5,584 research outputs found
Protective immune mechanisms against the metacestode of Echinococcus multilocularis.
No full textInfection with the larval stage of the fox tapeworm Echinococcus multilocularis results in a life-threatening hepatic disease concerning humans and intermediate rodent hosts. Immunoepidemiological surveys provided information that a large proportion of infected individuals may demonstrate either constitutional resistance to early post-oncospheral development of the parasite or late resistance to disease by exhibiting an intrahepatic died-out parasite lesion. Similar events have been found in secondary infections of laboratory rodents. Dissection of humoral and cell-mediated immune responses in susceptible versus resistant individuals provides insight into immunological pathways associated with the different outcome of infection. Survival strategy of the metacestode obviously focuses on the crucial role played by the parasite laminated layer. This layer protects the metacestode from host effector mechanisms which can potentially kill the proliferating germinative compartments in case of resistant hosts. Bruno Gottstein and Richard Felleisen here discuss the need to search for more parameters discriminating between the different immune pathways in order to find out (immunogenetic?) predispositions responsible for the respective phenomena
Purification and characterization of a specific antigen from Echinococcus multilocularis.
No full textA polypeptide (Em2a) purified by affinity chromatography from the Echinococcus multilocularis metacestode showed a high degree of purity as assayed by SDS-PAGE and analytical isoelectrical focusing. A minor contamination with host albumin was revealed. Estimation of relative mol. mass gave a value of 54,000. The isoelectric point was found to be 4.8. Antigenic activity of the polypeptide was demonstrated by immunoprecipitation and western blotting. In these assays the protein was recognized only by homologous sera from patients infected with larval E. multilocularis. This antigen (Em2a) did not react in the ELISA with sera from patients infected with heterologous helminths; these sera were highly cross-reacting with antigen from E. granulosus hydatid fluid. Seventy-three (94%) from 78 investigated patients (alveolar echinococcosis) showed a seropositive reaction with the polypeptide Em2a
An immunoassay for the detection of circulating antigens in human echinococcosis.
No full textAn immunoassay (double-antibody-sandwich-ELISA) was developed to detect circulating antigens (CAg) in patients with cystic (Echinococcus granulosus) echinococcosis. Echinococcus antigens derived from heterologous intermediate hosts were used to immunize rabbits and to purify the rabbit-IgG-fraction obtained by affinity-chromatography, thus avoiding major interference with host components. The purified rabbit anti-hydatid IgG was immunosorbed with bovine and human sera. One part of the resulting IgG served as coating agent in a double antibody sandwich-ELISA; the other part, coupled to alkaline phosphatase, as detecting conjugate. The specificity of the antibody reaction was demonstrated by immunoelectrophoresis. Sera of 21 patients with cystic echinococcosis were examined with this test system. In seven of the patients' sera CAg were detected in concentrations ranging between 310 ng and 680 ng protein per ml serum. Comparing pre- and postoperative serum samples obtained from nine patients operated on for cystic echinococcosis, four sera were found to be CAg-positive before and three after operation
[Toxoplasma gondii: perspectives for a vaccine].
No full textTo date no single vaccine has been commercialized in the field of human parasitology, and therefore a practical approach to a potential Toxoplasma vaccine in the field can only be discussed theoretically. The aim of such a vaccine would consist either in inhibiting endogenous parasite multiplication (tachyzoite formation) and thus dissemination, or in preventing the final formation of Toxoplasma cysts (bradyzoite formation). Immune protectivity should confer resistance to disease and parasite dissemination in pregnant women, in order to prevent congenital toxoplasmosis in the unborn infant, and prevent cyst formation in order to avoid reactivation in case of future immunosuppression of the individual. The establishment of a successful protective immunity was elucidated in the mouse model: the number of formed Toxoplasma cysts is primarily regulated by the function of Toxoplasma-specific CD8(+)-T-cells. Direct effector functions of cytotoxic CD8+ lymphocytes directly depend on local periparasitic gamma-interferon- and TNF alpha-concentrations. Immunological aberrance occurs if locally (cerebral) synthesized Il-10 and Il-6 induce anergistic immunosuppression. An experimental vaccine in the mouse demonstrated primary dependence of a protective immune response on CD8+ and CD4+ (Th) cells. Experimental vaccines within domestic animals concentrate mainly on the development of temperature-sensitive mutants of the T. gondii RH-strain, which will protect animals from disease but not from infection and cyst formation.(ABSTRACT TRUNCATED AT 250 WORDS
[Vaccination against echinococcosis (?)].
No full textTwo species of the genus Echinococcus occur sympatrically in central Europe, namely Echinococcus multilocularis, the causative agent of alveolar echinococcosis (AE), and E. granulosus, resulting in cystic echinococcosis (CE) in humans. The endemic area of Europe demonstrates an annual incidence of 0.02 to 1.4 new AE cases per 100000 inhabitants. The importance of the disease refers primarily to the high lethality observed in untreated cases. Therapeutically, radical surgical resection of hepatic lesions followed by continuous benzimidazole-therapy is anticipated. Recently, the strategic control of cystic echinococcosis in humans has considerably been improved by the development of an effective and efficient vaccine that will indirectly prevent humans from infection. The vaccine protects animal intermediate hosts (mainly farm ruminants), thus the lack of hydatid cysts in these animals will prevent dogs to become infected. This on the long-term will result in an abrogation of infection sources (Echinococcus eggs) for humans (and other intermediate hosts). Principally, it has been shown that a similar vaccination is also possible for E. multilocularis. Thus, a 14-3-3 and another Em95-vaccine have successfully been tested in the experimental murine model. As the parasite development mainly focuses on a wildlife cycle (wild rodents), a practical application of the vaccine can hardly be implemented. Nevertheless, AE is a very severe disease in humans, therefore one should discuss about the feasibility and the health-economic impact of large-scale vaccination of humans living in areas of high endemicity and thus being at high infection risk
[Cyst-forming Coccidia: Toxoplasma, Neospora, Sarcocystis].
No full textThe most important cyst-forming coccidian parasites in human and veterinary medicine belong the genera of Toxoplasma, Neospora and Sarcocystis. Toxoplasma gondii shows its clinical relevance in congenital infections and opportunistic infections in immunodeficient patients. In veterinary medicine the parasite is predominantly the cause of important economic loss in livestock production. Neospora causes diseases resembling toxoplasmosis; neosporosis is one of the most important causes of bovine abortion in the US. Neospora caninum leads to myositis and paralysis in dogs. The potential implication of Neospora in toxoplasmosis-like diseases in humans is not yet known. Sarcocystis is usually a relatively harmless intestinal parasite in humans. Recent data from tropical areas suggest that man can also become an intermediate host for certain Sarcocystis species, which potentially represents a source of opportunistic infection and disease in areas with increasing HIV prevalence. In veterinary medicine, Sarcocystis causes muscle diseases and also abortion or myeloencephalitis with lethal outcome in certain animal species. Molecular-epidemiological investigations have resulted in a new understanding of biological and population-genetic mechanisms relevant to the disease. Recently developed molecular techniques, such as transfection in protozoan parasites, are presently used not only to elucidate molecular-pathogenetic events in the course of disease, but also to prepare potential new immuno-therapeutic tools for future vaccination against infection or disease
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