Genetic Stability of the VP2 Hypervariable Region of Four Infectious Bursal Disease Virus Isolates after Serial Passage in Specific-Pathogen-Free Chicken Embryos

Abstract

Infectious bursal disease virus strains U2, 586, L1, and Q2 were isolated from pooled bursal samples collected from commercially reared broilers. These viruses were propagated in specific-pathogen-free (SPF) embryonated chicken eggs for 24 or 25 passages. Nucleotide sequences of a 743-bp reverse transcription (RT)/polymerase chain reaction (PCR) product containing the VP2 hypervariable region were compared before and after passage of the viruses in embryonated chicken eggs. To determine the genetic stability of the viruses, each isolate was compared with its egg-passed ancestor; virus isolates were not compared with each other. When the restriction enzymes BstNI and MboI were used, no differences were observed in the restriction fragment length polymorphism profiles of the RT/ PCR products after embryo passage. After embryo passage, six nucleotide changes were identified in the viruses. Among the four viruses examined, these nucleotide changes resulted in a total of five amino acid changes. The amino acid changes were S-222-L in virus 586, K-249-N in viruses U2, L1, and Q2, and G-281-V in virus Q2. Three of the five amino acid changes occurred at residue 249. The convergent nature of this residue shift in three of four of the chick embryo-passed viruses suggests the occurrence of a functional, as opposed to random, mutation. The original isolates caused typical signs of infectious bursal disease in 3-wk-old SPF chicks. Their embryo-passed ancestors also produced typical signs of infectious bursal disease in 3-wk-old SPF chicks, suggesting the amino acid mutations observed did not affect virulence of the viruses.

Genotyping of Canadian field strains of infectious bursal disease virus

“…Delaware E-related field IBDVs were identified in 33 samples; they were 98.3% to 100.0% identical to the prototype virus. Thirtyfour field strains showed the highest identity, 94.2% to 98.3%, to US IBDV strain 586 (Smiley & Jackwood, 2001). Five samples that contained vaccine-related viruses were also identified, while the remaining two field strains showed the best match to US Del A (Lana et al, 1992) and Spanish SP_04_02 (Dolz et al, 2005) IBDV strains (Figure 1).…”

“…The vvIBDV virulence is partly determined by its VP1 gene (Boot et al, 2000(Boot et al, , 2005, but vvIBDVs are antigenically similar to classic IBDVs and can be controlled with currently available IBDV vaccines (Tsukamoto et al, 1995;Eterradossi et al, 2004). The vvIBDVs are present in Europe, Asia, Africa and South America, but have not yet been detected in the USA, Canada, Australia and New Zealand (van den Berg et al, 2000).…”

Genetic characterization of South American infectious bursal disease virus reveals the existence of a distinct worldwide-spread genetic lineage

“…NonvvIBDVs are usually associated with less pathogenicity than vvIBDVs (van den Berg, 2000), a feature that is consistent with the absence of notorious clinical manifestations of the Uruguayan and Argentine dIBDVs. Coincidentally, subclinical manifestations were reported for several of the viruses clustered within the dIBDV lineage, suggesting that low pathogenicity is a common feature in this group of viruses (Ikuta et al, 2001;Smiley & Jackwood, 2001). …”

Characterization of the antigenic, immunogenic, and pathogenic variation of infectious bursal disease virus due to propagation in different host systems (bursa, embryo, and cell culture). I. Antigenicity and immunogenicity

“…Although these studies documented that changes in the pathogenicity of IBDV occurred following propagation in different host systems, antigenic and/or immunogenic changes were not described. More recently, it has been reported that small nucleotide changes in IBDV propagated in bursae or embryos induced small amino acid changes on VP 2 , but the pathogenicity of IBDV was very similar regardless of the propagation method (Smiley & Jackwood, 2001). This study used the restriction fragment length polymorphism profiles of the reverse transcriptionpolymerase chain reaction VP 2 products for their analysis.…”

“…The role that different propagation methods have in modifying the pathogenicity of infectious bursal disease virus (IBDV) is widely recognized Becht & Müller, 1991;Ismail & Saif, 1991;Tsai & Saif, 1992;Tanimura et al, 1995;Bayyari et al, 1996a;Hassan & Saif, 1996;Hassan et al, 1996a,b;Takase et al, 1996;Yamaguchi et al, 1996;Chen et al, 1998;Fussell, 1998;Van den Berg et al, 2000;Abdel-Alim & Saif, 2001a,b;Nagarajan et al, 2001;Smiley & Jackwood, 2001). Viruses passaged in birds maintain their pathogenicit y, whereas viruses propagated in embryos may maintain or lose their pathogenicity.…”