en fish disease fish disease پژوهشي Orginal research papers To understand how different vaccines, i.e., bivalent formalin-inactivated vaccine (<em>Lactococus garvie</em> and <em>Streptococcus iniae</em>), could affect the immune-related gene expressions, the TNF-alpha, IL-1&beta; and IL-8 genes of head kidney was measured in <em>Oncorhynchus mykiss</em>. To address this, 630 juvenile fish weighing 26&plusmn;3 g were initially (day 0) injected by three different treatments, including control group (normal saline only), AquaVac^TM Garvetil (Merck) and Iranian vaccine (Jehad-e-Daneshagahi) and followed by bath immersion into the same vaccine on day 30. The head kidney was withdrawn to measure immune-related gene expressions at the beginning of experiment (day 0), and following 14, 30, 45 and 60 days of post-vaccination. In the next step, control and both vaccinated groups were also subjected to either <em>L. garvie</em> or <em>S. iniae </em>challenge<em>.</em> Similar samples were taken immediately following bacteria injection (time= 0) and 12, 48, 72 h, and following 7 and 10 days of challenged test. The real-time PCR indicated up-regulation of all cytokine genes following vaccination at day 14 as compared to initial day (<em>p</em><0.05). In pre-challenged experiment, the higher induction in the level of those genes in the head kidney was related to AquaVac vaccine (<em>p</em><0.05). Injection by <em>S. iniae</em> and <em>L. garviae</em> induced the level of immune-related gene expression in the head kidney within the first few days with higher intensity in case of unvaccinated control group. Although the AquaVac produces higher up-regulation of inflammatory gene expression rather than Iranian vaccine, the immunostimulatory effects of both vaccines is a time-restricted. Cytokine genes, Pro-inflammatory genes, Bacterial infection, Passive vaccination, Oncorhynchus mykiss 1387 1408 http://jifro.ir/browse.php?a_code=A-10-3304-1&slc_lang=en&sid=1 H. Khaj Hosseinkhaj@yahoo.com 100319475328460041332 100319475328460041332 Yes Razi Vaccine and Serum Research Institute, Agriculture Research Education and Extension Organization, AREEO, Karaj, Iran M. Mesbah m.mesbah@scu.ac.ir 100319475328460041333 100319475328460041333 No Shahid Chamran University of Ahvaz M.R. Tabandeh m.tabandeh@scu.ac.ir 100319475328460041334 100319475328460041334 No Shahid Chamran University of Ahvaz T. Mohammadian t.mohammadian@scu.ac.ir 100319475328460041335 100319475328460041335 No Shahid Chamran University of Ahvaz M. Dadar maryamdadar@yahoo.com 100319475328460041336 100319475328460041336 No Shahid Chamran University of Ahvaz