ORIGINAL ARTICLE Virulence of a chimeric recombinant infectious haematopoietic necrosis virus expressing the spring viraemia of carp virus glycoprotein in salmonid and cyprinid fish E J Emmenegger 1 | S Biacchesi 2 | EM  erour 2 | J A Glenn 3 | A D Palmer 4 | M Br  emont 2 | G Kurath 1 1 US Geological Survey, Western Fisheries Research Center, Seattle, WA, USA 2 Virologie et Immunologie Mol eculaires (VIM), INRA, Universit e Paris-Saclay, Jouy- en-Josas, France 3 NanoString Technologies Inc., Seattle, WA, USA 4 Department of Microbiology, Chemical and Life Sciences Laboratories, University of Illinois at Urbana-Champaign, Urbana, IL, USA Correspondence Eveline J Emmenegger, USGS Western Fisheries Research Center, Seattle, WA, USA. Email: eemmenegger@usgs.gov Funding information Infectiologie Exp erimentale des Rongeurs et Poissons, INRA Abstract Infectious haematopoietic necrosis virus (IHNV) and spring viraemia of carp virus (SVCV) are both rhabdoviruses of fish, listed as notifiable disease agents by the World Organization for Animal Health. Recombinant rhabdoviruses with heterolo- gous gene substitutions have been engineered to study genetic determinants and assess the potential of these recombinant viruses for vaccine development. A recombinant IHNV (rIHNV), containing the full-length genome of a European IHNV strain, was modified by deleting the glycoprotein (G) gene and replacing it with a European SVCV G-gene to make the rIHNV-Gsvcv. The chimeric rIHNV-Gsvcv level of virulence in rainbow trout, common carp and koi was assessed, and its ability to induce a protective immune response in surviving koi against wild-type SVCV infec- tion was tested. The rIHNV-Gsvcv infection of trout led to high mortality, ranging from 78% to 92.5%, after immersion. In contrast, no deaths occurred in juvenile common carp after infection with rIHNV-Gsvcv by either immersion or intraperi- toneal (IP) injection. Similarly, koi infected with rIHNV-Gsvcv via IP injection had lit- tle to no mortality (≤9%). Koi that survived initial infection with a high dose of recombinant virus rIHNV-Gsvcv were protected against a virulent SVCV challenge resulting in a high relative per cent survival of 82.5%. KEYWORDS glycoprotein, infectious haematopoietic necrosis virus, koi, rainbow trout, recombinant virus, spring viraemia of carp virus 1 | INTRODUCTION Infectious haematopoietic necrosis virus (IHNV) and spring viraemia of carp virus (SVCV) are two of eight fish viruses listed by the World Organization for Animal Health (Office International des Epizooties). Both IHNV and SVCV are considered major threats in aquatic envi- ronments due to their highly contagious nature and potential severe disease outcomes in susceptible species. IHNV originated in North America infects primarily salmonid fish species that reside in cold water and is known to cause high fatalities in fish farms and hatch- eries (Bootland & Leong, 1999). IHNV has a limited replication temperature range of 10–18°C (Amend 1970; Hetrick, Fryer, & Knit- tel, 1979). SVCV was first discovered in cyprinid species of Europe and has a higher water temperature tolerance, with in vitro virus replication occurring up to 31°C (Ahne et al., 2002). Common carp (Cyprinus carpio carpio) and koi (C. carpio koi) are considered the most vulnerable fish species to SVCV infections (Walker & Winton, 2010). IHNV and SVCV are now present on both continents and associated with disease outbreaks in both cultured and wild fish populations (Dixon, Paley, Alegria-Moran, & Oidtmann, 2016; Good- win, 2002; de Kinkelin, Hattenberger, Torchy, & Lieffrig, 1987). Both viruses belong to the Rhabdoviridae family with a genome consisting Received: 13 March 2017 | Revised: 25 May 2017 | Accepted: 27 May 2017 DOI: 10.1111/jfd.12678 J Fish Dis. 2017;1–12. wileyonlinelibrary.com/journal/jfd © 2017 John Wiley & Sons Ltd | 1