Vaccination with Recombinant Adenoviruses Expressing the Peste des Petits Ruminants Virus F or H Proteins Overcomes Viral Immunosuppression and Induces Protective Immunity against PPRV Challenge in Sheep

Peste des petits ruminants (PPR) is a highly contagious disease of small ruminants caused by the Morbillivirus peste des petits ruminants virus (PPRV). Two recombinant replication-defective human adenoviruses serotype 5 (Ad5) expressing either the highly immunogenic fusion protein (F) or hemagglutinin protein (H) from PPRV were used to vaccinate sheep by intramuscular inoculation. Both recombinant adenovirus vaccines elicited PPRV-specific B- and T-cell responses. Thus, neutralizing antibodies were detected in sera from immunized sheep. In addition, we detected a significant antigen specific T-cell response in vaccinated sheep against two different PPRV strains, indicating that the vaccine induced heterologous T cell responses. Importantly, no clinical signs and undetectable virus shedding were observed after virulent PPRV challenge in vaccinated sheep. These vaccines also overcame the T cell immunosuppression induced by PPRV in control animals. The results indicate that these adenovirus constructs could be a promising alternative to current vaccine strategies for the development of PPRV DIVA vaccines.     

小反刍兽疫病毒结构与功能的研究进展

小反刍兽疫病毒属于副黏病毒科麻疹病毒属,主要感染山羊、绵羊和野生小反刍兽,临床症状以发热、肺炎、腹泻及呼吸道和消化道黏膜炎症为主要特征。迄今为止对于小反刍兽疫无特效药物进行治疗,该病可对家畜养殖业造成一定的经济损失,因此对小反刍兽疫病毒病原学、结构和功能的研究已成为迫切需求。主要综述了小反刍兽疫病毒的六种结构蛋白N、P、M、F、HN、L和两种非结构蛋白C、V的基因组结构及功能,探讨了新型疫苗的研发方向,以期为小反刍兽疫病毒的深入研究、小反刍兽疫的临床防控提供参考。     

Self-Assembly and Release of Peste des Petits Ruminants Virus-Like Particles in an Insect Cell-Baculovirus System and Their Immunogenicity in Mice and Goats

Peste des petits ruminants (PPR) is an acute, febrile, viral disease of small ruminants that has a significant economic impact. For many viral diseases, vaccination with virus-like particles (VLPs) has shown considerable promise as a prophylactic approach; however, the processes of assembly and release of peste des petits ruminants virus (PPRV) VLPs are not well characterized, and their immunogenicity in the host is unknown. In this study, VLPs of PPRV were generated in a baculovirus system through simultaneous expression of PPRV matrix (M) protein and hemaglutin in (H) or fusion (F) protein. The released VLPs showed morphology similar to that of the native virus particles. Subcutaneous injection of these VLPs (PPRV-H, PPRV-F) into mice and goats elicited PPRV-specific IgG production, increased the levels of virus neutralizing antibodies, and promoted lymphocyte proliferation. Without adjuvants, the immune response induced by the PPRV-H VLPs was comparable to that obtained using equivalent amounts of PPRV vaccine. Thus, our results demonstrated that VLPs containing PPRV M protein and H or F protein are potential “differentiating infected from vaccinated animals” (DIVA) vaccine candidates for the surveillance and eradication of PPR.     

小反刍兽疫病毒研究进展

小反刍兽疫（PPR）是由小反刍兽疫病毒（PPRV）引起的一种主要感染小反刍动物的急性、烈性、接触性A类传染病,患病率、死亡率高。本文就世界PPR流行状况、PPRV基因组及病毒结构蛋白、PPRV检测方法、最新的药物及疫苗、存在的问题等方面做了简要综述。     

Study on Passive Immunity:time of Vaccination in Kids Born to Goats Vaccinated Against Peste des petits ruminants

In this study,the decay of maternal peste des petits ruminants virus(PPRV) antibodies in kids born to goats vaccinated with Asian lineage IV PPR vaccine and the efficacy of passive immunity against PPRV was assessed to determine the appropriate period for vaccination in kids.Serum samples collected from kids born to vaccinated,unvaccinated and infected goats at different time intervals were tested by PPR competitive ELISA and serum neutralization test(SNT).Maternal antibodies in kids were detectable up to 6 months with a decline trend from the third month onwards and receded below the protective level by the fourth month.The kid with an SN titre of 1:8 at the time of immunization showed significant PPRV specific antibody response(percentage inhibition of 76;SN titers >1:16),when tested on 21 day post-vaccination and was completely protected from infection upon virulent PPRV challenge.Similarly,the kid with 1:8 SN titers was completely protected from PPR infection on active challenge.Therefore,PPR vaccination is recommended in kids,aged 4 months and born to immunized or exposed goats.This could be a suitable period to avoid window of susceptibility in kids to PPRV and the effort to eliminate PPR infection from susceptible populations.     

MVA recombinants expressing the fusion and hemagglutinin genes of PPRV protects goats against virulent challenge

Peste des Petits Ruminants (PPR) is a highly contagious animal disease caused by the Peste des Petits Ruminants virus (PPRV) belonging to the genus morbillivirus and family Paramyxoviridae. The disease results in high morbidity and mortality in goats, sheep and in some small wild ruminants. The presence of large number of small ruminants reared in endemic areas makes PPR a notorious disease threatening the livelihood of poor farmers. Conventional vaccination using a live, attenuated vaccine gives adequate protection but cannot be used in case of eradication of the disease due to difficulty in differentiation of infected animals from the vaccinated ones.     

A Rapid and Sensitive One Step-SYBR Green Based Semi Quantitative Real Time RT-PCR for the Detection of peste des petits ruminants Virus in the Clinical Samples

A sensitive and rapid single step real time (rt) RT-PCR was standardized using one-step Brilliant SYBR Green kit for detection and semi-quantitation of peste des petitis ruminants virus (PPRV) using the virus RNA and matrix (M) protein gene-specific primers and compared with established conventional RT-PCR and Taq Man RT-PCR. The assay amplifies a 124 bp fragment of the PPRV M gene with Tm of 78.28 to 78.50. The assay was linear within a range of 50 ng to 0.5 fg total virus RNA with a detection limit (sensitivity) of 0.5 fg. Based on the serial dilution of the live-attenuated PPR vaccine virus, the detection limit was ~0.0001 cell culture infectious dose 50% units (TCID50). Additionally, swab materials spiked with known titre of vaccine virus were equally well detected in the assay. The standardized rt RT-PCR was easily employed for the detection of PPRV nucleic acid directly in the field and experimental clinical samples. The assay detected the PPRV nucleic acid as early as 3 day post infection (dpi) and up to 20 dpi in swab materials from the experimental samples. The assay was rapid and more sensitive than TaqMan and conventional RT-PCR in the detection of PPRV nucleic acid from the PPR suspected clinical samples of sheep and goats. Therefore, the established, simplified SYBR green rt RT-PCR is an alternative test to the already existing various diagnostic assays and could be useful for rapid clinical diagnosis with advantage in reducing risk of contamination.     

Tissue distribution and expression of signaling lymphocyte activation molecule receptor to peste des petits ruminant virus in goats detected by real-time PCR

In the present study, we investigated the tissue distribution and expression of signaling lymphocyte activation molecule (SLAM) in 40 tissues and organs of goats by real-time RT-PCR, in order to determine the role of these receptors in tissue tropism. SLAM mRNA was detected in all the samples investigated. The expression of SLAM mRNA was detected at high levels in spleen, mesenteric lymph node, hilar lymph node, mandibular lymph node, superficial cervical lymph node, nasal mucosa, duodenum, heart, gallbladder, thymus and blood; this is similar to the tissue tropism of peste des petits ruminant virus. However, it was surprising that expression of SLAM was low in lungs, colon and rectum which are the major sites of replication of PPRV. In addition, very low levels were detected in larynx, tongue and esophagus, which suggest the possible presence of an alternative receptor for PPRV. This study provided the first data on caprine SLAM for use in further studies of the pathogenesis of PPRV in goats.     

Study on passive immunity: Time of vaccination in kids born to goats vaccinated against Peste des petits ruminants

In this study, the decay of maternal peste des petits ruminants virus (PPRV) antibodies in kids born to goats vaccinated with Asian lineage IV PPR vaccine and the efficacy of passive immunity against PPRV was assessed to determine the appropriate period for vaccination in kids. Serum samples collected from kids born to vaccinated, unvaccinated and infected goats at different time intervals were tested by PPR competitive ELISA and serum neutralization test (SNT). Maternal antibodies in kids were detectable up to 6 months with a decline trend from the third month onwards and receded below the protective level by the fourth month. The kid with an SN titre of 1:8 at the time of immunization showed significant PPRV specific antibody response (percentage inhibition of 76; SN titers >1:16), when tested on 21 day post-vaccination and was completely protected from infection upon virulent PPRV challenge. Similarly, the kid with 1:8 SN titers was completely protected from PPR infection on active challenge. Therefore, PPR vaccination is recommended in kids, aged 4 months and born to immunized or exposed goats. This could be a suitable period to avoid window of susceptibility in kids to PPRV and the effort to eliminate PPR infection from susceptible populations.     

羊α干扰素在家蚕中的表达及抗小反刍兽疫病毒活性测定

干扰素具有广谱抗病毒、抗肿瘤活性,可增强机体抗病毒能力,已经广泛应用于病毒性疾病的防控.小反刍兽疫病毒是危害山羊、绵羊等小反刍动物常见的病毒之一,该病毒的传播对全球养殖业造成了严重的影响.为了表达具有高效抗病毒活性的羊α干扰素(OviIFN-α),将OviIFN-α基因序列根据家蚕密码子偏好性进行优化合成,构建pVL1...     

Seroprevalence of Sheep and Goat Pox,Peste Des Petits Ruminants and Rift Valley Fever in Saudi Arabia

Sheep and goat pox, peste des petits ruminants and Rift Valley fever are important diseases of small ruminant livestock. Sheep and goat pox, along with peste des petits ruminants, are endemic throughout most of Africa, Asia and the Middle East. Whereas Rift Valley fever is endemic in Africa, outbreaks in the Middle East have been reported over the past decade, including the Arabian Peninsula. Saudi Arabia is a major importer of livestock, and understanding the prevalence of these viral infections would be useful for disease control. In this study, sera from sheep and goats were collected from 3 regions in Saudi Arabia. They were evaluated for antibodies specific to sheep and goat pox, peste des petits ruminants and Rift Valley fever by virus neutralization assays. To the best of our knowledge, this is the first study to evaluate the seroprevalence of these viruses in sheep and goats.     

Reverse Genetics for Peste des Petits Ruminants Virus: Current Status and Lessons to Learn from Other Non-segmented Negative-Sense RNA Viruses

Peste des petits ruminants (PPR) is a highly contagious transboundary animal disease with a severe socio-economic impact on the livestock industry, particularly in poor countries where it is endemic. Full understanding of PPR virus (PPRV) pathobiology and molecular biology is critical for effective control and eradication of the disease. To achieve these goals, establishment of stable reverse genetics systems for PPRV would play a key role. Unfortunately, this powerful technology remains less accessible and poorly documented for PPRV. In this review, we discussed the current status of PPRV reverse genetics as well as the recent innovations and advances in the reverse genetics of other non-segmented negative-sense RNA viruses that could be applicable to PPRV. These strategies may contribute to the improvement of existing techniques and/or the development of new reverse genetics systems for PPRV.     

Peste des petits ruminants (PPR): Disease appraisal with global and Pakistan perspective

Peste des petits ruminants (PPR), is a highly contagious viral disease affecting domestic and wild small ruminants. It is in the list of animal diseases to be notified to the World Organization for Animal Health (Office International des Epizooties, OIE). Because of the high magnitude of importance of sheep and goats for the poor and landless farmers, the control of disease, which has a negative impact on their productions, is aimed at poverty alleviation. A single injection of live attenuated monovalent vaccine (Nig/75/1) can induce protective immunity for at least the economic life of the animals, however vaccine efficacy only holds if the vaccination is done before exposure and when the animals at sub-clinical level of infection. In Pakistan, though published reports on existence of PPR in the country are few but findings on clinical signs and course of the disease are consistent with the internationally published reports on PPR elsewhere and the neighboring countries. The limited reports of incidence of PPR from few places/provinces do not exclude the possibility of presence of infection in other parts/province of the country. Therefore, the epidemiology, pathogenicity, host susceptibility/resistance and molecular nature of PPR virus have become multifaceted than considered formerly. It is anticipated that patent PPR vaccines and sophisticated diagnostic tests that differentiate infected and vaccinated animals might improve the diagnostic and epidemiological capabilities.     

Early Events following Experimental Infection with Peste-Des-Petits Ruminants Virus Suggest Immune Cell Targeting

Peste-des-petits ruminants virus (PPRV) is a viral pathogen that causes a devastating plague of small ruminants. PPRV is an economically significant disease that continues to be a major obstacle to the development of sustainable agriculture across the developing world. The current understanding of PPRV pathogenesis has been heavily assumed from the closely related rinderpest virus (RPV) and other morbillivirus infections alongside data derived from field outbreaks. There have been few studies reported that have focused on the pathogenesis of PPRV and very little is known about the processes underlying the early stages of infection. In the present study, 15 goats were challenged by the intranasal route with a virulent PPRV isolate, Côte d’Ivoire ’89 (CI/89) and sacrificed at strategically defined time-points post infection to enable pre- and post-mortem sampling. This approach enabled precise monitoring of the progress and distribution of virus throughout the infection from the time of challenge, through peak viraemia and into a period of convalescence. Observations were then related to findings of previous field studies and experimental models of PPRV to develop a clinical scoring system for PPRV. Importantly, histopathological investigations demonstrated that the initial site for virus replication is not within the epithelial cells of the respiratory mucosa, as has been previously reported, but is within the tonsillar tissue and lymph nodes draining the site of inoculation. We propose that virus is taken up by immune cells within the respiratory mucosa which then transport virus to lymphoid tissues where primary virus replication occurs, and from where virus enters circulation. Based on these findings we propose a novel clinical scoring methodology for PPRV pathogenesis and suggest a fundamental shift away from the conventional model of PPRV pathogenesis.     

Complete genome sequence of a peste des petits ruminants virus recovered from wild bharal in tibet, china

For the first time, here we announce the complete genome sequence of a field isolate of Peste des petits ruminants virus (PPRV) derived from macerated rectal tissue of a free living bharal (Pseudois nayaur) that displayed clinical disease consistent with severe infection with PPRV. Further, we compare the full genome of this isolate, termed PPRV Tibet/Bharal/2008, with previously available PPRV genomes, including those of virus isolates from domestic small ruminants local to the area where the reported isolate was collected. The current sequence is phylogenetically classified as a lineage IV virus, sharing high levels of sequence identity with previously described Tibetan PPRV isolates. Indeed, across the entire genome, only 26 nucleotide differences (0.16% nucleotide variation) and, consequently, 9 amino acid changes were present compared to sequences of locally derived viruses.     

Optimal time for vaccination against Peste des petits ruminants (PPR) disease in goats in humid tropical zone in southern Nigeria

Investigation of the incidence of peste des petits ruminants (PPR) disease in goats revealed seasonality in the natural occurrence of PPR disease in the environment. Tissue culture rinderpest vaccine was shown effective in protecting goats against the disease. The optimal time for vaccinating goats against PPR disease was when the least number of animals were incubating the disease. In the tropical humid zone, as in West Africa, the optimal time for vaccination against the PPR disease is from late November to middle of December.     

Combining viral genetic and animal mobility network data to unravel peste des petits ruminants transmission dynamics in West Africa

Peste des petits ruminants (PPR) is a deadly viral disease that mainly affects small domestic ruminants. This disease threaten global food security and rural economy but its control is complicated notably because of extensive, poorly monitored animal movements in infected regions. Here we combined the largest PPR virus genetic and animal mobility network data ever collected in a single region to improve our understanding of PPR endemic transmission dynamics in West African countries. Phylogenetic analyses identified the presence of multiple PPRV genetic clades that may be considered as part of different transmission networks evolving in parallel in West Africa. A strong correlation was found between virus genetic distance and network-related distances. Viruses sampled within the same mobility communities are significantly more likely to belong to the same genetic clade. These results provide evidence for the importance of animal mobility in PPR transmission in the region. Some nodes of the network were associated with PPRV sequences belonging to different clades, representing potential “hotspots” for PPR circulation. Our results suggest that combining genetic and mobility network data could help identifying sites that are key for virus entrance and spread in specific areas. Such information could enhance our capacity to develop locally adapted control and surveillance strategies, using among other risk factors, information on animal mobility.     

A rapid and sensitive one step-SYBR green based semi quantitative real time RT-PCR for the detection of <Emphasis Type="Italic">peste des petits ruminants</Emphasis> virus in the clinical samples

A sensitive and rapid single step real time (rt) RT-PCR was standardized using one-step Brilliant SYBR Green kit® for detection and semi-quantitation of peste des petitis ruminants virus (PPRV) using the virus RNA and matrix (M) protein gene-specific primers and compared with established conventional RT-PCR and TaqMan RT-PCR. The assay amplifies a 124 bp fragment of the PPRV M gene with T_m of 78.28 to 78.50. The assay was linear within a range of 50 ng to 0.5 fg total virus RNA with a detection limit (sensitivity) of 0.5 fg. Based on the serial dilution of the live-attenuated PPR vaccine virus, the detection limit was ～0.0001 cell culture infectious dose 50% units (TCID₅₀). Additionally, swab materials spiked with known titre of vaccine virus were equally well detected in the assay. The standardized rt RT-PCR was easily employed for the detection of PPRV nucleic acid directly in the field and experimental clinical samples. The assay detected the PPRV nucleic acid as early as 3 day post infection (dpi) and up to 20 dpi in swab materials from the experimental samples. The assay was rapid and more sensitive than TaqMan and conventional RT-PCR in the detection of PPRV nucleic acid from the PPR suspected clinical samples of sheep and goats. Therefore, the established, simplified SYBR green rt RT-PCR is an alternative test to the already existing various diagnostic assays and could be useful for rapid clinical diagnosis with advantage in reducing risk of contamination.     

Fluid, electrolyte and haematological changes in experimental peste des petits ruminants virus infection in West African dwarf goats

The changes in plasma volume, blood volume, erythrocyte indices, leucocyte indices and serum biochemical values during experimental pestes des petits ruminants (PPR) virus infection of West African dwarf goats (Fouta djallon) were investigated. There was a progressive decline of the plasma volume and serum sodium and potassium values in all the infected goats as from day 5 post-infection and this became quite marked between days 10 and 23 post-infection. The fall was severest in those animals which had diarrhoea. There were no significant changes in the chloride, bicarbonate, phosphate, urea, total protein and albumin values of the goats during the course of the diseases. Haemoconcentration and apparent polycythaemia in the early and terminal stages of the disease were associated with severe dehydration which characterized the infection. There was initial neutrophilic leucocytosis during the phase of fever followed by marked lymphopaenic leucopaenia which progressed terminally in most of the infected goats. The destructive effect of the virus on lymphocytes is suggested as a cause of lymphopaenia.     

小反刍兽疫研究概况

小反刍兽疫是严重危害山羊和绵羊等家畜的A类动物传染病,目前该病已经给我国养羊业造成了巨大的威胁。近年来,国内外学者对该病开展了许多研究工作,本文从病原学、流行病学、临床症状、发病机理、病理变化、诊断、防控措施等几个方面对该病研究概况进行了综述,为该病的有效防控提供有益的参考。