Aims: To determine the immune gene expression response of gilthead seabream (Sparus aurata) that is experimentally infected with the lymphocystivirus LCDV-Sa.
Methods and results: Viral DNA and transcripts were detected by qPCR in all samples from fish injected with LCDV-Sa, demonstrating that the virus establish a systemic and asymptomatic infection. The expression of 23 immune-related genes was also analysed by RT-qPCR in the head kidney (HK) and intestine at several times post-infection (dpi). In HK, the expression of five type I interferon (IFN)-related genes (ifn, irf3, mx2, mx3 and isg15), il10 and ck10 was upregulated at 1-3 dpi, while genes related to the inflammation process (tnfα, il1ß, il6, casp1) were not differentially expressed or even downregulated. The expression profile in the intestine was different regarding type I INF-related genes. An upregulated c3 and ighm expression was observed in both HK and intestine at 3-8 dpi. Finally, the transcription of nccrp1 and mhcIIα was induced in HK, whereas tcrβ expression was downregulated in both organs.
Conclusions: LCDV-Sa seems to trigger an immune response in gilthead seabream characterized by a partial activation of type I IFN system and a lack of systemic inflammatory response which may be related to viral persistence.
Significance and impact of the study: The immune response observed in gilthead seabream infected by LCDV-Sa could be implicated in the establishment of an asymptomatic persistent infection.
Keywords: asymptomatic infection; gilthead seabream (Sparus aurata); immune gene expression; lymphocystis disease virus; viral challenge.
© 2019 The Society for Applied Microbiology.