TYPING OF FRENCH ISOLATES OF INFECTIOUS HEMATOPOIETIC NECROSIS VIRUS (IHNV) WITH MONOCLONAL-ANTIBODIES USING INDIRECT IMMUNOFLUORESCENCE

Following the first isolation of infectious haematopoietic necrosis vi rus (IHNV) in France, many other isolates of the virus have been recov ered from rainbow trout populations. Of the 27 isolates typed using an indirect immunofluorescence (IIF) test with mouse monoclonal antibodi es (MAb), only 5 of the French isolates were recognized by MAb 1NDW14D , previously considered to be a universal IF reagent for IHNV. In cont rast, all 27 isolates shared the nucleocapsid epitope identified by MA b 2NH105B, currently thought to be specific for IHNV of electropheroty pe 2, although the French isolates did not appear to belong to this el ectropherotype. Considerable variation was noted among the isolates in other nucleocapsid epitopes, suggesting that some of the isolates hav e been present among rainbow trout, in Europe or elsewhere, for suffic ient time to evolve separately. Practically speaking, a multivalent IH NV reagent for IIF based upon MAbs should encompass both MAbs 1NDW14D and 2NH105B, especially if intended for European use.