IBDV particles packaged with only segment A dsRNA

Multi-segmented dsRNA viruses have been suggested to utilize cis-acting elements in the plus-strand RNA to accomplish genomic RNA assortment during viral packaging. It is not clear if bi-segmented dsRNA birnavirus uses the same strategy. By applying a reverse genetic technique, we generated IBDV particles packaged with only segment A by co-transfection DF-1 cells of cDNA from segment A and VP1 (without 5′ and 3′ noncoding region of segment B) supporting random assortment mechanism and indicating the packaging elements of segment B include sequences in the 5′ and 3′ NCR. However, gfp-containing IBDV could not be generated in the presence of gfp cDNA constructs flanked by 5′ and 3′ NCR from segment A or segment B. The data suggest additional packaging signals are required for IBDV genomic packaging. The presence of VP1 protein in the IBDV-A particles also suggests the formation of ribonucleoprotein (RNP) complexes might be involved in the assembly of viral particles.