Temporal modulation of proteasome and ubiquitin-mediated responses in rainbow trout kidneys during infectious pancreatic necrosis virus infection.

Infectious pancreatic necrosis virus (IPNV) poses a significant economic threat to aquaculture, yet understanding of the host-virus interaction remains limited. This study investigates the impact of IPNV on proteasomal response within rainbow trout kidneys during both subclinical (5 days post-infection, dpi) and clinical (10 dpi) stages of infection. Our results reveal a biphasic response: an initial stimulation of proteasomal activity at 5 dpi followed by inhibition at 10 dpi. Transcript analysis of proteasomal subunits in individual fish shows predominantly a correlation between their expression and proteasomal activity at 5 dpi, but this correlation was not seen by 10 dpi. Additionally, it was observed that the upregulation of immunoproteasome subunits by gamma interferon (γIFN) did not consistently cause a rise in proteasomal activity. Notably, a significant increase in free ubiquitin and ubiquitinated proteins was detected at 5 dpi, followed by a decrease at 10 dpi, indicative of dynamic changes in protein degradation, which agrees with proteasomal activity. The biphasic proteasome response suggests that early activation aids viral protein clearance, while later inhibition triggers cellular stress, potentially driving symptom development. Overall, this study underscores the significant impact of IPNV on proteasome activity in rainbow trout.