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

The patterns of transmission of Giardia lamblia and the potential contribution of strain differences to pathogenicity of infection is poorly understood. We used pulsed field gradient gel electrophoresis (PFGE) to separate chromosome-sized DNA molecules of 22 stocks of G. lamblia isolated from 13 individuals (6 symptomatic, 7 asymptomatic) living in Jerusalem. PGFE gels run under a variety of conditions revealed up to nine ethidium bromide-stained bands per isolate ranging in size from 0.7 to greater than 3 megabasepairs. Relative staining intensities indicated that some bands contained multiple chromosomes. Major differences in the number, size, and intensity of bands allowed a clear differentiation of the karyotypes of isolates from each of the different individuals. This is in contrast to previous studies where the karyotype of different isolates have been strikingly homogeneous. Hybridization of Southern blots with surface antigen, beta-tubulin, and ribosomal RNA genes revealed that these gene families were distributed to different sized chromosomes amongst the different isolates. PFGE thus revealed major differences in the karyotypes of different G. lamblia isolates that were obtained over a short period of time from a relatively confined geographic area. In contrast, karyotypes of isolates established either by direct cultivation of duodenal trophozoites or by excystation of stool cysts from the same individuals were almost identical. Also, isolates from the same individuals obtained over a prolonged period of time revealed only minor differences in their karyotype, suggesting that recurrent infection can be caused by genetically similar organisms. We conclude that chronic giardiasis can result from recurrence of occult infection or reinfection from a common source.
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PMID:Investigation of human giardiasis by karyotype analysis. 160 83

Antisera to two antigens of Giardia lamblia--plasma membrane (PM) protein and an affinity-purified surface antigen (SA56)--were raised in rabbits, and shown to agglutinate and kill trophozoites in vitro. These antibodies were also demonstrated by ELISA in the sera of paediatric patients with giardiasis. The titres of both antibodies were significantly higher in non-persistent (acute) and asymptomatic cases than in patients with persistent infection; and the latter group did not respond to anti-giardial therapy. The inability of this group to clear G. lamblia infection, in spite of therapy, may result from the low level of antibodies which mediate the killing of trophozoites.
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PMID:Serum antibodies to giardial surface antigens: lower titres in persistent than in non-persistent giardiasis. 258 73

Giardia lamblia is a primitive protozoan and a major cause of waterborne enteric disease throughout tropical and temperate zones. The ability to grow the infective trophozoites in culture as well as the discovery of the method of in vitro encystation made it possible to study the biology of this primitive protozoan and to characterize the surface antigens. Giardia trophozoites are exposed to high concentrations of fatty acids in the human small intestine. This raises the possibility that intestinal fatty acids may become incorporated into Giardia. Therefore, we determined the pattern of fatty acylation of Giardia surface molecules. By metabolic labeling with radiolabeled fatty acids we identified a single glycosylphosphatidylinositol (GPI)-anchored surface protein in Giardia. GP49 differs from the cysteine-rich variable surface antigens described previously. The presence of a GPI anchor in GP49 was supported by the metabolic incorporation of [14C]-ethanolamine, [3H]-myoinositol and fatty acids into the protein. This was confirmed by chemical and enzymatic cleavage experiments. Most interestingly, GP49 was found to be present in different isolates of Giardia and thus can be considered as an invariant surface antigen. Although the biological function of GP49 is not known, recently we have found that intact and soluble GP49 altered the electrolyte fluxes which regulate fluid secretion in the cultured human intestinal epithelial cell line, T84. These studies indicate that the GPI-anchored invariant antigen of Giardia may play an important role in the pathophysiology of giardiasis.
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PMID:GP49, an invariant GPI-anchored antigen of Giardia lamblia. 808 Dec 66

Previous experimental infections of mice with the intestinal protozoan Giardia lamblia had revealed that antigenic variation of the parasite was associated with the major surface antigen, named variant surface protein (VSP). In the present study, a gene segment of the VSP (VSPH7) from the well-characterized G. lamblia clone GS/M-83-H7 was expressed in the live-attenuated Salmonella typhimurium vaccine strain LT2M1C. The recombinant vaccine was assessed for its potential to induce both a systemic and a local antibody response in mice. Peroral administration of the vaccine stimulated synthesis of serum IgG and intestinal IgA antibodies directed against Salmonella antigens as well as against VSPH7. With respect to the anti-VSPH7 antibody concentrations, vaccination of animals resulted in systemic and local antibody responses similar to those induced by experimental or natural infections of mice with G. lamblia clone GS/M-83-H7. Subclass specification of serum anti-VSPH7 IgG demonstrated THelper 2-cell dependent IgG1- and/or IgG2b-type antibody production. No significant THelper 1-cell dependent IgG2a-type anti-VSPH7 antibody production was detected in infected or in vaccinated animals. Taken together, these data indicate a strong intrinsic antigenicity of VSPH7, which stimulates a THelper 2-cell pathway of the murine immune system, independent of the route of antigen administration. Furthermore, the high immunostimulatory potential of the recombinant Salmonella/VSPH7 model vaccine suggests application of LT2M1C as an enteric biocarrier for the identification of putative new target vaccines in giardiasis.
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PMID:Systemic and local antibody response in mice induced by a recombinant peptide fragment from Giardia lamblia variant surface protein (VSP) H7 produced by a Salmonella typhimurium vaccine strain. 929 14

To develop an improved serodiagnostic test for amoebiasis, we performed a detailed analysis of the immunodominant epitopes of the 29 kDa surface antigen and evaluated its sensitivity and specificity. Enzyme-linked immunosorbent assay (ELISA) based on the fragment containing the immunodominant epitope was evaluated further and compared with full-length recombinant 29 kDa protein. Specificity and sensitivity of the two ELISAs were assessed using 55 human sera of parasitic protozoa infection cases (25 amoebiasis, 20 giardiasis and 10 toxoplasmosis sera) and 10 healthy control sera. The immunodominant epitope of the 29 kDa antigen is localised only in the N-terminus 14-54 amino acid residues. The sensitivities of the two ELISAs were very high, 92 and 96%, respectively. The specificity of the fragment was 100%, whereas the specificity of the full-length 29 kDa protein was 86.6%. These results indicate that the fragment containing the immunodominant epitope of the 29 kDa protein can be used to accurately serodiagnose amoebiasis without cross-reactivity from other parasites.
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PMID:Serodiagnosis of amoebiasis using a recombinant protein fragment of the 29 kDa surface antigen of Entamoeba histolytica. 1142 40

Giardia lamblia is an intestinal protozoan parasite infecting humans and various other mammalian hosts. The most important clinical signs of giardiasis are diarrhoea and malabsorption. Giardia lamblia is able to undergo continuous antigenic variation of its major surface antigen, named VSP (variant surface protein). While intestinal antibodies, and more specifically anti-VSP IgA antibodies, were proven to be involved in modulating antigenic variation of the parasite the participation of the local antibody response in control of the parasite infection is still controversial. Conversely, previous studies based on experimental infections in mice showed that cellular immune mechanisms are essential for elimination of the parasite from its intestinal habitat. Furthermore, recent data indicated that inflammatory mast cells have a potential to directly, or indirectly, interfere in duodenal growth of G. lamblia trophozoites. However, this finding was challenged by other reports, which did not find a correlation between intestinal inflammation and resistance to infection. Since intestinal infiltration of inflammatory cells and/or CD8+T-cells were demonstrated to coincide with villus-shortening and crypt hyperplasia immunological reactions were considered to be a potential factor of pathogenesis in giardiasis. The contribution of physiological factors to pathogenesis was essentially assessed in vitro by co-cultivation of G. lamblia trophozoites with epithelial cell lines. By using this in vitro model, molecular (through surface lectins) and mechanical (through ventral disk) adhesion of trophozoites to the epithelium was shown to be crucial for increased epithelial permeability. This phenomenon as well as other Giardia-induced intestinal abnormalities such as loss of intestinal brush border surface area, villus flattening, inhibition of disaccharidase activities, and eventually also overgrowth of the enteric bacterial flora seem to be involved in the pathophysiology of giardiasis. However, it remains to be elucidated whether at least part of these pathological effects are causatively linked to the clinical manifestation of the disease.
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PMID:Recent insights into the mucosal reactions associated with Giardia lamblia infections. 1618 98