Complete nucleotide sequences of avian metapneumovirus subtype B genome.

Complete nucleotide sequences were determined for subtype B avian metapneumovirus (aMPV), the attenuated vaccine strain VCO3/50 and its parental pathogenic strain VCO3/60616. The genomes of both strains comprised 13,508 nucleotides (nt), with a 42-nt leader at the 3'-end and a 46-nt trailer at the 5'-end. The genome contains eight genes in the order 3'-N-P-M-F-M2-SH-G-L-5', which is the same order shown in the other metapneumoviruses. The genes are flanked on either side by conserved transcriptional start and stop signals and have intergenic sequences varying in length from 1 to 88 nt. Comparison of nt and predicted amino acid (aa) sequences of VCO3/60616 with those of other metapneumoviruses revealed higher homology with aMPV subtype A virus than with other metapneumoviruses. A total of 18 nt and 10 deduced aa differences were seen between the strains, and one or a combination of several differences could be associated with attenuation of VCO3/50.