Antigenic epitope characterization of matrix protein of Newcastle disease virus using monoclonal antibody approach: contrasting variability amongst NDV strains

Identification of Two Distinct Linear B Cell Epitopes of the Matrix Protein of the Newcastle Disease Virus Vaccine Strain LaSota

Matrix (M) protein of Newcastle disease virus (NDV) is an abundant protein that can induce a robust humoral immune response. However, its antigenic epitopes remain unknown. In this study, we used a pepscan approach to map linear B cell immunodominant epitopes (IDEs) of M protein with NDV-specific chicken antisera. The six epitopes with the highest reactivity by peptide scanning were obtained as IDE candidates. Among them, aa71-85 and aa349-363 were identified by immunological assays with NDV-specific or IDE-specific antisera. The minimal antigenic epitopes of the two IDEs were further characterized as ⁷⁷MIDDKP⁸² and ³⁵⁴HTLAKYNPFK³⁶³. Moreover, an amino acid sequence alignment and immunoblot analysis revealed the conservation of the two IDEs in the M protein of strains of different genotypes. These two IDEs of M protein could be genetically eliminated as negative markers in recombinant NDV for serologically differential diagnosis in the development of marker vaccines.

Application of green fluorescent protein-labeled assay for the study of subcellular localization of Newcastle disease virus matrix protein

Green fluorescent protein (GFP) used as a powerful marker of gene expression in vivo has so far been applied widely in studying the localizations and functions of protein in living cells. In this study, GFP-labeled assay was used to investigate the subcellular localization of matrix (M) protein of different virulence and genotype Newcastle disease virus (NDV) strains. The M protein of ten NDV strains fused with GFP (GFP-M) all showed nuclear-and-nucleolar localization throughout transfection, whereas that of the other two strains were observed in the nucleus and nucleolus early in transfection but in the cytoplasm late in transfection. In addition, mutations to the previously defined nuclear localization signal in the GFP-M fusion protein were studied as well. Single changes at positions 262 and 263 did not affect nuclear localization of M, while changing both of these arginine residues to asparagine caused re-localization of M mainly to the cytoplasm. The GFP-M was validated as a suitable system for studying the subcellular localization of M protein and could be used to assist us in further identifying the signal sequences responsible for the nucleolar localization and cytoplasmic localization of M protein.

Heterologous expression, characterization and evaluation of the matrix protein from Newcastle disease virus as a target for antiviral therapies

Newcastle disease virus (NDV) is an infectious agent of a large variety of birds, including chicken, which poses a real threat to the agriculture industry. Matrix (M) proteins of NDV and many other viruses perform critical functions during viral assembly and budding from the host cell. M-proteins are well conserved and therefore are potential targets for antiviral therapies. To validate this, we expressed the NDV M-protein in its native form in Saccharomyces cerevisiae and in inclusion bodies in Escherichia coli. Proper refolding of the recombinant protein produced in E. coli was verified using circular dichroism and infrared spectroscopies and electron microscopy. Immunization of chickens with the NDV M-protein elicited significant serum antibody titers. However, the antibodies conferred little protection against the ND following lethal viral challenges. We conclude that the M-protein is not exposed on the surface of the host cell or the virus at any stage during its life cycle. We discuss how the conserved M-protein can further be exploited as an antiviral drug target.

Inhibition of Newcastle disease virus replication by RNA interference targeting the matrix protein gene in chicken embryo fibroblasts

Newcastle disease (ND) is an infectious viral disease of birds caused by the Newcastle disease virus (NDV), also known as avian paramyxovirus type 1 (AMPV-1), which leads to severe economic losses in the poultry industry worldwide. In this study, the application of RNA interference (RNAi) for inhibiting the replication of NDV in cell culture by targeting the viral matrix protein gene (M) is described. Two M-specific shRNA-expressing plasmid constructs, named pS(M641) and pS(M827), were evaluated for antiviral activity against the NDV strain NA-1 by cytopathic effects (CPE), virus titration and real-time RT-PCR. After 36h of infection, both pS(M641) and pS(M827) reduced virus titers by 79.4- and 31.6-fold, respectively, and they down-regulated mRNA expression levels of the matrix protein gene M by 94.6% and 84.8%, respectively, in chicken embryo fibroblast (CEF) cells, while only pS(M641) significantly decreased CPE, compared to the control group. These results indicated that the M gene 641 and 827 sites represent potential antiviral therapy targets, and RNAi targeting of the M gene could not only represent an effective treatment in Newcastle disease but also aid as a method for studying the replication of NDV.

Molecular characterisation of three avian paramyxovirus type 1 isolated from pigeons in France

Three avian Paramyxovirus type 1 (aPMV-1) isolated from pigeons duringpigeon paramyxovirosis outbreaks were molecularly characterised by sequencing parts of the six genes (NP, P, M, F, HN and L) of each strain. Virulent 99143 isolate was found to be very closely related to non-pathogenic vaccine strains of aPMV-1, even for its F protein cleavage site motif. Strains 99299 and 99106, typical pigeon paramyxovirus type 1 (pPMV-1) variants, exhibited between 10% and 20% difference with aPMV-1 at the nucleotide level. The aPMV-1 specific pattern of eight amino acids in the intracellular domain of HN protein was found different by one residue for these two isolates, and might represent a specific pattern for pPMV-1. The unique sequence of the polycistronic P gene editing site of 99299 and 99106 was characterised by four instead of three cytosine residues, and might so have an influence on the expression level of the three proteins encoded by P. This work is also the first to provide molecular data on NP, P and L genes of typical pPMV-1.

Development of a RT-nested PCR test detecting pigeon Paramyxovirus-1 directly from organs of infected animals

A RT-nested PCR that amplifies part of the conserved nucleoprotein gene of avian Paramyxovirus type 1 is described. The technique allowed the detection of pigeon Paramyxovirus type 1 (pPMV-1) virus directly from a wide range of infected chicken and pigeon organs, and should be able to detect typical Newcastle disease viruses too. Compared with the reference method, the developed RT-nested PCR was found more sensitive, as it was able to detect virus genome in infected pigeon organs at late stage of infection, when virus isolation failed. Such a molecular technique represents an alternative method of diagnosis for research purposes on pPMV-1 variants, for example to study pathogenesis aspects of the infection or to assess the efficacy of vaccines.

Antigenic heterogeneity amongst the field isolates of Newcastle Disease Virus (NDV) in relation to the vaccine strain. Part II: studies on viruses isolated from domestic birds in Israel

Forty three Newcastle disease virus (NDV) strains isolated before and during 1997 in Israel from domestic birds were studied by means of the three panels of monoclonal antibodies prepared against all the viral envelope proteins in order to reveal the possible antigenic differences between them and the VH strain used in Israel for poultry vaccination. Three isolates were found to have significant antigenic differences in the hemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins as compared to the vaccine strain. As to the matrix protein, almost all the viruses isolated during the year 1997 were found to have considerable differences from the vaccine strain in two of four antigenic sites.

Antigenic heterogeneity among the field isolates of Newcastle disease virus (NDV) in relation to the vaccine strain: 1. Studies on viruses isolated from wild birds in Israel

In order to reveal the viruses strongly differing from the VH NDV strain used in Israel for poultry vaccination, 54 NDV strains isolated during the last 15 years in Israel from feral birds were studied by means of the panels of 39 monoclonal antibodies. Six isolates were found to have considerable antigenic differences in envelope proteins as compared to the vaccine strain. In four cases, the differences were related mostly to the hemagglutinin-neuraminidase glycoprotein, in one case to the fusion glycoprotein, and in one case to the matrix protein.

Molecular evolution of the Newcastle disease virus matrix protein gene and phylogenetic relationships among the paramyxoviridae

Matrix (M) gene sequences for recent field isolates and older reference Newcastle disease viruses (NDV) were examined to determine phylogenetic relationships and population trends among these viruses. Overall, the M gene has a majority of synonymous nucleotide sequence substitutions occurring among NDV isolates. However, several predicted amino acid changes in the M protein of specific NDV isolates have occurred that correlate to phylogenetic relationships. Nucleotide substitutions in these codons have a greater number of nonsynonymous base changes. The NDV isolates arising since the 1970s belong to a population of viruses that expanded worldwide at an exponential rate. These viruses may have their origins in free-living birds, are present worldwide, and continue to circulate causing disease in poultry. A specific NDV lineage composed of virulent isolates obtained in the US prior to 1970 appears to no longer exists among free-living birds or commercial poultry. However, "vaccine-like" viruses are common in the US and continue to circulate among commercial poultry. Based on M protein amino acid sequences, NDV separates as a clade most closely related to morbilliviruses and not with their current designated category, the rubulaviruses among the Paramyxoviridae. Consequently, avian paramyxoviruses should have their own taxonomic subfamily among the Paramyxovirinae.

Comparative characteristics of the Israeli Newcastle disease virus field strains by means of a wide panel of monoclonal antibodies against hemagglutinin-neuraminidase glycoprotein

Fourteen mouse monoclonal antibodies (MAB) were tested for their ability to react with 15 reference and 52 local Newcastle disease virus (NDV) strains isolated in Israel during the last decade from feral birds. All the field isolates had no antigenic difference when examined by classic serological tests. However, MAB-mediated analysis revealed wide antigenic heterogeneity amongst the studied viruses. By the pattern of the MAB reactivity, all the isolates could be distributed into 13 groups.

Mixed paramyxovirus infection of wild and domestic birds in Israel

Five cases of dual isolations of different serotypes of avian paramyxoviruses (APMV) from domestic and wild birds are described: one case of mixed infection by APMV-1 and APMV-4 and four cases of infection by APMV-1 and APMV-2 serotypes. The double infection was proven by consecutive isolations of two viruses from allantoic fluid samples derived from single swabs after their respective treatment by antisera against each suspected virus. The finding of double APMV infection in poultry farms appears to be important for epizootiology and pathogenesis of APMV-caused diseases.