Infectious bursal disease--B cell dependent immunodeficiency syndrome in chickens.

Infectious bursal disease of chickens can run an acute lethal course, or death can result from a B cell-dependent immunodefect due to destruction of the bursa of Fabricius following infection with infectious bursal disease virus (IBDV). This member of the Birnaviridae has been characterized, the nucleotide sequence and coding capacity of the two genomic segments of dsRNA has been determined, and the functional significance of the four structural proteins has been largely elucidated. The antigenic structure of the two main structural components permits differentiation of two serotypes; the antigenic domain responsible for the induction of neutralizing antibodies resides, in a conformation-dependent fashion, on one of these proteins. Various types of defective particles are formed and various degrees of pathogenicity appear, depending on the host cell in which the virus replicates. B cells in the bursa offer optimal conditions for virus replication. Pathogenic properties of the virus are also influenced by both genomic segments and cannot be attributed to a single gene. Many aspects of practical interest for disease control are briefly discussed.