Wide range of susceptibility to rhabdoviruses in homozygous clones of rainbow trout

Inbred lines differentially susceptible to diseases are a powerful   tool to get insights into the mechanisms of genetic resistance to  pathogens. In fish, chromosome manipulation techniques allow a quick   production of such homozygous lines. Using gynogenesis, we produced   nine homozygous clones of rainbow trout from a domestic population   (INRA Sy strain). We examined the variability between clones for   resistance to two rhabdoviruses, the viral haemorrhagic septicaemia   virus (VHSV) and the infectious haematopoietic necrosis virus   (IHNV). Intraperitoneal injections and waterborne infections were   performed in parallel for both viruses. No survival was recorded   after intraperitoneal injection of VHSV or IHNV, indicating that   fish from all clones were fully susceptible to both viruses by this   route of infection. In contrast, the different clones showed a wide   range of survival frequency after waterborne infection. The   resistance levels to VHSV ranged from   to 99% and resistance was   not abrogated when resistant and sensitive animals were mixed and   subjected to waterborne infection. VHSV was recovered from 1 % of   resistant fish after waterborne infection, confirming that virus   replication was possible in this context but effective only in a low   proportion of the population. The different clones also exhibited a   wide range of survival (  to 68%) after a waterborne infection with   IHNV. Although VHSV-resistant clones were not fully resistant to   IHNV, the susceptibility to IHNV and VHSV tended to be correlated,   suggesting that non-specific mechanisms common to both viruses were   involved.    (VHS); (VHSv); (viral hemorrhagic septicemia); (viral haemorrhagic   septicaemia); (viral hemmorrhagic septicemia); (infectious   haematopoietic necrosis virus); (IHNV)