Inhibition of in vitro leukocyte proliferation by morbilliviruses

Peste des petits ruminants virus non-structural V and C proteins interact with the NF-κB p65 subunit and modulate pro-inflammatory cytokine gene induction

Peste des petits ruminants virus (PPRV) is known to induce transient immunosuppression in infected small ruminants by modulating several cellular pathways involved in the antiviral immune response. Our study shows that the PPRV-coded non-structural proteins C and V can interact with the cellular NF-κB p65 subunit. The PPRV-C protein interacts with the transactivation domain (TAD) while PPRV-V interacts with the Rel homology domain (RHD) of the NF-κB p65 subunit. Both viral proteins can suppress the NF-κB transcriptional activity and NF-κB-mediated transcription of cellular genes. PPRV-V protein expression can significantly inhibit the nuclear translocation of NF-κB p65 upon TNF-α stimulation, whereas PPRV-C does not affect it. The NF-κB-mediated pro-inflammatory cytokine gene expression is significantly downregulated in cells expressing PPRV-C or PPRV-V protein. Our study provides evidence suggesting a role of PPRV non-structural proteins V and C in the modulation of NF-κB signalling through interaction with the NF-κB p65 subunit.

Inhibition of caspase-1-dependent apoptosis suppresses peste des petits ruminants virus replication

BACKGROUND

Peste des petits ruminants (PPR), caused by the PPR virus (PPRV), is an acute and fatal contagious disease that mainly infects goats, sheep, and other artiodactyls. Peripheral blood mononuclear cells (PBMCs) are considered the primary innate immune cells.

OBJECTIVES

PBMCs derived from goats were infected with PPRV and analyzed to detect the relationship between PPRV replication and apoptosis or the inflammatory response.

METHODS

Quantitative real-time polymerase chain reaction was used to identify PPRV replication and cytokines expression. Flow cytometry was conducted to detect apoptosis and the differentiation of CD4+ and CD8+ T cells after PPRV infection.

RESULTS

PPRV stimulated the differentiation of CD4+ and CD8+ T cells. In addition, PPRV induced apoptosis in goat PBMCs. Furthermore, apoptosis and the inflammatory response induced by PPRV could be suppressed by Z-VAD-FMK and Z-YVAD-FMK, respectively. Moreover, the virus titer of PPRV was attenuated by inhibiting caspase-1-dependent apoptosis and inflammation.

CONCLUSIONS

This study showed that apoptosis and the inflammatory response play an essential role in PPR viral replication in vitro, providing a new mechanism related to the cell host response.

Peste des petits ruminants virus induces ERS-mediated autophagy to promote virus replication

Peste des petits ruminants virus (PPRV) has long been a significant threat to small ruminant productivity worldwide. Virus infection-induced endoplasmic reticulum (ER) stress (ERS) and the subsequently activated unfolded protein response (UPR) play significant roles in viral replication and pathogenesis. However, the relationship between ERS and PPRV infection is unknown. In this study, we demonstrated that ERS was induced during PPRV infection in caprine endometrial epithelial cells (EECs). Importantly, we demonstrated that the induction of autophagy by PPRV was mediated by ERS. Furthermore, we found that the PERK/eIF2α pathway but not the ATF6 or IRE1 pathway was activated and that the activated PERK/eIF2α pathway participated in regulating ERS-mediated autophagy. Moreover, virus replication was required for PPRV infection-induced ERS-mediated autophagy and PERK pathway activation. Additionally, we revealed that either the viral nucleocapsid (N) or nonstructural protein C was sufficient to elicit ERS and activate the PERK/eIF2α pathway, which further increased autophagy. Taken together, these results suggest that PPRV N and C protein-induced autophagy enhances viral replication through the induction of ERS and that the PERK pathway may be involved in the activation of ERS-mediated autophagy during PPRV infection.

Systematic Determination of Herpesvirus in Free-Ranging Cetaceans Stranded in the Western Mediterranean: Tissue Tropism and Associated Lesions

The monitoring of herpesvirus infection provides useful information when assessing marine mammals’ health. This paper shows the prevalence of herpesvirus infection (80.85%) in 47 cetaceans stranded on the coast of the Valencian Community, Spain. Of the 966 tissues evaluated, 121 tested positive when employing nested-PCR (12.53%). The largest proportion of herpesvirus-positive tissue samples was in the reproductive system, nervous system, and tegument. Herpesvirus was more prevalent in females, juveniles, and calves. More than half the DNA PCR positive tissues contained herpesvirus RNA, indicating the presence of actively replicating virus. This RNA was most frequently found in neonates. Fourteen unique sequences were identified. Most amplified sequences belonged to the Gammaherpesvirinae subfamily, but a greater variation was found in Alphaherpesvirinae sequences. This is the first report of systematic herpesvirus DNA and RNA determination in free-ranging cetaceans. Nine (19.14%) were infected with cetacean morbillivirus and all of them (100%) were coinfected with herpesvirus. Lesions similar to those caused by herpesvirus in other species were observed, mainly in the skin, upper digestive tract, genitalia, and central nervous system. Other lesions were also attributable to concomitant etiologies or were nonspecific. It is necessary to investigate the possible role of herpesvirus infection in those cases.

Age-structure model for oncolytic virotherapy

A non-local delay differential system was developed by age-infected consideration to understand the interaction between tumor cells and oncolytic virus. The critical threshold value [Formula: see text] was obtained that dominates the dynamical behaviors of our model. By strongly [Formula: see text]-persistent and Comparison theorem, the global stability and uniformly strongly persistent were investigated. Our global sensitivity analyses indicate that [Formula: see text] is most sensitive to virus clearance rate [Formula: see text] while is least sensitive to viral life cycle [Formula: see text]. Finally, our model was used to fit with experimental data which indicates that viral life cycle [Formula: see text] plays a key role in data fitting. And the trained model shows perfect prediction in the testing data set with the coefficient of determination [Formula: see text].

MicroRNA-1 Negatively Regulates Peripheral NK Cell Function via Tumor Necrosis Factor-Like Weak Inducer of Apoptosis (TWEAK) Signaling Pathways During PPRV Infection

Peste des petits ruminants virus (PPRV) has emerged as a significant threat to the productivity of small ruminants worldwide. PPRV is lymphotropic in nature and induces in the hosts a transient but severe immunosuppression, especially innate immunity. However, it remains largely unknown how NK cells respond and are regulated at the earliest time points after an acute viral PPRV infection in goats. In this study, we revealed that multiple immune responses of goat peripheral NK cells were compromised during PPRV infection, including the cytolytic effector molecule expression and cytokine production. Importantly, we demonstrated that PPRV infection stimulated the expression of TWEAK, a negative regulator of cytotoxic function of NK cells, which may be involved in the suppression of cytotoxicity as well as cytokine production in infected goat NK cells. Furthermore, we found that PPRV infection induced TWEAK expression in goat NK cells involving post-transcription by suppressing miR-1, a novel negative miRNA directly targeting the TWEAK gene. Moreover, replication of virus is required for inhibition of miR-1 expression during PPRV infection, and the non-structural V protein of PPRV plays an important role in miR-1 mediated TWEAK upregulation. Additionally, we revealed that the regulation of NK cell immune responses by TWEAK is mediated by MyD88, SOCS1, and STAT3. Taken together, our results demonstrated that TWEAK may play a key role in regulating goat peripheral NK cell cytotoxicity and cytokine expression levels during PPRV infection.

MicroRNA-218 Regulates Signaling Lymphocyte Activation Molecular (SLAM) Mediated Peste des Petits Ruminants Virus Infectivity in Goat Peripheral Blood Mononuclear Cells

Peste des petits ruminants virus (PPRV) has emerged as a significant threat to the productivity of small ruminants worldwide. SLAM was identified as the primary receptor for PPRV and other Morbilliviruses, although the regulation of SLAM expression is not yet fully understood. In this study, we revealed a novel mechanism by which PPRV upregulates its receptor SLAM expression and thereby benefits its replication via suppressing miR-218, a novel negative miRNA directly targeting SLAM gene. We demonstrated that PPRV infection downregulates miR-218, which in turn enhances SLAM expression on the surface of goat peripheral blood mononuclear cells (PBMCs), thus promoting PPRV replication. Since SLAM signaling may modulate the immune responses induced by PPRV infection, we further examined the effect of SLAM expression on the production of various cytokines by PBMCs in the absence or presence of PPRV. We demonstrated that miR-218-mediated SLAM expression modulates the expression of IFN-γ, TNF-α, and IL-10, importantly, these modulatory effects were enhanced in the presence of PPRV infection. Furthermore, our data clearly showed that PPRV H protein is sufficient to regulate miR-218-mediated SLAM expression. Taken together, our results suggest a novel mechanism involving post-transcriptional regulation of SLAM receptor expression on goat PBMCs during PPRV infection.

Host Cellular Receptors for the Peste des Petits Ruminant Virus

Peste des Petits Ruminant (PPR) is an important transboundary, OIE-listed contagious viral disease of primarily sheep and goats caused by the PPR virus (PPRV), which belongs to the genus Morbillivirus of the family Paramyxoviridae. The mortality rate is 90–100%, and the morbidity rate may reach up to 100%. PPR is considered economically important as it decreases the production and productivity of livestock. In many endemic poor countries, it has remained an obstacle to the development of sustainable agriculture. Hence, proper control measures have become a necessity to prevent its rapid spread across the world. For this, detailed information on the pathogenesis of the virus and the virus host interaction through cellular receptors needs to be understood clearly. Presently, two cellular receptors; signaling lymphocyte activation molecule (SLAM) and Nectin-4 are known for PPRV. However, extensive information on virus interactions with these receptors and their impact on host immune response is still required. Hence, a thorough understanding of PPRV receptors and the mechanism involved in the induction of immunosuppression is crucial for controlling PPR. In this review, we discuss PPRV cellular receptors, viral host interaction with cellular receptors, and immunosuppression induced by the virus with reference to other Morbilliviruses.

Network pharmacology-based identifcation of potential targets of the flower of Trollius chinensis Bunge acting on anti-inflammatory effectss

The flower of Trollius chinensis Bunge was widely used for the treatment of inflammation-related diseases in traditional Chinese medicine (TCM). In order to clarify the anti-inflammatory mechanism of this Chinese herbs, a comprehensive network pharmacology strategy that consists of three sequential modules (pharmacophore matching, enrichment analysis and molecular docking.) was carried out. As a result, Apoptosis signal-regulating kinase 1 (ASK1), Janus kinase 1 (JAK1), c-Jun N-terminal kinases (JNKs), transforming protein p21 (HRas) and mitogen-activated protein kinase 14 (p38α) that related to the anti-inflammatory effect were filtered out. In further molecular dynamics (MD) simulation, the conformation of CID21578038 and CID20055288 were found stable in the protein ASK1 and JNKs respectively. The current investigation revealed that two effective compounds in the flower of Trollius chinensis Bunge played a crucial role in the process of inflammation by targeting ASK1 and JNKs, the comprehensive strategy can serve as a universal method to guide in illuminating the mechanism of the prescription of traditional Chinese medicine by identifying the pathways or targets.

Vaccination with recombinant adenovirus expressing peste des petits ruminants virus-F or -H proteins elicits T cell responses to epitopes that arises during PPRV infection

Peste des petits ruminants virus (PPRV) causes an economically important disease that limits productivity in small domestic ruminants and often affects the livestock of the poorest populations in developing countries. Animals that survive PPRV develop strong cellular and humoral responses, which are probably necessary for protection. Vaccination should thus aim at mimicking these natural responses. Immunization strategies against this morbillivirus using recombinant adenoviruses expressing PPRV-F or -H proteins can protect PPRV-challenged animals and permit differentiation of infected from vaccinated animals. Little is known of the T cell repertoire these recombinant vaccines induce. In the present work, we identified several CD4⁺ and CD8⁺ T cell epitopes in sheep infected with PPRV. We also show that recombinant adenovirus vaccination induced T cell responses to the same epitopes, and led to memory T cell differentiation. T cells primed by these recombinant adenovirus vaccines expanded after PPRV challenge and probably contributed to protection. These data validate the use of recombinant adenovirus expressing PPRV genes as DIVA strategies to control this highly contagious disease.

Interplay of Regulatory T Cell and Th17 Cells during Infectious Diseases in Humans and Animals

It is now clear that the outcome of an inflammatory process caused by infections depends on the balance of responses by several components of the immune system. Of particular relevance is the interplay between regulatory T cells (Tregs) and CD4⁺ T cells that produce IL-17 (Th17 cells) during immunoinflammatory events. In addition to discussing studies done in mice to highlight some unresolved issues in the biology of these cells, we emphasize the need to include outbred animals and humans in analyses. Achieving a balance between Treg and Th17 cells responses represents a powerful approach to control events during immunity and immunopathology.

Phenotyping and comparing the immune cell populations of free-ranging Atlantic bottlenose dolphins (Tursiops truncatus) and dolphins under human care

Background

Studies suggest that free-ranging bottlenose dolphins exhibit a suppressed immune system because of exposure to contaminants or microorganisms. However, due to a lack of commercially available antibodies specific to marine mammal immune cell surface markers, the research has been indecisive. The purpose of this study was to identify cross-reactive terrestrial-specific antibodies in order to assess the changes in the immune cell populations of dolphins under human care and free-ranging dolphins. The blood and PBMC fraction of blood samples from human care and free-ranging dolphins were characterized by H&E staining of cytospin slides and flow cytometry using a panel of terrestrial-specific antibodies.

Results

In this study, we show that out of 65 terrestrial-specific antibodies tested, 11 were cross-reactive and identified dolphin immune cell populations within their peripheral blood. Using these antibodies, we found significant differences in the absolute number of cells expressing specific markers within their lymphocyte and monocyte fractions. Interestingly, the peripheral blood mononuclear cell profile of free-ranging dolphins retained an additional population of cells that divided them into two groups showing a low (<27%) or high (>56%) percentage of smaller cells resembling granulocytes.

Conclusions

We found that the cross-reactive antibodies not only identified specific changes in the immune cells of free-ranging dolphins, but also opened the possibility to investigate the causal relationship between immunosuppression and mortality seen in free-ranging dolphins.

Fluorescent microbead-based immunoassay for anti-Erysipelothrix rhusiopathiae antibody detection in cetaceans

A fluorescent microbead-based immunoassay (FMIA) for detection of anti-Erysipelothrix rhusiopathiae antibodies in pigs was adapted for use in cetaceans. The FMIA was validated and adjusted using serum samples from 10 vaccinated captive bottlenose dolphins Tursiops truncatus collected between 1 and 13 mo after immunization. The technique was then used to analyze specimens from 15 free-ranging cetaceans stranded alive on the Valencian Mediterranean coast between 2006 and 2014: 11 striped dolphins Stenella coeruleoalba, 3 Risso's dolphins Grampus griseus and 1 bottlenose dolphin Tursiops truncatus. One of these wild animals was confirmed to have died from E. rhusiopathiae septicemia, but no anti-E. rhusiopathiae antibodies were detected in its serum, pericardial fluid or milk samples. Another free-ranging individual, which lacked any signs or lesions that might be indicative of E. rhusiopathiae infection, showed high fluorescence intensity similar to that measured in captive dolphins at 6-13 mo after vaccination. These results suggest that this animal underwent an E. rhusiopathiae infection several months before stranding. The findings in the present study suggest that FMIA can be useful for detecting anti-E. rhusiopathiae antibodies in cetaceans, and its application to free-ranging animals is particularly interesting because of the great value of these specimens. Furthermore, the FMIA can be multiplexed to allow the determination of up to 100 analytes per sample in a single well, thereby reducing the cost, time and sample volume needed.

Cetacean morbillivirus: current knowledge and future directions

We review the molecular and epidemiological characteristics of cetacean morbillivirus (CeMV) and the diagnosis and pathogenesis of associated disease, with six different strains detected in cetaceans worldwide. CeMV has caused epidemics with high mortality in odontocetes in Europe, the USA and Australia. It represents a distinct species within the Morbillivirus genus. Although most CeMV strains are phylogenetically closely related, recent data indicate that morbilliviruses recovered from Indo-Pacific bottlenose dolphins (Tursiops aduncus), from Western Australia, and a Guiana dolphin (Sotalia guianensis), from Brazil, are divergent. The signaling lymphocyte activation molecule (SLAM) cell receptor for CeMV has been characterized in cetaceans. It shares higher amino acid identity with the ruminant SLAM than with the receptors of carnivores or humans, reflecting the evolutionary history of these mammalian taxa. In Delphinidae, three amino acid substitutions may result in a higher affinity for the virus. Infection is diagnosed by histology, immunohistochemistry, virus isolation, RT-PCR, and serology. Classical CeMV-associated lesions include bronchointerstitial pneumonia, encephalitis, syncytia, and lymphoid depletion associated with immunosuppression. Cetaceans that survive the acute disease may develop fatal secondary infections and chronic encephalitis. Endemically infected, gregarious odontocetes probably serve as reservoirs and vectors. Transmission likely occurs through the inhalation of aerosolized virus but mother to fetus transmission was also reported.

Emergence of peste des petits ruminants virus lineage IV in Ismailia Province, Egypt

Peste des petits ruminants (PPR) is an acute, highly contagious fatal disease of small ruminants characterized by high fever, ocular and nasal discharge, pneumonia, erosive stomatitis and severe enteritis that ultimately results in high mortalities. Peste des petits ruminants virus (PPRV) is widely distributed and endemic in several African, middle eastern and south Asian countries and it poses a threat to European countries. Egyptian veterinary medical authorities stated that Egypt is free from PPRV and the only measures for disease control are test and slaughter of infected population to maintain the free status. The aim of our investigation was to detect PPRV in Ismailia province as an indicator of the infection status in Egypt and perform molecular characterization of the emerging virus to gain insight into the origin of circulating virus. A total of 40 representative clinical samples, from a single goat case and goat flock in 2010 and sheep flock in 2012, were tested for PPRV by RT-PCR. About 21 (52.5%) samples were positive. The phylogenetic analysis of the detected viruses revealed circulation of PPRV lineage IV. The circulating viruses are closely related to Sudanese and Saudia Arabian strains with nucleotide identity ranged from 99.2% to 99.6%, respectively. Also, it is closely related to Moroccan 2008 viruses with identities ranged from 97.6% to 98%. Epidemiological investigation at the national level is recommended for monitoring PPRV spread and implementing an appropriate control program.

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.

Monkey CV1 cell line expressing the sheep-goat SLAM protein: a highly sensitive cell line for the isolation of peste des petits ruminants virus from pathological specimens

Peste des petits ruminants (PPR) is an important economically transboundary disease of sheep and goats caused by a virus which belongs to the genus Morbillivirus. This genus, in the family Paramyxoviridae, also includes the measles virus (MV), canine distemper virus (CDV), rinderpest virus (RPV), and marine mammal viruses. One of the main features of these viruses is the severe transient lymphopaenia and immunosuppression they induce in their respective hosts, thereby favouring secondary bacterial and parasitic infections. This lymphopaenia is probably accounted for by the fact that lymphoid cells are the main targets of the morbilliviruses. In early 2000, it was demonstrated that a transmembrane glycoprotein of the immunoglobulin superfamily which is present on the surface of lymphoid cells, the signalling lymphocyte activation molecule (SLAM), is used as cellular receptor by MV, CDV and RPV. Wild-type strains of these viruses can be isolated and propagated efficiently in non-lymphoid cells expressing this protein. The present study has demonstrated that monkey CV1 cells expressing goat SLAM are also highly efficient for isolating PPRV from pathological samples. This finding suggests that SLAM, as is in the case for MV, CDV and RPV, is also a receptor for PPRV.

Morbillivirus and Toxoplasma exposure and association with hematological parameters for southern Beaufort Sea polar bears: potential response to infectious agents in a sentinel species

Arctic temperatures are increasing in response to greenhouse gas forcing and polar bears have already responded to changing conditions. Declines in body stature and vital rates have been linked to warming-induced loss of sea-ice. As food webs change and human activities respond to a milder Arctic, exposure of polar bears and other arctic marine organisms to infectious agents may increase. Because of the polar bear's status as arctic ecosystem sentinel, polar bear health could provide an index of changing pathogen occurrence throughout the Arctic, however, exposure and monitoring protocols have yet to be established. We examine prevalence of antibodies to Toxoplasma gondii, and four morbilliviruses (canine distemper [CDV], phocine distemper [PDV], dolphin morbillivirus [DMV], porpoise morbillivirus [PMV]) including risk factors for exposure. We also examine the relationships between antibody levels and hematologic values established in the previous companion article. Antibodies to Toxoplasma gondii and morbilliviruses were found in both sample years. We found a significant inverse relationship between CDV titer and total leukocytes, neutrophils, monocytes, and eosinophils, and a significant positive relationship between eosinophils and Toxoplasma gondii antibodies. Morbilliviral prevalence varied significantly among age cohorts, with 1-2 year olds least likely to be seropositive and bears aged 5-7 most likely. Data suggest that the presence of CDV and Toxoplasma gondii antibodies is associated with polar bear hematologic values. We conclude that exposure to CDV-like antigen is not randomly distributed among age classes and suggest that differing behaviors among life history stages may drive probability of specific antibody presence.

Presence of herpesvirus in striped dolphins stranded during the cetacean morbillivirus epizootic along the Mediterranean Spanish coast in 2007

A screening for herpesvirus (HV) was carried out using a tissue bank obtained from the cetacean morbillivirus (CeMV) mortality episode that occurred along the Mediterranean Spanish coast in 2007. A total of 14 cetaceans, including six long-finned pilot whales and eight striped dolphins, were studied using histopathology and molecular analysis to detect HV and CeMV. In five of the eight dolphins (62.5%) infected with CeMV, eight novel HV sequences were also detected. No HV lesions were found in any of the coinfected dolphins, which may indicate that HV did not contribute to the mortality in the CeMV outbreak. This is the first report of HV infection in any cetacean from the Mediterranean Sea.

Lymphotropism and host responses during acute wild-type canine distemper virus infections in a highly susceptible natural host

The mechanisms behind the in vivo virulence of immunosuppressive wild-type morbillivirus infections are still not fully understood. To investigate lymphotropism and host responses, we have selected the natural host model of canine distemper virus (CDV) infection in mink. This model displays multisystemic infection, similar to measles virus and rinderpest virus infections in their susceptible natural hosts. The wild-type CDVs investigated provoked marked virulence differences, inducing mild versus marked to severe acute disease. The mildly virulent wild-type virus induced transient lymphopenia, despite the development of massive infection of peripheral blood mononuclear cells (PBMCs) exceeding that determined for the highly virulent wild-type virus, indicating an inverse relationship between acute virulence and the extent of viraemia in the investigated wild-type viruses. Single-cell cytokine production in PBMCs was investigated throughout the acute infections. We observed Th1- and Th2-type cytokine responses beginning in the prodromal phase, and late inflammatory responses were shared between the wild-type infections.

Measles virus-induced immunosuppression

Immunosuppression is the major cause of infant death associated with acute measles and therefore of substantial clinical importance. Major hallmarks of this generalized modulation of immune functions are (1) lymphopenia, (2) a prolonged cytokine imbalance consistent with suppression of cellular immunity to secondary infections, and (3) silencing of peripheral blood lymphocytes, which cannot expand in response to ex vivo stimulation. Lymphopenia results from depletion, which can occur basically at any stage of lymphocyte development, and evidently, expression of the major MV receptor CD150 plays an important role in targeting these cells. Virus transfer to T cells is thought to be mediated by dendritic cells (DCs), which are considered central to the induction of T cell silencing and functional skewing. As a consequence of MV interaction, viability and functional differentiation of DCs and thereby their expression pattern of co-stimulatory molecules and soluble mediators are modulated. Moreover, MV proteins expressed by these cells actively silence T cells by interfering with signaling pathways essential for T cell activation.

Measles virus inhibits human immunodeficiency virus type 1 reverse transcription and replication by blocking cell-cycle progression of CD4+ T lymphocytes

Acute measles virus (MV) infection results in a decrease in plasma human immunodeficiency virus type 1 (HIV-1) RNA levels in co-infected children. An in vitro peripheral blood mononuclear cell (PBMC) culture system was used to assess the mechanisms by which MV blocks HIV-1 replication. MV inhibited proliferation of CD4(+) T lymphocytes, the target cell for HIV-1 replication. In the presence of MV, cells did not progress to G(1b) and S phases, steps critical for the completion of HIV-1 reverse transcription and productive replication. This block in cell-cycle progression was characterized by an increased proportion of CD4(+) and HIV-1-infected cells retained in the parental generation in PBMCs co-cultured with MV and HIV-1, and decreased levels of cyclins and RNA synthesis. Early HIV-1 replication was also inhibited in the presence of MV, as measured by reduced expression of a luciferase reporter gene and lower levels of both early (LTR) and late (LTR-gag) DNA intermediates of HIV-1 reverse transcription in the presence of CCR5-tropic HIV-1. The effects of MV on lymphoproliferation and p24 antigen production were reproduced by n-butyrate and hydroxyurea, drugs that block the cell cycle in G(1a) and G(1)/S, respectively. It was concluded that MV inhibits HIV-1 productive replication in part by blocking the proliferation of CD4(+) T lymphocytes.

Modeling of cancer virotherapy with recombinant measles viruses

The Edmonston vaccine strain of measles virus has potent and selective activity against a wide range of tumors. Tumor cells infected by this virus or genetically modified strains express viral proteins that allow them to fuse with neighboring cells to form syncytia that ultimately die. Moreover, infected cells may produce new virus particles that proceed to infect additional tumor cells. We present a model of tumor and virus interactions based on established biology and with proper accounting of the free virus population. The range of model parameters is estimated by fitting to available experimental data. The stability of equilibrium states corresponding to complete tumor eradication, therapy failure and partial tumor reduction is discussed. We use numerical simulations to explore conditions for which the model predicts successful therapy and tumor eradication. The model exhibits damped, as well as stable oscillations in a range of parameter values. These oscillatory states are organized by a Hopf bifurcation.

Semliki Forest virus vectors expressing the H and HN genes of measles and mumps viruses reduce immunity induced by the envelope protein genes of rubella virus

A Semliki Forest virus (SFV) recombinant particle vaccine vector was constructed expressing the viral E1 and E2 envelope proteins of the RA27/3 vaccine strain of rubella virus. This vector induced high titres of antibody after intramuscular administration to Balb/C mice, both following initial vaccination and a boost 4 weeks later. This occurred for antibody as measured by ELISA and as measured by a latex agglutination test. However, co-administration of similar particles expressing the measles virus H protein and the mumps virus HN protein with the rubella protein expressing vector resulted in reduction of the anti-rubella immune response.

The threat of peste des petits ruminants: progress in vaccine development for disease control

Peste des petits ruminants (PPR) is a highly contagious animal disease caused by a virus in the genus Morbillivirus, family Paramyxoviridae. This infection is responsible for high morbidity and mortality in sheep and goats and in some small wild ruminant species. The huge number of small ruminants, which are reared in the endemic areas makes PPR a serious disease threatening the livelihood of poor farmers. Taking advantage of the closely relationship between rinderpest and PPR viruses, the attenuated rinderpest vaccine was used in the control of PPR. It is now replaced by the homologous attenuated PPR vaccine. Unfortunately, animals that have received this vaccine cannot be distinguished serologically from infected animals. With the advent of DNA recombinant technology, efforts are being made to develop effective PPR marker vaccines to enable such differentiation and which would allow countries to implement both vaccination and disease surveillance programmes at the same time.

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.

Immunomodulatory properties of morbillivirus nucleoproteins

Morbillivirus infections have been known for a long time to be associated with an acute immunosuppression in their natural hosts. Here, we show that recombinant Morbillivirus nucleoproteins from canine distemper virus, peste-des-petits-ruminants virus, and Rinderpest virus bind B-lymphocytes from dogs, goats, and cattle, respectively, similarly to measles virus nucleoprotein in humans. The use of surface plasmon resonance imaging allowed the real time detection of differential interactions between Morbillivirus nucleoproteins and FcgammaRIIb (CD32). Moreover, those nucleoproteins which bind murine Fcgamma receptor inhibited the inflammatory immune responses in mice in a Fc receptor- dependent manner. In contrast, nucleoprotein from closely related Henipavirus genus, belonging to the Paramyxoviridae family as Morbillivirus, was devoid of capacity either to bind FcgammaRIIb or to inhibit inflammatory response. Altogether, these results suggest that nucleoprotein-FcR interaction is a common mechanism used by different Morbilliviruses to modulate the immune response.

Silencing T cells or T-cell silencing: concepts in virus-induced immunosuppression

The ability to evade or suppress the host's immune response is a property of many viruses, indicating that this provides an advantage for the pathogen to spread efficiently or even to establish a persistent infection. The type and complexity of its genome and cell tropism but also its preferred type of host interaction are important parameters which define the strategy of a given virus to modulate the immune system in an optimal manner. Because they take a central position in any antiviral defence, the activation and function of T cells are the predominant target of many viral immunosuppressive regimens. In this review, two different strategies whereby this could be achieved are summarized. Retroviruses can infect professional antigen-presenting cells and impair their maturation and functional properties. This coincides with differentiation and expansion of silencing T cells referred to as regulatory T cells with suppressive activity, mainly to CD8+ effector T cells. The second concept, outlined for measles virus, is a direct, contact-mediated silencing of T cells which acquire a transient paralytic state.

Mathematical modeling of cancer radiovirotherapy

Cancer virotherapy represents a dynamical system that requires mathematical modeling for complete understanding of the outcomes. The combination of virotherapy with radiation (radiovirotherapy) has been recently shown to successfully eliminate tumors when virotherapy alone failed. However, it introduces a new level of complexity. We have developed a mathematical model, based on population dynamics, that captures the essential elements of radiovirotherapy. The existence of corresponding equilibrium points related to complete cure, partial cure, and therapy failure is proved and discussed. The parameters of the model were estimated by fitting to experimental data. By using simulations we analyzed the influence of parameters that describe the interaction between virus and tumor cell on the outcome of the therapy. Furthermore, we evaluated relevant therapeutic scenarios for radiovirotherapy, and offered elements for optimization.

Inhibition of host peripheral blood mononuclear cell proliferation ex vivo by Rinderpest virus

Rinderpest, or cattle plague, is caused by Rinderpest virus (RPV), which is related most closely to human Measles virus (MV), both being members of the genus Morbillivirus, a group of viruses known to have strong immunosuppressive effects in vitro and in vivo. Here, it was shown that peripheral blood mononuclear cells (PBMCs) isolated from cattle experimentally infected with either wild-type or vaccine strains of RPV impaired the proliferation of PBMCs derived from uninfected animals; however, in contrast to either mild or virulent strains of wild-type virus, the inhibition induced by the vaccine was both weak and transient. Flow-cytometric analysis of PBMCs obtained from cattle infected with different strains of RPV showed that the proportion of infected cells was virus dose-dependent and correlated with lymphoproliferative suppression.

Rational attenuation of a morbillivirus by modulating the activity of the RNA-dependent RNA polymerase

Negative-strand RNA viruses encode a single RNA-dependent RNA polymerase (RdRp) which transcribes and replicates the genome. The open reading frame encoding the RdRp from a virulent wild-type strain of rinderpest virus (RPV) was inserted into an expression plasmid. Sequences encoding enhanced green fluorescent protein (EGFP) were inserted into a variable hinge of the RdRp. The resulting polymerase was autofluorescent, and its activity in the replication/transcription of a synthetic minigenome was reduced. We investigated the potential of using this approach to rationally attenuate a virus by inserting the DNA sequences encoding the modified RdRp into a full-length anti-genome plasmid from which a virulent virus (rRPV(KO)) can be rescued. A recombinant virus, rRPV(KO)L-RRegfpR, which grew at an indistinguishable rate and to an identical titer as rRPV(KO) in vitro, was rescued. Fluorescently tagged polymerase was visible in large cytoplasmic inclusions and beneath the cell membrane. Subcutaneous injection of 10(4) TCID(50) of the rRPV(KO) parental recombinant virus into cattle leads to severe disease symptoms (leukopenia/diarrhea and pyrexia) and death by 9 days postinfection. Animals infected with rRPV(KO)L-RRegfpR exhibited transient leukopenia and mild pyrexia, and the only noticeable clinical signs were moderate reddening of one eye and a slight ocular-nasal discharge. Viruses that expressed the modified polymerase were isolated from peripheral blood lymphocytes and eye swabs. This demonstrates that a virulent morbillivirus can be attenuated in a single step solely by modulating RdRp activity and that there is not necessarily a correlation between virus growth in vitro and in vivo.

Measles virus nucleoprotein induces cell-proliferation arrest and apoptosis through NTAIL-NR and NCORE-FcgammaRIIB1 interactions, respectively

Measles virus (MV) nucleoprotein (N) is a cytosolic protein that is released into the extracellular compartment after apoptosis and/or secondary necrosis of MV-infected cells in vitro. Thus, MV-N becomes accessible to inhibitory cell-surface receptors: FcgammaRIIB and an uncharacterized nucleoprotein receptor (NR). MV-N is composed of two domains: NCORE (aa 1-400) and NTAIL (aa 401-525). To assess the contribution of MV-N domains and of these two receptors in suppression of cell proliferation, a human melanoma HT144 cell line expressing (HT144IIB1) or lacking FcgammaRIIB1 was used as a model. Specific and exclusive NCORE-FcgammaRIIB1 and NTAIL-NR interactions were shown. Moreover, NTAIL binding to human NR predominantly led to suppression of cell proliferation by arresting cells in the G0/G1 phases of the cell cycle, rather than to apoptosis. NCORE binding to HT144IIB1 cells primarily triggered caspase-3 activation, in contrast to HT144IIB1/IC- cells lacking the FcgammaRIIB1 intra-cytoplasmic tail, thus demonstrating the specific inhibitory effect of the NCORE-FcgammaRIIB1 interaction. MV-N- and NCORE-mediated apoptosis through FcgammaRIIB1 was inhibited by the pan-caspase inhibitor zVAD-FMK, indicating that apoptosis was dependent on caspase activation. By using NTAIL deletion proteins, it was also shown that the region of NTAIL responsible for binding to human NR and for cell growth arrest maps to one of the three conserved boxes (Box1, aa 401-420) found in N of Morbilliviruses. This work unveils novel mechanisms by which distinct domains of MV-N may display different immunosuppressive activities, thus contributing to our comprehension of the immunosuppressive state associated with MV infection. Finally, MV-N domains may be good tools to target tumour cell proliferation and/or apoptosis.

A role for virus promoters in determining the pathogenesis of Rinderpest virus in cattle

Rinderpest virus (RPV) is a morbillivirus that causes cattle plague, a disease of large ruminants. The viral genome is flanked at the 3′ and 5′ genome termini by the genome promoter (GP) and antigenome promoter (AGP), respectively. These promoters play essential roles in directing replication and transcription as well as RNA encapsidation and packaging. It has previously been shown that individual changes to the GP of RPV greatly affect promoter activity in a minigenome assay and it was therefore proposed that individual nucleotide changes in the GP and AGP might also have significant effects on the ability of the virus to replicate and cause disease in cattle. The Plowright vaccine strain of RPV has been derived by tissue-culture passage from the virulent Kabete ‘O’ isolate (KO) and is highly attenuated for all ruminant species in which it has been used. Here, it was shown that swapping the GP and the first 76 nt of the AGP between virulent and avirulent strains affected disease progression. In particular, it was shown that flanking the virulent strain with the vaccine GP and AGP sequences, while not appreciably affecting virus growth in vitro, led to attenuation in vivo. The reverse was not true, since the KO promoters did not alter the vaccine's attenuated nature. The GP/AGP therefore play a role in attenuation, but are not the only determinants of attenuation in this vaccine.

Pathological and immunohistochemical study of experimental peste des petits ruminants virus infection in goats

Peste des petits ruminants (PPR) is an emerging, economically important viral disease of goats and sheep in the Indian subcontinent. In the present investigation, 15 hill goats were experimentally infected with 2 ml of 10% splenic suspension of a virulent isolate of PPR virus (PPR/Izatnagar/94) that had caused heavy mortality (>75%) in goats during 1994 outbreaks in northern India. More than 86% (13 of 15) animals died between 9 and 13 days post inoculation at the height of temperature or when temperatures were declining. Necropsy findings included congestion of gastrointestinal tract (GIT), nasal sinuses, consolidation of antero-ventral lobes of lungs, engorged spleen, and occasionally oedematous lymph nodes. Histopathological examination of major organs of GIT revealed degeneration and necrosis of labial mucosa, severe mucosal and submucosal congestion, degeneration and necrosis of intestinal epithelium and lymphoid cell depletion from Peyer's patches along with presence of syncytia at times. Lungs showed broncho-interstitial changes and presence of intracytoplasmic and intranuclear eosinophilic inclusions in alveolar macrophages and syncytial cells. These changes in lungs were frequently complicated with serofibrinous pneumonia (57%, eight of 14). Lymphocytolysis and occasional syncytia formation were evident in the lymphoid tissues. Immunohistochemical (IHC) findings included presence of PPR virus antigen in the labial, intestinal, and bronchiolar epithelial cells, pneumocytes, macrophages and syncytial cells in lungs, and lymphoid (intact and necrotic) and reticular cells in lymphoid organs. The findings of the study indicated the highly virulent nature of the PPR virus isolate (PPR/Izatnagar/94), causing 100% mortality and characteristic pathological changes in the target organs such as lungs, intestines and lymphoid tissues. The results of the IHC study suggested that indirect immunoperoxidase could be an alternative method in the absence of more sophisticated methods of laboratory diagnosis of PPR virus infection in goats.

Measles virus (MV) nucleoprotein binds to a novel cell surface receptor distinct from FcgammaRII via its C-terminal domain: role in MV-induced immunosuppression

During acute measles virus (MV) infection, an efficient immune response occurs, followed by a transient but profound immunosuppression. MV nucleoprotein (MV-N) has been reported to induce both cellular and humoral immune responses and paradoxically to account for immunosuppression. Thus far, this latter activity has been attributed to MV-N binding to human and murine FcgammaRII. Here, we show that apoptosis of MV-infected human thymic epithelial cells (TEC) allows the release of MV-N in the extracellular compartment. This extracellular N is then able to bind either to MV-infected or uninfected TEC. We show that recombinant MV-N specifically binds to a membrane protein receptor, different from FcgammaRII, highly expressed on the cell surface of TEC. This new receptor is referred to as nucleoprotein receptor (NR). In addition, different Ns from other MV-related morbilliviruses can also bind to FcgammaRII and/or NR. We show that the region of MV-N responsible for binding to NR maps to the C-terminal fragment (N(TAIL)). Binding of MV-N to NR on TEC triggers sustained calcium influx and inhibits spontaneous cell proliferation by arresting cells in the G(0) and G(1) phases of the cell cycle. Finally, MV-N binds to both constitutively expressed NR on a large spectrum of cells from different species and to human activated T cells, leading to suppression of their proliferation. These results provide evidence that MV-N, after release in the extracellular compartment, binds to NR and thereby plays a role in MV-induced immunosuppression.

Canine distemper virus infection: proliferation of canine footpad keratinocytes

The proliferation of footpad keratinocytes of canine distemper virus (CDV)-infected dogs was investigated. Footpads of 19 dogs inoculated experimentally with a virulent distemper strain (A75/17) and of two noninoculated control dogs were collected at necropsy. Dogs were divided into four groups according to results of the postmortem examination: dogs with severe distemper (group 1), dogs with mild distemper (group 2), inoculated dogs without distemper (group 3) and noninoculated dogs (group 4). There was no distinct difference of epidermal thickness among the four groups. Infection of the footpad epidermis with CDV was demonstrated using immunohistochemistry for viral nucleoprotein and in situ hybridization for nucleoprotein messenger ribonucleic acid (mRNA). Only group 1 dogs had viral antigen and mRNA in the footpad epidermis with the same distribution. Footpad epidermis of group 1 dogs had more mitotic figures in the basal layer, and significantly more basal keratinocytes were positive for the proliferation markers Ki-67 and proliferating cell nuclear antigen. Double-staining for Ki-67 and viral nucleoprotein identified rare double-labeled basal keratinocytes. These findings suggest that the presence of CDV particles in the footpad epidermis is associated with keratinocyte proliferation.