Detection and differentiation of Newcastle disease virus (avian paramyxovirus type 1)

Abstract

Substantial variation in the virulence of Newcastle disease virus (NDV) isolates means that the detection of NDV or evidence of infection is insufficient for an adequate diagnosis, as control measures for avirulent viruses are very different to those for virulent viruses. Diagnosis therefore requires further characterization, at least as to whether an isolate is virulent or avirulent. Conventional detection and differentiation of ND viruses is perceived as slow, laborious and requiring an undesirable use of in vivo techniques. In addition, further characterization is needed to give greater information on origin and spread. This review concentrates on the application of monoclonal antibody and molecular biological approaches. Panels of monoclonal antibodies were a major advance for the characterization of NDV isolates, although confirmation of virulence for poultry still required in vivo testing. As molecular-based techniques become easier and more reliable, they are likely to supersede the use of monoclonal antibodies, especially for characterizing viruses for epidemiological purposes. The attraction of molecular-based techniques is that they may be able to cover all three aspects of Newcastle disease diagnosis (detection of virus, characterization, including inference of virulence, and epidemiology) quickly, accurately and definitively in a single test. A number of approaches based on the reverse transcriptase polymerase chain reaction have been developed, with subsequent analysis of the product by restriction enzyme analysis, probe hybridization and nucleotide sequencing. Although extensive variation among NDVs still poses technical problems, the real and potential advantages of a molecular biological approach to Newcastle disease diagnosis appear to be overwhelming.

A Y527A mutation in the fusion protein of Newcastle disease virus strain LaSota leads to a hyperfusogenic virus with increased replication and immunogenicity

“…The NDV F protein is a trimer, and it is synthesized as an inactive precursor, F 0 (66 kDa), which is post-translationally cleaved by host cell proteases into two disulfidelinked subunits, N-terminal F 2 (12.5 kDa) and C-terminal F 1 (55 kDa). The ability of the F protein to be cleaved by proteases is a major determinant of virulence in NDV and a prerequisite for virus entry and cell-to-cell fusion (Aldous & Alexander, 2001).…”

“…NDV isolates are categorized into three pathotypes -lentogenic (low virulence), mesogenic (intermediate virulence) and velogenic (high virulence) -based on their pathogenicity in chickens (Aldous & Alexander, 2001). Several lentogenic strains, such as LaSota and B1, are being used as live vaccines all over the world.…”

Analysis of the Fusion Protein Cleavage Site of Newcastle disease virus Isolates from India Reveals Preliminary Evidence for the Existence of II, VI and VII Genotypes

“…The key contributor to APMV-1 pathogenicity is the formation of an active fusion protein (F) upon cleavage of the F protein precursor (F o ) [33,35] as well as the number of basic amino acid residues in the fusion protein cleavage site (FPCS) [12,39]. The FPCS sequence has not only been utilized to pathotype the isolates into lentogenic, mesogenic or velogenic [1,10,36] but also to group the APMV-1 that are circulating worldwide into class I (with nine genotypes) and class II (with eleven genotypes) [11]. The class I viruses are distributed worldwide in wild birds and generally avirulent to chickens [19] have been isolated from live bird market samples [19,20].…”

Pathotypic characterization of the Newcastle disease virus isolated from commercial poultry in northwest Iran

“…The velogenic and mesogenic strains have been identified as the causative agent in ND outbreaks in many countries. The lentogenic strains have been used as live vaccines to control the disease; however, outbreaks of ND have been consistently reported in vaccinated poultry (9).…”