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The aim of this study was to determine the ontogeny of antiviral Mx gene expression in different stages of development of Cirrhinus mrigala (mrigal). For this purpose, three experiments were designed; in the first experiment, Mx expression was observed in eggs, milt, poly I:C treated twitching stage and control twitching stage, and the Mx expression was maximum in eggs. In the second experiment, upregulation of Mx transcript was studied in hatchling stages of mrigal after poly I:C induction by bath treatment, while control hatchlings were studied as such. Hatchlings (both control and treated) were collected at 2-, 4-, 6- and 8-h interval after 24, 48, 72 and 96 h of poly I:C induction. The Mx gene expression showed an increasing trend up to 72 h, where it was highest 3.3-fold higher than the control and then decreased at 96 h where it was threefold higher when compared to the control. In the third experiment, expression of Mx transcript was studied in mrigal fry after intramuscular stimulation with poly I:C for a duration of 28 days. A gradual upregulation of Mx transcript was seen for the experimental period of 28 days. From the study, it is concluded that Mx gene is transmitted from egg and twitching stages and reduced in larvae and fry. Hence, ontogenically, without poly I:C induction, Mx gene is constitutively expressed at early stages indicating the antiviral defences transmitted from parents to offspring in the process of embryonic development. This indicates there is an antiviral Mx defence mechanism playing at early stages of the development for a period of 45 days. [ABSTRACT FROM AUTHOR]

Abstract: The expression of Mx transcripts and Mx protein was monitored at weekly intervals for 7weeks, by qRT-PCR and immunohistochemistry, in the kidney, liver, gill and blood of Atlantic salmon parr following injection of poly I:C. Elevated levels of Mx transcripts compared to PBS injected control fish were found in the tissues at week 1. Background levels were then found up to week 7, with the exception of week 4 when high levels were again found in poly I:C injected fish as well as control fish. Immunostaining for Mx protein in the kidney, liver and gill of poly I:C injected fish was higher than in control fish from weeks 1–4, but little staining was found in the tissues of both poly I:C treated and control fish thereafter. Blood monocytes stained consistently in all fish, suggesting that this leucocyte type constitutively expressed Mx protein. From weeks 2–4, lymphocytes of both groups consistently stained for Mx protein but the consistency decreased at weeks 5–7. Staining of neutrophils was also inconsistent. Western blots of plasma showed an immunoreactive band of 76kDa typical of salmon Mx protein. Semi-quantitative measurements of dot blots showed poly I:C injected fish to have higher levels of plasma Mx protein than controls on weeks 1–4 with very low levels on weeks 5–7. The results indicate that following induction of an interferon response with poly I:C, Atlantic salmon parr maintain elevated levels of Mx protein in tissues, leucocytes and blood plasma for about 4weeks. Production of Mx protein by blood monocytes appears to be constitutive, though production by lymphocytes and neutrophils was less consistent. [Copyright &y& Elsevier]