Differential virulence mechanisms of infectious hematopoietic necrosis virus in rainbow trout (Oncorhynchus mykiss) include host entry and virus replication kinetics.
Host specificity is a phenomenon exhibited by all viruses. For the fish rhabdovirus infectious hematopoietic necrosis virus (IHNV), differential specificity of virus strains from the U and M genogroups has been established both in the field and in experimental challenges. In rainbow trout (Oncorhynchus mykiss), M IHNV strains are consistently more prevalent and more virulent than U IHNV. The basis of the differential ability of these two IHNV genogroups to cause disease in rainbow trout was investigated in live infection challenges with representative U and M IHNV strains. When IHNV was delivered by intraperitoneal injection, the mortality caused by U IHNV increased, indicating that the low virulence of U IHNV is partly due to inefficiency in entering the trout host. Analyses of in vivo replication showed that U IHNV consistently had lower prevalence and lower viral load than M IHNV during the course of infection. In analyses of the host immune response, M IHNV-infected fish consistently had higher and longer expression of innate immune-related genes such as Mx-1. This suggests that the higher virulence of M IHNV is not due to suppression of the immune response in rainbow trout. Taken together, the results support a kinetics hypothesis wherein faster replication enables M IHNV to rapidly achieve a threshold level of virus necessary to override the strong host innate immune response.
Peñaranda
Ma Michelle D
MM
Interdisciplinary Graduate Program in Pathobiology, Department of Global Health, University of Washington, Seattle, WA 98195, USA.
Purcell
Maureen K
MK
Kurath
Gael
G
D000818:Animals; D005393:Fish Diseases / Q000235:genetics / Q000276:immunology / Q000821:virology*; D015870:Gene Expression; D005838:Genotype; D054884:Host-Pathogen Interactions; D029142:Infectious hematopoietic necrosis virus / Q000737:chemistry / Q000472:pathogenicity* / Q000502:physiology; D007700:Kinetics; D018353:Rhabdoviridae Infections / Q000235:genetics / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D014337:Trout / Q000235:genetics / Q000276:immunology / Q000821:virology*; D014774:Virulence; D053586:Virus Internalization; D014779:Virus Replication