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Biomedical subjects

M H Bessières

Publications and source records attributed to M H Bessières.

At least 19 recordsLinked to original sources
PubMed2006

Comparison between two amplification sets for molecular diagnosis of toxoplasmosis by real-time PCR.

PCR is now commonly applied to the diagnosis of toxoplasmosis. Although several methods are available, comparative studies are few, making it difficult to compare the performance of each technique. We compared the sensitivities of two real-time PCR assays through a prospective study on fetuses, neonates, and immunocompromised patients and on the ocular diagnosis of toxoplasmosis. The first system targeted the widely used B1 gene (GenBank accession number AF179871) while the second (RE) targeted a more recently described sequence repeated roughly 200 to 300 times (GenBank accession number AF146527). We demonstrated that molecular diagnosis requires the duplication of PCR assays, especially with the B1 system, as only one PCR was positive in 33.3% of cases. Our study showed that the RE target was more sensitive for all biological samples (amniotic fluid, placenta, aqueous humor, whole blood, and cerebrospinal and bronchoalveolar fluids) and significantly improved the performance of the diagnosis of toxoplasmosis. Taking into consideration all clinical samples, the mean gain in the crossing point value was 4.2 +/- 1.7 cycles and was even more significant for amniotic fluid (5.8 +/- 1.7 cycles).

Amniotic Fluid↗
PubMed2001

Multicenter evaluation of strategies for serodiagnosis of primary infection with Toxoplasma gondii.

The diagnostic performance of single-serum assays for toxoplasma-specific immunoglobulin (Ig)M. IgA. IgG, and IgE antibodies and of different combinations of such antibody assays in 20 European reference centers was assessed. A panel of 276 sera, of which 73 came from patients who seroconverted within 3 months (acute infection), 49 from patients who had seroconverted 3-12 months earlier (convalescence), and 154 from subjects who had two IgG-positive samples obtained 12 months apart (past infection), was tested with 20 toxoplasma-antibody assays and 195 combinations. In general, every assay with high diagnostic sensitivity showed low diagnostic specificity, i.e. no assay performed alone could reliably distinguish acute from past infection. Furthermore, no single assay (or combination) could separate convalescence from the other stages of toxoplasma infection. However, excellent diagnostic performances were reached by sequential use of highly sensitive IgM assays and methods examining IgG avidity or stage specificity. IgA or IgM assays were less suitable for confirmation of toxoplasma-IgM positivity. This study documents the strength of test combinations in assessing the stage of toxoplasma infection.

Acute Disease↗
PubMed2001

Neonatal screening for congenital toxoplasmosis in a cohort of 165 women infected during pregnancy and influence of in utero treatment on the results of neonatal tests.

The aim of this study was to determine the performances of methods used for the neonatal diagnosis of congenital toxoplasmosis. We included 165 pregnant women infected during pregnancy over a 10-year period. Fifty-seven cases of congenital toxoplasmosis were demonstrated (34.5%). Neonatal diagnosis gave positive results in 50 cases (88%). Parasites were isolated from placenta or cord blood in 61% of the infected newborns, more frequently from placenta (60%) than from cord blood (43%). This method was the only criterion of infection in 18% of these infected infants. The detection of specific IgM and IgA antibodies performed on 42 sera of infected infants allowed the diagnosis of congenital infection in 34 cases (81%). IgA antibodies were more frequently detected (60%) than specific IgM (50%). Neonatal and prenatal screening were carried out for 143 pregnant women. This combination diagnosed 39 of 40 infected infants (98%). Prenatal diagnosis identified 30 of 40 cases (75%). Nine cases were diagnosed through neonatal screening and one case with the postnatal follow-up. When prenatal diagnosis was positive, pyrimethamine and sulfadoxine were administered to the mothers (25 cases) in addition to spiramycin. Toxoplasma gondii was less frequently isolated in the placenta and the cord blood of these women (32% and 19%, respectively) than in women treated by spiramycin alone (83% and 63%) proving the antiparasitic action of these drugs. In conclusion, neonatal screening combining parasite detection in placenta and immunological methods on cord blood is essential particularly when prenatal diagnosis is negative. Therefore, when this diagnosis is positive, a treatment with pyrimethamine and sulfamide can be started in the first month of life.

Animals↗
PubMed2000

Toxoplasma gondii secretes a calcium-independent phospholipase A(2).

Phospholipases A(2) (PLA(2)) play an important role in Toxoplasma gondii host cell penetration. They are also key enzymes in the host cell response to the parasite invasion. PLA(2) hydrolyse cellular phospholipids, releasing multiple inflammatory lipidic mediators. We have investigated the biochemical characterisation of T. gondii PLA(2) activity in a mouse-cultured tachyzoite homogenate and in the peritoneal exudate from infected mice, using the hydrolysis of a fluorescent phosphatidylglycerol labelled at the sn-2 position. Spectrofluorimetry and thin-layer chromatography showed a PLA(2) activity (about 0.5-2 nmol/min per mg), calcium-independent, secreted into infected mice peritoneal exudate, with a broad pH activity ranging between 6.5 and 9.5 and resistant to a great number of potential PLA(2) inhibitors except dithio-nitrobenzoic acid (1 mM). An associated phospholipase A(1) activity was also displayed. These results suggest that Toxoplasma gondii displays specific phospholipases different from host enzymes and probably involved at critical steps of infectious cycle.

Animals↗
PubMed1998

A second European collaborative study on polymerase chain reaction for Toxoplasma gondii, involving 15 teams.

In order to investigate the accuracy and practicability of the polymerase chain reaction (PCR) in the antenatal diagnosis of congenital toxoplasmosis, a collaborative study involving 15 European laboratories was performed under the auspices of the Biomed 2 Programme of the European Community. Each team received 12 aliquots (four negative, eight positive) of 'artificial samples' made of amniotic fluid spiked with tachyzoites of the RH strain of Toxoplasma gondii. Each team performed its own PCR protocol (all were different). Nine of the 15 laboratories were able to detect a single parasite, but two of the 15 found all samples negative. Four of the 15 laboratories found one or more control samples to be falsely positive. This study highlights the lack of homogeneity between PCR protocols and performance and underlines the need for an external quality assurance scheme which could provide 'reference' samples that could be used by any laboratory wanting to establish and maintain an accurate diagnostic test based on PCR.

Amniotic Fluid↗
PubMed1997

Parasitemia and parasitic loads in acute infection and after anti-gamma-interferon treatment in a toxoplasmic mouse model.

Toxoplasma gondii infection was induced in Swiss-Webster mice by intraperitoneal inoculation of avirulent Beverley strain cysts. We studied parasitemia and parasitic loads first in acute toxoplasmosis, then in the chronic stage of the disease. In the latter stage a group of mice received weekly administration of a rabbit antiserum directed against mouse gamma-interferon. Parasitemia, sequentially determined by amplification of the B1 gene using polymerase chain reaction, persisted for more than 1 month in acute toxoplasmosis. Brain and lung parasitic loads, assessed by a tissue-culture method, were significantly increased in mice treated with anti-interferon. Moreover, this increase was prevented by concomitant administration of pyrimethamine and sulfadiazine, suggesting that early prophylaxis would be suitable. Surprisingly, the anti-interferon treatment induced neither abnormal clinical signs nor a significant rise in the parasitemia level. Such a model seems to be particularly appropriate for the comparison of different strains of Toxoplasma gondii in a moderately immunodeficient state.

Acute Disease↗
PubMed1994

Failure of mouse peritoneal macrophage activation by the purified excreted/secreted antigens of Toxoplasma gondii.

This study was carried out to evaluate the effect of excreted/secreted antigens on macrophages infected by Toxoplasma gondii. Six proteins 28, 30, 45, 58, 63 and 145 kDa were separated by different chromatographic techniques. Mouse peritoneal macrophages were treated in vitro and in vivo with these purified fractions. Penetration and proliferation assays of T. gondii in the macrophages were performed in vitro. The different antigens used did not change the rate of penetration and proliferation of the parasites. Therefore, the secreted products, which are capable of provoking an immune response, could not directly activate the macrophages. Furthermore, the secreted products were not cytotoxic and neither did they possess a visible phospholipasic activity which would have increased penetration.

Animals↗
PubMed1993

[Antenatal diagnosis of toxoplasmosis. 176 case reports].

OBJECTIVE: To determine the value of antenatal diagnosis of congenital toxoplasmosis by ultrasound guided aspiration of cord blood for testing. MATERIAL: This is a prospective study of 176 cases. As well as obtaining fetal blood and amniotic fluid the searched for specific IgM and A as well as culturing for the parasites on human fibroblasts and inoculation of mice, as well as researching them for non-specific signs of fetal infection. 149 children were able to be followed up one year after birth. RESULTS: 15% of the children (22/149) were infected with toxoplasmosis. 11 out of these were diagnosed positive antenatally. For the 11 others the diagnosis of fetal infection could only be made after birth, but the non-specific signs made it possible to expect early that they had been contaminated. 59% (13/22) had latent toxoplasmosis which only showed up after a mean interval of 34 months after birth. 41% (9/22) had clinical and/or paraclinical signs of toxoplasmosis (mainly unilateral non-macular chorioretinitis and intracranial calcifications) but they are well after a follow-up period averaging 30 months. COMMENTARY: Ultrasound alone, when it shows up fetal abnormalities, can make the diagnosis of the severity of the condition. The role of taking fetal specimens is to make clear those infants that are infected because of specific signs, and to find those fetuses which are at high risk because of non-specific signs in order to improve the management of the cases. This development has made it possible to avoid carrying out a large number of unnecessary terminations of pregnancy and has resulted in the birth of affected infants that had no functional sequelae from the infection.

Amniotic Fluid↗
PubMed1992

Analysis by immunoblotting of Toxoplasma gondii exo-antigens and comparison with somatic antigens.

Two soluble Toxoplasma gondii antigen preparations were compared using the immunoblotting technique. The first preparation, which is commonly employed in ELISA tests, corresponds to a lytic extract of the parasite. The second known as exo-antigen, has yielded good results in cell immunity research and is obtained from Toxoplasma gondii culture supernatants. In both preparations, components exhibiting same molecular weight of 57-52 (doublet), 43, 38, 35, 30 and 20 kDa were revealed. In addition, two major 27- and 78-kDa components were detected in exo-antigens. The 30 kDa protein was intensely recognised by all sera, confirming the advantage of its use as an antigen in serological reactions. Exo-antigens could be employed as a soluble antigenic solution because they are easy to obtain, they display good antigenicity and their antigenic composition has been defined. Moreover their preparation does not require mouse inoculation. An evaluation of the enzyme-linked immunosorbent assays (ELISAs) involving these antigens has yet to be performed.

Animals↗
PubMed1992

IgA antibody response during acquired and congenital toxoplasmosis.

Toxoplasma gondii specific IgA and IgM antibodies were quantitated by an antibody capture agglutination assay in 260 patients with acquired toxoplasmosis and from 94 fetuses suspected of congenital toxoplasmosis and 30 infected children. In acquired toxoplasmosis, IgA antibodies to T gondii were found in 95% of the cases. In congenital toxoplasmosis IgA antibodies were more frequently detected (75%) in cord blood than IgM antibodies (61%). They persisted after birth, in some cases for up to 24 months. IgA antibodies were also detected in fetuses whose mothers had toxoplasmosis during their pregnancy. In infected fetuses IgM and IgA antibodies were detected in fetal blood as early as week 24 of pregnancy. Detection of IgA T gondii antibodies may be useful for the diagnosis of some recently acquired infection and for the diagnosis and follow up of the infection in the fetus and neonate.

Adult↗
PubMed1992

[Predictive value of non-specific signs of fetal infection in congenital toxoplasmosis].

AIMS: To study the predictive value of 9 non-specific signs for congenital toxoplasmosis. METHOD: The work was carried out as a prospective study comparing non-specific signs in 22 fetuses infected with toxoplasmosis and 59 fetuses free of the disease. RESULTS: Four of the nine parameters were found to be statistically higher in the group of infected fetuses. These are the level of leucocytes (p < 0.05) gamma glutamyl transferase (p < 0.001) total M immunoglobulin (p < 0.0001) and C4 fraction of complement (p < 0.0001). This last sign which is non-specific for infection has never been looked at until now in congenital toxoplasmosis but is seems to be of great importance because its sensitivity is much greater than of all the other parameters that have been used up till now (81%) and the positive predictive value is excellent (72%). On the other hand the value of a raised leucocyte count is a matter for discussion. CONCLUSION: The presence of even one abnormally raised feature in the fetal blood of these non-specific signs is enough to screen for a population which is of high risk for congenital toxoplasmosis and sufficient to change our attitude to treating the condition.

Complement C4↗
PubMed1992

[Biological reference values in the human fetus. 106 cord blood sampling in utero].

The authors give biological reference figures obtained from 106 fetuses that were sampled in utero between the 20th and 34th week of amenorrhoea. These fetuses were considered to be normal because there was no clinical or ultrasound evidence of an abnormality. Furthermore the biological values sought in antenatal testing and the absence of all pathology in the first year of life, confirmed that these were normal fetuses. The result has been expressed as a global figure for all 106 fetuses; then they have been divided up according to the gestational age groups (20-23, 24-27, and 28-34 weeks of amenorrhoea). These biological reference values and their changes as the age of the fetuses advanced are discussed and compared with the figures reported in the literature.

Age Factors↗
PubMed1990

[Effects of cotrimoxazole on some macrophage functions: microbicide, tumoricide, production of free oxygen radicals, prostaglandins and leukotrienes].

In order to demonstrate an immunomodulating effect of cotrimoxazole, we investigated its influence on some macrophage (M phi) functions in culture: P815 tumor cells killing, Toxoplasma gondii killing, production of free oxygen radicals by luminol-dependent chemiluminescence, prostaglandins and leukotrienes secretion evaluated after incorporation of tritiated arachidonic acid. In vitro, cotrimoxazole inhibited in a dose-dependent fashion the chemiluminescence of murine resident peritoneal or guinea pig alveolar M phi. Production of prostaglandin (PG) 6-keto-F1 alpha, PGF2 alpha, and 5-hydroxyeicosatetraenoic acid by resident peritoneal M phi was also inhibited. However, PGD2 synthesis by alveolar M phi was enhanced. A second study was performed on peritoneal M phi, resident or elicited in vivo by one intra-peritoneal injection of an extract from Mycobacterium Tuberculosis membranes and obtained from mice pretreated or not by cotrimoxazole per os. Resident M phi from cotrimoxale-treated animals showed increased production of leucotriene B4 compared to M phi from controls. 6-keto-PGF1 alpha and free oxygen radicals production by elicited M phi was greatly enhanced by cotrimoxazole whereas thromboxane B2 was reduced. Finally cotrimoxazole enhanced intracellular killing of Toxoplasma gondii and cytotoxicity for tumor cells P815 by resident but not by elicited M phi. It is concluded that cotrimoxazole can modulate MO activation and some M phi functions involved in immune homeostasis. This data could help to understand why an antibiotic such as cotrimoxazole, which is known to be frequently used in immunocompromised hosts, is also efficient in Wegener's granulomatosis.

Animals↗
PubMed1988

[Enhancement of resistance of mice Toxoplasma gondii by 2 polysaccharides beta 1-3, beta 1-6 (PSAT and Scleroglucan)].

The protective effect of PSAT and Scleroglucan (beta 1-3, beta 1-6 polysaccharides), has been studied in mice infected with different strains of Toxoplasma gondii (RH, attenuated RH or Prugniaud strains). Intramuscular or intravenous administration of PSAT before infection of mice by the attenuated RH strain, resulted in a significant enhancement of survival: 100% of survival in the treated group, compared to 33% in controls and 50% in mice pretreated with Scleroglucan (10 mg/kg, intravenously). In contrast, there was no difference in the survival rate between the group treated with PSAT (1 mg/kg, IV) and the control in mice infected with the virulent RH strain: all mice died between day 7 and day 8. In mice infected with 15 cysts of the Prugniaud strain a decrease in the chemiluminescence (CL) of peritoneal macrophages and of the number of cysts in the brain of mice were observed in mice treated either with PSAT (1 mg/kg, IM) or scleroglucan (10 mg/kg, IM).

Adjuvants, Immunologic↗