Characterization of Snakehead Rhabdovirus Infection in Zebrafish ( Danio rerio )

Abstract

The zebrafish, Danio rerio, has become recognized as a valuable model for the study of development, genetics, and toxicology. Recently, the zebrafish has been recognized as a useful model for infectious disease and immunity. In this study, the pathogenesis and antiviral immune response of zebrafish to experimental snakehead rhabdovirus (SHRV) infection was characterized. Zebrafish 24 h postfertilization to 30 days postfertilization were susceptible to infection by immersion in 10 6 50% tissue culture infective doses (TCID 50 ) of SHRV/ ml, and adult zebrafish were susceptible to infection by intraperitoneal (i.p.) injection of 10 5 TCID 50 of SHRV/ ml. Mortalities exceeded 40% in infected fish, and clinical presentation of infection included petechial hemorrhaging, redness of the abdomen, and erratic swim behavior. Virus reisolation and reverse transcription-PCR analysis of the viral nucleocapsid gene confirmed the presence of SHRV. Histological sections of moribund embryonic and juvenile fish revealed necrosis of the pharyngeal epithelium and liver, in addition to congestion of the swim bladder by cell debris. Histopathology in adult fish injected i.p. was confined to the site of injection. The antiviral response in zebrafish was monitored by quantitative real-time PCR analysis of zebrafish interferon (IFN) and Mx expression. IFN and Mx levels were elevated in zebrafish exposed to SHRV, although expression and intensity differed with age and route of infection. This study is the first to examine the pathogenesis of SHRV infection in zebrafish. Furthermore, this study is the first to describe experimental infection of zebrafish embryos with a viral pathogen, which will be important for future experiments involving targeted gene disruption and forward genetic screens.

Identification of the Zebrafish IFN Receptor: Implications for the Origin of the Vertebrate IFN System

“…Our results probably explain why, in a model of snakehead rhabdovirus infection, Phelan et al (14) only found a very modest zIFN mRNA increase despite strong MX induction.…”

“…Although human and mice have a single gene coding for IFN-␥, some teleosts (including zebrafish) have more than one gene, but in all instances these genes have three introns. In contrast, the designation of fish virus-induced IFNs has been more problematic and most authors merely called them "IFN" (13,14). Based on their similarity with mammalian IFNs some authors call them type I IFNs (15)(16)(17)(18)(19).…”

Identification of an additional two-cysteine containing type I interferon in rainbow trout Oncorhynchus mykiss provides evidence of a major gene duplication event within this gene family in teleosts

“…Although induction of type I IFNs is apparent after virus infection or treatment with killed viruses, the kinetics of induction vary dependent on the virus, host and infection route (McBeath et al 2007;Robertsen 2008). For example, zebrafish infected with snakehead rhabdovirus for 7 days exhibited maximal accumulation of IFN messenger RNA (mRNA; Phelan et al 2005). Unmethylated CpG containing DNA also activates IFN gene transcription in Atlantic salmon leucocytes (Pedersen et al 2006;Strandskog et al 2008).…”

A review of the need and possible uses for genetically standardized Atlantic salmon (Salmo salar) in research

“…63 -66 It is also easier to standardize husbandry factors for smaller animals, so reproducibility between studies on laboratory fish is therefore easier to attain. However, the extrapolation of the results from, for example, zebrafish to salmonids is often difficult 67 as these species are more distantly related than the mouse is to man. Performing experiments directly on the production animals is also essential in many cases, such as in vaccine development.…”