Article

Chronic exposure to the parasite Enteromyxum leei (Myxozoa: Myxosporea) modulates the immune response and the expression of growth, redox and immune relevant genes in gilthead sea bream, Sparus aurata L

Fish Pathology Group, Department of Marine Species Biology, Culture and Pathology, Instituto de Acuicultura de Torre de la Sal, Consejo Superior de Investigaciones Científicas, Torre de la Sal, Ribera de Cabanes, Castellón, Spain.
Fish & Shellfish Immunology (Impact Factor: 2.67). 06/2008; 24(5):610-9. DOI: 10.1016/j.fsi.2008.01.014
Source: PubMed

ABSTRACT

The myxosporean parasite Enteromyxum leei invades the intestine of gilthead sea bream producing a slow-progressing disease, which may end in the death of fish. The present work aimed to better know the host immune response and the underlying molecular mechanisms, which may help to understand why some individuals seem to be refractory to the disease. Three main aspects involved in fish health and welfare (immune, growth and redox status) were studied in fish exposed to E. leei-contaminated effluent, in comparison with control animals (not exposed to the disease). After chronic exposure (113days), prevalence of infection was 67.8%. Among exposed fish, parasitized and non-parasitized fish exhibited clear differences in some of the measured innate immune factors (respiratory burst, serum peroxidases, lysozyme and complement), and in the expression of immune, antioxidant and GH-related genes. The respiratory burst of parasitized fish was significantly higher, and serum peroxidases and lysozyme were significantly decreased both in parasitized and non-parasitized fish. The gene expression of GHR-I, GHR-II, IGF-I and IGF-II was measured in head kidney (HK) samples, and that of interleukin (IL)-1beta, tumour necrosis factor (TNF)-alpha, alpha-2M, GR, GPx-1 and GRP-75 was measured in intestine and HK samples, by rtqPCR. Parasitized fish exhibited a down-regulation of IL-1beta, TNF-alpha and GPx-1 in the intestine, and GHR-I and IGF-I were also down regulated in HK. alpha-2M and GRP-75 were over-expressed in the intestine of parasitized animals. Non-parasitized fish had increased transcripts of GHR-I and IGF-I with respect to control animals, which could furnish their immunocytes with an advantage to combat the parasite. The expression of GHR-II and IGF-II was not altered by the parasite challenge.

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Available from: Alfonso Saera-Vila, Apr 15, 2015
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    • "In contrast, the non-infected individuals showed increased IGF-I and GHR expression levels. From these results, the authors concluded that an increase in IGF-I and GHR expression might be advantageous for immune cells in response to the parasite[41]. The role of autocrine/paracrine IGF-I as related to endocrine IGF-I is also not that clear to date[53,73], and even less is known with respect to fish health. "
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    ABSTRACT: A role for GH and IGF-I in the modulation of the immune system has been under discussion for decades. Generally, GH is considered a stimulator of innate immune parameters in mammals and teleost fish. The stimulatory effects in humans as well as in bony fish often appear to be correlated with elevated endocrine IGF-I (liver-derived), which has also been shown to be suppressed during infection in some studies. Nevertheless, data are still fragmentary. Some studies point to an important role of GH and IGF-I particularly during immune organ development and constitution. Even less is known about the potential relevance of local (autocrine/paracrine) IGF-I within adult and developing immune organs, and the distinct localization of IGF-I in immune cells and tissues of mammals and fish has not been systematically defined. Thus far, IGF-I has been localized in different mammalian immune cell types, particularly macrophages and granulocytes, and in supporting cells, but not in T-lymphocytes. In the present study, we detected IGF-I in phagocytic cells isolated from rainbow trout head kidney and, in contrast to some findings in mammals, in T-cells of a channel catfish cell line. Thus, although numerous analogies among mammals and teleosts exist not only for the GH/IGF-system, but also for the immune system, there are differences that should be further investigated. For instance, it is unclear whether the primarily reported role of GH/IGF-I in the innate immune response is due to the lack of studies focusing on the adaptive immune system, or whether it truly preferentially concerns innate immune parameters. Infectious challenges in combination with GH/IGF-I manipulations are another important topic that has not been sufficiently addressed to date, particularly with respect to developmental and environmental influences on fish growth and health.
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    • "Interestingly , the same lesion occurs in E. leei-infected sharpsnout sea bream (Diplodus puntazzo, Cetti) [60], a species that, as turbot, presents a high susceptibility to this myxozoan parasitosis, but not in diseased gilthead sea bream. In this sense, it is noteworthy to highlight that in E. leei-infected gilthead sea bream no significant differences in TNFa expression were found in blood or lymphohaematopietic organs (head kidney and spleen) at any time point (17 and 64 DPI in anal infection and 113 DPI in effluent infection) [34] [50]. In fact, all the changes found in the expression of cytokines were at the local intestinal level. "
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    • "Growth hormone receptor (GHR)-1 and insulinlike growth factor (IGF)-1 were down-regulated in the kidney of E. leei-infected fish and upregulated in non-infected fish (). Other immune-related genes examined in the intestine of E. leei-infected GSB include mortalin (a heat-shock protein) and glutathione peroxidase (an anti-oxidant enzyme), the former being up-regulated and the latter downregulated (Sitjà-Bobadilla et al. 2008). Modulation of endocrine and other immune-related genes was also observed in a recent transcriptomic study in order to assess changes associated with a vegetable oil replacement (66VO) diet compared to a fish oil diet in E. leei infected GSB (Calduch-Giner et al. 2012). "
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