Virulence of infectious pancreatic necrosis virus is associated with the larger RNA segment (RNA segment A)

Abstract

Infectious pancreatic necrosis virus (IPNV) contains two segments of doublestranded RNA (the larger RNA segment. A; and a smaller RNA segment, B). The IPNVBuhl isolate belongs to the VR299 serotype, and eel virus European (EVE) is serologically the same as the Ab serotype. IPNV-Buhl is virulent to rainbow trout fry, Oneorhynchus mykiss (Walbaum), whereas EVE is avirulent. To determine the genetic basis for the difference of the virulence, intertypic reassortants were made between IPNV-Buhl and EVE. The reassortants with the genotypes of F/E (segment A of IPNV-Buhl and segment B of EVE) and E/P (segment A of EVE and segment B of IPNV-Buhl) were studied for their pathogenicity to rainbow trout fry. The P/E reassortant was highly virulent, similar to the IPNV-Buhl parent (P/P), while the E/P reassortant was avirulent, as was the EVE parent (E/E). A high level of viral replication was observed in almost all organs of the fry infected with the P/E reassortant and the IPNV-Buhl parent. In contrast, viral replication was restricted to the epidermal eells of the fry infected with the E/P reassortant and the EVE parent-The results demonstrate that the larger RNA segment (RNA segment A) of IPNV is related to eell tropism in vivo and is responsible for virulenee in rainbow trout fry.

Molecular characterization of Sp serotype strains of infectious pancreatic necrosis virus exhibiting differences in virulence

“…This result is also in accordance with that of Sano et al (1992), who generated reassortants between virulent and avirulent strains of 2 different serotypes and demonstrated that the virulence of IPNV is associated with Segment A. Similarly, Bruslind & Reno (2000) found 2 amino acid differences in the VP2 at Positions 217 and 286 between the virulent and avirulent Buhl-subtype isolates of IPNV.…”

“…Sp serotype strains are predominant in Europe, whereas the West Buxton (WB) strain is more prevalent in the United States. Since virulence of IPNV has been associated with Segment A (Sano et al 1992), there may be differences at the molecular level within Segment A that makes the closely related isolates of IPNV so varied in their virulence. Recently, Bruslind & Reno (2000) identified 2 amino acid differences within the VP2 region of a virulent and avirulent Buhl strain of IPNV that was used to infect brook trout fry.…”

Viral diseases of wild and farmed European eel Anguilla anguilla with particular reference to the Netherlands

“…However, T. Sano et al (1981) did not find any significant signs or mortality in rainbow trout fry exposed to EVE by bath immersion at 10°C over a 40 d period. The Ab serotypes of EVE isolated from farmed Anguilla anguilla and A. japonica from the UK and Japan, respectively, did not cause disease in rainbow trout fry either (Hudson et al 1981, Okamoto et al 1983, M. Sano et al 1992. The EVE isolate serotype Ab from A. rostrata appeared to be non-virulent to brook trout Salvelinus fontinalis fry 42 d old at 12°C; a Japanese EVE isolate was weakly virulent (3% virus associated mortality), and another Japanese EVE isolate was highly virulent (87% virus-associated mortality) (McAllister & Owens 1995 (1984) resulted in 25 to 35% mortality in intraperitoneally injected juvenile common carp Cyprinus carpio and hybrid tilapia at 20 to 25°C.…”

“…Survivors of the epizootic disease may become lifelong carriers. Host specificity and cell tropism are determined by viral proteins encoded by the larger RNA segment A (M. Sano et al 1992), and the occurrence of natural reassortment has recently been shown (Romero-Brey et al 2009). Interspecies transmission has not yet been demonstrated, but it would explain the wide range of host species (Bandin & Dopazo 2011).…”

Molecular characterisation of Australasian isolates of aquatic birnaviruses

“…While virulence of IPNV isolates has been linked to Segment A (Sano et al 1992), no specific sequences or motifs have been identified that correlate with virulence. An attempt to determine specific markers of virulence was recently reported by Santi et al (2004).…”