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

Abstract

Infectious Bursal Disease Virus (IBDV) is one of the most concerning sanitary problems to the world poultry production. IBDV comprises four well-defined evolutionary lineages known as classic (cIBDV), classic virulent (cvIBDV), variant (vaIBDV) and hypervirulent (vvIBDV) strains. In the present study, we characterized IBDV samples in Argentina and Uruguay by sequencing the coding region of the hypervariable domain of the capsid protein VP2. Samples belonging to three strains (cIBDV, vvIBDV, and cvIBDV) were unambiguously classified by the presence of molecular markers and phylogenetic analysis. Notably, a high proportion of samples (60 %) could not be accurately assign to any of the previously described strains, and were then denoted as novel IBDV (nIBDV). These Uruguayan and Argentine nIBDVs constitute an independent evolutionary lineage that also includes viruses from others countries of America and Asia. The hypervariable VP2 sequence of these nIBDVs shares amino acids markers with other IBDV strains, but has a unique and conserved molecular signature (272T, 289P, 290I and 296F) that may be considered a diagnostic character for classification. A discriminant analysis of principal components (DAPC) also identified the nIBDVs as a cluster of genetically related viruses separated from the typical IBDV strains. DAPC and genetic distance estimation indicated that the nIBDV is one of the most genetically divergent lineages of IBDV. Together, the present study suggests that the highly divergent nIBDV lineage is a previously undescribed IBDV group that is widely circulating in the world poultry production. Further studies using antigenic, pathogenic, epidemiologic, and additional genetic studies are needed to completely characterize this lineage and determine if it should be considered alongside conventional IBDV strains.