Complete genome sequences of avian paramyxovirus serotype 2 (APMV-2) strains Bangor, England and Kenya: Evidence for the existence of subgroups within serotype 2

The complete consensus genome sequences of avian paramyxovirus (APMV) serotype 2 strains Bangor, England and Kenya were determined and compared with those of APMV-2 prototype strain Yucaipa and other paramyxoviruses. The genome lengths of APMV-2 strains Bangor, England and Kenya are 15,024, 14,904, 14,916 nucleotides (nt), respectively, compared to 14,904 nt for Yucaipa. Each genome consists of six non-overlapping genes in the order of 3′N-P/V/W-M-F-HN-L5′, with a 55-nt leader at the 3′ end. The length of the trailer at the 5′ end of strain Bangor was 173 nt, compared to 154 nt for strains England, Kenya, and Yucaipa. In general, sequence comparison of APMV-2 strains England and Kenya with strain Yucaipa have 94.5 and 88% nt and 96 and 92% aggregate amino acid (aa) identity, respectively. In contrast, strain Bangor has a much lower percent nt identity (70.4, 69.4, and 70.8%) and aa identity (75.3, 76.2, and 76.3%) with strains Yucaipa, England, and Kenya, respectively. Furthermore, strain Bangor has a single basic aa residue (101TLPSAR↓F108) at the fusion protein cleavage site compared to the dibasic aa (93DKPASR↓F100) found in those of other three strains. Reciprocal cross-hemagglutination inhibition (HI) and cross-neutralization assays using post-infection chicken sera indicated that strain Bangor is antigenically related to the other APMV-2 strains, but with a 4- to 8-fold difference in homologous versus heterologous HI titer. These differences in antigenic relatedness suggest that these four APMV-2 strains represent a single serotype with two antigenic subgroups, and this is strongly supported by the dimorphism in nt and aa sequence identity.