Parasite infections revisited

Studying parasites helps reveal basic mechanisms in immunology. For long this has been recognized for studies on the immune system of mice and man. But it is not true for immunological studies on fish. To support this argument we discuss selected examples of parasite infections not only in warm-blooded but also in cold-blooded vertebrates. We point out that parasite infections deserve more attention as model systems in comparative immunolog

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Not AvailableThe antioxidant defence and immune response of rainbow trout (Oncorhynchus mykiss) that had received plant oils, rich in either n-3 polyunsaturated fatty acids (PUFA; linseed oil) or n-6 PUFA (safflower oil) was evaluated upon antigen expo sure. The fish employed in this study had been offered the diets for 18 months from the first feeding. Rainbow trout from each group were injected intraperitoneally with formalin killed bacteria (Aeromonas hydrophila) or were sham-injected and observations were made 24 h later. Though the fish fed safflower oil seemed to be under relatively greater oxidative stress, the antioxidant defences (superoxide dismutase, cata lase, glutathione peroxidase) were as effective as in those fed linseed oil. The humoral (alternate complement activity and lysozyme activity) and cellular (phagocytic activity and lymphocyte proliferation) immune responses were not significantly affected by the oil offered. With the exception of reactive oxygen production that was significantly greater in the linseed oil fed fish, both groups did not differ greatly in their immune responses after antigen exposure. Thus, fish fed safflower oil that was deficient in n-3 PUFA was able to sustain most of the critical responses similar to those fed linseed oil suggesting that plant oils of both fatty acid categories were effective for this fresh water fish.Not Availabl

Differential contribution of neutrophilic granulocytes and macrophages to nitrosative stress in a host-parasite animal model

Tyrosine nitration is a hallmark for nitrosative stress caused by the release of reactive oxygen and nitrogen species by activated macrophages and neutrophilic granulocytes at sites of inflammation and infection. In the first part of the study, we used an informative host¿parasite animal model to describe the differential contribution of macrophages and neutrophilic granulocytes to in vivo tissue nitration. To this purpose common carp (Cyprinus carpio) were infected with the extracellular blood parasite Trypanoplasma borreli (Kinetoplastida). After infection, serum nitrite levels significantly increased concurrently to the upregulation of inducible nitric oxide synthase (iNOS) gene expression. Tyrosine nitration, as measured by immunohistochemistry using an anti-nitrotyrosine antibody, dramatically increased in tissues from parasite-infected fish, demonstrating that elevated NO production during T. borreli infection coincides with nitrosative stress in immunologically active tissues. The combined use of an anti-nitrotyrosine antibody with a panel of monoclonal antibodies specific for several carp leukocytes, revealed that fish neutrophilic granulocytes strongly contribute to in vivo tissue nitration most likely through both, a peroxynitrite- and an MPO-mediated mechanism. Conversely, fish macrophages, by restricting the presence of radicals and enzymes to their intraphagosomal compartment, contribute to a much lesser extent to in vivo tissue nitration. In the second part of the study, we examined the effects of nitrosative stress on the parasite itself. Peroxynitrite, but not NO donor substances, exerted strong cytotoxicity on the parasite in vitro. In vivo, however, nitration of T. borreli was limited if not absent despite the presence of parasites in highly nitrated tissue areas. Further, we investigated parasite susceptibility to the human anti-trypanosome drug Melarsoprol (Arsobal), which directly interferes with the parasite-specific trypanothione anti-oxidant system. Arsobal treatment strongly decreased T. borreli viability both, in vitro and in vivo. All together, our data suggest an evolutionary conservation in modern bony fish of the function of neutrophilic granulocytes and macrophages in the nitration process and support the common carp as a suitable animal model for investigations on nitrosative stress in host¿parasite interactions. The potential of T. borreli to serve as an alternative tool for pharmacological studies on human anti-trypanosome drugs is discussed

Effects of an anthropogenic saltwater inlet on three-spined stickleback (Gasterosteus aculeatus) (Teleostei: Gasterosteidae) and their parasites in an inland brook

In industrialised areas, teleost fish are often exposed to anthropogenic changes of the water quality. These often have negative effects on species with a narrow ecological range. Species with a wider ecological range, such as the three-spined stickleback (Gasterosteus aculeatus Linneaus, 1758), might benefit if water quality alteration reduces interspecific competition and/or parasite infection pressure. In the present study, we investigated sticklebacks in an inland brook, in which the inlet of warm and salty coal mine drainage water increases water temperature and changes the brook from freshwater to brackish (approx. 20 mS cm−1) conditions. We collected sticklebacks up- and downstream of the saltwater inlet (henceforth called freshwater and saltwater sites or habitats) in monthly intervals from April to October 2010, and monitored their body condition parameters and parasite infections. In particular during spring, the water temperature was higher (3.7–4.5°C) in the saltwater habitat and juvenile sticklebacks occurred earlier and grew faster compared to juveniles in the freshwater habitat. In the saltwater habitat, fewer parasite species were detected compared to the freshwater situation (7 vs. 10). Moreover, parasite index, which peaked in young-of-the-year sticklebacks in September, was lower in sticklebacks from the saltwater site. The present study suggests that changes of freshwater conditions by the inlet of warm and salty coal mine drainage water match the adaptive range of three-spined sticklebacks, which grew faster and had lower parasite burden in the altered habitat

Receptor-Mediated and Lectin-Like Activities of Carp (Cyprinus carpio) TNF-¿

Functional characterization of TNF- in species other than mammalian vertebrates is limited, and TNF- has been studied in a limited number of fish species, primarily in vitro using recombinant proteins. Studies on TNF- from different fish species so far pointed to several inconsistencies, in particular with respect to some receptor-mediated activities of fish TNF-, such as the ability to directly activate phagocytes. In the present study a comprehensive analysis of in vitro as well as in vivo biological activities of two isoforms of carp TNF- was performed. Our results show that carp TNF- directly primes carp phagocytes and indirectly promotes typical receptor-mediated activities such as phagocyte activation by acting via endothelial cells. Additionally, for the first time in nonmammalian vertebrate species, the lectin-like activity of fish TNF- homologs was investigated. Our results show an evolutionary conservation of function of this receptor-independent activity of TNF- not only in cyprinid fish, but also in perciform and salmonid fish. The role of TNF- in vivo, during infections of carp with the blood parasite Trypanoplasma borreli, was examined using three fundamentally different but complementary approaches: (1) inhibition of TNF- expression, (2) overexpression of TNF-, and (3) inhibition of shedding of membrane-bound TNF-. Our results show that, also in fish, a tight regulation of TNF- expression is important, since depletion or excess of TNF- can make an important difference to survival of infection. Finally, we demonstrate a crucial protective role for membrane-bound TNF-, which has a yet unexploited function in fish. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fac

Environmental temperature variation influences fitness trade-offs and tolerance in a fish-tapeworm association

BACKGROUND: Increasing temperatures are predicted to strongly impact host-parasite interactions, but empirical tests are rare. Host species that are naturally exposed to a broad temperature spectrum offer the possibility to investigate the effects of elevated temperatures on hosts and parasites. Using three-spined sticklebacks, Gasterosteus aculeatus L., and tapeworms, Schistocephalus solidus (Müller, 1776), originating from a cold and a warm water site of a volcanic lake, we subjected sympatric and allopatric host-parasite combinations to cold and warm conditions in a fully crossed design. We predicted that warm temperatures would promote the development of the parasites, while the hosts might benefit from cooler temperatures. We further expected adaptations to the local temperature and mutual adaptations of local host-parasite pairs.RESULTS: Overall, S. solidus parasites grew faster at warm temperatures and stickleback hosts at cold temperatures. On a finer scale, we observed that parasites were able to exploit their hosts more efficiently at the parasite’s temperature of origin. In contrast, host tolerance towards parasite infection was higher when sticklebacks were infected with parasites at the parasite’s ‘foreign’ temperature. Cold-origin sticklebacks tended to grow faster and parasite infection induced a stronger immune response.CONCLUSIONS: Our results suggest that increasing environmental temperatures promote the parasite rather than the host and that host tolerance is dependent on the interaction between parasite infection and temperature. Sticklebacks might use tolerance mechanisms towards parasite infection in combination with their high plasticity towards temperature changes to cope with increasing parasite infection pressures and rising temperatures.</p