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.     

Adult worms of the rodent intestinal nematode,Strongyloides venezuelensis,successfully invade chick intestinal mucosa

In order to study the mucosal invasion of a rodent intestinal nematode in bird intestine, chicks were infected with the intestinal nematode of rodents, Strongyloides venezuelensis, by subcutaneous larva inoculation and adult worm implantation. No evidence was obtained for larvae reaching the lungs or the intestine after infective larva inoculation. Adult worms implanted in the small intestine invaded the mucosa and remained there at least for 24 h, whereas those implanted in the caecum were trapped by mucus, and did not invade the mucosa. Mucosal invasion of adult worms in the small intestine was confirmed by histological examination. The number of adult worms in the intestinal mucosal tissue dropped rapidly within the first 24 h, which was associated with infiltrating granulocytes around the worms. The present study suggests that S. venezuelensis adult worms are able to invade the intestinal tissue of chicks, which do not belong to the vertebrate class of its normal definitive host, but that they are eliminated rapidly by mucosal defense system of the bird.     

Counterregulation of Th2 immunity by interleukin 12 reduces host defenses against Strongyloides venezuelensis infection

The aim of this study was to investigate the role of interleukin 12 (IL-12) during Strongyloides venezuelensis infection. IL-12^−/− and wild-type C57BL/6 mice were subcutaneously infected with 1500 larvae of S. venezuelensis. On days 7, 14, and 21 post-infection, we determined eosinophil and mononuclear cell numbers in the blood and broncoalveolar lavage fluid (BALF), Th2 cytokine secretion in the lung parenchyma, and serum antibody levels. The numbers of eggs in the feces and worm parasites in the duodena were also quantified. The eosinophil and mononuclear cell counts and the concentrations of IL-3, IL-5, IL-10, IL-13, and IgG1 and IgE antibodies increased significantly in infected IL-12^−/− and wild-type mice as compared with uninfected controls. However, the number of eosinophils and mononuclear cells in the blood and BALF and the Th2 cytokine levels in the lungs of infected IL-12^−/− mice were greater than in infected wild-type C57BL/6 mice. In addition, serum IgE and IgG1 levels were also significantly enhanced in the infected mice lacking IL-12. Meanwhile, parasite burden and fecal egg counts were significantly decreased in infected IL-12^−/− mice. Together, our results showed that the absence of IL-12 upregulates the Th2 immune response, which is important for control of S. venezuelensis infection.     

Strongyloides stercoralis: antigenic analysis of infective larvae and adult worms

The protein composition of Strongyloides stercoralis infective larvae and adult worms solubilized sequentially in water, sodium deoxycholate and sodium dodecyl sulphate (SDS) and their excretory/secretory products were analysed by one- and two-dimensional SDS-polyacrylamide electrophoresis. These extracts were demonstrated to be complex mixtures containing many proteins, some of which were common and others which were stage-specific. Western blot analysis of these antigens with infected human sera showed most sero-reactivity against larval antigens, whilst normal human sera were unreactive. These data identify immunogenic antigens which may be available for detection in an antigen assay.     

Strongyloides ratti: formation of protection in rats by excretory/secretory products of adult worms

Formation of a marked protective immunity against the challenge infection was found in the rats immunized with excretory/secretory (ES) products of Strongyloides ratti adult worms. Immunization by intraduodenal injection of ES products reduced both the fecal egg counts and the adult worm burden by subcutaneous inoculation of infective larvae and by an intraduodenal implantation. The duration of parasitism in the immunized rats, however, was not shortened compared with that of control rats. The normal migration of subcutaneously challenged larvae was not affected by ES product immunization. Intestinal mastocytosis occurred according to the appearance of adult worms in the small intestine of the immunized rats earlier than it did in controls. This result suggests that mastocytosis is involved in the induction of protection by ES products of S. ratti adult worms.     

Strongyloides ratti: the role of enteral antigenic stimuli by adult worms in the generation of protective immunity in rats

Immunogenicity of adult Strongyloides ratti was studied in rats. Immunization of rats by intraduodenal implantation of adult worms could completely inhibit the egg production and hasten the expulsion of challenged worms which were developed from subcutaneously inoculated L3 or were implanted intraduodenally as adults. Enteral immunization by intraduodenal implantation of adult worms was, however, not able to affect the esophageal larval output of the challenge infection with L3. In contrast to enteral immunization with adult worms, immunization by full sequence of a primary infection or by a combination of drug-abbreviated infection and adult worm implantation could suppress the esophageal larval output of the challenge infection. The relationship between the host defense mechanism and the life cycle of S. ratti is discussed.     

Mechanisms of the airway hyperresponsiveness induced by Strongyloides venezuelensis infection in rats: role of capsaicin-sensitive neurons

Strongyloides venezuelensis migrates through the lungs and induces airway hyperresponsiveness (AHR). The present study evaluated the role of C-fibers in mediating airway inflammation and AHR after infection of rats with S. venezuelensis. Neonatal treatment with capsaicin effectively depleted sensory nerves. This was accompanied by inhibition of the AHR induced by S. venezuelensis infection. In contrast, capsaicin treatment greatly enhanced pulmonary inflammation, eosinophil influx and the local production of TNF-α. In conclusion, this is the first demonstration that, akin to viral and allergic AHR, permanent loss of sensory nerve C-fibers also reduces AHR induced by infection with a helminth.     

Strongyloides ratti: the role of interleukin-5 in protection against tissue migrating larvae and intestinal adult worms

To determine the role of interleukin-5 (IL-5) and eosinophils in protection against Strongyloides ratti, mice treated with anti-IL-5 monoclonal antibody (mAb) were infected with S. ratti larvae. Strongyloides ratti egg numbers in faeces (EPG) in mAb treated mice were higher than those in control mice on days 6 and 7 after inoculation. The numbers of migrating worms in mAb treated mice 36 h after inoculation were higher than those observed in control mice. Intestinal worm numbers in mAb treated mice 5 days after inoculation were higher than those in control mice. These results show that eosinophils effectively protected the host against S. ratti infection by mainly the larval stage in primary infections. The involvement of eosinophils in protection against secondary infection was also examined. Before secondary infection, mice were treated with anti-IL-5 mAb and infected with S. ratti. Patent infections were not observed in either mAb treated or control Ab treated mice. The numbers of migrating worms in the head and lungs of mAb treated mice increased to 60% of that in primary infected mice. Intestinal worms were not found in mAb treated mice or in control mice after oral implantation of adult worms. Eosinophils were therefore mainly involved in protection against tissue migrating worms in secondary infections.     

Intraepithelial infiltration of eosinophils and their contribution to the elimination of adult intestinal nematode,Strongyloides venezuelensis in mice

Eosinophils were examined for the capacity of attacking Strongyloides venezuelensis adult worms in the intestinal mucosa by using interleukin (IL)-5 transgenic mice. In IL-5 transgenic mice, most of the subcutaneously inoculated infective larvae were killed during migration, and only a few worms could reach the small intestine. When the same number of adult worms were surgically implanted in the small intestine of IL-5 transgenic and control mice, fecal egg output as well as the number of adult worms recovered from the intestine was significantly lower in IL-5 transgenic mice. In the intestinal mucosa of IL-5 transgenic mice, large number of eosinophils was present in the lamina propria even before adult worm implantation. The number of eosinophils increased significantly as early as 24 h after implantation and tripled by day 3, whereas mucosal eosinophilia remained low in wild-type mice. Most notably, eosinophils infiltrated into the intestinal epithelium and surrounded adult worms in IL-5 transgenic mice, which was never seen in wild-type control mice. However, IL-5 transgenic mice required the same period as normal mice to completely expel implanted adult worms. The amount of specific IgA as well as total IgA in the stool was high in IL-5 transgenic mice before adult worm implantation, and dropped rapidly after adult worm implantation. The present study suggests that eosinophils are capable of attacking adult nematodes in the intestinal epithelia, probably in conjunction with secretory IgA, although they are not enough for the complete worm expulsion.     

Strongyloides venezuelensis alkaline extract for the diagnosis of human strongyloidiasis by enzyme-linked immunosorbent assay

The present study was conducted to detected IgG antibodies using Strongyloides venezuelensis alkaline extract for the diagnosis of human strongyloidiasis by the enzyme-linked immunosorbent assay (ELISA). Sera from 90 subjects were analyzed (30 with strongyloidiasis, 30 with other parasites and 30 healthy individuals). Results were expressed in antibody titers, which were considered as positive when titer was >80. Sensibility and specificity of the assay were 100% and 96.7%, respectively. It can be concluded that the heterologous alkaline extract could be employed in ELISA as a diagnostic aid in human strongyloidiasis, due to its advantages as easiness of obtaining, practicability in preparing, and high indexes of sensitivity and specificity.     

Strongyloides venezuelensis: the antigenic identity of eight strains for the immunodiagnosis of human strongyloidiasis

The antigens of eight strains of Strongyloides venezuelensis were identified by means of the indirect immunofluorescence antibody (IFAT), enzyme-linked immunosorbent assay (ELISA) and immunoblot (IB) tests. Infective larvae (L3) from these strains were obtained from Rattus norvegicus feces cultures. For IFAT, sections of L3 were used while the ELISA and IB, tests were conducted with alkaline extract. Ninety serum samples were tested: 30 from patients with S. stercoralis, 30 from patients with other parasitic diseases, and 30 from healthy subjects (free of parasites). Average sensitivity and specificity among all eight strains, both for IFAT and ELISA, were, respectively, 93% and 100%. In the IB, anti-S. stercoralis IgG recognized a single antigenic fraction with 45 kDa. Serum samples from patients with S. stercoralis revealed antigens from different strains of S. venezuelensis, indicating antigenic identity for possible use in the synthesis of recombinant antigen that could be useful in immunodiagnosis and vaccine against this parasite.     

Intestinal distribution of worms and host ingesta in Nippostrongylus brasiliensis.

The gastrointestinal nematode Nippostrongylus brasiliensis is thought to feed on host ingesta, and it is generally thought that the presence of ingesta determines the distribution of this parasite within the host intestine. However, these assertions have not been supported by direct evidence. The purpose of this study was to test the hypothesis that N. brasiliensis worms are preferentially found in regions of the host small intestine containing ingesta. The relationship between worm and ingesta distribution was investigated using mice infected with N. brasiliensis and killed on day 8 postinfection at 0130, 0730, 1330, or 1930 hr. There was an inverse relationship between worm and ingesta distributions, and the worms were distributed significantly more anteriad in the intestine than host ingesta, at all times during the 24 hr. To determine what the worms fed on, host ingesta, tissue, and blood were differentially labeled with the fluorescent dyes rhodamine B and Fluoresbrite. The results of this study suggest that N. brasiliensis feeds on the host's intestinal wall, and that habitat distribution of this parasite within the small intestine is not directly related to the presence of luminal ingesta.     

Inhibition of virus-induced diabetes mellitus by interferon is influenced by the host strain

The diabetogenic variant of encephalomyocarditis virus (EMC-D) induces a diabetes-like syndrome in certain strains of mice. A study was done to determine if virus-induced diabetes could be prevented by interferon (IFN). It was found that the production of diabetes by EMC-D was blocked by either IFN beta or a variety of IFN-inducers in SWR/J, but not ICR Swiss mice. The replication of EMC-D in cell culture was inhibited by IFN beta. It is concluded that the response of pancreatic beta cells to the protective effect of IFN, is probably under genetic control.     

Responsiveness of cardiometabolic-related microbiota to diet is influenced by host genetics

Intestinal microbial community structure is driven by host genetics in addition to environmental factors such as diet. In comparison with environmental influences, the effect of host genetics on intestinal microbiota, and how host-driven differences alter host metabolism is unclear. Additionally, the interaction between host genetics and diet, and the impact on the intestinal microbiome and possible down-stream effect on host metabolism is not fully understood, but represents another aspects of inter-individual variation in disease risk. The objectives of this study were to investigate how diet and genetic background shape microbial communities, and how these diet- and genetic-driven microbial differences relate to cardiometabolic phenotypes. To determine these effects, we used the 8 progenitor strains of the collaborative cross/diversity outbred mapping panels (C57BL/6J, A/J, NOD/ShiLtJ, NZO/HILtJ, WSB/EiJ, CAST/EiJ, PWK/PhJ, and 129S1/SvImJ). 16s rRNA profiling of enteric microbial communities in addition to the assessment of phenotypes central to cardiometabolic health was conducted under baseline nutritional conditions and in response to diets varying in atherogenic nutrient (fat, cholesterol, cholic acid) composition. These studies revealed strain-driven differences in enteric microbial communities which were retained with dietary intervention. Diet–strain interactions were seen for a core group of cardiometabolic-related microbial taxa. In conclusion, these studies highlight diet and genetically regulated cardiometabolic-related microbial taxa. Furthermore, we demonstrate the progenitor model is useful for nutrigenomic-based studies and screens seeking to investigate the interaction between genetic background and the phenotypic and microbial response to diet.     

Intestinal microbiota composition in fishes is influenced by host ecology and environment

The digestive tracts of vertebrates are colonized by complex assemblages of micro-organisms, collectively called the gut microbiota. Recent studies have revealed important contributions of gut microbiota to vertebrate health and disease, stimulating intense interest in understanding how gut microbial communities are assembled and how they impact host fitness (Sekirov et al. 2010). Although all vertebrates harbour a gut microbiota, current information on microbiota composition and function has been derived primarily from mammals. Comparisons of different mammalian species have revealed intriguing associations between gut microbiota composition and host diet, anatomy and phylogeny (Ley et al. 2008b). However, mammals constitute <10% of all vertebrate species, and it remains unclear whether similar associations exist in more diverse and ancient vertebrate lineages such as fish. In this issue, Sullam et al. (2012) make an important contribution toward identifying factors determining gut microbiota composition in fishes. The authors conducted a detailed meta-analysis of 25 bacterial 16S rRNA gene sequence libraries derived from the intestines of different fish species. To provide a broader context for their analysis, they compared these data sets to a large collection of 16S rRNA gene sequence data sets from diverse free-living and host-associated bacterial communities. Their results suggest that variation in gut microbiota composition in fishes is strongly correlated with species habitat salinity, trophic level and possibly taxonomy. Comparison of data sets from fish intestines and other environments revealed that fish gut microbiota compositions are often similar to those of other animals and contain relatively few free-living environmental bacteria. These results suggest that the gut microbiota composition of fishes is not a simple reflection of the micro-organisms in their local habitat but may result from host-specific selective pressures within the gut (Bevins & Salzman 2011).     

Strongyloides stercoralis: oral transfer of parasitic adult worms produces infection in mice and infection with subsequent autoinfection in gerbils.

Oral transfer of parasitic adult Strongyloides stercoralis produced patent infections in gerbils, C57BL/6J and SCID mice. In gerbils receiving adult worms, 7.3% of the transferred worms established and autoinfective L3 were found beginning on day 5 post-transfer, with peak numbers seen on days 6 and 7 post-transfer and few seen by 9 days post-transfer. These results suggest that development of autoinfective L3 in the gerbil is limited by the immune response of the host. When given orally to mice, between 7.2% (C57BL/6J) and 19.5% (SCID) of the adult worms established. These levels are higher than those previously obtained by the subcutaneous infection of SCID mice with infective larvae. No autoinfective larvae were found in infected mice and the ratio of L1/adult worms was small compared with that seen in gerbils. Thus, mice infected orally can be used as a model to study the interaction between the adult worm and the host, and since autoinfection has not been seen in the murine model, as developed to date, orally infected mice may be useful as a model to study mechanisms preventing autoinfection.     

Protease resistant interleukin-3 stimulating components in excretory and secretory products from adult worms of Strongyloides ratti.

Excretory and secretory (ES) products collected from adult worms of Strongyloides ratti stimulated interleukin-3 (IL-3) production with mesenteric lymph node cells from infected C57BL/6 mice, but not with normal mesenteric lymph node cells. The IL-3 stimulating components were not major IgG binding antigens. Activity of the IL-3 stimulating components was stable by treatment with protease, although reduced by heating in boiling water.