LIMITED ANTIGENIC VARIATION AMONG RECENT INFECTIOUS BURSAL DISEASE VIRUS ISOLATES FROM FRANCE

Seven neutralizing monoclonal antibodies (Mabs) to infectious bursal d isease virus (IBDV) were used in an antigen-capture ELISA for the anti genic characterization of 58 IBDV isolates obtained in France since 19 89. Fifty-six isolates exhibited an antigenic profile which was differ ent from reference strain Faragher 52/70, and similar to French very v irulent IBDV strain 89 163 (no binding of two Mabs). Two strains (3.4 %), isolated in 1991 and 1994, showed additional antigenic modificatio ns resulting in suppressed or reduced binding activity of three other Mabs. The two atypical viruses were not re-identified in field samples subsequently collected, hence showing that antigenic variants of IBDV do not tend to replace the antigenically dominant 89 163-like strains that have prevailed in France since 1989.