Comparative analysis of the acute response of the trout, O-mykiss, head kidney to in vivo challenge with virulent and attenuated infectious hematopoietic necrosis virus and LPS-induced inflammation

Summary

Background: The response of the trout, O. mykiss, head kidney to bacterial lipopolysaccharide ( LPS) or active and attenuated infectious hematopoietic necrosis virus ( IHNV and attINHV respectively) intraperitoneal challenge, 24 and 72 hours post-injection, was investigated using a salmonid- specific cDNA microarray. Results: The head kidney response to i.p. LPS-induced inflammation in the first instance displays an initial stress reaction involving suppression of major cellular processes, including immune function, followed by a proliferative hematopoietic-type/ biogenesis response 3 days after administration. The viral response at the early stage of infection highlights a suppression of hematopoietic and protein biosynthetic function and a stimulation of immune response. In fish infected with IHNV a loss of cellular function including signal transduction, cell cycle and transcriptional activity 72 hours after infection reflects the tissue-specific pathology of IHNV infection. attIHNV treatment on the other hand shows a similar pattern to native IHNV infection at 24 hours however at 72 hours a divergence from the viral response is seen and replace with a recovery response more similar to that observed for LPSis observed. Conclusion: In conclusion we have been able to identify and characterise by transcriptomic analysis two different types of responses to two distinct immune agents, a virus, IHNV and a bacterial cell wall component, LPS and a 'mixed' response to an attenuated IHNV. This type of analysis will lead to a greater understanding of the physiological response and the development of effective immune responses in salmonid fish to different pathogenic and pro-inflammatory agents.