The genetic basis for the antigenicity of the VP2 protein of the infectious bursal disease virus

Abstract

The genomic region coding for the antigenic structure responsible for the induction of neutralizing antibodies was localized in the central variable region of the VP2 gene by comparing the nucleotide sequence of five escape mutants derived from the standard infectious bursal disease virus strain Cu-1. Exchange of a single amino acid at one of the prominent hydrophilic parts of this region proved to be sufficient for altering the neutralizing properties. The reactivity of neutralizing antibodies with peptides expressed in vitro encompassing both hydrophilic areas suggests that the entire variable region is engaged in the formation of this conformationdependent antigenic site. VP2-specific, non-neutralizing monoclonal antibodies directed against the sequencedependent epitope of the serotype I strain Cu-1 and the serotype II strain 23/82 cross-reacted with peptides located towards the carboxy terminus of VP2; no reaction occurred with peptides derived from the aminoterminal side adjacent to the variable region.

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

“…Four of these nt changes were silent mutations, hence the deduced aa sequence was also very similar to that of 89163 (Figure 1) and presented the four aa positions 222A, 256I, 284I and 299S, which have been found in every vvIBDV so far characterized, with the two exceptions of an early IBDV strain from Ivory Coast that has not been reisolated since 1988 (Brown et al, 1994;Cao et al, 1998;To et al, 1999;Zierenberg et al, 2000) and of Indonesian strain Tasik94, which differs from typical vvIBDVs by lacking residue 222A (Rudd et al, 2002). However, the 99323 isolate also exhibited three non-silent nt changes, which encoded three aa changes that have not so far been found in any other vvIBDV-like viruses; namely, Y220 0/ F, G254 0/ S and A321 0/ T. These changes occurred in regions that are known to be important for antigenicity: VP2 major hydrophilic peak A (position 220), VP2 first minor hydrophilic peak (position 254) and VP2 second major hydrophilic peak (position 321) (Schnitzler et al, 1993;Vakharia et al, 1994;van den Berg et al, 1996). The significant genetic relationships of isolate 99323 with vvIBDVs were confirmed by the phylogenetic analysis (Figure 2).…”

“…The full length VP2 gene of isolate 99323 was not sequenced, so that the molecular basis for the modified antigenicity of this isolate is not yet known with certainty. However, it is apparent from the partial sequence encoding VP2 variable domain that this isolate exhibits aa changes in three of the hydrophilic regions previously reported to be critical for IBDV antigenicity (Schnitzler et al, 1993;Vakharia et al, 1994;van den Berg et al, 1996;Eterradossi et al, 1998).…”

Sequence Comparison of the VP2 Variable Region of Infectious Bursal Disease Virus Isolates from Vietnam.

“…Previous findings indicate that the molecular basis of antigenic variation between strains is clustered in a variable domain of VP2 which is highly hydrophobic and flanked by two hydrophilic regions, the first hydrophilic region being from amino acids 212 to 224 and the other from 314 to 324 [3,18,25,27]. The first region has been speculated to be responsible for stabilizing the conformation epitope and the second region for recognition by the virus-neutralizing MAbs [10].…”

Molecular Characterization of Infectious Bursal Disease Virus From Commercial Poultry in Pakistan

“…VP2, structural protein has a major virus neutralizing conformational epitopes in hypervariable region [8][9][10]. Antigenicity and virulence of the IBDV has been studied extensively on the genetic basis to control IBD [11][12][13][14].…”