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Query: UMLS:C0017536 (giardiasis)
 1,714 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Giardiasis is recognized as a worldwide public health problem. Seroprevalence data from both the developing and developed world show high rates of carriage in populations at risk for fecal-oral transmission, such as children in day-care centers. Outbreak investigation has expanded our understanding of reservoirs for Giardia lamblia and of the routes of transmission. Various host factors have been associated with infection. The pathogenesis of giardial infections is being elucidated, in particular the role of lectin activation in producing disease. Three standard chemotherapeutic agents are available in the United States. The institution of community-wide prevention measures is equally important. Current areas of investigation including antigenic composition and enzymatic variants should result in effective forms of immunotherapy, while more effective forms of chemoprophylaxis could assist in eradicating the pathogen from institutional settings.
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PMID:From Leningrad to the day-care center. The ubiquitous Giardia lamblia. 221 72

We recently reported the isolation and identification of a Giardia lamblia-specific antigen (GSA 65) that is shed in the stool of giardiasis patients. In the present study, this antigen was affinity purified from sonic extracts of axenically cultured G. lamblia trophozoites and characterized to better understand its biological function and its potential usefulness in the design of coprodiagnostic assays for giardiasis. GSA 65 was resistant to proteolytic digestion with trypsin, chymotrypsin, and protease but was sensitive to treatment with NaIO4 as assessed by Western blotting. This antigen was also stable during prolonged storage at 4 and -20 degrees C in 10% Formalin or distilled H2O as assessed by counterimmunoelectrophoresis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing gel banding patterns, in conjunction with protein and carbohydrate assays and lectin binding studies, confirmed that this antigen is a highly glycosylated glycoprotein. The resistance of GSA 65 to proteolytic degradation, together with previous immunofluorescence data that indicate the antigen is an integral part of the G. lamblia cyst wall, suggests that this molecule may play a role in maintaining the integrity of the cyst in vivo. The ability of GSA 65 to maintain its antigenic structure under a wide variety of conditions makes it an ideal antigen around which to design sensitive immunodiagnostic assays for giardiasis.
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PMID:Physical and chemical characterization of a Giardia lamblia-specific antigen useful in the coprodiagnosis of giardiasis. 353 98

Four immunological methods for diagnosis of giardiasis comprising complement fixation (CF) test, indirect hemagglutination (IHA) test, enzyme-linked immuno sorbent assay (ELISA) and lectin immuno test (LIT) were studied. Fifty sera from asymptomatic giardiasis patients, 40 from patients with other diseases and 50 from healthy controls were evaluated. The seropositive rates in asymptomatic giardiasis were 36% for CF, 58% for LIT, 30% for IHA and 72% for ELISA. The seropositive rates in patients with other diseases were 22.5% for CF, 52.5% for LIT, 12.5% for IHA and 67.5% for ELISA. The results suggest that the test of choice for giardiasis was CF with 88% specificity, nevertheless this test showed low sensitivity (36%). Other two tests, ELISA and LIT were more sensitive than CF with percent sensitivity of 72 and 58 respectively, but these two tests had severe disadvantages in being less specific with percentage specificity of 48 and 60 respectively.
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PMID:A comparative study of four methods for detecting antibody in asymptomatic giardiasis. 373 13

The intestinal parasite Giardia lamblia is a significant cause of diarrheal disease, which is perpetuated by the infective cyst form of the parasite. Although a rational approach to the control of giardiasis would be to inhibit cyst formation, nothing is known of the chemical composition of the cyst wall or of its biosynthesis. In these studies, we have shown that chitin is a major structural component of G. lamblia and G. muris cyst walls. This conclusion is based on the finding that chitinase specifically destroys the cyst wall, as revealed by electron microscopy. The presence of chitin was also shown directly by lectin binding studies. Of 12 lectins with diverse carbohydrate recognition specificity, only the N-acetylglucosamine-specific lectins wheat germ agglutinin, succinylated wheat germ agglutinin, and tomato lectin bound to cyst walls, as shown by fluorescence microscopy and cytochemistry. Wheat germ agglutinin binding was completely abolished by treatment of the cysts with purified chitinase. This effect was specific since it could be prevented by incubating the enzyme with chitin before treatment of the cysts. Treatment of cysts with N-acetyl-beta-glucosaminidase partially inhibited wheat germ agglutinin binding, whereas other glycosidases and proteases had no effect. These findings indicate that chitin is a major structural component of Giardia cyst walls and raise the possibility that inhibitors of chitin synthesis may be of use in preventing encystation and thus controlling spread of the disease.
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PMID:Identification of chitin as a structural component of Giardia cysts. 403 95

After oral administration of cysts of the intestinal protozoan parasite, Giardia muris, young male C3H/He mice are chronically infected, whereas BALB/c mice demonstrate a rapidly resolving pattern of infection. Both strains of mice injected with trophozoites in adjuvant and challenged orally with cysts develop serum antibodies to numerous trophozoite proteins. A limited number of these protein antigens was differentially immunoprecipitated by sera from resistant BALB/c and susceptible C3H/He mice exposed to G. muris. 35S-methionine-labelled protein antigens better recognized by immune BALB/c sera included molecules of relative mobility (Mr) 82,000 and a series of proteins of Mr 25,000 to 32,000. Differential recognition extended to a subset of solubilized trophozoite antigens that bind to the lectin, wheat germ agglutinin (WGA), and that can be radio-iodinated. In particular, a complex of 4 acidic protein antigens of approximate Mr 32,000, and designated collectively as Gm32, was better recognized by immune BALB/c serum than C3H/He serum. Isolated WGA-binding antigens were not able to consistently vaccinate BALB/c mice against subsequent G. muris infection. Moreover, preliminary evidence has been obtained that lack of antibody responsiveness to Gm32 does not segregate strictly with susceptibility to chronic infection in (BALB/c X C3H/He)F2 mice. These data, plus the observation that drug-cured C3H/He mice are highly resistant to reinfection, has led to examination of whether mice differ in the capacity of the intestines to support inflammatory responses. Mast cell deficient Wf/Wf mice, unlike wild-type litter-mates, developed chronic giardiasis although no reconstitution of resistance has yet been achieved with inocula of bone marrow cells from +/+ mice. BALB/c mice injected with the antihistamine and antiserotonin drug, cyproheptadine, also showed prolonged infections with G. muris. The data suggest that analysis of specificity differences in immune responses of mice varying in susceptibility to intestinal parasites must be supplemented by examination of the capacity of the intestine to support induced immune responses.
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PMID:An examination of differences in serum antibody specificities and hypersensitivity reactions as contributing factors to chronic infection with the intestinal protozoan parasite, Giardia muris, in mice. 668 64

Giardia lamblia, a cause of diarrheal disease throughout the world, is a protozoan parasite that thrives in the small intestine. It is shown here that wheat germ agglutinin (WGA), a naturally occurring lectin widely consumed in normal human diets, reversibly inhibits the growth of G. lamblia trophozoites in vitro, and reduces infection by G. muris in the adult mouse model of giardiasis. The inhibitory effect was dose related, not associated with cytotoxicity and reversed by N-acetyl-D-glucosamine in accordance with the known specificity of the lectin and in agreement with the presence of GlcNAc residues on the surface membrane of G. lamblia trophozoites. Cell cycle analysis revealed that parasites grown in the presence of WGA are arrested in the G2/M phase, providing an explanation for the lectin-induced inhibition of cell proliferation. Comparison of electrophoretic profiles by lectin blot analysis revealed both glycoprotein induction and suppression in growth-arrested organisms. Our findings raise the possibility that blocking trophozoite growth with naturally occurring dietary lectins may influence the course of giardiasis. In addition, the study of cell cycle arrest by WGA may provide a model to study the regulation of cell division in lower eukaryotes.
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PMID:Growth inhibition of the intestinal parasite Giardia lamblia by a dietary lectin is associated with arrest of the cell cycle. 798 83

Giardiasis is the most common small intestinal protozoal infection and is found worldwide. The mechanisms by which Giardia duodenalis (= G. lamblia) produces chronic diarrhoea and malabsorption have still not been clearly defined. Many infections are associated with mild to moderate mucosal damage which, in animal models of infection, have functional correlates. Possible mechanisms include direct physical injury, release of parasite products such as proteinases or lectin, and mucosal inflammation associated with T cell activation and cytokine release. Other possible mechanisms of malabsorption include associated bacterial overgrowth and bile salt deconjugation, bile salt uptake by the parasite with depletion of intraluminal bile salts, and inhibition of pancreatic hydrolytic enzymes. Thus, there is no single mechanism to explain the diarrhoea and malabsorption caused by Giardia, which currently should be regarded as a multifactorial process.
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PMID:Diarrhoeal disease: current concepts and future challenges. Pathogenesis of giardiasis. 810 43

Giardia lamblia infection has been shown to modify the glycosylation process of microvillus membranes in mice intestine. Sialic acid content of the membranes was enhanced 3-fold but there was no change in fucose content of infected animals compared to the controls. The binding of 125I-wheat germ agglutinin was augmented and that of Ulex Europeus agglutinin was unaltered to infected membranes. The binding of 125I-peanut agglutinin to brush borders was however, significantly reduced in Giardia infected mice. Kinetic analysis revealed that the observed binding of peanut agglutinin to the membrane was associated with reduced number of the lectin reactive sites (control = 649 and infected 380 nmole/protein) with no change in the affinity constant (Ka = 95.7 nmole/ml) in Giardia infected mice intestine.
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PMID:Changes in glycosylation of microvillus membranes in Giardia lamblia infected mice intestine. 811 64

Alpha-1 giardin is an immunodominant protein in the intestinal protozoan parasite Giardia lamblia. The Triage((R)) parasite panel, used to detect copro-antigens in stool from giardiasis patients, reacts with an epitope between amino acids 160 and 200 in alpha-1 giardin. This region of the protein is also highly immunogenic during human infections. Alpha-1 giardin is related to annexins and like many other annexins it was shown to be plasma membrane associated. Immunoelectron and immunofluorescence microscopy revealed that some alpha-1 giardin are displayed on the surface of recently excysted cells. Recombinant alpha-1 giardin displayed a Ca(2+)-dependent binding to glycosaminoglycans (GAGs), in particular heparan sulphate, a common GAG in the intestinal tract. Recombinant alpha-1 giardin bound to thin sections of human small intestine, a binding which could be inhibited by adding increasing concentrations of sulphated sugars. A surface associated trypsin activated Giardia lectin (taglin) has been suggested to be important for G. lamblia attachment. In this study we show that a monoclonal antibody that inhibits taglin recognises alpha-1 and alpha-2 giardin. Thus, alpha-1 giardin is a highly immunoreactive GAG-binding protein, which may play a key role in the parasite-host interaction. Our results further show a conserved function of annexins from lower to higher eukaryotes.
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PMID:Characterisation of alpha-1 giardin: an immunodominant Giardia lamblia annexin with glycosaminoglycan-binding activity. 1452 17