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Biomedical subjects

F de Meuter

Publications and source records attributed to F de Meuter.

6 recordsLinked to original sources
PubMed1998

Identification and characterization of a Fc receptor activity on the Toxoplasma gondii tachyzoite.

The Immunoglobulin (Ig) binding capacity of Toxoplasma gondii tachyzoites was investigated using fluorescence flow-cytometry analysis. Polyclonal mouse, human and rat immunoglobulins without specific anti-Toxoplasma activity bound to parasites in a concentration-dependent manner, saturating them at circulating serum concentrations. The immunoglobulin class and subclass specificity of binding was investigated using irrelevant monoclonal antibodies. IgM, IgA and IgG reacted with the parasite membrane. The attachment of mouse IgM to the parasite surface was hampered by mouse IgG1, IgG2a, IgG2b and IgG3. The binding of mouse IgG was proportionally reduced with increasing concentrations of mouse monoclonal IgM. The binding of murine immunoglobulin was diminished when in presence of human IgG. Purified Fc- but not Fab portions of immunoglobulins, fixed to parasites. Using labelled calibrated beads, the Ig binding capacity of parasites was estimated to be 6900 +/- 500 sites per tachyzoite. The Kd of the T. gondii Fc Receptor (FcR) activity was determined at 1.4 +/- 0.1 microM (mean +/- SEM). Such FcR activity was reduced by phospholipase C, trypsin and pronase treatment of the parasites. These data show a low affinity FcR activity on T. gondii tachyzoites which recognizes Ig of different species and isotypes and is likely supported by a glycosyl-phosphatidylinositol (GPI)-anchored surface protein of the parasite.

Animals↗
PubMed1993

Serodiagnosis of toxoplasmosis by using a recombinant form of the 54-kilodalton rhoptry antigen expressed in Escherichia coli.

A 330-residue carboxy-terminal antigenic fragment of the Toxoplasma gondii 54-kDa rhoptry protein (ROP2) was expressed in Escherichia coli as a fusion polypeptide containing a 48-amino-acid sequence derived from phage lambda protein Cro and E. coli protein LacI followed by six consecutive histidyl residues. Metal chelate affinity chromatography provided an easy way to isolate the recombinant product in a highly purified form (> 95%). When this material was used to develop an immunoglobulin G (IgG) enzyme-linked immunosorbent assay for diagnosis of toxoplasmosis, the test reached a sensitivity of 89%. The sensitivity of the assay was similar whether the sera contained T. gondii-specific IgM or were devoid of such IgM. It was also found that ROP2 is a conserved antigen since antibodies against the recombinant antigen could be detected in mice experimentally infected with 11 independent T. gondii isolates originating from infected human tissues tested. Thus, the 54-kDa rhoptry antigen could advantageously complement other previously described T. gondii antigens for the development of more-sensitive and more-informative recombinant antigen-based tests for toxoplasmosis diagnosis.

Animals↗
PubMed1991

Human T cell clone identifies a potentially protective 54-kDa protein antigen of Toxoplasma gondii cloned and expressed in Escherichia coli.

Protective immunity against Toxoplasma gondii is recognized to be cell mediated and IFN-gamma is considered to be the major mediator of resistance. Thus, protective Ag of the parasite must induce IFN-gamma-producing T cells. In order to identify such Ag, we have constructed a T. gondii cDNA library in the cloning/expression vector lambda gt11, screened this library with a pool of sera of immune donors, and further screened the set of selected recombinant Ag using, as probe, a T. gondii-reactive T-cell clone (TCC) derived from an infected/immune individual and producing a high level of IFN-gamma. One recombinant Ag was shown to induce TCC proliferation and was characterized. The corresponding mature T. gondii Ag has an apparent molecular mass of 54 kDa and the sequence of the cDNA clone suggests that it is membrane associated. The epitope defined by the TCC on this Ag was found to be present in three Toxoplasma strains independently of their phenotype (virulent or cyst forming). Recognition of this Ag by the TCC was shown to be restricted by HLA-DPw4, the most frequent allele in the Caucasian population (approximately 40%). The use of this Ag as a vaccine component is proposed.

Amino Acid Sequence↗
PubMed1990

Prenatal diagnosis of congenital toxoplasmosis.

Prenatal diagnosis of congenital toxoplasmosis was attempted in 50 pregnant women at risk for giving birth to an affected child. Fifteen of these patients seroconverted during pregnancy and 35 had a high initial antibody level in their first serum sample. Prenatal diagnosis consisted of a combination of ultrasound screening, amniocentesis, and funipuncture at about 20 weeks' gestation. Diagnosis of congenital toxoplasmosis was based on a positive toxoplasma culture of amniotic fluid or fetal blood and on the presence of specific immunoglobulin M antibodies in fetal blood. In addition, alterations in fetal hematology, cellular immunology, and fetal liver tests were indicative of infection. Fetal infection was detected in six fetuses; two died in utero as a consequence of the infection and four were born after 37 weeks' gestation. Despite antibiotic treatment with pyrimethamine and sulfadiazine, one child has internal hydrocephalus and chorioretinitis and another has unilateral chorioretinitis. In the two other children, the disease is still subclinical. Of the 44 children born after a negative prenatal diagnosis, 35 have reached the age of 1 year; toxoplasma antibodies have disappeared in all of them. Investigation of the remaining nine children showed a decrease in toxoplasma antibodies, suggesting that none of them are affected. Prenatal diagnosis was never associated with fetal loss, and premature delivery occurred in only two cases. We conclude that prenatal diagnosis of congenital toxoplasmosis is safe and reliable.

Amniotic Fluid↗