Newcastle disease virus: current status and our understanding

Abstract

Newcastle disease (ND) is one of the highly pathogenic viral diseases of avian species. ND is economically significant because of the huge mortality and morbidity associated with it. The disease is endemic in many third world countries where agriculture serves as the primary source of national income. Newcastle disease virus (NDV) belongs to the family Paramyxoviridae and is well characterized member among the avian paramyxovirus serotypes. In recent years, NDV has lured the virologists not only because of its pathogenic potential, but also for its oncolytic activity and its use as a vaccine vector for both humans and animals. The NDV based recombinant vaccine offers a pertinent choice for the construction of live attenuated vaccine due to its modular nature of transcription, minimum recombination frequency, and lack of DNA phase during replication. Our current understanding about the NDV biology is expanding rapidly because of the availability of modern molecular biology tools and high-throughput complete genome sequencing.

Keywords: Newcastle disease virus; Paramyxovirus; Pathogenicity; Reverse genetics system.

Fig. 1

The global scenario of Newcastle disease virus (NDV) outbreaks in different parts of the world.

Fig. 2

Phylogenetic analysis of Newcastle disease virus (NDV) isolated from different countries. The accession numbers against which the tree is build are as follows: GU978777, JX524203, EF065682, GU187941, FJ794269, GQ288383, FJ939313, HM117720, AY562988, JX119193, JN800306, AY562989, GU187941, AY741404, GQ918280, and AY562985.

Fig. 3

Schematic diagram of Newcastle disease virus structure.

Fig. 4

Schematic representation of Newcastle disease virus genome highlighting the rule of six essentially means that a nucleocapsid protein can bind effectively to six nucleotides. The area between the genes shown in black represents Inter Genomic Sequences that vary in size from 1 to 47 nucleotides.

Fig. 5

Phenomenon of RNA editing in Newcastle disease virus. Incorporation of single G or two G residues at the RNA editing site could give rise to V or W, respectively.

Fig. 6

Schematic representation of Newcastle disease virus replication. Entry of the virus into the host cell system is mediated by the interaction of glycoproteins (F, HN) on viral surface and binding to sialic acid-containing compounds such as gangliosides and N-glycoproteins receptors on cell surface, resulting in fusion of the virus to host cells. The viral nucleocapsid is then pushed into the host cytoplasm where the negative sense viral RNA is transcribed to produce the structural mRNAs, with the help of virus associated RNA dependent RNA polymerase in a gradient fashion. The respective proteins are translated and folded using host cell machinery. Once a threshold of the first transcribed N mRNA is reached, the negative sense genomic RNA is converted to positive sense anti-genome template for the synthesis of new negative sense RNA genome. This newly formed genomic RNA is then wrapped in N, P and L proteins to form the nucleocapsid that is assembled with matrix and surface glycoproteins and released from the host cell.