Comprehensive analysis of amino acid sequence diversity at the F protein cleavage site of Newcastle disease virus in fusogenic activity

Abstract

Newcastle disease virus (NDV) is a contagious agent of Newcastle disease in avian species and seriously affects the poultry industry. The cleavage site of the viral F protein (Fcs) is a key determinant of membrane fusion and viral virulence. In this study, we investigated the precise effect of variable amino acid sequences of the Fcs on fusogenic activity. Based on viral pathogenicity, the Fcs sequences of natural isolates (n = 1572) are classified into eight types of virulent Fcs (VFcs) with the motif “G/R/K-R-Q/R/K-R/K-R↓F” and ten types of the avirulent Fcs (AFcs) with the motif “G/R/E-R/K/Q-Q-G/E-R↓L”. The VFcs is only found in the Class II cluster of viral classification and not in Class I. The AFcs exists in both Class I and II isolates. The VFc and AFc types present an evolutionary relationship with temporal distribution and host species. Using a fusion assay in vitro, VFcs-1 “RRQKR↓F” and VFcs-2 “RRQRR↓F” show the highest efficiency in triggering membrane fusion. The neutral residue Q at the P3 position of the VFcs plays an enhancing role compared to effect of the basic residues R and K. A single residue K at P3 or P5 is less efficient of the fusogenic activity in the VFcs with all basic residues. Moreover, the cleavage efficiencies of F0 proteins with different types of Fcs motifs do not appear to affect membrane fusion. Our findings offer insight into the effect of amino acid variation of the Fcs on the fusion triggered by NDV.

Emergence of a virulent genotype VIIi of Newcastle disease virus in Iran

“…Viruses of the avian Paramyxovirus serotype 1, synonymous with Newcastle disease virus (NDV), have a broad host range in avian species. They are of high and growing concern in terms of economics (Wang et al, 2017). The aetiologic agent belongs to the genus Avulavirus in the family Paramyxoviridae (Afonso et al, 2016).…”

“…The viral genome is a negative sense, single-stranded RNA, containing six genes in order 3 ′ -NP-P-M-F-HN-L-5 ′ . The genome encodes nucleocapsid (N) protein, phosphoprotein (P), matrix (M) protein, fusion (F) protein, haemagglutinin-neuraminidase (HN) and large polymerase protein (L) (Aldous et al, 2003;Wang et al, 2017). The F and HN proteins are surface glycoproteins and protective antigens of NDV.…”

“…The pathotype can be determined by in vivo pathogenicity tests including mean death time, intracerebral pathogenicity index (ICPI) and intravenous pathogenicity index. Alternatively, the virulence can be evaluated by the analysis of the amino acid sequence of the F0 protein cleavage site (position 112-117) (Kim et al, 2014;Wang et al, 2017). By the sequences of the F gene, NDV strains have been separated into two classes.…”

Molecular characterization of full genome sequences of Newcastle disease viruses circulating among vaccinated chickens in Egypt during 2011–2013

“…Results of the present study indicated continuous circulation of the NDV single sub- Here, 10 representative NDV strains were classified as virulent based on the aa sequence motif 112 R/G/K-R-Q/K-K/R-R-F 117 at the F protein cleavage site [3,41]. The presence of several basic aa residues and the phenylalanine at position 117 were found to be characteristic to highly virulent strains [5].…”

“…According to this approach, virulent strains have the aa sequence motif 112 R/G/K-R-Q/K-K/R-R-F 117 at the F cleavage site. In contrast, the motif in avirulent NDV strains is 112 G-R/K-Q-G-R-L 117 [3,41]. Although all NDV strains belong to a single serotype, significant genetic diversity has been observed among different NDV isolates [7].…”