Infectious salmon anemia virus: causative agent, pathogenesis and immunity

Area of Science:

• Virology
• Aquaculture Pathology
• Fish Immunology

Background:

• Infectious salmon anemia virus (ISAV) is an emerging pathogen impacting marine aquaculture.
• ISAV belongs to the Orthomyxoviridae family, genus Isavirus, with a segmented RNA genome.
• Two hemagglutinin subtypes (North American and European) have been identified in ISAV isolates.

Purpose of the Study:

• To characterize the structural properties and genetic diversity of ISAV.
• To investigate the immune response and potential mechanisms of virulence enhancement in ISAV infections.
• To understand the disease dynamics and host-pathogen interactions of ISAV in farmed fish.

Main Methods:

• Analysis of ISAV isolates to identify hemagglutinin subtypes.
• Examination of viral genome structure and protein encoding.
• In vitro studies using fish cell lines to investigate antibody-mediated viral uptake.
• Experimental infections in Atlantic salmon and rainbow trout to assess virulence.

Main Results:

• ISAV possesses an enveloped virion with specific surface glycoproteins (HE) and an eight-segment RNA genome.
• Two distinct hemagglutinin subtypes of ISAV have been identified globally.
• Antibody-mediated uptake and replication in cell lines suggest potential antibody-dependent enhancement (ADE) of ISAV infection in vivo.
• ISAV causes variable mortality in Atlantic salmon and fatal disease in rainbow trout, with identified virulence correlates.

Conclusions:

• ISAV presents a significant threat to salmonid aquaculture due to its virulence and potential for immune evasion.
• Further research into ADE mechanisms is crucial for developing effective control strategies against ISAV.
• Understanding ISAV virulence factors is key to managing its emergence as a global fish pathogen.