Development and Characterization of Monoclonal Antibodies against the Snakehead Rhabdovirus

—Monoclonal antibodies (MAbs) directed against the snakehead rhabdovirus (SHRV) were produced. These MAbs were characterized by immunofluorescence and neutralization tests, and by their ability to immunoprecipitate viral proteins. Of 15 MAbs developed, 9 were isotyped as IgGl and 6 were IgG2a. Eight of the MAbs recognized the viral glycoprotein in an immuno precipitation assay. Three of these, designated El-9 A, P10C, and O10F, had neutralizing activity. By immunofluorescence, 12 MAbs showed good binding activity in SHRV-infected epithelioma papulosum cyprini cells. In an indirect fluorescence assay, the MAbs gave varied staining patterns depending upon the viral structural proteins recognized. A rhabdovirus that is serologically different from other fish rhabdoviruses (Ahne et ai. 1988; Kasornchandra et al. 1991) was isolated (Wattanavijarn et al. 1986) from chevron snakehead Channa (=Ophicephalus) striata during an outbreak of ulcerative disease in southeast Asia. The snakehead rhabdovirus (SHRV) is one of the several potential pathogenic organisms isolated from animals with this disease, but the etiologic agent has not been established (Boonyaratpalin 1989; Frerichs et al. 1989). Kasornchandra et al. (1991) found that SHRV contained five structural proteins similar to those of infectious hematopoietic necrosis virus (IHNV) and viral hemorrhagic septicemia virus (VHSV). Replication of the SHRV and production of cytopathic effect is rapid in susceptible cell lines. In the epithelioma papulosum cyprini (EPQ cell line (Fijan et al. 1983) and the snakehead fin cell line (Kasornchandra et al. 1988), cytopathic effect is apparent within 14 h and complete in 24-48 h at 27°C (Kasornchandra et al. 1991). Although polyclonal antibodies were produced in rabbits and used for identification of SHRV by serum neutralization assay, the rabbit anti-SHRV sera had low titers and were toxic to the cells. In immunofluorescence assays, the rab1 To whom correspondence should be addressed. bit antisera had extensive nonspecific binding with high levels of background fluorescence both in the control and the infected cell lines tested. To improve methods for identification of this virus, monoclonal antibodies (MAbs) against SHRV were developed. The purpose of this study was to produce MAbs against SHRV for use in immunodiagnosis. These MAbs were characterized by immunoprecipitation, immunofluorescence, and serum neutralization.