INVOLVEMENT OF RAINBOW-TROUT LEUKOCYTES IN THE PATHOGENESIS OF INFECTIOUS HEMATOPOIETIC NECROSIS

Rainbow trout Oncorhynchus mykiss leucocytes were tested for their abi lity to support replication of infectious hematopoietic necrosis virus (IHNV). Viral replication occurred in vitro using leucocytes cultured from peripheral blood, kidney, and thymus where viral titers peaked a t 2 to 4 d post-inoculation. Leucocytes collected from trout following waterborne challenge with IHNV were cocultured on EPC cell monolayers . These assays detected IHNV in leucocytes infected in vivo as early a s 6 h post-exposure before the challenge virus had undergone replicati on. These data showed that leucocyte populations could serve as target cells in the initial phase of IHNV infection.