximately 0.65 microg/ml. The jird-S. stercoralis model has not only made studies on various aspects of parasite biology possible, but also provided an in vivo system to examine the efficacy as well as the mode of action of IVM against this intestinal nematode.

Animals↗
PubMed2000

Strongyloides ratti: thermokinetic behavior of third-stage larvae on a temperature gradient.

We examined the thermokinetic behaviors of infective third-stage larvae (L3) of the rodent parasitic nematode Strongyloides ratti on temperature gradients using an in vitro agarose tracking assay method. Observed behaviors included both negative and positive thermokineses, the direction of movement depending both on the gradient temperature at which larvae were initially placed and on prior experience of culture temperature. Larvae isolated from rat feces cultured at 25 degrees C and placed on a gradient at temperatures between 22 degrees and 29 degrees C tended to move toward higher temperatures. At higher placement temperatures, most larvae moved little and showed no directional response, whereas at lower placement temperatures, many migrated toward cooler temperatures. At placement temperatures of 20 degrees C or below, few or no larvae moved toward the zone of higher temperature. Larvae isolated from rat feces cultured at 20 degrees C tended to migrate to a high temperature area regardless of placed temperature. Those cultured at 30 degrees C did not respond to the temperature gradient. L3 cultured at 30 degrees C were significantly less infective to rats than those cultured at 25 degrees or 20 degrees C. Additional experiments were designed to demonstrate thermokinetic behaviors during the period after reaching the L3 stage. Larvae incubated in double distilled water (DDW) for 24 h at 37 degrees C lost their ability to respond to lower temperatures, while in those incubated in DDW at 15 degrees and 25 degrees C, responses were still apparent. The thermokinetic behavior of S. ratti L3 is affected by surrounding environmental temperatures and this may have an important role in host finding.

Animals↗
PubMed2000

Strongyloides venezuelensis: heparin-binding adhesion substances in immunologically damaged adult worms.

Immunologically damaged Strongyloides venezuelensis adult worms were examined for their mucosal invasion ability and secretion of heparin-binding adhesion substances. S. venezuelensis was expelled from male Wistar rats 4 to 5 weeks after infection. Four-week-old adult worms were smaller and had fewer eggs than 1-week-old adult worms. One-week-old, 4-week-old, and 5-week-old adult worms equally established in the recipient mouse intestine when surgically implanted. Adult worms of 4 and 5 weeks of age secreted adhesion substances as much as 1-week-old adult worms. There was no difference in the heparin-binding activities and the lectin-binding profile of adhesion substances among adult worms of different ages. The rate of secretion of adhesion substances from the mouth was also identical. Heparin-binding activities were detected in crude adult worm proteins; however, proteins of 5-week-old adult worms had weaker heparin-binding activities than those of 1-week-old adult worms. Western blotting revealed that a number of heparin-binding proteins were lost in 5-week-old adult worms. A heparin-binding protein of 42. 0 kDa, which was consistently expressed in adult worms, was a possible component of heparin-binding adhesion substances which are secreted from the mouth.

Animals↗
PubMed1982

Immunisation of mice against Strongyloides ratti.

Experimental infections of C57Bl/6 mice with strongyloides ratti produced marked resistance to challenge. Resistance to reinfection was induced by as few as six filariform larvae. The degree of resistance produced by soluble somatic antigens prepared from filariform larvae of S. ratti was comparable to that seen after a primary infection. The addition of Freund's adjuvants to the antigen did not increase resistance significantly. Intraperitoneal implantation of micropore chambers containing filariform larvae failed to induce resistance to reinfection. Considerable resistance to a challenge infection with S. ratti was found after infection with S. stercoralis.

Animals↗
PubMed1983

Light and electron microscopical studies of the location of Strongyloides ratti in the mouse intestine.

This study was designed to define the precise anatomical location of Strongyloides ratti in the intestinal mucosa of the mouse. Light microscopy showed adult worms in vacuoles in close relationship with the columnar epithelium. Serial sections indicated that the adults wound their way circuitously through the mucosa, usually close to the crypts. Portions of worms were sometimes seen in the intestinal lumen. Electron microscopy demonstrated that adult worms were situated between the epithelial cells. They were never observed to penetrate the basement lamina and enter the lamina propria. Enterocytes were in close proximity to the cephalic end of worms, suggesting that the head of the moving worm forced the cells apart. More posteriorly along the worm, a fluid-filled vacuole surrounded the nematode. The surrounding epithelial cells were compressed and distorted but there was never any evidence of syncytial cell formation. The external cortical layer of worms was seen in some vacuoles, suggesting that ecdysis may occur in tunnels in the epithelium. It appears that S. ratti may create epithelial tunnels through which it moves, moults and deposits eggs. Since S. ratti is a mucosal-dwelling parasite, it is susceptible to attack by cellular elements of the host's defences.

Animals↗
PubMed1986

IgE response in Strongyloides ratti-infected rats with special reference to the life cycle of the parasite.

Parasite-specific IgE antibody response was examined in Strongyloides ratti-infected rats. The results showed that the parasite-specific IgE antibody response was generated after a primary infection. However, repeated infections rather depressed the level of parasite-specific IgE antibody in the serum. Immunization limited to specific stages of the parasite revealed that stimulation of parasite-specific IgE antibody was related to the intestinal adult stage. On the other hand, depression of IgE titers was related to the tissue-migrating larval stage. The capacity of the each stage of the parasite to induce specific IgE response may be related to the variable results of the IgE responses in human strongyloidiasis.

Animals↗
PubMed2000

A cDNA encoding a nuclear hormone receptor of the steroid/thyroid hormone-receptor superfamily from the human parasitic nematode Strongyloides stercoralis.

A cDNA encoding a nuclear hormone receptor of the steroid/thyroid receptor superfamily was obtained from third-stage larvae(L3) of the parasitic roundworm Strongyloides stercoralis. A recombinant clone was isolated via screening of an S. stercoralis cDNA library with a polymerase chain reaction (PCR)-generated probe. The insert of 2,583 bp contained the complete coding sequence of the receptor homologue. The conceptually translated amino acid sequence of this open reading frame encodes a 753-amino-acid-residue protein with an apparent molecular weight of 83.6 kDa and a predicted isoelectric point (pI) of 8.52. The coding sequence is 69% AT and the noncoding sequence is 72% AT, reflecting a characteristic A/T codon bias of S. stercoralis. In this report the amino acid sequence of the S. stercoralis nuclear hormone receptor of the steroid/thyroid receptor superfamily is compared with that of nuclear hormones of Caenorhabditis elegans, human orphan nuclear receptors, and insect ecdysone receptors. The potential role of steroids in the induction of hyperinfection syndrome is also discussed.

Amino Acid Sequence↗
PubMed2000

Effects of various treatments on the chemokinetic behavior of third-stage larvae of Strongyloides ratti on a sodium chloride gradient.

In observations of the movements of the infective third-stage larvae of a rodent parasitic nematode, Strongyloides ratti, on a sodium chloride gradient set up on agarose plates, two types of chemokinetic behavior were seen: a unidirectional avoidance movement on initial placement of the larvae in unfavorable environmental conditions and a random dispersal movement on their placement within an area of favorable conditions. Track patterns were straight in the avoidance movement but included multiple changes of direction and loops in the dispersal movement. In the present study we examined the interventional activity of treatment with various enzymes, lectins, and chemicals by analyzing the unidirectional avoidance movements of the larvae. We observed that beta-glucosidase, hyaluronidase, beta-galactosidase, trypsin, protease, lipase, phospholipase C, soybean agglutinin, wheat germ agglutinin, and spermidine exerted inhibitory actions on those movements, which may be guided by the chemosensory function of this nematode.

Animals↗
PubMed2001

The effect of interleukin-4 on the induction of intestinal mast cells and chronological cytokine profiles during intestinal nematode Strongyloides ratti infection.

The effect of interleukin-4 (IL-4) on the induction of intestinal mast cells and cytokine profiles during Strongyloides ratti infection was studied using IL-4 knockout (IL-4 KO) mice. The antigen-specific proliferative response of mesenteric lymph node cells was not impaired in IL-4 KO mice. The number of intestinal mast cells induced in IL-4 KO mice during S. ratti infection was 2- to 3-fold lower than that observed in WT mice. Intestinal mastocytosis had disappeared in IL-4 KO mice by day 21 postinfection, when significant mastocytosis continued to be observed in WT mice. In mesenteric lymphnode of IL-4 KO, IL-3 production decreased and mice IFN-gamma production significantly increased as compared with those of WT mice. The numbers of eggs excreted per gram of feces (EPG) by IL-4 KO mice were greater than those excreted by WT mice on day 6 postinfection, but no difference was observed in the subsequent period. In conclusion, intestinal mast cells are induced during S. ratti infection in the absence of IL-4, and IL-4 is not essential for protection against intestinal adult worms of S. ratti.

Animals↗
PubMed2004

Prevalence of parasite eggs (Strongyloides westeri, Parascaris equorum, and strongyles) and oocysts (Emeria leuckarti) in the feces of Thoroughbred foals on 14 farms in central Kentucky in 2003.

Prevalence of internal parasites was determined by fecal examination for eggs and oocysts in Thoroughbred foals in central Kentucky in 2003. Fecal samples were examined from 733 foals on 14 farms. This included 70 trips to the farms and a total of 2,346 fecal samplings. Monthly collection of fecal samples was begun for four farms in February, six in March, three in April, and one farm in May. Termination of the study for all farms was the end of July. A criterion was that the foals be at least 10 days old for initial samplings. If available, the same foals were sampled each time, in addition to foals born in the interim between farm visits. Ages of the foals for the complete study varied from 10 to 223 days. Prevalence (mean %) was determined for eggs of Strongyloides westeri (1.5%), Parascaris equorum (22.4%), and strongyles (27.6%) and for oocysts of Eimeria leuckarti (41.6%) in feces of foals. Foals had infections of S. westeri on six farms (42.9%), of P. equorum on 12 farms (86%), and of strongyles and E. leuckarti on all 14 farms (100%).

Animals↗
PubMed2005

Strongyloides ratti: thermokinesis of glycolytic enzyme- and lectin-treated third-stage infective larvae in vitro.

The infective third-stage larvae (L3s) of a parasitic nematode of rodents, Strongyloides ratti, showed three types of thermokinesis on a temperature gradient using an in vitro agarose tracking assay method. These depended both on the pattern of gradient temperature and the prior culture temperature. Most L3s (> or = 80%) isolated from rat feces cultured at 25 degrees C and placed on a gradient at temperatures between 30 degrees C and 37 degrees C showed no directional response, at 22-29 degrees C more than 50% of the L3s showed positive thermokinesis, at 21 degrees C L3s showed positive, negative and no directional responses in the same ratio, while at 18-20 degrees C, L3s showed negative thermokinesis (approx. 40%) or no directional response (approx. 60%) as in our previous study. The present study describes the effects of glycolytic enzyme- and lectin-treated positive thermokinesis of L3s. alpha-Glucosidase or concanavalin A significantly exhibited inhibitory effects on thermokinesis.

Animals↗
PubMed2000

The crucial role of granulocytes in the early host defense against Strongyloides ratti infection in mice.

The involvement of granulocytes in the host early defense against the nematode, Strongyloides ratti, was studied. It was confirmed that granulocytes were effectively depleted for 4 days by anti-granulocyte monoclonal antibody (anti-Gr-1). To examine the involvement of granulocytes in the host defense against migrating larvae, 2,000 S. ratti infective larvae (L3) were inoculated subcutaneously 1 day after antibody treatment. The number of S. ratti eggs secreted in feces (EPG) was higher in the granulocyte-depleted group than in the control group. The number of migrating larvae also increased in the granulocyte-depleted group in accordance with the increase in EPG. Therefore granulocytes are crucial for the host early defense against migrating larvae of S. ratti. Next, the involvement of granulocytes in the intestinal early defense was examined. Mice were treated with the antibody on day 3 post-infection. On that day, almost all inoculated larvae reached the intestine and molted to become adults. EPG on day 5 post-infection was increased by the antibody treatment, but no effect was observed on intestinal worm numbers. The fecundity (EPG/worm number) of S. ratti adult worms in the granulocyte-depleted group was higher than that in the control group. Thus granulocytes are also involved in the intestinal early defense through suppressing fecundity of the adult worms. On the other hand, the depletion of granulocytes had no effect on the late adaptive response against S. ratti adult worms (e.g. number of intestinal mucosal mast cells, time of worm expulsion). These results suggest that granulocytes are mainly involved in the host early defense against parasites.

Animals↗