Identification of Newcastle disease virus P-gene editing using next-generation sequencing.

Avian paramyxoviruses 1 has the ability to edit its P gene to generate three amino-coterminal proteins (P, V and W), but its kinetic change is unclear. In this study, next-generation sequencing (NGS) was used to analyze the P-gene editing of Newcastle disease virus (NDV). Transcriptome analysis of chicken embryonic tissues and bursa of fabricius showed the P-gene editing frequencies were 45.46-52.70%. To investigate the rules of P-gene editing along time, the ratio of PVW was determined by PCR based deep sequencing at multiple time points in cells infected with velogenic and lentogenic strain respectively. The results confirmed similar editing frequencies with transcriptome data and the PVW ratios were stable along time among different NDVs, but had a greater V-gene transcript on velogenic strain infection (P<0.001), which were different from previous reports. Also, it was shown that the number of inserted G residues in P-derived transcripts was not limited to +9G, and +10G transcripts were identified. These results confirmed the NDV P-gene editing frequencies and provided a novel point of view on NDV P-gene editing with NDV virulence.

Newcastle disease virus selectively infects dividing cells and promotes viral proliferation.

Newcastle disease virus (NDV) can select cells to infect, but the mechanism of its cell selectivity has not been comprehensively investigated. Here, we use HeLa cells to establish that NDV can selectively infect cells at the single-cell level. We labeled proliferating cells with 5'-bromo-2-deoxyuridine (BrdU) and examined the colocalization of BrdU with NDV in cells to clarify the relationships between NDV infection and cell proliferation. Receptors at the plasma membrane mediate NDV entry into host cells. We labeled sialic acid receptor isoforms, compared their densities between different cell types and measured the sialic acid receptor densities in different cell phases. Our results suggest that NDV displays host tropism to HeLa cells compared to BHK cells and that the differences in the receptor isoform expression patterns between cell types contribute to the selection of HeLa by NDV. At the single-cell level, the dynamics of receptor expression changes during different cell phases contributing to the selection of cells in S/G2 phase for NDV infection. Furthermore, cell proliferation benefits viral replication, and enhanced virus replication leads to increased damage to cells. The elucidation of the mechanisms underlying host cell selection by NDV may help in the screening and characterizing of additional candidate oncolytic virus strains.

Newcastle disease virus V protein inhibits apoptosis in DF-1 cells by downregulating TXNL1.

Many viral proteins are related to suppressing apoptosis in target cells and are hence beneficial to viral replication. The V protein of Newcastle disease virus (NDV) is one such protein that plays an important role in inhibiting apoptosis in a species-specific manner. However, to date, there have been no reports clarifying the antiapoptotic mechanisms of the V protein. The present study was undertaken to determine the apoptotic potential of the V protein in a chicken embryo fibroblast cell line (DF-1 cell) and to elucidate its molecular mechanisms of action. Here, a yeast two-hybrid system was used to screen the host proteins that interact with the V protein and identified thioredoxin-like protein 1 (TXNL1) as a potential binding partner. Immuno-colocalization of V protein and TXNL1 protein in DF-1 cells further verified the interaction of the two proteins. Through the overexpression of TXNL1 protein and knockdown of TXNL1 protein in DF-1 cells, the effects of NDV replication and cell apoptosis were examined. Cell apoptosis was detected by flow cytometry. The mRNA and protein expression levels of Bax, Bcl-2 and Caspase-3 were detected by quantitative real-time PCR (Q-PCR) and Western blotting. NDV expression was detected by Q-PCR and plaque assay. The results revealed that the TXNL1 protein induced apoptosis and inhibited NDV replication in DF-1 cells. Furthermore, the Western blot and Q-PCR results suggested that TXNL1 induced cell apoptosis through a pathway involving Bcl-2\Bax and Caspase-3. Finally, this work provides insight into the mechanism by which the V protein inhibits apoptosis.