Comparative Studies on Structural and Antigenic Properties of Two Serotypes of Infectious Bursal Disease Virus

Abstract

SUMMARYThe electrophoretic mobilities of the two genome segments and the structural polypeptides of the chicken strain Cu-1 (serotype I) and the turkey isolate 23/82 (serotype II) of infectious bursal disease virus were compared. There is a close antigenic relationship between the smaller of the two major structural proteins (32K) of both strains. Neutralizing monoclonal antibodies are induced by the larger protein (40K in Cu-1) which differentiates between the two serotypes. The 40K structural protein also has epitopes which do not induce neutralizing antibodies and which are common to both strains. There is evidence that the antigenic region responsible for the production of neutralizing antibodies is highly conformation-dependent. Passively administered neutralizing antibodies directed against the 40K structural polypeptide of Cu-1 confer protective immunity to susceptible chickens, whereas antibodies directed against the 32K structural protein do not have any protective effect. INTRODUCTIONThe basic structure of the infectious bursal disease virus (IBDV), the aetiological agent of a disease of chickens which results in the destruction of the bursa of Fabricius, has been elucidated (Nick et al., 1976; M/iller et al., 1979) and has been shown to exhibit the structural characteristics of the Birnaviridae (Dobos et al., 1979;Brown, 1986). During the past few years isolates of IBDV from turkeys have been reported to be essentially identical to the chicken strains, but the turkey isolates were not pathogenic and could be distinguished by neutralization (McNulty et al., 1979;Jackwood et al., 1982); a second serotype was therefore established (McFerran et al., 1980). In order to localize the antigenic determinants on the structural proteins of IBDV which are responsible for the induction of neutralizing antibodies, a more detailed comparative analysis of the two types of viruses was necessary. Attempts were therefore made to obtain more precise information about the size of the two genomic segments ofdsRNA and the structural proteins of the turkey strain in relation to the known elements of the chicken virus. The antigenic sites which both types of viruses have in common and those which permit their distinction were traced with monoclonal antibodies. The need for a more precise analysis of the antigenic structure of IBDV was underlined by the attempts of other authors to describe antigenic regions which would lend themselves to the production of a vaccine in Escherichia coli or by peptide synthesis (Fahey et al., 1985a,b;Azad et al., 1986;Hudson et al., 1986).

Evidence of genomic variations between infectious pancreatic necrosis virus strains determined by restriction fragment profiles

“…The numbering of the strains corresponds to that in region covers the C-terminal part of VP2 and the Nterminal part of the NS protein whereas all MAbs developed against IPNV are either VP2-or VP3-specific (Caswell-Reno et al, 1986;Lecomte et al, 1992). Similar data were also obtained with IBDV (Azad et al, 1987;Becht et al, 1988;Fahey et al, 1989;Jagadish & Azad, 1991). Because the precise location of the junction between the two proteins on genome segment A has not yet been determined, it is not possible to calculate the exact proportion of each protein represented in the eDNA fragment.…”

T-Cell suppression by cyclosporin-A enhances infectious bursal disease virus infection in experimentally infected chickens

“…Protection against IBDV is considered to be chiefly antibody mediated. The major host protective immunogen of IBDV (VP2) contains at least two or three closely-linked antigenic sites capable of inducing virus-neutralizing antibodies in chickens (Becht et al, 1988). Vaccination with VP2 expressed in prokaryotic and eukaryotic vectors is capable of eliciting neutralizing antibodies in chickens, and chickens are protected against clinical disease and mortality following challenge but not against bursal damage (Dybing & Jackwood, 1998).…”

A comparison of the sequences of segment A of four infectious bursal disease virus strains and identification of a variable region in VP2

“…VP3 has been used to induce antibodies but these were only very weakly neutralizing (Fahey et aL, 1985b). Monoclonal antibodies (MAbs) have been raised against VP2 and VP3, but only those reacting to VP2 have the ability to neutralize the virus (Azad et al, 1987;Becht et al, 1988;Snyder et al, 1988). One neutralizing MAb recognition site has been mapped to a specific region of VP2 between amino acids 206 and 350 (Azad et al, 1987).…”

“…Neutralizing antibodies are elicited by VP2 (Becht et al, 1988;Fahey et al, 1989). VP3 has been used to induce antibodies but these were only very weakly neutralizing (Fahey et aL, 1985b).…”