en fish disease fish disease پژوهشي Orginal research papers <span lang="TR" style="font-size:11.0pt"><span calibri="" style="font-family:"><span style="color:black">This study investigates the expression of <i>miR-462</i> in rainbow trout (<i>Oncorhynchus mykiss</i>) during viral hemorrhagic septicemia (VHS) infection to understand its role in disease pathogenesis and immune defense. MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression at the post-transcriptional level. VHS is a highly contagious and economically significant viral disease affecting farmed rainbow trout. In this study, 300 rainbow trout were divided into three groups: a negative control group (uninfected), a positive control group (infected without intervention), and an experimental group (infected via intraperitoneal injection with VHS virus). Brain tissue samples were collected over 14 days, and <i>miR-462</i> expression levels were quantified using molecular techniques. The results showed a significant upregulation of <i>miR-462</i> in the experimental group, with a 3.5-fold increase compared to controls (<i>p</i><0.05), indicating its involvement in the immune response to VHS infection. These findings suggest that <i>miR-462</i> plays a role in the host&#39;s response to viral infection. The study highlights the need for further investigation into the specific pathways regulated by <i>miR-462</i> and its potential as a biomarker for VHS. Limitations include sample size variability, and future studies should explore the functional implications of <i>miR-462</i> upregulation and its utility in disease management strategies.</span></span></span> Immune defense, MicroRNA expression, miR-462, VHSV, Viral hemorrhagic septicemia 1175 1186 http://jifro.ir/browse.php?a_code=A-10-5254-1&slc_lang=en&sid=1 G. Pournik gita.pournik@gmail.com 100319475328460057321 100319475328460057321 No Department of Biology, North Tehran Branch, Islamic Azad University, Tehran, Iran. M.R. Bigdeli bigdelimohammadreza@yahoo.com 100319475328460057322 100319475328460057322 Yes Department of Physiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, Iran M. Bananej b.bananej@gmail.com 100319475328460057323 100319475328460057323 No Department of Biology, North Tehran Branch, Islamic Azad University, Tehran, Iran. K. Nazari kks.nazari@gmail.com 100319475328460057324 100319475328460057324 No Agricultural Research and Education Organization of Iran, Tehran, Iran