The nucleotide sequence of the fusion protein gene of the peste des petits ruminants virus: the long untranslated region in the 5'-end of the F-protein gene of morbilliviruses seems to be specific to each virus

Plasminogen activator urokinase interacts with the fusion protein and antagonizes the growth of Peste des petits ruminants virus

Peste des petits ruminants is an acute and highly contagious disease caused by the Peste des petits ruminants virus (PPRV). Host proteins play a crucial role in viral replication. However, the effect of fusion (F) protein-interacting partners on PPRV infection is poorly understood. In this study, we found that the expression of goat plasminogen activator urokinase (PLAU) gradually decreased in a time- and dose-dependent manner in PPRV-infected goat alveolar macrophages (GAMs). Goat PLAU was subsequently identified using co-immunoprecipitation and confocal microscopy as an F protein binding partner. The overexpression of goat PLAU inhibited PPRV growth and replication, whereas silencing goat PLAU promoted viral growth and replication. Additionally, we confirmed that goat PLAU interacted with a virus-induced signaling adapter (VISA) to antagonize F-mediated VISA degradation, increasing the production of type I interferon. We also found that goat PLAU reduced the inhibition of PPRV replication in VISA-knockdown GAMs. Our results show that the host protein PLAU inhibits the growth and replication of PPRV by VISA-triggering RIG-I-like receptors and provides insight into the host protein that antagonizes PPRV immunosuppression.IMPORTANCEThe role of host proteins that interact with Peste des petits ruminants virus (PPRV) fusion (F) protein in PPRV replication is poorly understood. This study confirmed that goat plasminogen activator urokinase (PLAU) interacts with the PPRV F protein. We further discovered that goat PLAU inhibited PPRV replication by enhancing virus-induced signaling adapter (VISA) expression and reducing the ability of the F protein to degrade VISA. These findings offer insights into host resistance to viral invasion and suggest new strategies and directions for developing PPR vaccines.

Development of cell culture based peste des petits ruminants (PPR) virus vaccine candidate from Bangladeshi isolates

This study was conducted to develop a cell culture based PPR virus vaccine candidate using recent Bangladeshi strain of peste des petits ruminant's (PPR) virus. PPR virus was isolated from field outbreaks, confirmed by RT-PCR and used as viral inoculum for serial passaging in Vero cells for adaptation and attenuation. 60th serial passage had completed and RT-PCR and real time RT-PCR were done in every 5 passages for confirmation of PPR virus in tissue culture fluid (TCF). To assess the adaptation and attenuation cytopathology, virus titration, sequencing of both F and N genes and live animal experimentation were done. Different cellular alterations produced by PPR virus in infected Vero cells including syncytia formation, development of both intranuclear and intra cytoplasmic inclusion bodies and finally cell degradation are the indications of adaptation. The virus titre was found 2.5, 3.31, 3.55, 4.44, 4.71 and 6.5 Log₁₀ TCID₅₀/ml at 10th, 20th, 30th, 40th, 50th and 60th passages level respectively. In F gene sequence analysis it has been observed that few nucleotide (nt) and mino acid (aa) has been substituted as the effects of serial passaging of PPR virus in Vero cells. TCF at 60th passage level was found effective to produced protective antibody (Ab) titre in live animal experimentation. It is concluded that serially passaged and Vero cells adapted PPR virus TCF could be used as a vaccine candidate for further use to develop a potent & effective vaccine against PPR diseases.

Immunoinformatics Approach for Epitope Mapping of Immunogenic Regions (N, F and H Gene) of Small Ruminant Morbillivirus and Its Comparative Analysis with Standard Vaccinal Strains for Effective Vaccine Development

BACKGROUND

Outbreaks of small ruminant morbillivirus (SRMV) are regularly occurring in Pakistan despite vaccine availability. This study was designed to identify substitutions within the immunogenic structural and functional regions of the nucleocapsid, fusion, and hemagglutinin genes of SRMV and their comparison with vaccinal strains of Nigerian and Indian origin.

METHODS

Swabs and tissue samples were collected from diseased animals. RT-PCR was used to characterize selected genes encoded by viral RNA. The study's N, F, and H protein sequences and vaccinal strains were analyzed for B and T cell epitope prediction using ABCpred, Bipred, and IEDB, respectively.

RESULTS

Significant substitutions were found on the C terminus of the nucleocapsid, within the fusion motif region of the fusion gene and in the immunoreactive region of the hemagglutinin gene.

CONCLUSION

Our results emphasize the need for the development of effective vaccines that match the existing variants of SRMV strains circulating in Pakistan.

Expression and Evaluation of a Novel PPRV Nanoparticle Antigen Based on Ferritin Self-Assembling Technology

Peste des Petits Ruminants (PPR) is a highly pathogenic disease that is classified as a World Organization for Animal Health (OIE)-listed disease. PPRV mainly infects small ruminants such as goats and sheep. In view of the global and high pathogenicity of PPRV, in this study, we proposed a novel nanoparticle vaccine strategy based on ferritin (Fe) self-assembly technology. Using Helicobacter pylori (H. pylori) ferritin as an antigen delivery vector, a PPRV hemagglutinin (H) protein was fused with ferritin and then expressed and purified in both Escherichia coli (E. coli) and silkworm baculovirus expression systems. Subsequently, the nanoparticle antigens’ expression level, immunogenicity and protective immune response were evaluated. Our results showed that the PPRV hemagglutinin–ferritin (H-Fe) protein was self-assembled in silkworms, while it was difficult to observe the correctly folded nanoparticle in E. coli. Meanwhile, the expression level of the H-Fe protein was higher than that of the H protein alone. Furthermore, the immunogenicity and protective immune response of H-Fe nanoparticle antigens expressed by silkworms were improved compared with the H antigen alone. Particularly, the protective immune response of H-Fe antigens expressed in E. coli did not change, as opposed to the H antigen, which was probably due to the incomplete nanoparticle structure in E. coli. This study indicated that the use of ferritin nanoparticles as antigen delivery carriers could increase the expression of antigen proteins and improve the immunogenicity and immune effect of antigens.

Nucleotide amplification and sequencing of the GC-rich region between matrix and fusion protein genes of peste des petits ruminants virus

Peste des petits ruminants virus (PPRV) causes a highly devastating disease of sheep and goats, that threatens the conservation of small wild ruminants. The development of PPRV vaccines, diagnostics and therapeutics, greatly depends on in-depth genomic data. Yet, high guanine-cytosine (GC) content between matrix (M) and fusion (F) genes of PPRV poses difficulty for both primer design and nucleotide amplification. In turn, this has led into absence or low nucleotide sequence coverage in this region. This poses a risk of missing important part of the genome that could help to infer viral evolution. Here, an overlapping long-read primer-based amplification strategy was developed to amplify the GC-rich fragments between M-F gene junction using nexus gradient polymerase chain reaction (PCR). The resulting amplicons were sequenced by dideoxynucleotide cycle sequencing and compared with other PPRV nucleotide sequences available at GenBank. Our findings indicate clear PCR amplification products with expected size of the GC-rich fragments on agarose gel electrophoresis. The sequencing results of these fragments indicate 99.5 % nucleotide identity with PPRV strain KY628761. An extremely difficult PCR target of 67.4 % GC contents was successfully amplified and sequenced using this long-read primer approach. The long-read primer set may be used in tiling multiplex PCR for complete genome sequencing of PPRV.

Complete Genome Sequencing of Field Isolates of Peste des Petits Ruminants Virus from Tanzania Revealed a High Nucleotide Identity with Lineage III PPR Viruses

Peste des petits ruminants virus (PPRV) causes a highly devastating disease of sheep and goats that threatens food security, small ruminant production and susceptible endangered wild ruminants. With policy directed towards achieving global PPR eradication, the establishment of cost-effective genomic surveillance tools is critical where PPR is endemic. Genomic data can provide sufficient in-depth information to identify the pockets of endemicity responsible for PPRV persistence and viral evolution, and direct an appropriate vaccination response. Yet, access to the required sequencing technology is low in resource-limited settings and is compounded by the difficulty of transporting clinical samples from wildlife across international borders due to the Convention on International Trade in Endangered Species (CITES) of Wild Fauna and Flora, and Nagoya Protocol regulations. Oxford nanopore MinION sequencing technology has recently demonstrated an extraordinary performance in the sequencing of PPRV due to its rapidity, utility in endemic countries and comparatively low cost per sample when compared to other whole-genome (WGS) sequencing platforms. In the present study, Oxford nanopore MinION sequencing was utilised to generate complete genomes of PPRV isolates collected from infected goats in Ngorongoro and Momba districts in the northern and southern highlands of Tanzania during 2016 and 2018, respectively. The tiling multiplex polymerase chain reaction (PCR) was carried out with twenty-five pairs of long-read primers. The resulting PCR amplicons were used for nanopore library preparation and sequencing. The analysis of output data was complete genomes of PPRV, produced within four hours of sequencing (accession numbers: MW960272 and MZ322753). Phylogenetic analysis of the complete genomes revealed a high nucleotide identity, between 96.19 and 99.24% with lineage III PPRV currently circulating in East Africa, indicating a common origin. The Oxford nanopore MinION sequencer can be deployed to overcome diagnostic and surveillance challenges in the PPR Global Control and Eradication program. However, the coverage depth was uneven across the genome and amplicon dropout was observed mainly in the GC-rich region between the matrix (M) and fusion (F) genes of PPRV. Thus, larger field studies are needed to allow the collection of sufficient data to assess the robustness of nanopore sequencing technology.

Peste des petits ruminants in Africa: a review of currently available molecular epidemiological data, 2020

Small ruminants (e.g., sheep and goats) contribute considerably to the cash income and nutrition of small farmers in most countries in Africa and Asia. Their husbandry is threatened by the highly infectious transboundary viral disease peste des petits ruminants (PPR) caused by peste-des-petits-ruminants virus (PPRV). Given its social and economic impact, PPR is presently being targeted by international organizations for global eradication by 2030. Since its first description in Côte d’Ivoire in 1942, and particularly over the last 10 years, a large amount of molecular epidemiological data on the virus have been generated in Africa. This review aims to consolidate these data in order to have a clearer picture of the current PPR situation in Africa, which will, in turn, assist authorities in global eradication attempts.

Interaction with the Receptor SLAM and Baculovirus Surface Display of Peste des petits ruminants Virus Hemagglutinin

Peste des petits ruminants (PPR) is an acute, highly infectious, and highly pathogenic disease, which mainly damages small ruminants such as goats and sheep. Hemagglutinin protein (H), the main antigenic protein of peste des petits ruminants virus (PPRV), has been a hot spot in the research of genetic engineering vaccine for PPRV. In this study, the silkworm baculovirus surface display technology is combined with the transmembrane structure of the silkworm baculovirus envelope protein GP64 and different characteristics of the promoters to display four kinds of fusion proteins, which contain Pph-H, Pph-HJ, Pie1-H, and Pie1-HJ. The fusion proteins displayed on baculovirus surface have been detected by western blotting, cell surface immunofluorescence, and immunogold electron microscopy. In addition, the dominant form of PPR H displayed on baculovirus surface has been determined which is fusion protein mediated by Pph containing the hemagglutinin protein and full-length GP64, Pph-H. Furthermore, by comparing the fluorescence intensity of binding of hemagglutinin protein and signaling lymphocyte activation molecules (SLAM) in Vero-SLAM cells by immunocytochemistry, Pph-H can be combined with the receptor protein of PPRV, SLAM. It provides technical support for displaying the different structure of hemagglutinin and exploring the key sites of hemagglutinin and SLAM binding. Meanwhile, it is important for exploring the pathogenesis and immune mechanism of PPRV.

Productive replication of peste des petits ruminants virus Nigeria 75/1 vaccine strain in vero cells correlates with inefficiency of maturation of the viral fusion protein

Peste des petits ruminants virus (PPRV), a member of the genus Morbillivirus, in the family Paramyxoviridae expresses two membrane glycoproteins, the fusion (F) and haemagglutinin (H) glycoproteins which mediate virus-to-cell fusion and cell-to-cell fusion leading to the induction of syncytia in PPRV infected cells. In the context of the characterization of the virulent lineage IV strain PPRV Kurdistan 2011, isolated from wild goats from the Kurdistan region in Iraq, we observed that both PPRV Kurdistan 2011 and the PPRV Nigeria 75/1 vaccine strain led to induction of large syncytia in Vero-dogSLAM cells within 48 h whereas both failed to induce detectable cell-cell fusion events in two Vero cell lines of differing passage histories. We were unable to detect syncytium formation in transiently transfected cells expressing PPRV F or H alone whereas co-expression of F and H induced large syncytia - in Vero-dogSLAM cells only. In Vero_Montpellier cells expressing PPRV F and H, fused cells were rarely detectable indicating that PPRV mediated cell fusion activity is impaired in this cell line. Surprisingly, on Vero-dogSLAM cells the vaccine strain grew to titers of 10^5.25 TCID₅₀/ml, whereas infectious virus yield was about 200-fold higher on Vero_Montpellier and Vero-76 cells. In contrast, the virulent Kurdistan 2011 strain grew to a maximum titer of 10^7.0 TCID₅₀/ml on Vero-dogSLAM cells and only 10^4.5 TCID50/ml on normal Vero cells. This was as expected since Vero cells lacking the SLAM receptor for PPRV are regarded as not so permissive for infection. To elucidate the divergent productive replication behaviour of PPRV Nigeria 75/1 vaccine strain on Vero vs Vero-dogSLAM cells, we examined whether intracellular transport and/or maturation of the viral envelope glycoproteins F and H might be implicated with this phenomenon. The results indicate that F in contrast to the H glycoprotein matures inefficiently during intracellular transport in Vero_Montpellier cells, thus leading to an absence of detectable syncytia formation. However, in the case of the PPRV Nigeria 75/1 vaccine strain this did not impair efficient virus assembly and release.

Efficient isolation on Vero.DogSLAMtag cells and full genome characterization of Dolphin Morbillivirus (DMV) by next generation sequencing

The Dolphin Morbillivirus (DMV) genome from the first Mediterranean epidemic (1990-’92) is the only cetacean Morbillivirus that has been completely sequenced. Here, we report the first application of next generation sequencing (NGS) to morbillivirus infection of aquatic mammals. A viral isolate, representative of the 2006-’08 Mediterranean epidemic (DMV_IZSPLV_2008), efficiently grew on Vero.DogSLAMtag cells and was submitted to whole genome characterization by NGS. The final genome length was 15,673 nucleotides, covering 99.82% of the DMV reference genome. Comparison of DMV_IZSPLV_2008 and 1990-’92 DMV strain sequences revealed 157 nucleotide mutations and 47 amino acid changes. The sequence similarity was 98.7% at the full genome level. Whole-genome phylogeny suggested that the DMV strain circulating during the 2006-’08 epidemics emerged from the 1990-’92 DMV strain. Viral isolation is considered the “gold standard” for morbillivirus diagnostics but efficient propagation of infectious virus is difficult to achieve. The successful cell replication of this strain allowed performing NGS directly from the viral RNA, without prior PCR amplification. We therefore provide to the scientific community a second DMV genome, representative of another major outbreak. Interestingly, genome comparison revealed that the neglected L gene encompasses 74% of the genetic diversity and might serve as “hypervariable” target for strain characterization.

Full genome sequence of a peste des petits ruminants virus (PPRV) from Ghana

The full genome of a peste des petits ruminants virus (PPRV) isolated from a sheep lung sample collected in Ghana, Western Africa, in 2010, has been sequenced. Phylogenetic analysis demonstrated that the virus clustered within the lineage II clade while comparison of its full genome with those of other PPRV strains revealed the highest identity (96.6 %) at a nucleotide level with the PPRV strain Nigeria/76/1. This is the first full genome sequence generated for a PPRV lineage II isolated since 1976.

Peste des petits ruminants virus infection of small ruminants: a comprehensive review

Peste des petits ruminants (PPR) is caused by a Morbillivirus that belongs to the family Paramyxoviridae. PPR is an acute, highly contagious and fatal disease primarily affecting goats and sheep, whereas cattle undergo sub-clinical infection. With morbidity and mortality rates that can be as high as 90%, PPR is classified as an OIE (Office International des Epizooties)-listed disease. Considering the importance of sheep and goats in the livelihood of the poor and marginal farmers in Africa and South Asia, PPR is an important concern for food security and poverty alleviation. PPR virus (PPRV) and rinderpest virus (RPV) are closely related Morbilliviruses. Rinderpest has been globally eradicated by mass vaccination. Though a live attenuated vaccine is available against PPR for immunoprophylaxis, due to its instability in subtropical climate (thermo-sensitivity), unavailability of required doses and insufficient coverage (herd immunity), the disease control program has not been a great success. Further, emerging evidence of poor cross neutralization between vaccine strain and PPRV strains currently circulating in the field has raised concerns about the protective efficacy of the existing PPR vaccines. This review summarizes the recent advancement in PPRV replication, its pathogenesis, immune response to vaccine and disease control. Attempts have also been made to highlight the current trends in understanding the host susceptibility and resistance to PPR.

Translational enhancing activity in 5' UTR of peste des petits ruminants virus fusion gene

The fusion gene of peste des petits ruminants virus (PPRV-F), a paramyxovirus, contains an unusual long 5' untranslated region (5' UTR) with a high GC content that is capable of folding into secondary structure proximally to the 5' cap. Sequence analysis further suggested that the proximal end of this UTR contains a nine-nucleotide sequence which could perfectly complement the 18S rRNA and might affect translation through mRNA-rRNA interaction. Based on these features, we examined the functional role of the proximal PPRV-F 5' UTR on translational efficiency compared with two other morbilliviruses. From reporter gene assays, PPRV-F 5' UTR functioned as a strong enhancer of translational efficiency independent of cell and gene specificity. Northern blot analysis of the accumulative RNA levels and mRNA stability suggested that elevated gene expression driven by PPRV-F 5' UTR was accompanied by an increased mRNA level and enhanced mRNA stability. Deletion analysis identified the complementary sequence and distal nucleotides necessary for the enhancing activity, and results suggest RNA structural conformation is important. Taken together, we conclude that the proximal PPRV-F 5' UTR functions as a translational enhancer by promoting translation efficiency and mRNA stability.

Sequence and phylogenetic analyses of the structural genes of virulent isolates and vaccine strains of peste des petits ruminants virus from India

Peste des petits ruminants (PPR) is an acute, highly contagious, notifiable and economically important transboundary viral disease of sheep and goats. In this study, sequence and phylogenetic analyses of structural protein genes, namely the nucleocapsid (N), the matrix (M), the fusion (F) and the haemagglutinin (H) coding sequences of virulent and vaccine strains of PPR virus (PPRV), were undertaken to determine the genetic variations between field isolates and vaccine strains. The open reading frame (ORF) of these genes of the isolates/strains was amplified by RT-PCR, cloned and sequenced. The ORF of N, M, F and H genes was 1578, 1008, 1641 and 1830 nucleotides (nt) in length and encodes polypeptides of 525, 335, 546 and 609 amino acids (aa), respectively, as reported earlier. Comparative sequence analyses of these four genes of isolates/strains were carried out with published sequences. It revealed an identity of 97.7-100% and 97.7-99.8% among the Asian lineage IV and 89.6-98.7% and 89.8-98.9% with other lineages of PPRV at nt and aa levels, respectively. The phylogenetic analyses of these isolates based on the aa sequences showed that all the viruses belonged to lineage IV along with other Asian isolates. This is in agreement with earlier observations that only PPRV lineage IV is in circulation in India since the disease was first reported. Further, sequence analysis of the thermostable/thermo-adapted vaccine strains showed no significant changes in the functional or structural surface protein-coding gene sequences. It is important to monitor the circulation of the PPRV in susceptible animals by H gene-based sequence comparisons in addition to the F gene- and N gene-based approaches to identify the distribution and spread of virus in the regular outbreaks that occur in endemic countries like India.

Full genome sequences of two virulent strains of peste-des-petits ruminants virus, the Côte d'Ivoire 1989 and Nigeria 1976 strains

Peste-des-petits ruminants virus (PPRV) causes acute febrile illness in both farmed and wild small ruminants, with associated mortality rates of 50-80%. PPRV is a member of the Morbillivirus genus within the Paramyxovirus family and although there are many full length genome sequences available for members of this family, their availability for PPRV in particular is limited. We have determined the full length sequences representing two virulent strains of PPRV, the Côte d'Ivoire 1989 (CI/89) and Nigeria 1976 (Ng76/1) strains. We present an alignment of the promoter regions of these viruses with other available PPRV promoter sequences and have identified domains in PPRV proteins believed to be critical for paramyxovirus promoter attenuation. We have also analysed the proteins of these viruses, comparing them to other available PPRV protein sequences and identified motifs that were previously recognised as being required for the function of other paramyxovirus proteins.

Sequence analysis of the haemagglutinin and fusion protein genes of peste-des-petits ruminants vaccine virus of Indian origin

The amino acid composition of the two surface proteins of peste-des-petits ruminants vaccine virus belonging to lineage four from India were deduced from the nucleotide sequence. The fusion (F) protein gene of PPRV Sungri/96 is 2405 nucleotides long and in relation to the length, it is 80 nucleotides longer than that of PPRV Nigeria/75/1 which are found to be present at the 5'UTR of this virus. The complete F gene alignment with other morbillivirus reveals a homology of 89% with PPRV/Nigeria/75/1 and 48-51% with other morbilliviruses. The F protein of PPRV Sungri/96 exhibited characteristics similarity to those of other morbillivirus F proteins. The overall amino acid similarity with its counterpart PPRV Nigeria/75/1 was 96%; with other morbilliviruses it is 65-74%. The PPRV Sungri/96 haemagglutinin (H) protein gene is 1954 nucleotides long and showed a sequence homology of 90.7% with PPRV/Nigeria/75/1 and with other morbilliviruses it ranged from 33% to 45%. At amino acids level, PPRV Sungri/96 showed a homology of 92.3% with PPRV/Nigeria/75/1 and 34-49% with other morbilliviruses. The phylogenetic tree constructed for F and H gene reveals four separate groups which is very similar to that found in other genes. To the best of our knowledge this is the first report describing the F and H genes of an Indian isolate.

Long untranslated regions of the measles virus M and F genes control virus replication and cytopathogenicity

Measles is still a major cause of mortality mainly in developing countries. The causative agent, measles virus (MeV), is an enveloped virus having a nonsegmented negative-sense RNA genome, and belongs to the genus Morbillivirus of the family Paramyxoviridae. One feature of the moribillivirus genomes is that the M and F genes have long untranslated regions (UTRs). The M and F mRNAs of MeV have 426-nucleotide-long 3' and 583-nucleotide-long 5' UTRs, respectively. Though these long UTRs occupy as much as approximately 6.4% of the virus genome, their function remains unknown. To elucidate the role of the long UTRs in the context of virus infection, we used the reverse genetics based on the virulent strain of MeV, and generated a series of recombinant viruses having alterations or deletions in the long UTRs. Our results showed that these long UTRs per se were not essential for MeV replication, but that they regulated MeV replication and cytopathogenicity by modulating the productions of the M and F proteins. The long 3' UTR of the M mRNA was shown to have the ability to increase the M protein production, promoting virus replication. On the other hand, the long 5' UTR of the F mRNA was found to possess the capacity to decrease the F protein production, inhibiting virus replication and yet greatly reducing cytopathogenicity. We speculate that the reduction in cytopathogenicity may be advantageous for MeV fitness and survival in nature.

Analysis of the matrix protein gene sequence of the Asian lineage of peste-des-petits ruminants vaccine virus

The M gene nucleotide sequence of an Indian peste-des-petits ruminants (PPRV) vaccine virus ("PPRV Sungri/96") belonging to Asian lineage was determined. The gene is 1476 nucleotides long with a single open reading frame (ORF). The nucleotide and predicted amino acid sequence was compared with the homologous region of the African Lineage Vaccine virus "PPRV/Nigeria/75/1". The nucleotide sequence of the "PPRV Sungri/96" was 86% identical to that of "PPRV/Nigeria/75/1", while a homology of 93% and 95% could be observed in the ORF and amino acids level, respectively. The M gene encodes a protein of 335 amino acids, with a predicted molecular weight (MW) of 37.8 kDa. The ORF is flanked by a 3' untranslated region of 436 nucleotides and a high level of sequence divergence (approximately 30%) could be observed in this region between the vaccine viruses of Asian and African lineages. A high degree of conservation of several amino acids of this protein observed previously was also confirmed in this study.

Full genome sequence of peste des petits ruminants virus, a member of the Morbillivirus genus

Peste des petits ruminants virus (PPRV) causes an acute febrile illness in small ruminant species, mostly sheep and goats. PPRV is a member of the Morbillivirus genus which includes measles, rinderpest (cattle plague), canine distemper, phocine distemper and the morbilliviruses found in whales, porpoises and dolphins. Full length genome sequences for these morbilliviruses are available and reverse genetic rescue systems have been developed for the viruses of terrestrial mammals, with the exception of PPRV. This paper presents the first published full length genome sequence for PPRV. The genome was found to be consistent with the rule-of-six and open reading frames (ORFs) were identified that encoded the eight proteins characteristic of morbilliviruses. At the nucleotide (nt) level, the full length genome of PPRV was most similar to that of rinderpest, the other ruminant morbillivirus. However, at the protein level five of the six structural proteins and the V protein showed a greater similarity to the dolphin morbillivirus (DMV) while only the C and L proteins showed a high relationship to rinderpest.

The fusion core complex of the peste des petits ruminants virus is a six-helix bundle assembly

We describe the properties of the two heptad repeats (HR1 and HR2) of the Peste des petits ruminants virus (PPRV) fusion protein (F) to obtain insights into the mechanism by which these repeats influence PPRV-mediated cell fusion. Both HR1 and HR2 inhibit PPRV-mediated syncytia formation in Vero cells in vitro. Of these, HR2 was found to be more effective than HR1. We studied the mechanism of fusion inhibition by these two repeats by using various biophysical and biochemical methods either separately or together. CD spectral analysis of these repeats revealed that the alpha-helical content of HR1 and HR2 when used together is higher than that of their simulated spectrum in the mixture, suggesting the formation of a highly structured complex by these repeats. Protease protection assays confirmed that such a complex is highly stable. Electrospray mass spectrometry of protease-digested products of the HR1-HR2 complex showed protection of fragments corresponding to both HR1 and HR2 sequences involved in complex formation. By employing size-exclusion chromatography and chemical cross-linking experiments, we show that three units each of HR1 and HR2 form a complex in which HR1 is a trimer and HR2 is a monomer. Homology-based three-dimensional modeling of this complex showed that HR1 and HR2 together form a six-helix and trimeric coiled-coil bundle. In this model, the HR1 trimer forms the core whereas HR2, while interacting with HR1 in an antiparallel orientation, forms a two-stranded coiled-coil structure and lies at the periphery of the structure. These results are discussed in the context of a common fusion mechanism among paramyxoviruses.

Development of a dual recombinant vaccine to protect small ruminants against peste-des-petits-ruminants virus and capripoxvirus infections

A recombinant capripoxvirus vaccine containing a cDNA of the peste-des-petits-ruminants virus (PPRV) fusion protein gene was constructed. A quick and efficient method was used to select a highly purified recombinant virus clone. A trial showed that a dose of this recombinant as low as 0.1 PFU protected goats against challenge with a virulent PPRV strain.

The fusion protein of Peste des petits ruminants virus mediates biological fusion in the absence of hemagglutinin-neuraminidase protein

To study the process of membrane fusion in Morbilliviruses, the fusion (F) glycoproteins of Peste des petits ruminants virus (PPRV) and Rinderpest virus (RPV) were expressed transiently in mammalian cells. The recombinant F proteins were found to be localized at the surface of transfected cells. The fusion activity, as evident from cell fusion assays and lysis of chicken erythrocytes, documented that transiently expressed PPRV F glycoprotein induces cell fusion in the absence of homotypic hemagglutinin-neuraminidase (HN) attachment glycoprotein. The coexpression of homotypic HN increased the extent of fusion by twofold, while the efficiency of fusion was found to be substantially enhanced. In contrast, in RPV F-expressing cells, fusion was detected only when homotypic hemagglutinin (H) or heterotypic HN protein was coexpressed. This differs from the strict type-specific requirement for the attachment protein as in the fusion process of most of the paramyxoviruses. Further, we demonstrate by fluorescence transfer experiments that while PPRV F brings about both hemifusion and complete fusion on its own, RPV F induces only hemifusion while it brings about complete fusion in the presence of homotypic or heterotypic attachment protein.

Recovery and characterization of a chimeric rinderpest virus with the glycoproteins of peste-des-petits-ruminants virus: homologous F and H proteins are required for virus viability

Rinderpest (RP) and peste-des-petits-ruminants (PPR) are two important diseases of domestic ruminants. To improve on currently available vaccines against PPR, we have created cDNA copies of the RP virus genome in which either the fusion (F) or hemagglutinin (H) gene, or both, was replaced with the corresponding gene from PPR virus. It was necessary to develop a modified rescue system in which the T7 RNA polymerase was provided by a recombinant fowlpox virus and the entire rescue procedure took place in Vero cells before we could obtain live virus from these chimeric constructs. No virus was recovered when only one of the glycoprotein genes was changed, but a chimeric virus containing both F and H genes from PPR virus was reproducibly rescued from cDNA, indicating that a virus-specific functional interaction takes place between the F and H proteins. The rescued virus expressing the PPR glycoproteins grew more slowly in tissue culture than either parental virus and formed abnormally large syncytia. Goats infected with the chimera showed no adverse reaction, as assessed by clinical signs, temperature, leukocyte count, virus isolation, and serology, and were protected from subsequent challenge with wild-type PPR virus.

The matrix protein gene sequence analysis reveals close relationship between peste des petits ruminants virus (PPRV) and dolphin morbillivirus

The gene encoding the matrix protein of peste des petits ruminants virus (PPRV) has been cloned and its nucleotide sequence determined. This gene is 1466 nucleotides long and contains an open reading frame (ORF) capable of encoding a basic protein of 335 amino acid residues with a predicted molecular weight of 38,057 Da. This ORF starts at position 33-35 and ends with the codon TAA at position 1038-1040 thus leaving a long untranslated region (426 nucleotides) at the 3' end of the messenger RNA. This fragment is very G/C rich (68.5%) and in contrast to the ORF region appears to be least conserved in the M gene sequence of the morbilliviruses. A comparison of the PPRV M protein with those of other viruses in the group confirms the previously noted high degree of conservation for this protein sequence. The percent of identity within the group ranges from 76.7 to 86.9%, the highest being with the dolphin morbillivirus matrix protein.

Genetic analysis of the central untranslated genome region and the proximal coding part of the F gene of wild-type and vaccine canine distemper morbilliviruses

Located between the open reading frames encoding the matrix (M) and the fusion (F) protein the morbillivirus genome contains an unusually large non-coding intercistronic region (M-F UTR) of up to 5.6% of the full length genome. Any function(s) of this region have largely remained obscure. Here, we analyze the M-F UTR and the proximal coding part of the downstream F gene of several recent canine distemper morbillivirus (CDV) wild-type (wt) isolates and vaccine strains. While the F gene coding part appeared to be highly conserved (about 93% homology), a considerable degree of strain-specific variation of up to 21.4% was evident when comparing the M-F UTR. Phylogenetic analysis revealed a co-circulation of several contemporary CDV genotypes within a close geographic range (central Europe). A remarkably distinct CDV wt lineage, so far detected only in mustelids, is displayed. A rather non-scattered pattern of mutations within the M-F UTR suggested superimposition of RNA sequence and/or secondary structure constraints. Extensive folding in the long (460 nt) and moderately GC-rich 5'-UTR of the F mRNA was evident, particularly around the putative F protein translation initiation codon (AUG461 of the Onderstepoort vaccine strain). The region immediately preceding the putative F initiation site also harbored the only mutation unique to both vaccine strains within the F-5'UTR (position 455: Awt vs. Cvac). The putative F protein start codon, AUG461, was found to be mutated to AUA or GUA in all wt isolates analyzed and in another vaccine strain (Rockborn). Possible consequences for F protein translation initiation in wt CDV are discussed.

Measles virus fusion protein is palmitoylated on transmembrane-intracytoplasmic cysteine residues which participate in cell fusion

[3H]palmitic acid was metabolically incorporated into the viral fusion protein (F) of Edmonston or freshly isolated measles virus (MV) during infection of human lymphoid or Vero cells. The uncleaved precursor F0 and the F1 subunit from infected cells and extracellular virus were both labeled, indicating that palmitoylation can take place prior to F0 cleavage and that palmitoylated F protein was incorporated into virus particles. [3H]palmitic acid was released from F protein upon hydroxylamine or dithiothreitol treatment, indicating a thioester linkage. In cells transfected with the cloned MV F gene, in which the cysteines located in the intracytoplasmic and transmembrane domains (Cys 506, 518, 519, 520, and 524) were replaced by serine, a major reduction of [3H]palmitic acid incorporation was observed for F mutated at Cys 506 and, to a lesser extent, at Cys 518 and Cys 524. We also observed incorporation of [3H]palmitic acid in the F1 subunit of canine distemper virus F protein. Cell fusion induced by cotransfection of cells with MV F and H (hemagglutinin) genes was significantly reduced after replacement of Cys 506 or Cys 519 with serine in the MV F gene. Transfection with the F gene with a mutation for Cys 518 abolished cell fusion, although less mutant protein was detected on the cell surface. These results suggest that the F protein transmembrane domain cysteines 506 and 518 participate in structures involved in cell fusion, possibly mediated by palmitoylation.

Geographic distribution and epidemiology of peste des petits ruminants virus

Peste des petits ruminants (PPR) is an important viral disease of goats and sheep prevalent in West Africa and the Middle East. In recent years, PPR has emerged in India, first in the South India and later in North India. To study the genetic relationships between viruses of distinct geographical origin we have sequenced a 322 nucleotide cDNA fragment of the fusion protein gene generated using reverse transcription followed by polymerase chain reaction (PCR) amplification. Viruses from nineteen independent PPR outbreaks were compared; these included the prototype African strain from Senegal and viruses from disease outbreaks which have occurred at different times and locations across Africa, Arabia, the Near East and the Indian subcontinent. Four separate lineages of the virus were identified and the virus isolates from Asia over the past 2 years were all of one lineage which had not previously been identified in Africa or Asia.

The isolation of peste des petits ruminants virus from northern India

The aetiological agent responsible for an epizootic of a rinderpest-like disease afflicting sheep and goats in three states of northern India was confirmed as peste des petits ruminants virus. To differentiate the virus from rinderpest a number of diagnostic tests were used, including immunocapture ELISA, specific oligonucleotide primers in a reverse transcriptase polymerase chain reaction, immunofluorescence with virus specific monoclonal antibodies and virus isolation. The virulence profile of one isolate in cattle sheep and goats was established. Infected animals developed specific antibody responses and excreted specific antigen in their lachrymal secretions.

Evaluation of polymerase chain reaction for the detection and characterisation of rinderpest and peste des petits ruminants viruses for epidemiological studies

The high sequence variability found in RNA viruses makes it difficult to design primers for reverse transcription-polymerase chain reaction amplification which will be certain to work with all new field isolates. To overcome this problem for the detection and differential diagnosis of rinderpest (RP) and peste des petits ruminants (PPR) viruses (V), we have designed several sets of primers, based on well-conserved sequences in the P and F genes. Analysis of a large number of field isolates from every region of the world where RPV and PPRV are found showed that no sample failed to react with more than one of the primer sets. To facilitate the multiple analyses, the reverse transcription step was performed using random hexanucleotide primers and aliquots of the cDNA were then amplified using a panel of primer sets to identify and differentiate between the virus nucleic acids in the samples. Evaluation of the method was carried out using eye swabs collected from cattle experimentally infected with RPV and goats infected with PPRV during the course of vaccine trials and on field samples such as whole blood, mouth swabs, lung, spleen and other tissues submitted to the laboratory for diagnosis. Sequencing the PCR products enabled us to examine the genetic relationships between new and previous field isolates from different geographical areas.