Research Article: 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-۱β and IL-۸ genes of head kidney was measured in Oncorhynchus mykiss. To address this, ۶۳۰ juvenile fish weighing ۲۶±۳ g were initially (day ۰) 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 ۳۰. The head kidney was withdrawn to measure immune-related gene expressions at the beginning of experiment (day ۰), and following ۱۴, ۳۰, ۴۵ and ۶۰ days of post-vaccination.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= ۰) and ۱۲, ۴۸, ۷۲ h, and following ۷ and ۱۰ days of challenged test. The real-time PCR indicated up-regulation of all cytokine genes following vaccination at day ۱۴ as compared to initial day (p<۰.۰۵). In pre-challenged experiment, the higher induction in the level of those genes in the head kidney was related to AquaVac vaccine (p<۰.۰۵). 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.

Keywords:

Cytokine genes , Pro-inflammatory genes , Bacterial infection , Passive vaccination , Oncorhynchus mykiss