Limited antigenic variation among recent infectious bursal disease virus isolates from France

Seven neutralizing monoclonal antibodies (Mabs) to infectious bursal disease virus (IBDV) were used in an antigen-capture ELISA for the antigenic characterization of 58 IBDV isolates obtained in France since 1989. Fifty-six isolates exhibited an antigenic profile which was different from reference strain Faragher 52/70, and similar to French very virulent IBDV strain 89,163 (no binding of two Mabs). Two strains (3.4%), isolated in 1991 and 1994, showed additional antigenic modifications 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.