Identification of novel Newcastle disease virus sub-genotype VII-(j) based on the fusion protein.

Newcastle disease virus (NDV) is believed to be the cause of fatal poultry disease worldwide. The fusion (F) protein plays a key role in virus pathogenesis, and it is also used for Newcastle disease virus classification. In this study, we determined the complete coding sequence of the F gene in new velogenic NDV isolates with an intravenous pathogenicity index (IVPI) of 1.8 and a mean death time (MDT) of 72 or 48 h. Complete sequences of the F genes of new Iranian isolates were amplified and sequenced in both directions. These isolates were compared to 195 nucleotide sequences from GenBank (available as of 07/17/2016). A phylogenetic tree was constructed for the F gene, using MEGA6 software with statistical analysis based on 500 bootstrap replicates. Evolutionary distances revealed that the new virulent isolates from Iran belonged to genotype VII in a new distinct sub-genotype named VII-(j). This new sub-genotype showed 3% divergence from genotype VIId. Recombination analysis showed that these new isolates were not recombinant NDVs.