Modified activity of a VP2-located neutralizing epitope on various vaccine, pathogenic and hypervirulent strains of infectious bursal disease virus

Abstract

Nine monoclonal antibodies (Mabs) to a vaccine strain of infectious bursal disease virus (IBDV) of intermediate virulence were characterized in Western-blot, radioimmunoprecipitation, ELISA additivity, and neutralization assays. At least two distinct serotype 1-specific conformation-dependent overlapping neutralizing antigenic domains were shown to be present on IBDV-VP2, and were respectively probed by Mabs 3 and 4, and by Mabs 6 and 7. Ten serotype 1 vaccine or pathogenic IBDV strains were tested for neutralization. Most mild or intermediate vaccine strains were efficiently neutralized by all Mabs, whereas US variant A, European pathogenic strain Faragher 52/70 and French hypervirulent isolate 89163 were not neutralized by Mabs 3 and 4. In addition, these two Mabs were shown to bind to the Faragher 52/70 strain, but not to the 89163 isolate, in an antigen-capture ELISA. These results suggest that a neutralizing epitope is possibly modified in European pathogenic IBDV strains, and that Mabs 3 and 4 may prove useful for antigenic differentiation between European classical and hypervirulent isolates.

Extensive antigenic changes in an atypical isolate of very virulent infectious bursal disease virus and experimental clinical control of this virus with an antigenically classical live vaccine

“…The vaccine can be described as exhibiting a ''classical'' antigenicity, as shown by the fact that most mAbs, especially mAbs 3 and 4 that probe VP2 major hydrophilic peak A, bound to the vaccine virus in AC-ELISA. The fact that mAb 5 yielded a low percent reactivity against the vaccine virus is consistent with previous results showing that mAb 5, possibly due to a low affinity (Eterradossi et al, 1997a), may present a wide range of reactivity when tested against viruses with a typical minor hydrophilic peak 1 (Eterradossi et al, unpublished observations 1997).…”

“…mAb pairs (3 and 4) and (6 and 7) are targeted at two overlapping antigenic sites, with the binding of mAbs 3 and 4 depending on the presence of Proline and Glycine residues at aa positions 222 to 223 and the binding of mAbs 6 and 7 depending on aa changes at positions 318 to 323. VP2 major hydrophilic peak B is recognized by mAb 8, the binding of which depends on a Glutamine residue at aa position 324 (Eterradossi et al, 1997a(Eterradossi et al, , 1998. mAb 5 probes an epitope involving the first minor hydrophilic peak 1 (249Q) (Eterradossi et al, unpublished results 1998(Eterradossi et al, unpublished results Á/2000.…”

“…Micro virus neutralization (VN) tests were performed as described previously (Eterradossi et al, 1992): serial two-fold dilutions of the sera were mixed with 100 median tissue infective doses (TCID 50 ) of the CT IBDV strain (serotype 1 antigen, cell culture adapted; final volume of mix, 50 ml). The classical antigenicity of strain CT and the nt sequence encoding the variable domain of VP2 in this virus strain have been described previously (Eterradossi et al, 1997a(Eterradossi et al, , 1998. Virus neutralization was allowed for 45 min at room temperature.…”

Assessment of genetic, antigenic and pathotypic criteria for the characterization of IBDV strains

“…Antigenic characterization was performed using a previously described mAb-based AC-ELISA (Eterradossi et al ., 1997a). Briefly, 96-well polystyrene ELISA plates (Costar, Cambridge, MA, USA) were coated with a convalescent chicken anti-F52/70 serum diluted in phosphate-buffered saline (PBS) (pH 7.4, 1 h at 378C).…”

“…Three criteria can be used for the characterization of IBDV strains: antigenicity, genetic relatedness and pathogenicity. Three panels of neutralizing monoclonal antibodies (mAbs) have been used in antigen capture enzyme-linked immunosorbent assays (AC-ELISA) for antigenic characterization of serotype 1 isolates of IBDV (Fahey et al, 1991;Snyder et al, 1992;Eterradossi et al, 1997a). Neutralizing mAbs have been shown to bind to VP2 within a restricted region, called the variable domain, between amino acids 206 and 350, which is highly hydrophobic but has short hydrophilic regions at each end (Bayliss et al, 1990).…”