1,721,366 research outputs found
[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
Hydatid lung disease (echinococcosis/hydatidosis).
No full textTwo Echinococcus species may exhibit medical relevance as causative agents of pulmonary forms of echinococcosis. Most importantly, infections with Echinococcus granulosus result in "cystic hydatid disease" or "cystic echinococcosis," which affects the lungs in a considerable ratio of cases. Echinococcus multilocularis, which causes "alveolar echinococcosis," affects the lungs relatively rarely and then usually upon metastasizing from primary hepatic lesions. Cystic echinococcus and alveolar echinococcus differ pathologically and clinically so greatly that they are considered separately in this article, although alveolar echinococcus is covered minimally because of its minor importance regarding lung infections
["Arbitrarily primed PCR". Or: chance in the service of science].
No full text"Arbitrarily primed PCR" (AP-PCR) methods are based on the amplification of DNA with arbitrarily selected primers. In the present review article two selected applications of this methodical approach are summarized. Using the RAPD ("Random Amplified Polymorphic DNA") technique the genetic variability of different organisms can be analyzed by generating a genomic fingerprint. Echinococcus granulosus isolates (metacestodes) from Spain and Switzerland were comparatively characterized by the use of this molecular epidemiological tool. The following groups of genetically related isolates could be identified: (a) equine isolates (horse/donkey) from Spain and Switzerland, (b) cattle isolates from Switzerland, (c) goat isolates from Spain and pig isolates from both countries, (d) sheep, cattle and human isolates from Spain. Isolates derived from Swiss patients were forming a separate group with respect to their genetic relatedness. As a further application of the AP-PCR, the development of a novel technique for the construction of cDNA libraries from minute amounts of starting material using an Echinococcus multilocularis metacestode library as an example is presented
A European perspective on Neospora caninum.
No full textSince the identification of Neospora caninum in 1984 as a parasite separate from Toxoplasma gondii by Bjerkas et al., and its subsequent characterization and classification in 1988 by Dubey and co-workers, this parasite has attracted increasing attention, primarily as an important causative agent of abortion in cattle and neuromuscular disease in dogs, but also as a complementary model system to T. gondii for investigating the basic biology of intracellular parasitism. During November 11-14, 1999, the COST 820 Annual meeting (Vaccines against coccidioses) took place in Interlaken, Switzerland. Almost half of the papers presented at that meeting were on N. caninum and neosporosis, reflecting the increasing awareness of the importance of this parasite on part of the scientific community in Europe. On the occasion of the meeting, participants in this COST Action involved in Neospora research in Europe were asked to participate in this invited review in order to document the growing interest in N. caninum and the disease it causes. Thus, this paper is a unique collection of contributions provided by several European experts in the field. It is comprised of 10 reviews or original papers on different aspects of Neospora research including epidemiology, immunology, application and development of serological tools, and molecular characterisation of the parasite currently carried out throughout Europe. In addition, two distinguished invited speakers from overseas (Milton McAllister and John Ellis) provided valuable contributions. This invited review demonstrates that the COST 820 Action has brought together scientists from all over Europe and other parts of the world, and has laid the basis for many fruitful collaborations. The studies described here will contribute in assessing the relevance of neosporosis as a potential risk factor not only for animals, but also for human health
Antigenic variation and the murine immune response to Giardia lamblia.
No full textThe protozoan parasite Giardia lamblia is an important causative agent of acute or chronic diarrhoea in humans and various animals. During infection, the parasite survives the host's reactions by undergoing continuous antigenic variation of its major surface antigen, named VSP (variant surface protein). The VSPs form a unique family of cysteine-rich proteins that are extremely heterogeneous in size. The relevance of antigenic variation for the survival in the host has been most successfully studied by performing experimental infections in a combined mother/offspring mouse system and by using the G. lamblia clone GS/M-83-H7 (human isolate) as model parasite. In-vivo antigenic variation of G. lamblia clone GS/M-83-H7 is characterised by a diversification of the intestinal parasite population into a complex mixture of different variant antigen types. It could be shown that maternally transferred lactogenic anti-VSP IgA antibodies exhibit cytotoxic activity on the Giardia variant-specific trophozoites in suckling mice, and thus express a modulatory function on the proliferative parasite population characteristics. Complementarily, in-vitro as well as in-vivo experiments in adult animals indicated that non-immunological factors such as intestinal proteases may interfere into the process of antigen variation in that they favour proliferation of those variant antigen-type populations which resist the hostile physiological conditions within the intestine. These observations suggest that an interplay between immunological and physiological factors, rather than one of these two factor alone, modulates antigenic diversification of a G. lamblia population within an experimental murine host and thus influences the survival rate and strategy of the parasite
- …
