Genetic and Antigenic Characterization of Infectious Bursal Disease Viruses Isolated in Italy During the Period 2002–2005

• Published in: Avian diseases 2007-12, Vol.51 (4), p.863-872
• Main Authors: Martin, Ana Moreno, Fallacara, Francesca, Barbieri, Ilaria, Tosi, Giovanni, Rivallan, Gaelle, Eterradossi, Nicolas, Ceruti, Raffaella, Cordioli, Paolo
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Animals; antigenic characterization; antigenic variation; Antigens, Viral - genetics; Birnaviridae Infections - epidemiology; Birnaviridae Infections - veterinary; Birnaviridae Infections - virology; Chickens; Enzyme-Linked Immunosorbent Assay; epidemiological studies; Epidemiology; genetic variation; genome; genotype; infectious bursal disease; Infectious bursal disease virus; Infectious bursal disease virus - genetics; Infectious diseases; Italy; Italy - epidemiology; Livestock industries; longitudinal studies; Medical genetics; molecular epidemiology; Molecular Sequence Data; monoclonal antibodies; Neutralization Tests; nucleotide and amino acid sequence analysis; nucleotide sequences; pathogenicity; pathotypes; Phylogeny; Poultry Diseases - epidemiology; Poultry Diseases - virology; Regular s; reverse transcriptase polymerase chain reaction; serotypes; strains; Time Factors; Transcriptional regulatory elements; Vaccination; Viral diseases; Viral Structural Proteins - chemistry; Viral Structural Proteins - genetics; Viruses; VP2 hypervariable region
• ISSN: 0005-2086; 1938-4351
• DOI: 10.1637/7904-020107-REGR.1

During the period 2002–2005, 109 infectious bursal disease virus (IBDV) field strains were isolated from bird flocks located in various parts of Italy. Out of these strains, 91 were isolated from broilers, 12 from pullets, and six from backyard flocks. Forty-two IBDV strains were further investigated and characterized on the basis of the geographical origin, source, and clinical signs. Antigenic and genetic characterizations were carried out using a monoclonal antibody (MAb)–based antigen-capture (AC) enzyme-linked immunosorbent assay (ELISA) or a virus neutralization assay and a reverse transcription, amplification, and direct sequencing of a genome fragment encoding the VP2 variable domain. The viruses were compared with reference IBDV strains, F52/70 (classical, 1970), 89163 (typical very virulent [vv]IBDV, 1989), 91168 (antigenically modified vvIBDV, 1991) and 94432 (antigenically modified vvIBDV, 1994) among others. All 42 strains were genetically characterized, and the comparison of their nucleotide sequences revealed the presence of six clusters having 100% identity, named group 1, 2, 3, 4, 5, and 6. Twelve strains, representative of each molecular group and/or with interesting amino acid sequence, were also antigenically characterized. The antigenic characterization showed six strains—151573, 157185 (group1), 192294 (group 2), 77882 (group 3), 217 (group 4), and 192304—with the profile typical of vvIBDV (lack of binding of MAbs 3 and 4). Two strains, 77165 and 204875 (group 6), were also related to vvIBDV but did not react with MAb 5. Three isolates exhibited a profile of cell culture–adapted viruses and classical strains but with some differences: strain 157776 reacted with all MAbs; strain 168026 with all MAbs except MAb 4, which weakly neutralized it; and strain 72293 with all MAbs except MAb 9, which is rather unusual. The last strain, 213622, showed a very uncommon antigenic profile with missing or reduced binding of MAbs 3, 4, 5, 6, 8, and 9. Genetic characterization revealed 37 strains identified as vvIBDV viruses divided in 26 isolates (including groups 1, 2, 3, and 4) with the four amino acids residues typical of vvIBDV (222A, 256I, 294I, 299S) and 11 isolates (including groups 5, 6, and 213622) with some other amino acid exchanges. Four isolates (72293, 168026, 196783, and 222220) presented an amino acid sequence closely related to attenuated classical viruses whereas the last isolate (157776) exhibited a rather different sequence with so