Immunomodulatory properties of morbillivirus nucleoproteins

Potential role of peste des petits ruminants virus in small ruminant abortions

The aim of the present study was to investigate the frequency, genetic variability, and phylogeny of the peste des petits ruminants virus (PPRV) in ovine and caprine fetuses. During 2014 and 2017, a total of 1054 embryos/fetuses were collected in Turkey. A real-time RT-PCR assay was used for the detection of the PPRV RNA. Genetic characterization and phylogenetic analysis of the PPRV field isolates were conducted by sequencing fusion (F) protein and nucleoprotein (N) gene segments. Samples were also collected from ewes (n = 83) and nanny goats (n = 3) that had aborted and whose embryos/fetuses were found to be PPRV positive. PPRV positive embryos/fetuses were also tested for the presence of Listeria monocytogenes, Campylobacter spp., Coxiella burnetii, Chlamydophila abortus, Brucella spp., akabane virus, aino virus, bluetongue virus, border disease virus, bovine viral diarrhea virus, Cache Valley virus, and Schmallenberg virus. PPRV RNA was detected in 123 (11.7%) of the 1054 embryos/fetuses, 78 of the 83 (94%) ewes and 3 (100%) nanny goats. Border disease virus RNA and Chlamydophila abortus DNA were detected in 7 and 12 PPRV positive sheep fetuses, respectively, while other bacterial and viral agents were not detected. Phylogenetically, the field isolates in this study belong to lineage IV, and compared to other strains of lineage IV considered in this study, they showed 1 and 5 new amino acid substitutions in the F and N gene sequences, respectively. The results of the study suggest that PPRV plays an important role in abortion. Therefore, PPRV needs to be taken into consideration in sheep and goats abortions.

Recombinase polymerase amplification-lateral flow dipstick (RPA-LFD) designed for rapid detection of canine distemper virus

In the present study, recombinase polymerase amplification (RPA) was combined with the colloidal gold lateral flow dipstick (LFD) method to establish a new, stable, and efficient assay for the detection of canine distemper virus (CDV). We designed a set of specific primers labeled with biotin and a specific probe labeled with dSpacer and C3 spacer, according to the conserved region in the N-terminal gene sequence of CDV. The reaction conditions and systems were then optimized, and the sensitivity and specificity were analyzed for potential clinical application. The results showed that the RPA-LFD assay for CDV detection was successfully established. We also found that the temperature in a closed fist (35°C) is optimal for the RPA reaction. The optimal ratio of primer to probe was 2:1. The minimum detection limit of the RPA-LFD assay was 1 × 101 the median tissue culture infective dose (TCID50)/mL. Using this assay with samples from experimentally infected dogs, CDV was detected in nasal secretions, eye secretions, and blood on the fourth day post infection. In summary, this novel RPA-LFD assay for CDV detection is simple to use, and preliminary findings indicate its high specificity and sensitivity.

Comparison of some cytokines, acute phase proteins and citrulline levels in healthy and canine distemper infected dogs

Canine distemper virus (CDV) is the etiological agent of severe disease in domestic and wild carnivores. Clinical diagnosis of CDV is challenging because of its similarity to other canine respiratory and intestinal diseases. We aimed to determine certain cytokine (interleukin [IL]-1β, IL-2, IL-4, IL-6, IL-10, and tumor necrosis factor-α [TNF-α]), interferon (IFN)-γ, canine serum amyloid A (SAA), and canine citrulline (CIT) levels for the first time in CDV-positive dogs. For this purpose, 10 CDV-positive dogs with compatible clinical findings (i.e., neurological symptoms such as tremors and myoclonus, ocular and nasal discharge, and wheezing) and 10 healthy dogs based on the clinical examinations and rapid test results were enrolled. It was observed that the CIT, INF-γ, IL-1β, IL-2, IL-6, and TNF-α levels were significantly decreased in the CDV-positive dogs than that of the healthy ones (P<0.05). As a result, it was observed that CDV causes immunosuppression and accordingly, the inflammatory response might cause decreased cytokine and acute-phase protein synthesis. Therefore, it was concluded that further investigation of inflammatory pathways and CIT interactions may provide crucial clinical information at different stages of CDV, and aforementioned parameters may serve as important biomarkers for CDV in terms of demonstrating the presence of immunosuppression.

Nebulized fusion inhibitory peptide protects cynomolgus macaques from measles virus infection

Measles is the most contagious airborne viral infection and the leading cause of child death among vaccine-preventable diseases. We show here that aerosolized lipopeptide fusion inhibitor, derived from heptad-repeat regions of the measles virus (MeV) fusion protein, blocks respiratory MeV infection in a non-human primate model, the cynomolgus macaque. We use a custom-designed mesh nebulizer to ensure efficient aerosol delivery of peptide to the respiratory tract and demonstrate the absence of adverse effects and lung pathology in macaques. The nebulized peptide efficiently prevents MeV infection, resulting in the complete absence of MeV RNA, MeV-infected cells, and MeV-specific humoral responses in treated animals. This strategy provides an additional means to fight against respiratory infection in non-vaccinated people, that can be readily translated to human trials. It presents a proof-of-concept for the aerosol delivery of fusion inhibitory peptides to protect against measles and other airborne viruses, including SARS-CoV-2, in case of high-risk exposure.

Antiviral Effectivity of Favipiravir Against Peste Des Petits Ruminants Virus Is Mediated by the JAK/STAT and PI3K/AKT Pathways

Peste des petits ruminants virus (PPRV), belonging to the genus Morbillivirus in the family Paramyxoviridae, causes severe infectious disease in small ruminants and has been rapidly spreading in many parts of Africa, the Middle East, and Asia. Although vaccination is considered to be an effective means of controlling PPR, the heat-sensitive nature of the vaccines against PPRV greatly limits their application in areas with a hot climate. In the present study, we investigated the anti-PPRV effects of favipiravir and sought to identify the underlying mechanisms in vitro using the Vero cell line. MTT assays, Western blotting, indirect immunofluorescence assays, virus plaque formation assays, and qRT-PCR were used to assess the effects of favipiravir on the life cycle of PPRV and the expression of RNA-dependent RNA polymerase (RdRp). Additionally, the expression levels of JAK1, STAT1, phosphorylated (p)-STAT1, PI3K, AKT, and p-AKT, as well as those of signaling molecules acting downstream of the JAK/STAT and PI3K/AKT signaling pathways, were determined by Western blotting and qRT-PCR. The results indicated that, in PPRV-infected, favipiravir-treated Vero cells, the attachment, invasion, replication, and release of PPRV were significantly inhibited, as was the expression of RdRp, when compared with that in untreated PPRV-infected cells. Furthermore, in favipiravir-treated cells, the expression of JAK1 and STAT1 was downregulated, whereas that of p-STAT1 was significantly upregulated. Similarly, the expression levels of PKR, IRF9, ISG54, and MxA proteins that are associated with innate antiviral activity in host cells were also markedly increased. Moreover, with favipiravir treatment, the expression of PI3K and p-AKT and the p-AKT/AKT ratio were significantly decreased, whereas the expression of AKT was noticeably upregulated. The expression of GSK3, NF-κB p65, p-NF-κB p65, and BAD was also increased with favipiravir treatment, while the expression of CREB, p-CREB, p-GSK3, and Bcl-2 was slightly decreased. In addition, all the p-GSK3/GSK3, p-CREB/CREB, p-NF-κB/NF-κB, and p-BAD/BAD ratios were significantly reduced in favipiravir-treated cells. These results implied that the antiviral effectivity of favipiravir against PPRV is mediated by the JAK/STAT and PI3K/AKT pathways and that favipiravir has potential for use as an effective antiviral agent against PPRV.

Dysregulation of the RIG-I-like Receptor Pathway Signaling by Peste des Petits Ruminants Virus Phosphoprotein

Peste des petits ruminants virus (PPRV) is a Morbillivirus that causes highly contagious and severe disease in various ruminants. PPRV infection leads to a severe inhibition of host antiviral immune response. Our previous study demonstrated that PPRV V protein blocks IFN response by targeting STAT proteins. In the current study, we identified the phosphoprotein (P) as a novel antagonistic factor of PPRV to counteract host antiviral innate immune response. PPRV P protein significantly suppressed RIG-I-like receptor pathway signaling and impaired IFN-β and ISGs expression by targeting IFN regulatory factor (IRF)3 in both human embryonic kidney 293T cells and primary goat fibroblasts. The 1-102 region of P protein was critical for the antagonistic function of P protein. P protein interacted with IRF association domain (IAD) of IRF3 to block the interaction between TBK1 and IRF3. The interaction between TBK1 and the IAD of IRF3 is responsible for triggering the phosphorylation of IRF3. P protein competed with TBK1 to bind to the IAD of IRF3 that contributed to the decreased phosphorylation of IRF3, which, in turn, interfered with the dimerization of IRF3 and blocked IRF3 nuclear transportation. Besides, we also found that P protein interacted with IRF5 and IRF8. However, the involved mechanism remains unknown. Taken together, our results reveal a novel mechanism by which PPRV P protein antagonizes host antiviral innate immune response by interacting with the transcription factor IRF3, thereby inhibiting the type I IFN production and promoting viral replication.

Peste des Petits Ruminants Virus Nucleocapsid Protein Inhibits Beta Interferon Production by Interacting with IRF3 To Block Its Activation

Peste des petits ruminants is a highly contagious animal disease affecting small ruminants, which threatens both small livestock and endangered susceptible wildlife populations in many countries. The causative agent, peste des petits ruminants virus (PPRV), often causes acute immunosuppression in its natural hosts during infection. Here, for the first time, we demonstrate that N protein, the most abundant protein of PPRV, plays an extremely important role in suppression of interferon regulatory factor 3 (IRF3) function and type I interferon (IFN) production by interfering with the formation of the TBK1-IRF3 complex. This study explored a novel antagonistic mechanism of PPRV.

Peste des petits ruminants virus (PPRV) is the etiological agent of peste des petits ruminants, causing acute immunosuppression in its natural hosts. However, the molecular mechanisms by which PPRV antagonizes the host immune responses have not been fully characterized. In particular, how PPRV suppresses the activation of the host RIG-I-like receptor (RLR) pathway has yet to be clarified. In this study, we demonstrated that PPRV infection significantly suppresses RLR pathway activation and type I interferon (IFN) production and identified PPRV N protein as an extremely important antagonistic viral factor that suppresses beta interferon (IFN-β) and IFN-stimulated gene (ISG) expression. A detailed analysis showed that PPRV N protein inhibited type I IFN production by targeting interferon regulatory factor 3 (IRF3), a key molecule in the RLR pathway required for type I IFN induction. PPRV N protein interacted with IRF3 (but not with other components of the RLR pathway, including MDA5, RIG-I, VISA, TBK1, and MITA) and abrogated the phosphorylation of IRF3. As expected, PPRV N protein also considerably impaired the nuclear translocation of IRF3. The TBK1-IRF3 interaction was involved significantly in IRF3 phosphorylation, and we showed that PPRV N protein inhibits the association between TBK1 and IRF3, which in turn inhibits IRF3 phosphorylation. The amino acid region 106 to 210 of PPRV N protein was determined to be essential for suppressing the nuclear translocation of IRF3 and IFN-β production, and the 140 to 400 region of IRF3 was identified as the crucial region for the N-IRF3 interaction. Together, our findings demonstrate a new mechanism evolved by PPRV to inhibit type I IFN production and provide structural insights into the immunosuppression caused by PPRV.

IMPORTANCE Peste des petits ruminants is a highly contagious animal disease affecting small ruminants, which threatens both small livestock and endangered susceptible wildlife populations in many countries. The causative agent, peste des petits ruminants virus (PPRV), often causes acute immunosuppression in its natural hosts during infection. Here, for the first time, we demonstrate that N protein, the most abundant protein of PPRV, plays an extremely important role in suppression of interferon regulatory factor 3 (IRF3) function and type I interferon (IFN) production by interfering with the formation of the TBK1-IRF3 complex. This study explored a novel antagonistic mechanism of PPRV.

Advances in peste des petits ruminants vaccines

Peste des petits ruminants (PPR) is a highly contagious disease of small ruminants that leads to high morbidity and mortality thereby results in devastating economic consequences to the livestock industry. PPR is currently endemic across most parts of Asia and Africa, the two regions with the highest concentration of poor people in the world. Sheep and goats in particularly contribute significantly towards the upliftment of livelihood of the poor and marginal farmers in these regions. In this context, PPR directly affecting the viability of sheep and goat husbandry has emerged as a major hurdle in the development of these regions. The control of PPR in these regions could significantly contribute to poverty alleviation, therefore, the Office International des Epizooties (OIE) and Food and Agricultural Organization (FAO) have targeted the control and eradication of PPR by 2030 a priority. In order to achieve this goal, a potent, safe and efficacious live-attenuated PPR vaccine with long-lasting immunity is available for immunoprophylaxis. However, the live-attenuated PPR vaccine is thermolabile and needs maintenance of an effective cold chain to deliver into the field. In addition, the infected animals cannot be differentiated from vaccinated animals. To overcome these limitations, some recombinant vaccines have been developed. This review comprehensively describes about the latest developments in PPR vaccines.

Systems Perspective of Morbillivirus Replication

Systems biology refers to system-wide changes in biological components such as RNA/DNA (genomics), protein (proteomics) and lipids (lipidomics). In this review, we provide comprehensive information about morbillivirus replication. Besides discussing the role of individual viral/host proteins in virus replication, we also discuss how systems-level analyses could improve our understanding of morbillivirus replication, host-pathogen interaction, immune response and disease resistance. Finally, we discuss how viroinformatics is likely to provide important insights for understanding genome-genome, genome-protein and protein-protein interactions.

Protection from Hendra virus infection with Canarypox recombinant vaccine

Hendra virus (HeV) is an emerging zoonotic pathogen, which causes severe respiratory illness and encephalitis in humans and horses. Since its first appearance in 1994, spillovers of HeV from its natural reservoir fruit bats occur on almost an annual basis. The high mortality rate in both humans and horses and the wide-ranging reservoir distribution are making HeV a serious public health problem, especially for people exposed to sick horses. This study has aimed to develop an efficient low-cost HeV vaccine for horses based on Canarypox recombinant vector expressing HeV glycoproteins, attachment glycoprotein (G) and fusion protein (F). This vaccine was used to immunise hamsters and then challenged intraperitoneally with HeV 3 weeks later. The higher tested dose of the vaccine efficiently prevented oropharyngeal virus shedding and protected animals from clinical disease and virus-induced mortality. Vaccine induced generation of seroneutralising antibodies and prevented virus-induced histopathological changes and a production of viral RNA and antigens in animal tissues. Interestingly, some vaccinated animals, including those immunised at a lower dose, were protected in the absence of detectable specific antibodies, suggesting the induction of an efficient virus-specific cellular immunity. Finally, ponies immunised using the same vaccination protocol as hamsters developed strong seroneutralising titres against both HeV and closely related Nipah virus, indicating that this vaccine may have the ability to induce cross-protection against Henipavirus infection. These data suggest that Canarypox-based vectors encoding for HeV glycoproteins present very promising new vaccine candidate to prevent infection and shedding of the highly lethal HeV.

Order and Disorder in the Replicative Complex of Paramyxoviruses

In this review we summarize available data showing the abundance of structural disorder within the nucleoprotein (N) and phosphoprotein (P) from three paramyxoviruses, namely the measles (MeV), Nipah (NiV) and Hendra (HeV) viruses. We provide a detailed description of the molecular mechanisms that govern the disorder-to-order transition that the intrinsically disordered C-terminal domain (NTAIL) of their N proteins undergoes upon binding to the C-terminal X domain (XD) of the homologous P proteins. We also show that a significant flexibility persists within NTAIL-XD complexes, which therefore provide illustrative examples of "fuzziness". The functional implications of structural disorder for viral transcription and replication are discussed in light of the ability of disordered regions to establish a complex molecular partnership and to confer a considerable reach to the elements of the replicative machinery.

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.

Dynamic changes of Foxp3(+) regulatory T cells in spleen and brain of canine distemper virus-infected dogs

Canine distemper virus (CDV) infection causes immunosuppression and demyelinating leukoencephalitis in dogs. In viral diseases, an ambiguous function of regulatory T cells (Treg), with both beneficial effects by reducing immunopathology and detrimental effects by inhibiting antiviral immunity, has been described. However, the role of Treg in the pathogenesis of canine distemper remains unknown. In order to determine the effect of CDV upon immune homeostasis, the amount of Foxp3(+) Treg in spleen and brain of naturally infected dogs has been determined by immunohistochemistry. In addition, splenic cytokine expression has been quantified by reverse transcriptase polymerase chain reaction. Splenic depletion of Foxp3(+) Treg was associated with an increased mRNA-expression of tumor necrosis factor and decreased transcription of interleukin-2 in the acute disease phase, indicative of disturbed immunological counter regulation in peripheral lymphoid organs. In the brain, a lack of Foxp3(+) Treg in predemyelinating and early demyelinating lesions and significantly increased infiltrations of Foxp3(+) Treg in chronic demyelinating lesions were observed. In conclusion, disturbed peripheral and CNS immune regulation associated with a reduction of Treg represents a potential prerequisite for excessive neuroinflammation and early lesion development in canine distemper leukoencephalitis.

Peste des Petits Ruminants, the next eradicated animal disease?

Peste des Petits Ruminants (PPR) is a widespread viral disease caused by a Morbillivirus (Paramyxoviridae). There is a single serotype of PPR virus, but four distinct genetic lineages. Morbidity and mortality are high when occurring in naive sheep and goats populations. Cattle and African buffaloes (Syncerus caffer) are asymptomatically infected. Other wild ruminants and camels may express clinical signs and mortality. PPR has recently spread in southern and northern Africa, and in central and far-east Asia. More than one billion sheep and goats worldwide are at risk. PPR is also present in Europe through western Turkey. Because of its clinical incidence and the restrictions on animal movements, PPR is a disease of major economic importance. A live attenuated vaccine was developed in the 1980s, and has been widely used in sheep and goats. Current researches aim (i) to make it more thermotolerant for use in countries with limited cold chain, and (ii) to add a DIVA mark to shorten and reduce the cost of final eradication. Rinderpest virus-another Morbillivirus-was the first animal virus to be eradicated from Earth. PPRV has been proposed as the next candidate. Considering its wide distribution and its multiple target host species which have an intense mobility, it will be a long process that cannot exclusively rely on mass vaccination. PPR specific epidemiological features and socio-economic considerations will also have to be taken into account, and sustained international, coordinated, and funded strategy based on a regional approach of PPR control will be the guarantee toward success.

Dolphin morbillivirus infection in a captive harbor seal (Phoca vitulina)

During the second morbillivirus epidemic (2007 to 2011) in cetaceans along the Italian coastline, dolphin morbillivirus (DMV) was detected by molecular analyses in a captive harbor seal (Phoca vitulina), with pathological findings consistent with morbillivirus infection. This report confirms interspecies DMV transmission from cetaceans to pinnipeds.

Characterization of the interactions between the nucleoprotein and the phosphoprotein of Henipavirus

The Henipavirus genome is encapsidated by the nucleoprotein (N) within a helical nucleocapsid that recruits the polymerase complex via the phosphoprotein (P). In a previous study, we reported that in henipaviruses, the N-terminal domain of the phosphoprotein and the C-terminal domain of the nucleoprotein (N(TAIL)) are both intrinsically disordered. Here we show that Henipavirus N(TAIL) domains are also disordered in the context of full-length nucleoproteins. We also report the cloning, purification, and characterization of the C-terminal X domains (P(XD)) of Henipavirus phosphoproteins. Using isothermal titration calorimetry, we show that N(TAIL) and P(XD) form a 1:1 stoichiometric complex that is stable under NaCl concentrations as high as 1 M and has a K(D) in the μM range. Using far-UV circular dichroism and nuclear magnetic resonance, we show that P(XD) triggers an increase in the α-helical content of N(TAIL). Using fluorescence spectroscopy, we show that P(XD) has no impact on the chemical environment of a Trp residue introduced at position 527 of the Henipavirus N(TAIL) domain, thus arguing for the lack of stable contacts between the C termini of N(TAIL) and P(XD). Finally, we present a tentative structural model of the N(TAIL)-P(XD) interaction in which a short, order-prone region of N(TAIL) (α-MoRE; amino acids 473-493) adopts an α-helical conformation and is embedded between helices α2 and α3 of P(XD), leading to a relatively small interface dominated by hydrophobic contacts. The present results provide the first detailed experimental characterization of the N-P interaction in henipaviruses and designate the N(TAIL)-P(XD) interaction as a valuable target for rational antiviral approaches.

Peptide-protein microarrays and surface plasmon resonance detection: biosensors for versatile biomolecular interaction analysis

Biosensors in microarray format provide promising tools for high-throughput analyses of complex samples. Although they are able to detect, quantify and characterize a multitude of compounds, most of the available devices are specialized in the analysis of one type of interaction, limiting their application to a define area. The aim of our work was to develop and characterize versatile protein (or peptide) microarrays suitable for the simultaneous analysis of a large panel of biological interactions. Our system involved a simple procedure to immobilized proteins or peptides, based on pyrrole electropolymerization, and ligand binding was detected by imaging the surface plasmon resonance. We demonstrated its suitability in three different contexts, i.e. humoral response characterization, ion binding analysis and cell detection. This work evidences the potentiality of this approach which allows multiparametric, high-throughput and label-free analysis of biological samples suitable for the detection of compounds as various as proteins, ions or cells and the characterization of their interaction with peptides or proteins.

Interplay between virus-specific effector response and Foxp3 regulatory T cells in measles virus immunopathogenesis

Measles is a highly contagious childhood disease associated with an immunological paradox: although a strong virus-specific immune response results in virus clearance and the establishment of a life-long immunity, measles infection is followed by an acute and profound immunosuppression leading to an increased susceptibility to secondary infections and high infant mortality. In certain cases, measles is followed by fatal neurological complications. To elucidate measles immunopathology, we have analyzed the immune response to measles virus in mice transgenic for the measles virus receptor, human CD150. These animals are highly susceptible to intranasal infection with wild-type measles strains. Similarly to what has been observed in children with measles, infection of suckling transgenic mice leads to a robust activation of both T and B lymphocytes, generation of virus-specific cytotoxic T cells and antibody responses. Interestingly, Foxp3(+)CD25(+)CD4(+) regulatory T cells are highly enriched following infection, both in the periphery and in the brain, where the virus intensively replicates. Although specific anti-viral responses develop in spite of increased frequency of regulatory T cells, the capability of T lymphocytes to respond to virus-unrelated antigens was strongly suppressed. Infected adult CD150 transgenic mice crossed in an interferon receptor type I-deficient background develop generalized immunosuppression with an increased frequency of CD4(+)CD25(+)Foxp3(+) T cells and strong reduction of the hypersensitivity response. These results show that measles virus affects regulatory T-cell homeostasis and suggest that an interplay between virus-specific effector responses and regulatory T cells plays an important role in measles immunopathogenesis. A better understanding of the balance between measles-induced effector and regulatory T cells, both in the periphery and in the brain, may be of critical importance in the design of novel approaches for the prevention and treatment of measles pathology.

Pathogenesis and immunopathology of systemic and nervous canine distemper

Canine distemper is a worldwide occurring infectious disease of dogs, caused by a morbillivirus, closely related to measles and rinderpest virus. The natural host range comprises predominantly carnivores. Canine distemper virus (CDV), an enveloped, negative-sense RNA virus, infects different cell types, including epithelial, mesenchymal, neuroendocrine and hematopoietic cells of various organs and tissues. CDV infection of dogs is characterized by a systemic and/or nervous clinical course and viral persistence in selected organs including the central nervous system (CNS) and lymphoid tissue. Main manifestations include respiratory and gastrointestinal signs, immunosuppression and demyelinating leukoencephalomyelitis (DL). Impaired immune function, associated with depletion of lymphoid organs, consists of a viremia-associated loss of lymphocytes, especially of CD4+ T cells, due to lymphoid cell apoptosis in the early phase. After clearance of the virus from the peripheral blood an assumed diminished antigen presentation and altered lymphocyte maturation cause an ongoing immunosuppression despite repopulation of lymphoid organs. The early phase of DL is a sequel of a direct virus-mediated damage and infiltrating CD8+ cytotoxic T cells associated with an up-regulation of pro-inflammatory cytokines such as interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-alpha and IL-12 and a lacking response of immunomodulatory cytokines such as IL-10 and transforming growth factor (TGF)-beta. A CD4+-mediated delayed type hypersensitivity and cytotoxic CD8+ T cells contribute to myelin loss in the chronic phase. Additionally, up-regulation of interferon-gamma and IL-1 may occur in advanced lesions. Moreover, an altered balance between matrix metalloproteinases and their inhibitors seems to play a pivotal role for the pathogenesis of DL. Summarized, DL represents a biphasic disease process consisting of an initial direct virus-mediated process and immune-mediated plaque progression. Immunosuppression is due to early virus-mediated lymphocytolysis followed by still poorly understood mechanisms affecting antigen presentation and lymphocyte maturation.

Canine distemper virus

Vaccine-based prophylaxis has greatly helped to keep distemper disease under control. Notwithstanding, the incidence of canine distemper virus (CDV)-related disease in canine populations throughout the world seems to have increased in the past decades, and several episodes of CDV disease in vaccinated animals have been reported, with nation-wide proportions in some cases. Increasing surveillance should be pivotal to identify new CDV variants and to understand the dynamics of CDV epidemiology. In addition, it is important to evaluate whether the efficacy of the vaccine against these new strains may somehow be affected.

Pathogen evolution and disease emergence in carnivores

Emerging infectious diseases constitute some of the most pressing problems for both human and domestic animal health, and biodiversity conservation. Currently it is not clear whether the removal of past constraints on geographical distribution and transmission possibilities for pathogens alone are sufficient to give rise to novel host-pathogen combinations, or whether pathogen evolution is also generally required for establishment in novel hosts. Canine distemper virus (CDV) is a morbillivirus that is prevalent in the world dog population and poses an important conservation threat to a diverse range of carnivores. We performed an extensive phylogenetic and molecular evolution analysis on complete sequences of all CDV genes to assess the role of selection and recombination in shaping viral genetic diversity and driving the emergence of CDV in non-dog hosts. We tested the specific hypothesis that molecular adaptation at known receptor-binding sites of the haemagglutinin gene is associated with independent instances of the spread of CDV to novel non-dog hosts in the wild. This hypothesis was upheld, providing compelling evidence that repeated evolution at known functional sites (in this case residues 530 and 549 of the haemagglutinin molecule) is associated with multiple independent occurrences of disease emergence in a range of novel host species.

Measles virus nucleoprotein induces a regulatory immune response and reduces atherosclerosis in mice

BACKGROUND

Recent studies clearly suggest that regulatory T cells play a critical role in the control of the immunoinflammatory response in atherosclerosis and substantially limit lesion development. Measles virus infection or vaccination is associated with immune depression, in part through the induction of an antiinflammatory response by measles virus nucleoprotein. We hypothesized that the antiinflammatory properties of measles virus nucleoprotein may limit the development atherosclerosis.

METHODS AND RESULTS

Here, we show for the first time that repetitive administration of measles virus nucleoprotein to apolipoprotein E-deficient mice promotes an antiinflammatory T-regulatory-cell type 1-like response and inhibits macrophage and T-cell accumulation within the lesions. Treatment with measles virus nucleoprotein significantly reduces the development of new atherosclerotic plaques and markedly inhibits the progression of established lesions. The antiatherosclerotic potential of nucleoprotein is retained in its short N-terminal segment. The protective effects on lesion size are lost in mice with lymphocyte deficiency.

CONCLUSIONS

Our findings identify a novel mechanism of immune modulation by measles virus nucleoprotein through the promotion of a regulatory T-cell response and suggest that this property may be harnessed for treating atherosclerosis, the first cause of heart disease and stroke.

Involvement of morbilliviruses in the pathogenesis of demyelinating disease

Two members of the morbillivirus genus of the family Paramyxoviridae, canine distemper virus (CDV) and measles virus (MV), are well-known for their ability to cause a chronic demyelinating disease of the CNS in their natural hosts, dogs and humans, respectively. Both viruses have been studied for their potential involvement in the neuropathogenesis of the human demyelinating disease multiple sclerosis (MS). Recently, three new members of the morbillivirus genus, phocine distemper virus (PDV), porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV), have been discovered. These viruses have also been shown to induce multifocal demyelinating disease in infected animals. This review focuses on morbillivirus-induced neuropathologies with emphasis on aetiopathogenesis of CNS demyelination. The possible involvement of a morbillivirus in the pathogenesis of multiple sclerosis is discussed.

Mapping and structural analysis of B-cell epitopes on the morbillivirus nucleoprotein amino terminus

By analysing the antigenic structure of the morbillivirus nucleoprotein (N) using a competitive-binding assay of monoclonal antibodies (mAbs), six different antigenic sites were identified previously. By using Pepscan methodology complemented by analysis of truncated N proteins, a better characterization of five of these antigenic sites was provided: I, II, III, IV and VI. mAbs specific to Rinderpest virus, defining antigenic sites II, III and IV, and those common to four morbilliviruses, delineating sites I and VI, were analysed in the present study. It was found that all but one mapped to the same region, between aa 120 and 149 of N. However, the mAb 3-1 epitope was located in the carboxy-terminal region (aa 421-525). This result may indicate the high immunogenicity of the amino-terminal variable region, at least in the mouse. It was surprising that the epitope of mAb 33-4, antigenic site VI, which recognized all morbilliviruses so far tested, was located in one of the two non-conserved regions between morbillivirus N proteins. It is shown that the conserved amino acid motif (126)EAD(128)----(131)F-------(148)EN(149) is critical for epitope constitution and recognition.