Molecular characterization of infectious bursal disease virus (IBDV) isolated in Argentina indicates a regional lineage

Abstract

In Argentina, classical vaccines are used to control infectious bursal disease virus (IBDV); however, outbreaks of IBDV are frequently observed. This could be due to failures in the vaccination programs or to the emergence of new strains, which would be able to break through the protection given by vaccines. Hence, genetic characterization of the viruses responsible for the outbreaks that occurred in recent years is crucial for the evaluation of the control programs and the understanding of the epidemiology and evolution of IBDV. In this study, we characterized 51 field samples collected in Argentina (previously identified as IBDV positive) through the analysis of previously identified apomorphic sequences. Phylogenetic analysis of regVP2 showed that 42 samples formed a unique cluster (Argentinean lineage), seven samples were typical classical strains (one of them was a vaccine strain), and two belonged to the very virulent lineage (vvIBDV). Interestingly, when the analysis was performed on the regVP1 sequences, the field samples segregated similarly to regVP2; thus, we observed no evidence of a reassortment event in the Argentinean samples. Amino acid sequence analysis of regVP2 showed a particular pattern of residues in the Argentinean lineage, particularly the presence of T272, P289 and F296, which had not been reported before as signature sequences for any IBDV phenotype. Notably, the residue S254, characteristic of the antigenic variant, was not present in any of the Argentinean samples.

Origin and global spreading of an ancestral lineage of the infectious bursal disease virus

“…The dIBDV markers detected in the hvVP2 region were S222, T272, P289, I290 and F296, which is in accordance with previous observations (Table ) (de Fraga et al, ; Hernández et al, ; Vera et al, ). However, S222 and T272 occurred in some cIBDV vaccine strains and the G7 strains, respectively, and should then be considered less robust markers compared to P289, I290 and F296.…”

Genome Sequence of a Distinct Infectious Bursal Disease Virus

“…Phylogenetic analyses have consistently recovered the clades or lineages corresponding to these strains, including a clade composed of vaccine-like strains and a recently described distinct global lineage ( 4 ). This distinct lineage (dIBDV) is widely distributed in South America ( 4 , 5 ).…”

Development of an RT-qPCR assay for the specific detection of a distinct genetic lineage of the infectious bursal disease virus

“…By analysing the hvVP2 sequences available in the GenBank, we inferred that more than 10% of the IBDV sequences correspond to dIBDVs, suggesting a high frequency of this lineage in the global virus population. Countries such as Argentina, Canada and Uruguay have reported a high prevalence of this lineage circulating in the poultry production, while in countries such as Brazil, Colombia, Hungary, Poland, Puerto Rico, Russia, South Korea and the United States, there are only sporadic reports of dIBDVs (Shcherbakova et al, 1998;Kwon et al, 2000;Ikuta et al, 2001;Jackwood et al, 2001;Smiley & Jackwood, 2001;Domanska et al, 2004;Remorini et al, 2006;Jackwood & Sommer-Wagner, 2007;Ojkic et al, 2007;Hernández et al, 2015;Tomás et al, 2015;Vera et al, 2015). This uneven prevalence among different countries needs to be confirmed by performing more extensive studies with a specific diagnostic method, taking into consideration that dIBDVs can be easily ignored during routine surveillance due to the apparent lack of differential clinical signs (Ikuta et al, 2001;Domanska et al, 2004).…”

“…Most isolates that are now classified as dIBDV were initially considered atypical classic or variant strains that harboured unique nucleotide and amino acid changes as a consequence of local differentiation (Kwon et al, 2000;Ikuta et al, 2001;Domanska et al, 2004;Remorini et al, 2006;Jackwood & Sommer-Wagner, 2007;Ojkic et al, 2007). Some dIBDV isolates have exhibited mild clinical signs and antigenic differences (Ikuta et al, 2001;Domanska et al, 2004;Vera et al, 2015) but further phenotypic studies are needed to understand the epidemiological and sanitary relevance of this lineage that contains part of the genetic variability of the virus (Hernández et al, 2015).…”