Giardia induces proliferation and interferon gamma production by intestinal lymphocytes.
(1/636)
BACKGROUND: Murine intraepithelial lymphocytes kill Giardia lambia; responses of human intestinal lymphocytes to this parasite are unknown. AIMS: To examine giardia induced proliferation, interferon gamma production, migration, and cytotoxicity by lymphocytes from the human intestine and peripheral blood. METHODS: Giardia were added to intraepithelial lymphocytes, lamina propria lymphocytes, and peripheral blood lymphocytes, obtained from jejunal mucosa and blood of otherwise healthy patients undergoing gastric bypass surgery for morbid obesity. Proliferation was measured by 3H-thymidine incorporation; frequency of proliferation precursors, by limiting dilution analysis; interferon gamma production, by ELISA; cytotoxicity, by 51Cr release of radiolabelled giardia and by release of serine esterases by effector lymphocytes that mediate cytotoxicity. RESULTS: The CD4+ T lymphocytes from intestine and blood proliferated in response to giardia. The stimulus by the parasite was mitogenic rather than antigenic due to the fact that the peak response was on day 3 rather than day 6, and the large number of precursors was in the range of that for mitogens. CD4+ T lymphocytes from both sites produced interferon gamma in response to giardia. Lymphocytes did not migrate towards or kill the parasite. CONCLUSIONS: Giardia induced the same degree of proliferation and interferon gamma production by CD4+ T lymphocytes in intestine and blood, but did not trigger cytotoxicity or migration. (+info)
Infectious diarrhea in tourists staying in a resort hotel.
(2/636)
An outbreak of infectious diarrhea with 70 laboratory-confirmed cases (58 with Giardia lamblia) and 107 probable cases occurred in U.K. tourists who stayed in a hotel in Greece. After a cluster of six cases in persons who had stayed at the hotel was reported, the Communicable Disease Surveillance Centre began active case ascertainment. This outbreak illustrates the value of an approach to surveillance that integrates routine surveillance data with active case ascertainment. (+info)
Point mutations in the guanine phosphoribosyltransferase from Giardia lamblia modulate pyrophosphate binding and enzyme catalysis.
(3/636)
Guanine phosphoribosyltransferase (GPRTase) from Giardia lamblia, an enzyme required for guanine salvage and necessary for the survival of this parasitic protozoan, has been kinetically characterized. Phosphoribosyltransfer proceeds through an ordered sequential mechanism common to many related purine phosphoribosyltransferases (PRTases) with alpha-D-5-phosphoribosyl-1-pyrophosphate (PRPP) binding to the enzyme first and guanosine monophosphate (GMP) dissociating last. The enzyme is a highly unique purine PRTase, recognizing only guanine as its purine substrate (K(m) = 16.4 microM) but not hypoxanthine (K(m) > 200 microM) nor xanthine (no reaction). It also catalyzes both the forward (kcat = 76.7 s-1) and reverse (kcat = 5.8.s-1) reactions at significantly higher rates than all the other purine PRTases described to date. However, the relative catalytic efficiencies favor the forward reaction, which can be attributed to an unusually high K(m) for pyrophosphate (PPi) (323.9 microM) in the reverse reaction, comparable only with the high K(m) for PPi (165.5 microM) in Tritrichomonas foetus HGXPRTase-catalyzed reverse reaction. As the latter case was due to the substitution of threonine for a highly conserved lysine residue in the PPi-binding loop [Munagala et al. (1998) Biochemistry 37, 4045-4051], we identified a corresponding threonine residue in G. lamblia GPRTase at position 70 by sequence alignment, and then generated a T70K mutant of the enzyme. The mutant displays a 6.7-fold lower K(m) for PPi with a twofold increase in the K(m) for PRPP. Further attempts to improve PPi binding led to the construction of a T70K/A72G double mutant, which displays an even lower K(m) of 7.9 microM for PPi. However, mutations of the nearby Gly71 to Glu, Arg, or Ala completely inactivate the GPRTase, suggesting the requirement of flexibility in the putative PPi-binding loop for enzyme catalysis, which is apparently maintained by the glycine residue. We have thus tentatively identified the PPi-binding loop in G. lamblia GPRTase, and attributed the relatively higher catalytic efficiency in the forward reaction to the unusual loop structure for poor PPi binding in the reverse reaction. (+info)
Giardia intestinalis is unlikely to be a major cause of the poor growth of rural Gambian infants.
(4/636)
Parasite-specific plasma immunoglobulins have been used to indicate the presence of Giardia intestinalis infection in 60 infants living in a rural area of The Gambia. Infants were studied longitudinally between 2 and 8 mo of age. The median age for first exposure to G. intestinalis was between 3 and 4 mo, and by 8 mo all but 3 infants (95%) showed a positive titer on at least one occasion. Raised Giardia-specific IgM titers were associated with reduced weight gain in the 2 wk preceding a positive titer, but catch-up growth occurred in the following 2 wk. IgM antibody titers were also positively associated with intestinal permeability (lactulose/mannitol ratio), urinary lactose excretion, plasma concentrations of alpha1-antichymotrypsin and total IgM, IgA and IgG immunoglobulins. However, infant growth over the whole 6-mo period (i.e., between 2 and 8 mo of age) was not related to mean Giardia-specific antibody titers, nor the time of first exposure to the parasite. The data suggest that giardiasis in these very young breast-fed children occurs as a mild, acute disease, and its presence could not explain the marked, long-term growth faltering observed in many of the subjects. (+info)
Review article: the management of Giardiasis.
(5/636)
Giardiasis is the intestinal infection resulting from infestation with the human parasite Giardia intestinalis, also called Giardia lamblia. The infection may be asymptomatic or present with a variety of symptoms such as diarrhoea, weight loss, abdominal cramps, and failure to thrive. Giardiasis is most often diagnosed after recent travel or in day care centres. The organism has two stages in its life cycle. It is usually ingested as a cyst with as few as 10-25 cysts being sufficient to cause infection. After excystation, the organism is a replicative trophozoite which may attach to the small bowel wall. Giardia intestinalis does not invade the bowel wall. Trophozoites may encyst and be shed in faeces for future ingestion by another host. Diagnosis of infection is by stool examination which may also eliminate other possible infectious agents. Small bowel biopsy may be necessary in difficult individual cases or to rule out non-infectious illnesses, and stool ELISA may serve for large population screening examinations. The mainstay of treatment is metronidazole 250-400 mg three times per day by mouth for 5 days. (+info)
Axenic cultivation and characterization of Giardia lamblia isolated from humans in Korea.
(6/636)
Inoculating of human fecal cysts to suckling Mongolian gerbils, two Giardia lamblia isolates, K1 and K2, were established as axenic cultures. Using this in vitro culture, both isolates were characterized as a "medium-rate grower" upon its growth pattern. These two Giardia isolates were grouped by using two genetic analysis. With genetic analysis of SSU-rDNA sequences, both K1 and K2 were found as members of Hopkins' group 1, despite some nucleotide differences noticed in K2 (5 differences/292 bases). The other genetic study used PCR-RFLP of the tim (triose phosphate isomerase) gene. Both of K1 and K2 were found to belong to Nash's group 2. Our results suggest that Nash's group 2 can not be a separate group, but a part of Hopkins' group 1. (+info)
Identification and characterization of a ran gene promoter in the protozoan pathogen Giardia lamblia.
(7/636)
The promoter elements that regulate transcription initiation in Giardia lamblia are poorly understood. In this report, the promoter of the Giardia ran gene was studied using a luciferase expression plasmid pRANluc+ to monitor transcription efficiency. An AT-rich sequence spanning -51/-20 relative to the translation start site of the ran gene was identified and was found to be required for efficient luciferase expression by deletion and mutation mapping of pRANluc+. The -51/-20 sequence was also sufficient for promoter activity as revealed from studies on a 32-base pair synthetic promoter derived from this region. Deletion mapping of the synthetic promoter revealed two minimal promoter elements, -51/-42 and -30/-20, sufficient for 6- and 30-fold luciferase expression above background, respectively. The transcription start sites on luc+ messenger RNA were determined by the position of the synthetic promoter in the luciferase expression plasmids as shown by primer extension experiments. Results from electrophoretic mobility shift assays revealed multiple DNA-protein complexes upon binding of nuclear proteins with either DNA strand but not the double-stranded DNA derived from the ran promoter. Our results delineate the first promoter sequence of the Giardia gene (ran), which provides an excellent model for future studies on transcription regulation in this protozoan parasite. (+info)
Immunochromatographic strip-based detection of Entamoeba histolytica-E. dispar and Giardia lamblia coproantigen.
(8/636)
BIOSITE Triage was 68.3% sensitive and 100% specific for the detection of Entamoeba histolytica-E. dispar (n = 71) compared to Alexon-Trend's ProSpecT test (reference standard) using fresh-frozen stool. Neither test is able to distinguish E. histolytica from E. dispar. Triage was 83.3% sensitive and 100% specific compared to microscopy (formalin-ether concentrates and permanent stains) for the detection of Giardia lamblia. (+info)