Matrix protein gene sequence analysis of avian paramyxovirus 1 isolates obtained from pigeons

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.

A single R36Q mutation in the matrix protein of pigeon paramyxovirus type 1 reduces virus replication and shedding in pigeons

Pigeon paramyxovirus type 1 (PPMV-1) is considered an antigenic and variant of avian paramyxovirus type 1 (APMV-1) that has adapted to pigeons as hosts. However, how this host-specific adaption of PPMV-1 is related to its biological characteristics is unknown. In this study, seven unique amino acids in PPMV-1 that are not present in other APMV-1 strains (n = 39 versus n = 106) were identified. R36 of the M protein was found to be not only a unique amino acid but also a positive-selection site. To investigate the role of R36 in host adaptation, a recombinant PPMV-1 with R36Q mutation was constructed. Our results indicated that the an R36Q mutation significantly attenuates pathogenicity in chickens, viral growth in both chicken embryo fibroblasts (CEFs) and pigeon embryo fibroblasts (PEFs), and virus replication and shedding in pigeons in comparison with the wild-type virus, suggesting that R36 is a key residue that evolved during the adaptation of PPMV-1 in pigeons.

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.

Phylogenetic analysis and comparison of eight strains of pigeon paramyxovirus type 1 (PPMV-1) isolated in China between 2010 and 2012

Eight strains of pigeon paramyxovirus type 1 (PPMV-1) were isolated and identified in this study, from diseased pigeon flocks suspected to be infected with PPMV-1 in China between 2010 and 2012. These PPMV-1 isolates were purified using specific-pathogen-free (SPF) chicken embryo cells before full-length genomic sequencing. The complete genome of these isolates contained 15,192 nucleotides, similar to those of Newcastle disease virus (NDV) strains in genotypes V-XI, with the gene order 3'-NP-P-M-F-HN-L-5'. A six-nucleotide insertion was found to be located in the 5' non-coding region of the nucleoprotein gene in our eight PPMV-1 strains when compared with those of genotypes I, II, III, IV and V. The cleavage site of the fusion protein was (112)RRQKRF(117), a feature generally associated with virulent NDV strains. The structural proteins were in accordance with those of other PPMV-1 strains, with the exception of the W protein of pigeon/CHINA/LJL/100605. The length of the W protein was 227 amino acids, in common with PPMV-1 strains, whereas that of pigeon/CHINA/LJL/100605 was only 181 amino acids. Phylogenetic analysis, based on the genomic sequences and sequences of the fusion gene, revealed that our eight isolates should be classified as class II genotype VIb NDVs. To our knowledge, this is the first report to show that the strain pigeon/CHINA/LLN/110713 is similar to strains isolated abroad, but it was isolated in China, which implies that it may have been introduced to China from overseas. Differences between the Chinese and foreign strains were identified in three regions (nucleotide positions 1632-2229, 3023-3310 and 6103-6439). In addition, the values of ICPI and MDT demonstrated that PPMV-1 isolates were mesogenic or lentogenic, and virulence studies showed that these PPMV-1 strains were non-pathogenic in chickens, but they induced the generation of antibodies in vivo.

Genotypic and pathotypic characterization of Newcastle disease viruses from India

Newcastle disease virus (NDV) is an avian paramyxovirus that causes significant economic losses to the poultry industry in most parts of the world. The susceptibility of a wide variety of avian species coupled with synanthropic bird reservoirs has contributed to the vast genomic diversity of this virus as well as diagnostic failures. Since the first panzootic in 1926, Newcastle disease (ND) became enzootic in India with recurrent outbreaks in multiple avian species. The genetic characteristics of circulating strains in India, however, are largely unknown. To understand the nature of NDV genotypes in India, we characterized two representative strains isolated 13 years apart from a chicken and a pigeon by complete genome sequence analysis and pathotyping. The viruses were characterized as velogenic by pathogenicity indices devised to distinguish these strains. The genome length was 15,186 nucleotides (nt) and consisted of six non-overlapping genes, with conserved and complementary 3′ leader and 5′ trailer regions, conserved gene starts, gene stops, and intergenic sequences similar to those in avian paramyxovirus 1 (APMV-1) strains. Matrix gene sequence analysis grouped the pigeon isolate with APMV-1 strains. Phylogeny based on the fusion (F), and hemagglutinin (HN) genes and complete genome sequence grouped these viruses into genotype IV. Genotype IV strains are considered to have “died out” after the first panzootic (1926–1960) of ND. But, our results suggest that there is persistence of genotype IV strains in India.

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

Newcastle disease virus (NDV) has been a threat to poultry industry in most of the developing countries with a wide variety of avian species being susceptible, coupled with the presence of mobile wild bird reservoirs contributing not only to the vast genomic diversity of this virus but also to the diagnostic failures. NDV of multiple genotypes (I-XI) is known to be prevalent and reported worldwide. However, there is a paucity of information on the circulating genotypes of NDV in India. This study utilized the fusion protein cleavage site (FPCS) sequence to determine the different genotypes of NDV circulating in India. Our results indicate that majority of NDV isolates from southern states of India namely, Tamil Nadu, Kerala and Karnataka were found to belong to genotype II. However, some of the strains from Tamil Nadu and most from Uttar Pradesh belong to genotype groups VI and VII. Interestingly, three isolates recovered from Tamil Nadu grouped with genotype IV viruses (namely Herts/33) which had not been hitherto reported to GenBank since 1989. This preliminary information points to the existence of multiple genotypes and also the need for efficacy studies with vaccines incorporating multiple genotypes in controlling virulent NDV (vNDV) outbreaks in India.

Reassessing conflicting evolutionary histories of the Paramyxoviridae and the origins of respiroviruses with Bayesian multigene phylogenies

The evolution of paramyxoviruses is still poorly understood since past phylogenetic studies have revealed conflicting evolutionary signals among genes, and used varying methods and datasets. Using Bayesian phylogenetic analysis of full length single and concatenated sequences for the 6 genes shared among paramyxovirus genera, we reassess the ambiguous evolutionary relationships within the family, and examine causes of varying phylogenetic signals among different genes. Relative to a pneumovirus outgroup, the concatenated gene phylogeny, splits the Paramyxovirinae into two lineages, one comprising the avulaviruses and rubulaviruses, and a second containing the respiroviruses basal to the henipaviruses, and morbilliviruses. Phylogenies for the matrix (M), RNA dependent RNA polymerase (L) and the fusion (F) glycoprotein genes, are concordant with the topology from the concatenated dataset. In phylogenies derived from the nucleocapsid (N) and phosphoprotein (P) genes, the respiroviruses form the most basal genus of the Paramyxovirinae subfamily, with the avulaviruses and rubulaviruses in one lineage, and the henipaviruses, and morbilliviruses in a second. The phylogeny of the hemagglutinin (H) gene places the respiroviruses basal to the avula-rubulavirus group, but the relationship of this lineage with henipa and morbillviruses is not resolved. Different genes may be under varying evolutionary pressures giving rise to these conflicting signals. Given the level of conservation in the M and L genes, we suggest that together with F gene, these or concatenated datasets for all six genes are likely to reveal the most reliable phylogenies at a family level, and should be used for future phylogenetic studies in this group. Split decomposition analysis suggests that recombination within genera, may have a contributed to the emergence of dolphin morbillivirus, and several species within respiroviruses. A partial L gene alignment, resolves the relationship of 25 unclassified paramxyoviruses into 4 clades (Chiopteran-, Salmon-, Rodentian- and Ophidian paramyxoviruses) which group with rubula-, respiro-, morbilliviruses, and within the paramxyovirinae respectively.

A molecular epidemiological investigation of isolates of the variant avian paramyxovirus type 1 virus (PPMV-1) responsible for the 1978 to present panzootic in pigeons

A sequence of 375 nucleotides, which included the region encoding the cleavage activation site and signal peptide of the fusion protein gene, was determined for 178 isolates of the pigeon variant strain of Newcastle disease virus (PPMV-1). These were compared with the sequences of 47 similar isolates published by GenBank, which included 30 isolates from pigeons and 17 representatives from each sublineage of avian paramyxovirus type 1. The resulting alignment was analysed phylogenetically using maximum likelihood and the results are presented as unrooted phylogenetic trees. By phylogenetic analysis all the PPMV-1 isolates except one were placed in lineage 4b (VIb). Within this lineage there was considerable genetic heterogeneity, which appears to be predominantly influenced by the date of isolation and, to a lesser extent, geographical origins of the isolates. There were two large distinguishable groups, 4bi and 4bii. The earliest isolate available, PIQPI78442, isolated in 1978 in Iraq, was situated at the node from which the two groups diverge.

Phylogenetic relationships among virulent Newcastle disease virus isolates from the 2002-2003 outbreak in California and other recent outbreaks in North America

Isolates from the 2002-2003 virulent Newcastle disease virus (v-NDV) outbreak in southern California, Nevada, Arizona, and Texas in the United States were compared to each other along with recent v-NDV isolates from Mexico and Central America and reference avian paramyxovirus type 1 strains. Nucleotide sequencing and phylogenetic analyses were conducted on a 1,195-base genomic segment composing the 3' region of the matrix (M) protein gene and a 5' portion of the fusion (F) protein gene including the M-F intergenic region. This encompasses coding sequences for the nuclear localization signal of the M protein and the F protein cleavage activation site. A dibasic amino acid motif was present at the predicted F protein cleavage activation site in all v-NDVs, including the California 2002-2003, Arizona, Nevada, Texas, Mexico, and Central America isolates. Phylogenetic analyses demonstrated that the California 2002-2003, Arizona, Nevada, and Texas viruses were most closely related to isolates from Mexico and Central America. An isolate from Texas obtained during 2003 appeared to represent a separate introduction of v-NDV into the United States, as this virus was even more closely related to the Mexico 2000 isolates than the California, Arizona, and Nevada viruses. The close phylogenetic relationship between the recent 2002-2003 U.S. v-NDV isolates and those viruses from countries geographically close to the United States warrants continued surveillance of commercial and noncommercial poultry for early detection of highly virulent NDV.

Development of a real-time reverse-transcription PCR for detection of newcastle disease virus RNA in clinical samples

A real-time reverse-transcription PCR (RRT-PCR) was developed to detect avian paramyxovirus 1 (APMV-1) RNA, also referred to as Newcastle disease virus (NDV), in clinical samples from birds. The assay uses a single-tube protocol with fluorogenic hydrolysis probes. Oligonucleotide primers and probes were designed to detect sequences from a conserved region of the matrix protein (M) gene that recognized a diverse set (n = 44) of APMV-1 isolates. A second primer-probe set was targeted to sequences in the fusion protein (F) gene that code for the cleavage site and detect potentially virulent NDV isolates. A third set, also directed against the M gene, was specific for the North American (N.A.) pre-1960 genotype that includes the common vaccine strains used in commercial poultry in the United States. The APMV-1 M gene, N.A. pre-1960 M gene, and F gene probe sets were capable of detecting approximately 10(3), 10(2), and 10(4) genome copies, respectively, with in vitro-transcribed RNA. Both M gene assays could detect approximately 10(1) 50% egg infective doses (EID(50)), and the F gene assay could detect approximately 10(3) EID(50). The RRT-PCR test was used to examine clinical samples from chickens experimentally infected with the NDV strain responsible for a recent epizootic in the southwestern United States. Overall, a positive correlation was obtained between the RRT-PCR results and virus isolation for NDV from clinical samples.