Biomedical subjects

A F Petavy

Publications and source records attributed to A F Petavy.

At least 19 recordsLinked to original sources

PubMed2006

Aspects of the cytological activity of edelfosine, miltefosine, and ilmofosine in Leishmania donovani.

To discover the mode of action of alkyl-lysophospholipids in Leishmania donovani, we studied the effects of edelfosine, miltefosine, and ilmofosine on intracellular pH, the parasite's cell cycle, and the induction of apoptosis. The effect of the alkyl-lysophospholipids was combined with that of inhibitors of some pumps and exchange regulators of intracellular pH (Na+/ H+; Cl-/CO- 3; and the Na+/K+ ATPase). The effect of the 3 alkyl-lysophospholipids on intracellular pH was indirect; the primary action occurred in the parasite's cell membrane. To determine intracellular pH, we used flow cytometry for the macrophages and axenic amastigotes and spectrofluorometry for the promastigote forms. Apoptosis and the cell cycle were studied by flow cytometry. Treatment of the extracellular promastigote form of L. donovani with the 3 alkyl-lysophospholipids induced death by apoptosis, whereas in the infected cell they caused necrosis rather than apoptosis. Miltefosine and ilmofosine at doses of 38 microM caused G2/M cell cycle inhibition in L. donovani promastigotes.

Animals↗

PubMed2005

Immunogenicity of two Echinococcus granulosus antigens EgA31 and EgTrp in mice.

Here, we investigate in mice the immunogenicity of two antigens EgA31 and EgTrp which are expressed by the larval stage of Echinococcus granulosus. These recombinant proteins were used alone or as a mixture (EgA31-EgTrp) to immunize BALB/c mice. By flow cytometry, we have shown that the ratio CD4+/CD8+ of splenocytes were significantly higher in the antigen-immunized groups. The specific antibody in the sera and cytokine producing splenocytes was evaluated by enzyme-linked immunosorbent assay. EgA31, EgTrp or EgA31-EgTrp elicited high antibody titer of IgG and IgA. Among IgG isotypes, IgG1 was predominant for each antigen tested alone or combined. The production of IL-12, IFN-gamma, IL-10 and IL-6 cytokines was significantly higher in mice immunized with recombinant proteins. Our results suggest that, in BALB/c mice, a mixed Th1/Th2, response to EgA31, EgTrp and EgA31-EgTrp is obtained. The use of both antigens separately or in combination as candidate vaccine proteins is discussed.

Animals↗

PubMed2004

An in vitro model to evaluate the cytokine response in Echinococcus infections.

With the aim of proposing an alternative model to animal experimentation, we investigated cytokine production in response to antigens in an in vitro system. This is a co-culture system of healthy human leukocytes and enterocyte-like Caco-2 cells. The antigens tested, EgA31, EgTrp, and FABP1, are candidates for vaccines in infections caused by Echinococcus spp. in the gut. All three have previously been described in the protoscolex stage and belong to protein families which confer protective immunity against several helminths. In this study, we evaluate the Th1/Th2 profile (Th1: IL-12, IFN-gamma; Th2: IL-6, IL-10) in response to protoscoleces, EgA31 and the mixture of EgA31, EgTrp and FABP1. No cytokine production was detected in response to protoscoleces. Neither IFN-gamma nor IL-6, but a significant IL-10 and IL-12 concentration was detected in response to both types of antigens. These findings suggest that EgA31 and the mixture EgA31/EgTrp/FABP1 generated an immunogenic response associated with a mixed Th1/Th2 cytokine.

Animals↗

PubMed2000

Cellular immune response of lymph nodes from dogs following the intradermal injection of a recombinant antigen corresponding to a 66 kDa protein of Echinococcus granulosus.

A recombinant polypeptide (referred to as EgA31), which represents a 66kDa protein, was prepared from an Echinococcus granulosus cDNA library. In order to assess its potential to induce cellular immune responses, dog popliteal and prescapular lymph nodes were sensitized with this recombinant polypeptide. Subpopulations of lymphocytes were then analyzed by flow cytometry and immunohistochemistry on lymph node sections. Five days after the sensitization, the paracortical areas of the lymph nodes appeared hypertrophic, the number of CD3+, CD4+, CD8+ and CD5+ cells increased, the number of B-cells began to augment and some secondary follicles occurred, and a number of CD4+ cells appeared in germinal centers. Many large secondary follicles and a significantly augmented number of CD5+ cells in cords of medullae were observed 10 days after the sensitization. These active cellular responses strengthen the interest for further studies on the development of a vaccine with this recombinant polypeptide.

Animals↗

PubMed2000

Echinococcus multilocularis in domestic cats in France. A potential risk factor for alveolar hydatid disease contamination in humans.

In France, in North of Alps and South of Jura, around the Swiss town of Geneva, the cestode E. multilocularis was found in three out of 81 domestic cats necropsied given by veterinarians. Morphological and morphometric features established the identity of this species. In an endemic area of alveolar hydatid disease, the prevalence of E. multilocularis in the domestic cat confirms that it is a risk factor for human beings and mainly for veterinarians.

Animals↗

PubMed2000

Effects of artesunate, dihydroartemisinin, and an artesunate-dihydroartemisinin combination against Toxoplasma gondii.

The effect of artesunate and its metabolite dihydroartemisinin against the cerebral cysts of Toxoplasma gondii was studied. In vitro experiments were performed with the THP-1 cell line and showed an inhibition of parasite growth of approximately 70% with 0.1-0.5 microg/ml of dihydroartemisinin for 96 hr. However, with artesunate, dihydroartemisinin, or a combination (50:50) of them, the number of tachyzoites decreased approximately 40-50% and they appeared motionless. Fifty-eight to 72 hr after washing of the tachyzoites and THP-1 cells in culture, parasitized cells reappeared. In vivo, the 50:50 artesunate-dihydroartemisinin combination produced a decrease in cerebral cysts of approximately 40% after only 5 days of treatment. However, transplantations into naive mice using brains of treated mice gave positive results.

Animals↗

PubMed1999

A new potent antigen from Echinococcus granulosus associated with muscles and tegument.

An immunoscreening of a cDNA library derived from the adult stage of the parasitic platyhelminth Echinococcus granulosus has been carried out with sera from infected dogs. The EgA31 clone encodes a fibrous protein which shares some sequence elements with paramyosins. The corresponding gene is present as a single copy in the genome. As revealed by an antibody obtained against a fusion protein produced in bacteria, the polypeptide has a molecular weight of 66 kDa. This polypeptide is present at all developmental stages studied and is a potent antigen during an infection by the adult stage in the dog and during cyst growth in human patients. By immunohistology, it was shown that it is present in the tegument and subtegumental parenchyma of the adult with a main location in the region of the suckers where it rapidly accumulates at the time of the head evagination. It is also present in the germinal layer of the cyst and on the protoscolex.

Amino Acid Sequence↗

PubMed1998

Purine metabolism in Echinococcus multilocularis.

The activities of the enzymes in Echinococcus multilocularis metacestodes involved in purine salvage were studied by HPLC. As in most parasites, this cestode relies entirely on salvage of preformed bases and nucleosides for its purine requirement. Therefore, these enzymes may be targets for drugs in the chemotherapeutic treatment of diseases caused by this parasite. The animals used in this study were gerbils (Meriones unguiculatus). Enzyme activities from sera and hepatic tissue in control and infected animals were similar with the exception of adenine phosphoribosyltransferase which showed an activity 4-fold greater in the serum from control than in serum from infected animals. In the parasite, adenine and hypoxanthine-guanine phosphoribosyltransferases and adenosine deaminase had the highest activities. Therefore, in E. multilocularis metacestodes, this pathway seems to be important for the parasite's metabolism.

Adenine Phosphoribosyltransferase↗

PubMed1998

Phenylalanine derivatives active against Toxoplasma gondii brain cysts in mice.

The action of phenylalanine derivatives against a cyst forming strain of Toxoplasma gondii was tested in vitro and in vivo in mice. These compounds were Phe-Phe-OMe (dipeptide methyl ester) 1 and its cyclized product, 3,6-dibenzyl-2,5-dioxopiperazine 2, Boc-L-Phe 3, L-Phe-OMe 4, Boc-L-Phe-L-Phe-OMe 5. After a 48 hr incubation in vitro, the compounds 3 and 5 induced a higher inhibition than the control molecule, pyrimethamine. In the in vivo studies, the compound 3 induced a 77% decrease in the number of cerebral cysts, comparable to pyrimethamine. Compounds 1, 5 and 4 induced a decrease of about 63% in the cyst number. A size reduction and an alteration of the wall of treated cysts were often noted. In a histological study, a reduction in cyst size without either inflammation or intervention of the nevroglial cells was observed. The present study provides evidence on the efficacy of phenylalanine derivatives and especially Boc-Phe 3, against T.gondii brain cysts in mice.

Animals↗

PubMed1998

Alterations of Toxoplasma gondii induced by 2',3'-dideoxyinosine in vitro.

The time-course of action of the antiviral agent 2',3'-dideoxyinosine (ddI) against Toxoplasma gondii tachyzoites in vitro and its effects at the ultrastructural level were investigated. The very short latency of effect and high efficacy of ddI were evidenced by the fact that the drugs' effects on parasite growth occurred 2 hr after addition to the culture medium, and that an IL90 value of 0.5 microg/ml was reached after 72 hr. Although without apparent effect on uninfected cells, ddI clearly acted on the intracellular parasites, which tended to disappear. Remaining tachyzoites were almost exclusively extracellularly located and often exhibited a clustering of mitochondria-like bodies and subsequent deep alterations of their plasma membranes. These results confirm previous findings and emphasize the potential usefulness of ddI in the management of cerebral toxoplasmosis, a major health problem in acquired immune deficiency syndrome patients.

Animals↗

PubMed1997

Antibodies against Echinococcus multilocularis alkaline phosphatase as markers for the specific diagnosis and the serological monitoring of alveolar echinococcosis.

The immunological properties of the purified alkaline phosphatase (pAP) of Echinococcus multilocularis metacestodes have been investigated using alveolar echinococcosis (AE) patient sera in ELISA tests. A comparative study was done with EmC-Ag (crude antigen) and pAP-Ag (purified antigen). When the parasite purified enzyme pAP was used as antigen, the specificity of the ELISA was markedly increased since it reached 100% without any decrease of its sensitivity (100%). The serologic follow-up of AE patients was conducted during several months with these two antigens in three categories of patients: cured, stabilized and aggravated. There was a good correlation between clinical and serologic data when the pAP was used as antigen in ELISA tests. The anti-pAP antibodies titres did change more rapidly than anti-EmC antibodies titres when a recurrence occurred. Modifications of the anti-pAP antibodies levels were also observed during the patient's therapy: mebendazole, albendazole and Isoprinosine. These results suggest that pAP-Ag should be used for the diagnosis and the follow-up of AE patients.

Alkaline Phosphatase↗

PubMed1997

Effects of 2',3'-dideoxyinosine on Toxoplasma gondii cysts in mice.

The activity against Toxoplasma gondii of 2',3' dideoxyinosine (ddI), an anti-human immunodeficiency virus drug, was examined in an in vitro and in vivo study. Cell cultures infected with a strain known to cause chronic infections were used to show the dose-dependent effect of this drug compared with spiramycin and sulfadiazine. When a dose of 4 microg/ml was used, no infected THP-1 cells or parasites were found after 60 h of incubation. An electron-microscopic study confirmed that after 12 h at 1 microg/ml, the few parasites observed were severely altered. The treatment of chronically infected mice 3 months postinfection showed that a 30-day treatment with 2 mg of ddI/ml induced a significant reduction in the number of T. gondii cysts in the cerebral tissue. These cysts were not viable, as confirmed by immunofluorescence and reinfection experiments. These experiments suggest a possible role for ddI in the treatment of toxoplasmosis, and this possibility deserves further investigation.

Animals↗

PubMed1997

Histochemical observations of alkaline phosphatase activity of Echinococcus multilocularis during in vivo development in golden hamsters, an alternative definitive host.

Histochemical observations of alkaline phosphatase activity of Echinococcus multilocularis during the in vivo development in golden hamster, an alternative definitive host. The present work reports on the ability of protoscoleces from a European fox strain of E. multilocularis to differentiate and develop into the adult form in the small intestine of male golden hamsters treated with prednisolone. Detection of alkaline phosphatase activity on various stages of the developing worm was performed by histochemical methods. The enzyme activity was not demonstrable in the early stages of infection but occurred with strobilization. Age-related changes in the distribution of the enzyme activity took place during strobilization. Alkaline phosphatase activity was evident in the excretory ducts of 8 to 11 day old strobila and in the tegument of mature proglottis of 16 day old worms. This in vivo procedure with rodents as definitive hosts provides interesting preliminary results on the biology of the E. multilocularis adult. Further investigations on membrane-bound enzymes involved in physiological and nutritional processes are in progress.

Alkaline Phosphatase↗

PubMed1997

Increases in the effects of albendazole on Echinococcus multilocularis metacestodes by the dipeptide methyl ester (Phe-Phe-OMe).

Three months after infection with Echinococcus multilocularis, Mongolian gerbils were given either the dipeptide methyl ester (Phe-Phe-OMe) or a combination of Phe-Phe-OMe plus albendazole to treat alveolar echinococcosis. Each drug was given orally at the daily dose of 50 mg/kg of body weight following various administration regimens. Histologic and ultrastructural studies of parasites recovered from infected gerbil tissues showed that the dipeptide methyl ester increases the effect of albendazole.

Albendazole↗

PubMed1995

Free ceramides of Echinococcus multilocularis metacestodes.

Free ceramides were isolated and purified from the metacestodes of Echinococcus multilocularis. Two different fractions were obtained by preparative thin-layer chromatography. Their structure was determined by gas chromatography and electron impact mass spectrometry of trimethylsilylated derivatives. The ceramide with the higher thin-layer chromatographic migration rate contained exclusively erythro-sphinganine associated with saturated C16, C18 and very-long-chain fatty acids (up to C30) and unsaturated C24 fatty acid. The second ceramide contained 90.3% sphingosine and 9.7% sphinganine associated with saturated C16 and C24 and unsaturated C18 and C24 fatty acids. These findings were discussed with regard to the structure and metabolic pathway of neutral and acid glycosphingolipids found in the metacestodes.

Animals↗

PubMed1995

Effects of Isoprinosine on Echinococcus multilocularis and E. granulosus metacestodes.

An in vivo study of the effect of Isoprinosine on Echinococcus multilocularis and E. granulosus metacestodes (Cestoda) was performed. Short- and long-term treatments with different doses were tested in experimental hosts: jirds for E. multilocularis and mice for E. granulosus. Modifications in the weight of animals as well as macroscopical and ultrastructural aspects were registered for each animal group. The results obtained showed a considerable ultrastructural alteration in E. multilocularis metacestodes after short-term treatment with the highest dose, and the tissue transplants were negative. In E. granulosus cysts the ultrastructural damage was also very important and its severity increased as the dose was raised. For the two parasites, the macroscopical aspect and weight of the lesions were profoundly changed.

Abdominal Muscles↗

PubMed1995

Echinococcus multilocularis protoscoleces and hepatic cell activity in vitro.

E. multilocularis protoscoleces were co-cultured with hepatic cells in the presence of IAR 20 or BALB/c 3T3 cells. Hepatocyte activity was determined by assaying transferrin and albumin secretion in culture media. The level of these 2 plasma proteins is higher in hepatic/BALB/c 3T3 co-culture medium. In the presence of parasites, the transferrin level is unchanged while the production of albumin is stimulated during the first 48 h. Our results suggest that the albumin production could be attributed to a complex cellular cooperation between hepatocytes and activated Kupffer cells as previously observed in the acute inflammatory reaction.

3T3 Cells↗

PubMed1995

Echinococcus granulosus, E. multilocularis and mammalian liver-type alkaline phosphatases: a comparative study.

The alkaline phosphatases (EC 3.1.3.1) from Echinococcus granulosus and E. multilocularis (Cestoda) were compared to each other and to a liver-type enzyme. The purified proteins (210 and 220 kDa, respectively) had a tetrameric structure composed of 4, 56/53 kDa subunits. Enzymatic removal of their N-linked sugar moieties abolished the differences in their apparent molecular weight under reducing conditions. After phase separation in Triton X-114, the E. multilocularis enzyme was the most amphiphilic, and treatment with PI-P1C reduced the amount of the parasite alkaline phosphatases that were in a hydrophobic form by about 50%. Both parasite enzymes were highly resistant to heat denaturation and insensitive to the inhibitors L-phenylalanine and L-leucine. In addition, L-homoarginine, levamisole and ZnCl2 can be used to differentiate the parasite and mammalian liver-type enzymes from each other. The Echinococcus alkaline phosphatases have original biochemical properties when compared to the mammalian liver-type enzyme.

Alkaline Phosphatase↗