Characteristics and pathogenicity of a novel herpesvirus isolated from adult and subadult white sturgeon Acipenser transmontanus

Abstract

ABSTRACT. A syncytlum-inducing viral agent was initially isolated from the ovarian fluld of a domestic white sturgeon Acipenser transrnontanus female using the sturgeon spleen cell line WSS-2. Examination of infected cells by transmission electron microscopy revealed ultrastructural characteristics typical of the Herpesviridae. On the basis of differences shown by comparative in vitro growth studies and serological assays, the new adult isolate was tentatively designated WSHV-2 to distinguish it from a previously reported herpesvirus from juvenile white sturgeon. WSHV (WSHV-1). A water-borne transmission trial at 3 virus concentrations was conducted to determine the susceptibility of juvenile sturgeon to the newly isolated virus. At virus doses of lo5 and 104 TCID,, ml-' cumulative mortality reached 80% within 6 wk at a water temperature of 17°C. Virus was reisolated from all mortallties with concentrations approaching 10' TCIDSo g-I in cutaneous eplthelial tissues where severe hyperplastic lesions were observed. Challenge with 103 TCIDSo m l -' of WSHV-2 falled to induce clinical signs or mortality, although chronic subclinical infections were detected in a majority of survivors 70 d postchallenge. During our investigations of WSHV-2 from adult sturgeon, a second virus isolation was obtained from ulcerative skin lesions of naturally infected subadult white sturgeon. This virus induced identical cytopathic effects in WSS-2 cells to that caused by the adult isolate from ovarian fluid. Serum anti-WSHV-2 neutralizing activity was detected In subadults with skin lesions and among fish recovering from these lesions. Serum from naturally-infected juveniles and serum from adults hyperimmunized with the WSHV-2 from the ovarian fluid were used to compare the adult and subadult viruses. The 2 agents were neutralized with these 2 sera which conversely failed to neutralize WSHV-1 at the lowest dilution tested Our studies demonstrate that at least 2 pathogenic herpesviruses are found among white sturgeon The newly recognized WSHV-2 can cause both acute and chronic infections and possibly a latent carrier state in white sturgeon. WSHV-2 is the fourth virus to be observed as a cause of juvenile mortality among intensively reared white sturgeon populations.

Replication and pathogenesis of white sturgeon iridovirus (WSIV) in experimentally infected white sturgeon Acipenser transmontanus juveniles and sturgeon cell lines

“…Among these cell lines the newly established WSGO line shows the best ability to replicate WSIV. However, the amount of WSIV produced by any of these lines is substantially (100-to 1000-fold) below that observed with a second virus, WSHV-2, from white sturgeon (Watson et al 1995) and that observed with the systemic iridoviruses from several fish species (Langdon et al 1986, Ogawa et al 1990, Nakajima et al 1995. The more rapidly lytic CPE of the systemic iridoviruses contrast to WSIV, which induces a slower cellular change including enlargement, pseudosyncytium formation and detachment from adjacent cells and the substrate.…”

Phylogenetic relationships in the family Alloherpesviridae

“…See Table 1 for abbreviation nivirus) to contain these viral species (Cyprinid herpesvirus 1, 2 and 3). In regard to Clade 2, the distinctiveness of the 2 ictalurid (Hedrick et al 2003), 3 salmonid (Hedrick et al 1987, Hayashi et al 1989, McAllister 1993, Yoshimizu et al 1995, Sung et al 1996, 2 ranid (Tweedell 1989, and 2 acipenserid (Hedrick et al 1991, Watson et al 1995 HVs has been established previously. The present study supports sister status within these groupings, except for the acipenserid HVs.…”

“…HV particles have been observed by electron microscopy and on occasion isolated from neoplastic or hyperplastic epithelial lesions in salmonid, cyprinid, anguillid, osmerid, esocid, silurid, percid, pleuronectid, and acipenserid fishes (Hedrick et al 1991, Anders & Yoshimizu 1994, Watson et al 1995. Neoplastic lesions have been associated with the following fish and amphibian HV infections: several isolates of SalHV2 (i.e.…”

“…Moreover, evidence for a long-term carrier state, which may or may not involve latency, has been described in several fish HVs, including IcHV1 (Wise et al 1985, Boyle & Blackwell 1991, Baek & Boyle 1996, Gray et al 1999, Thompson et al 2005 Members of the family Alloherpesviridae often induce proliferative epithelial lesions in their respective hosts. HV particles have been observed by electron microscopy and on occasion isolated from neoplastic or hyperplastic epithelial lesions in salmonid, cyprinid, anguillid, osmerid, esocid, silurid, percid, pleuronectid, and acipenserid fishes (Hedrick et al 1991, Anders & Yoshimizu 1994, Watson et al 1995. Neoplastic lesions have been associated with the following fish and amphibian HV infections: several isolates of SalHV2 (i.e.…”

Herpesviruses of Fish, Amphibians and Invertebrates

“…AciHV-1 was later isolated from other farmed white sturgeons in California and Italy (Kelley et al, 2005;Kurobe et al, 2008). Few years later another herpesvirus called white sturgeon herpesvirus 2, or Acipenserid herpesvirus 2 (AciHV-2), was isolated from dermal lesions of subadult white sturgeon and ovarian fluids of a mature white sturgeon (Watson et al, 1995). Mortality among experimentally infected juvenile white sturgeons reached a cumulative total of 80%.…”