Virulence in Newcastle disease virus: A genotyping and molecular evolution spectrum perspective

In our research, the molecular evolutions of NDV F and HN genes were analyzed. The phylogenetic analyses of NDV sequences indicated that NDV could be divided into two genotypes: Class I (lentogenic strains) and Class II (velogenic or mesogenic strains). Each genotype possesses high gene homology. Furthermore, the selected pressure analysis showed that the dN/dS of velogenic, mesogenic NDV strains F gene was significantly high and the ω(dN/dS) is 1.1725 > 1. These results imply that mutations in velogenic, mesogenic NDV F gene are favored by positive natural selection and it has acted to diversify NDV virulence at the nucleotide and amino acid level. We estimated that the subsequent rapid adaptation of the Newcastle disease virus to chickens were likely dependent on a high rate of mutation and the positive selection of mutations in the major F gene.