Protective responses of rainbow trout following intraperitoneal injection with a live virulent or avirulent isolate of Renibacterium salmoninarum

Understanding the immune response of fish to renibacterium salmoninarum (rs),the causative agent of bacterial kidney disease (bkd),would help in the development of a vaccine against the disease. the aim of the present study was to examine the protection and antibody response of rainbow trout following intraperitoneal (i.p.) injection of either a live virulent (ncimb 1113) or an avirulent (ncimb 1111) isolate of rs and subsequently,also after a following challenge with the virulent strain. following subsequent challenge with rs 1113,fish initially injected with rs 1113 demonstrated a higher rate of survival and higher antibody levels with a longer duration compared to fish initially immunized with rs 1111. in addition,higher numbers of mortalities were observed in fish initially immunized with the avirulent isolate rs 1111 than fish injected with rs 1113 and phosphate buffered saline (pbs) injected group. these results show that there appears to be an increased susceptibility to bkd from initially challenging the fish with avirulent rs 1111 and this increased susceptibility might be due to antibodies produced which may be counterproductive to protection. copyright 2010 zoological society of pakistan.