Comparative effect of different vaccines on immune-related gene expressions of rainbow trout (Oncorhynchus mykiss) and experimentally infected with Streptococcus iniae and Lactococus garvie

To understand how different vaccines, i.e., bivalent formalin-inactivated vaccine (Lactococus garvie and Streptococcus iniae), could affect the immune-related gene expressions, the TNF-alpha, IL-1β and IL-8 genes of head kidney was measured in Oncorhynchus mykiss. To address this, 630 juvenile fish weighing 26±3 g were initially (day 0) injected by three different treatments, including control group (normal saline only), AquaVacTM 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 The head kidney was withdrawn to measure immune-related gene expressions at the beginning of experiment (day 0), and following 14, 30, 45 and 60 days of post-vaccination.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 L. garvie or S. iniae challenge. 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 (p<0.05). In pre-challenged experiment, the higher induction in the level of those genes in the head kidney was related to AquaVac vaccine (p<0.05). Injection by S. iniae and L. garviae 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.