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In the present study, antigens from parthenogenetic females and eggs of Strongyloides venezuelensis, or anti-parthenogenetic-female and anti-egg antigens were used to detect specific IgG and immune complex responses, respectively. Serum samples from experimentally infected immunocompetent and immunosuppressed rats were analysed on days 5, 8, 13 and 21 post-infection (dpi). An enzyme-linked immunosorbent assay (ELISA) was performed using alkaline parasite extract for specific IgG detection, and anti-parthenogenetic-female or anti-egg antigens for immune complex detection. The data were analysed using analysis of variance (ANOVA), followed by a Bonferroni test. When parthenogenetic female or egg extracts were used as antigens, specific IgGs were not detected in either immunocompetent or immunosuppressed rats. When anti-parthenogenetic-female or anti-S. venezuelensis-eggs were used, immune complexes were detected for the duration of the infection in immunosuppressed animals and were only detected between 5 and 13 dpi in immunocompetent animals. The duration of infection was not significantly different between the immunocompetent and immunosuppressed groups when anti-parthenogenetic-female or anti-S. venezuelensis-eggs were used. Parthenogenetic female extracts yielded significant differences between antibody and immune complex responses in immunocompetent rats from 5 to 13 dpi, but only on day 5 dpi in immunosuppressed rats. Exposure to S. venezuelensis egg extract yielded significant differences in both antibody and immune complex detection between immunocompetent and immunosuppressed rats for the duration of the infection. In conclusion, ELISA using alternative antigens may be a successful strategy for identifying immune complexes in serum samples and diagnosing active strongyloidiasis, particularly under conditions of immunosuppression.

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Little is known about the actin cytoskeleton architecture in female Strongyloides venezuelensis and thus to investigate the distribution and concentration of actin, female worms were labelled with phalloidin-rhodamine and visualized under confocal microscopy. Our results demonstrate that filamentous actin accumulates in the vulva and the concentration of F-actin at this site suggests its important role, especially during oviposition, in the life cycle of S. venezuelensis.

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The aim of this study was to use larval, parasitic female and egg antigens from Strongyloides venezuelensis to detect parasite-specific IgG and immune complexes in human serum samples by enzyme-linked immunosorbent assay (ELISA). In total, 95 serum samples were analysed, consisting of 30 patients harbouring S. stercoralis larvae, 30 healthy subjects and 35 patients with other parasites. Sensitivity, specificity and diagnostic efficiency were calculated. A significant statistical difference was found in the detection of immune complexes and antibodies in patients harbouring S. stercoralis larvae from larval and eggs antigens, with higher positivity using larval antigen. The larval antigen showed the highest values for sensitivity, specificity and diagnostic efficiency in ELISA from detection of immune complexes. For the first time we used IgG anti-larvae, IgG anti-parasitic females or IgG anti-eggs for immune complex detection. We concluded that the association of antibody and immune complex detection could be used in the diagnosis of human strongyloidiasis.

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The present study, investigated the mechanisms involved in the immune responses of Major Histocompatibility Complex class I or class II knockout mice, following Strongyloides venezuelensis infection. Wild-type C57BL/6 (WT), MHC II(-/-) and MHC I(-/-) mice were individually inoculated with 3000 larvae (L3) of S. venezuelensis and sacrificed on days 1, 3, 5, 8, 13 and 21 post-infection (p.i.). Samples of blood, lungs and small intestines were collected. The tissue samples were stained with hematoxylin-eosin for the pathological analysis. The presence of the parasite was demonstrated by immunoperoxidase analysis. MHC II(-/-) mice presented a significantly higher number of adult worms recovered from the small intestine on day 5p.i. and presented elevated numbers of eggs in the feces. The infection by S. venezuelensis was completely eliminated 13 days after infection in WT as well as in MHC I(-/-) mice. In MHC II(-/-) mice, eggs and adult worms were still found on day 21 p.i., however, there was a significant reduction in their numbers. In the lung, the parasite was observed in MHC I(-/-) on day 1 p.i. and in MHC II(-/-) mice on days 1 and 5 p.i. In the small intestine of WT mice, a larger number of parasites were observed on day 8 p.i. and their absence was observed after day 13 p.i. Through immunohistochemistry analysis, the parasite was detected in the duodenum of WT on days 5 and 8 p.i., and in knockout mice on days 5, 8 and 13 p.i.; as well as in posterior portions of the small intestine in MHC I(-/-) and MHC II(-/-) on day 13 p.i., a finding which was not observed in WT mice. We concluded that immunohistochemistry analysis contributed to a more adequate understanding of the parasite localization in immunodeficient hosts and that the findings aid in the interpretation of immunopathogenesis in Strongyloides infection.

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In human hosts and in murine models, the immune response to Strongyloides spp. is Th2 type. In addition, the profile of the host immune response follows various symptoms induced by Strongyloides spp. In the present study, we demonstrated that the L2 and L49 strains of Strongyloides venezuelensis obtained from Bolomys lasiurus and Nectomys squamipes induced significant and similar increases in eosinophil/mononuclear cell counts in the blood, peritoneal cavity fluid and bronchoalveolar lavage fluid when compared with uninfected mice. However, in the first 3 days of infection, IL-4, IL-5 and IFN-gamma levels were higher in the lungs of mice infected with the L2 strain, which also presented greater production of IgG and IgG1 than did mice infected with the L49 strain. The higher antibody and cytokine levels induced by the L2 strain correlated with a decrease in the number of female parasites recovered in the faeces of mice on post-infection day 7. The results demonstrate that the L2 strain was a more potent stimulant of the humoral immune response, which can result in more efficient antibody-dependent cell-mediated cytotoxicity, a mechanism involved in eosinophil activation and parasite elimination. Further studies are needed in order to elucidate the molecular differences among parasites.

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BACKGROUND: Strongyloides stercoralis is a world wide distributed small intestinal nematode parasite. In immunocompetent individuals S stercoralis can produce asymptomatic infections or a moderate clinical picture of diarrhea, some cases become chronic. In immunocompromised patients, a disseminated disease may appear, sometimes fatal. In Chile, there is little epidemiological information about S stercoralis infections and appropriate diagnostic techniques are usually not used. AIM: To evaluate the yield of an ELISA test for the diagnosis of strongyloidiasis in Chilean patients. MATERIAL AND METHODS: Ten serum samples from patients with S stercoralis infections confirmed by a positive stool examination, 66 samples from individuals with other infections by tissue helminthes (24 toxocariasis, 15 trichinellosis, 11 hydatidosis, 12 fascioliasis and 4 cysticercosis), 13 samples from subjects with autoimmune diseases and 49 samples from apparently healthy individuals with a normal eosinophil count, were studied. ELISA antigen was prepared using a filariform larval extract obtained from a murine species of Strongyloides, maintained in laboratory animals. RESULTS: Using 0.33 optical density units as a cut off value, 9 of 10 sera of S stercoralis infected individuals, had a positive ELISA test. No cross reactions were observed with sera of patients with other helminthic infections, autoimmune diseases or in healthy individuals. Thus, specificity, positive and negative predictive values were 100 per cent. CONCLUSIONS: The results obtained are similar with those found by other investigators. ELISA test for strongyloidiasis is a useful tool for the diagnosis of clinical cases and for seroepidemiological studies of this nematode infection in Chile.

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Xiphidiocercariae, aquatic larval stages of some trematodes are considered a potential instrument for biological control of mosquitoes. In this study we evaluated its natural occurrence in Campinas region and two places in Vale do Ribeira (Registro and Miracatu), São Paulo State. Snails were obtained from fresh water collections from September 1996 to February 1999. The species collected were Lymnaea columella, Physa marmorata, Biomphalaria tenagophila, Biomphalaria sp., Drepanotrema cimex, D. lucidum and Drepanotrema sp. Fasciola hepatica, xiphidiocercariae (Haematoloechidae) and echinostomatid cercariae were detected in the lymnaeids snails from Miracatu, SP. In the same locality were found planorbids snails parasitized by furcocercariae, echinostomatid cercariae and xiphidiocercariae. The xiphidiocercariae found in the planorbids were different from those obtained from lymnaeids. One Biomphalaria sp. infected with furcocercariae was found in Louveira, SP. In the ROSA place (Campinas, SP) an individual of Biomphalaria sp. and one of L. columella were found infected by the furcocercariae and echinostomatid cercariae, respectively. In the place UNI-I, in Campinas, one L. columella was infected by furcocercariae. Double infection in snails from Miracatu was also observed.

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The aim of the experiments was to explain the high number of worms found in chickens from a poultry facility. Infections by Raillietina laticanalis were achieved in chickens kept in the laboratory. Thirty cysticercoids obtained from beetles (Dermestes ater) caught at the poultry facility were administered by pipette to each chicken. The rate of recovered worms was employed to evaluate the persistence of the infection, the influence of bird age on susceptibility to infection, and the possibility of reinfection. To verify the persistence of the infection, a group of ten chickens was infected. At each of five different intervals, two chickens were necropsied. Tapeworms were recovered up to the 46th day. To verify the influence of bird age on susceptibility to infection, three different age groups were used in the experimental design: 3-4 weeks, 6-9 weeks, and 17-20 weeks. There was no difference in susceptibility to the infections across the groups. To investigate the possibility of reinfection, a group of birds received an additional dose of cysticercoids a few days after the first doses. Another group received the second dose only after the worms had already been established. There was a significant increase in the number of recovered worms in both groups when compared with the control. The short worms found in some experiments may be due to natural destrobilization. Thus, the high number of worms found in chickens from the poultry facility could result from both infections being acquired earlier and infections acquired at the laying stage, since we demonstrated the possibility of reinfection and the long lifespan of the worm.(ABSTRACT TRUNCATED AT 250 WORDS)

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