Salmon Erythrocytes Sequester Active Virus Particles in Infectious Salmon Anaemia

• Published in: Viruses Vol. 14; no. 2; p. 310
• Main Authors: Fosse, Johanna Hol, Aamelfot, Maria, Sønstevold, Tonje, Weli, Simon Chioma, Vendramin, Niccolò, Petersen, Petra Elisabeth, Solhaug, Anita, Amundsen, Marit Måsøy, Heffernan, Inger Austrheim, Cuenca, Argelia, Christiansen, Debes Hammershaimb, Falk, Knut
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 02.02.2022; MDPI
• Subjects: adsorption; Anemia; Animals; Blood; decoy; Endothelial cells; Endothelial Cells - virology; Endothelium; Erythrocytes; Erythrocytes - virology; Fish Diseases - blood; Fish Diseases - virology; Hypotheses; Infections; isavirus; Isavirus - genetics; Isavirus - isolation & purification; Isavirus - physiology; Orthomyxoviridae Infections - blood; Orthomyxoviridae Infections - veterinary; Orthomyxoviridae Infections - virology; orthomyxovirus; Pathogenesis; red blood cell; Replication; Salmo salar; Salmo salar - blood; Salmo salar - virology; Salmon; Transcription; Trout; Viral Proteins - genetics; Viral Proteins - metabolism; viral replication; Virion - genetics; Virion - isolation & purification; Virion - physiology; Virus Replication; Viruses; United States > US; Norway; Iceland; viral replication; adsorption; isavirus; orthomyxovirus; decoy; nucleated erythrocyte; red blood cell
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v14020310

Infectious salmon anaemia virus (ISAV) binds circulating Atlantic salmon erythrocytes, but the relevance of this interaction for the course of infection and development of disease remains unclear. We here characterise ISAV-erythrocyte interactions in experimentally infected Atlantic salmon and show that ISAV-binding to erythrocytes is common and precedes the development of disease. Viral RNA and infective particles were enriched in the cellular fraction of blood. While erythrocyte-associated ISAV remained infectious, erythrocytes dose-dependently limited the infection of cultured cells. Surprisingly, immunostaining of blood smears revealed expression of ISAV proteins in a small fraction of erythrocytes in one of the examined trials, confirming that ISAV can be internalised in this cell type and engage the cellular machinery in transcription and translation. However, viral protein expression in erythrocytes was rare and not required for development of disease and mortality. Furthermore, active transcription of ISAV mRNA was higher in tissues than in blood, supporting the assumption that ISAV replication predominantly takes place in endothelial cells. In conclusion, Atlantic salmon erythrocytes bind ISAV and sequester infective virus particles during infection, but do not appear to significantly contribute to ISAV replication. We discuss the implications of our findings for infection dynamics and pathogenesis of infectious salmon anaemia.