Molecular Characterization of Recently Classified Newcastle Disease Virus Genotype VII.1.1 Isolated from Egypt

Abstract

Newcastle disease virus (NDV) is classified as Avian OrthoAvulavirus-1 (AOAV-1) and is still one of the most important poultry diseases in the world. Collected tissue specimens (trachea, cecal tonsils, and spleen) from 85 chicken flocks (broilers, layers, and native breeds) raised in 5 Egyptian governorates (El-Qalubia, El-Behaira, El-Menofia, El-Gharbia, and Alexandria) in the period between March 2019 to February 2020. The flocks had a history of vaccination against ND and showed clinical signs and lesions of infection. We characterized the isolates molecularly using conventional RT-PCR via amplifying the NDV full Fusion protein gene. The analysis of the full F-gene sequence revealed that our isolates were classified as genotype VII with the characteristic amino acids motif in the fusion protein cleavage site for the velogenic NDV (vNDV) strains. Among the molecularly identified NDV Genotype VII isolates, 5 representative isolates in different 5 Egyptian Governorates were sequenced for full fusion protein gene (sequence). The obtained sequences were submitted on GenBank: MW580389, MW580388, MW580387, MW566177, and MW590306. The five isolates' full-length F protein gene amino acid sequences revealed 99.5% identity with the Reference GenBank NDV/Egypt/ch/MN51/2019 strain isolate. The deduced amino acids sequences' comparative alignment of the five Avian OrthoAvulavirus-1 isolates confirmed the presence of motif of virulent strains (RRQKRF) between 112 and 117 residues of fusion protein cleavage site. All five AOAV-1 isolates from 2019 and 2020 belonged to the NDV genotype classified as genotype VII.1.1 depending on full Fusion gene sequences; those five isolates were grouped with subgenotype VIId. Through significant genetic changes in vNDV observed in our study, continuous monitoring of the multiple vNDV outbreaks in vaccinated chicken and targeted evaluation of the used vaccines.