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Modulation of the gene expression of IgM and distribution of IgM+ cells by nutritional background and infection by Enteromyxum leei (Myxozoa) in gilthead sea bream (Sparus aurata)

AuthorsEstensoro, Itziar ; Calduch-Giner, Josep A. ; Kaushik, Sadasivam; Pérez-Sánchez, Jaume ; Sitjà-Bobadilla, Ariadna
Issue Date2011
PublisherEuropean Association of Fish Pathologists
Citation15th International Conference on Diseases of Fish and Shellfish (2011)
AbstractFarmed fish are constantly exposed to different types of stressors such as high density culture conditions, inadequate diets or parasitic infections which might immunocompromise them. Enteromyxum leei is a wide-spread enteric myxosporean parasite causing heavy economic losses in Mediterranean sparid farms. In gilthead sea bream (GSB), it causes severe enteritis with an intense inflammatory response in the intestine. The increasing interest in replacing fish meal and oil by vegetable ingredients in aquafeeds has focused research on finding diets with optimum growth performance results without detrimental effects on fish immune status. GSB were fed during 9 months a fish oil (FO) based diet or a diet in which FO was 66% replaced by a mixture of vegetable oils (66VO). Recipient fish (R) were challenged by exposure to E. leei-contaminated effluent for 102 days and control (C) animals were kept unexposed [1]. As fish were periodically and non-lethally sampled to know their infection status, R fish were categorized as exposed but not infected (R-NonPAR), and parasitized (R-PAR) at early or late times. Samples of anterior (Ai) and posterior intestine (Pi), head kidney (Hk) and spleen were Bouin-fixed and paraffin sections of samples from the four groups (R-VO, R-66VO, C-VO and C-66VO) were immunohistochemically probed with an polyclonal antibody against GSB IgM [2]. Immunoperoxidase-stained cells were counted in 10 digital fields at x 500 for each fish and tissue. Samples of Pi and Hk for gene expression analyses were frozen in liquid nitrogen and relative IgM gene expression values were obtained by real-time PCR. A significant increase of IgM+ cells in both intestine segments, parallel to an increase in IgM gene expression in Pi in both R fish groups, regardless of the nutritional background. However, the expression values were higher in R-PAR-66VO than in R-PAR-FO. There was a clear time-dependent effect on gene expression, since only those R fish early infected had significantly higher values than the remaining fish categories. Within early-infected fish, R-66VO fish had even significantly higher values than R-FO ones. There was also an increase in Hk-IgM+ cells in all R fish that was not paralleled in IgM gene expression in the tissue of those fish. R-NonPAR fish did not differ from C fish in any case. These results evidenced that 66VO diet did not modify the basal IgM profile of GSB, but the myxosporean infection increased both the presence of IgM+ cells and gene expression, mainly in Pi, and this effect was more pronounced in early infected R-66VO fish, which would reflect the higher disease signs in this group [1]. The high mobilisation and activation of IgM+ cells at the local level is outlined.
DescriptionPonencia presentada en el 15th International Conference on Diseases of Fish and Shellfish celebrado en Croacia del 12 al 16 de septiembre de 2011
Appears in Collections:(IATS) Comunicaciones congresos
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