COMPARISON OF DIFFERENT PROCEDURES FOR SEROTYPING AQUATIC BIRNAVIRUS

The current classification of aquatic birnaviruses is based on seroneu tralization assays with polyclonal antibodies, In this study a compari son of several procedures used for serotyping aquatic birnaviruses was made with 10 virus strains (4 reference strains from salmonids and 6 birnaviruses isolated from turbot [Scophthalmus maximus]). The relatio nships among the birnavirus strains were studied by seroneutralization assay with polyclonal antibodies and by immunodot assay with both pol yclonal and monoclonal antibodies. The results were compared with a pr esumptive classification obtained from analysis of restriction enzyme patterns of cDNA products obtained by PCR amplification. No correlatio n was found among the results obtained by the different procedures. Th e seroneutralization and the immunodot assays with polyclonal antibodi es were not useful in classifying these birnavirus strains; however, p atterns of reaction with monoclonal antibodies emphasized the individu ality of the strains, particularly in the ease of two strains (231 and 460) whose patterns did not correspond to established serotypes. The application of PCR and restriction enzyme analysis is a promising syst em for approaching the classification of this viral group on the basis of genomic differences and similarities, The variable results obtaine d in this comparison lead us to think that the current classification of aquatic birnavirus may not be the most accurate and there is a need for modification incorporating recent isolates, not only from salmoni d species but also from marine fish.