Coding‐complete genome sequencing suggests that Newcastle disease virus challenge strain Herts’33 (IVMP) may represent a distinct genotype Enikő Fehér1 · Ádám Bálint2 · Szilvia Marton1 · Krisztina Bali1 · Sándor Belák3 · Krisztián Bányai1

We determined the genomic sequence of a Newcastle disease virus (NDV) line obtained directly from the first NDV isolate, named Herts’33. This strain shared ≤ 90% nucleotide sequence identity with the NDV sequences available in the GenBank database, and formed a distinct branch in a phylogenetic tree. This branch may be considered to represent a separate NDV genotype. Our study indicates that investigation of the genomic sequences of old NDV strains that originated from the early outbreaks of Newcastle disease may alter the phylogenetic grouping of the NDV strains and provide data on the evolution of viral genomes over time. Newcastle disease virus (NDV) (species Avian orthoavulavirus 1) belongs to the genus Orthoavulavirus, family Paramyxoviridae, order Mononegavirales. The enveloped virion has a single-stranded, negative-sense RNA genome with a length of ~ 15.2 kb [1, 2]. The viral genome is composed of six genes in the following order: 3’-NP-P-M-F-HN-L-5’ (letters designate the nucleoprotein (NP), the phosphoprotein (P), the matrix protein (M), the fusion protein (F), the hemagglutinin-neuraminidase (HN) and the RNA polymerase (L). Based on a number of criteria, the most recent genetic characterization classifies strains belonging to the species Avian orthoavulavirus 1 into genotypes I to XXI and numerous subgenotypes within a subset of genotypes [1]. NDV infection may affect a wide range of wild and domestic avian species, causing serious losses during the epizootics [2]. The disease is controlled by vaccination of poultry, typically using live attenuated strains [2, 3]. For example, the viscerotropic Herts’33 strain was originally isolated from a field sample after an outbreak in 1933 in Hertfordshire (UK) and subsequently became an important strain for control and prevention of Newcastle disease (ND). The mesogenic H vaccine line was considered a derivate of the Herts’33 field strain and used as a potent live, attenuated vaccine on multiple continents, including Europe [4]. In addition, descendants of the original velogenic Herts’33 strain have been commonly used as challenge strains for testing ND vaccine efficacy. With the introduction of molecular characterization methods, it has become possible to compare the genetic features of different descendants of Herts’33 and to analyze the homogeneities and differences in their genomes. In a 2003 paper, Czeglédi et al. [4] revealed that the descendant lines of Herts’33, including the vaccine strain H, differed in their F protein gene coding sequences, and three genetic groups were identified by phylogenetic analysis. It was hypothesized that the phylogenetic lineage that includes the Weybridge-origin Herts’33 strain might be a descendant of the isolate from the first ND case, while the Herts’33 lines that clustered phylogenetically with genotype IV sequences were of unknown origin. Interestingly, the vaccine strain H clustered with genotype III strains, including other vaccine strains (e.g., Mukteswar) [4]. Handling Editor: Bert K. Rima. * Krisztián Bányai bkrota@hotmail.com 1 Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Hungária krt. 21, Budapest 1143, Hungary 2 Veterinary Diagnostic Directorate, National Food Chain Safety Office, Budapest, Hungary 3 Department of Biomedical Sciences and Veterinary Public Health (BVF), The OIE Collaborating Centre for the Biotechnology-Based Diagnosis of Infectious Diseases in Veterinary Medicine, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden