Feline Morbillivirus Infection in Domestic Cats: What Have We Learned So Far?

Feline morbillivirus (FeMV) was identified for the first time in stray cats in 2012 in Hong Kong and, since its discovery, it was reported in domestic cats worldwide. Although a potential association between FeMV infection and tubulointerstitial nephritis (TIN) has been suggested, this has not been proven, and the subject remains controversial. TIN is the most frequent histopathological finding in the context of feline chronic kidney disease (CKD), which is one of the major clinical pathologies in feline medicine. FeMV research has mainly focused on defining the epidemiology, the role of FeMV in the development of CKD, and its in vitro tropism, but the pathogenicity of FeMV is still not clear, partly due to its distinctive biological characteristics, as well as to a lack of a cell culture system for its rapid isolation. In this review, we summarize the current knowledge of FeMV infection, including genetic diversity of FeMV strains, epidemiology, pathogenicity, and clinicopathological findings observed in naturally infected cats.

Liquid Biomolecular Condensates and Viral Lifecycles: Review and Perspectives

Viruses are highly dependent on the host they infect. Their dependence triggers processes of virus-host co-adaptation, enabling viruses to explore host resources whilst escaping immunity. Scientists have tackled viral-host interplay at differing levels of complexity-in individual hosts, organs, tissues and cells-and seminal studies advanced our understanding about viral lifecycles, intra- or inter-species transmission, and means to control infections. Recently, it emerged as important to address the physical properties of the materials in biological systems; membrane-bound organelles are only one of many ways to separate molecules from the cellular milieu. By achieving a type of compartmentalization lacking membranes known as biomolecular condensates, biological systems developed alternative mechanisms of controlling reactions. The identification that many biological condensates display liquid properties led to the proposal that liquid-liquid phase separation (LLPS) drives their formation. The concept of LLPS is a paradigm shift in cellular structure and organization. There is an unprecedented momentum to revisit long-standing questions in virology and to explore novel antiviral strategies. In the first part of this review, we focus on the state-of-the-art about biomolecular condensates. In the second part, we capture what is known about RNA virus-phase biology and discuss future perspectives of this emerging field in virology.

Molecular mimicry between varicella, measles virus and Hsp60 in type 1 diabetes associated HLA-DR3/DR4 molecules

BACKGROUND AND AIMS

Type 1 diabetes (T1D) is a multifactorial autoimmune disease that combines genetics and environmental factors. The aim of this study is to determine the environmental risk factors and to investigate how virals infections are risks factors for type 1 diabetics whom have HLA DR3/DR4 predisposition in our population.

METHODS

This study includes 233 subjects, 145 diabetics and 88 controls from regions of the extreme western of Algeria. All the informations related to the disease were collected using predesigned questionnaire. Using in silico approach, we attempt to improve the understanding of this analytical result by molecular mimicry, which is associated with the breakdown of several autoimmune pathologies.

RESULTS

The statistical study showed that history of varicella and measles infection and T1D related inheritance and type 2 diabetes are risk factors for T1D in the population of Tlemcen. We have determined the homologous antigenic regions between the glycoprotein "gE" of the varicella virus, the "hemagglutinin" of measles and the human protein "HSP60" at the level of their sequence and 3D structure. These cross-reactive epitopes bind to MHC class II molecules (HLA DR3/DR4) that predispose to T1D but not to MHC class II molecules (HLA DR2) that protect against T1D. This epitopes induce Th2 cells but only "hemagglutinin" and "Hsp60" can activate Th1 differentiation. This indicates their potential to destroy pancreatic cells β.

CONCLUSION

Our study can allow us to adapt biological markers to genetically predisposed T1D and to establish a preventive strategy for healthy genetic predisposed individuals in Tlemcen population.

Animal morbilliviruses and their cross-species transmission potential

Like measles virus (MV), whose primary hosts are humans, non-human animal morbilliviruses use SLAM (signaling lymphocytic activation molecule) and PVRL4 (nectin-4) expressed on immune and epithelial cells, respectively, as receptors. PVRL4's amino acid sequence is highly conserved across species, while that of SLAM varies significantly. However, non-host animal SLAMs often function as receptors for different morbilliviruses. Uniquely, human SLAM is somewhat specific for MV, but canine distemper virus, which shows the widest host range among morbilliviruses, readily gains the ability to use human SLAM. The host range for morbilliviruses is also modulated by their ability to counteract the host's innate immunity, but the risk of cross-species transmission of non-human animal morbilliviruses to humans could occur if MV is successfully eradicated.

Canine and Phocine Distemper Viruses: Global Spread and Genetic Basis of Jumping Species Barriers

Canine distemper virus (CDV) and phocine distemper (PDV) are closely-related members of the Paramyxoviridae family, genus morbillivirus, in the order Mononegavirales. CDV has a broad host range among carnivores. PDV is thought to be derived from CDV through contact between terrestrial carnivores and seals. PDV has caused extensive mortality in Atlantic seals and other marine mammals, and more recently has spread to the North Pacific Ocean. CDV also infects marine carnivores, and there is evidence of morbillivirus infection of seals and other species in Antarctica. Recently, CDV has spread to felines and other wildlife species in the Serengeti and South Africa. Some CDV vaccines may also have caused wildlife disease. Changes in the virus haemagglutinin (H) protein, particularly the signaling lymphocyte activation molecule (SLAM) receptor binding site, correlate with adaptation to non-canine hosts. Differences in the phosphoprotein (P) gene sequences between disease and non-disease causing CDV strains may relate to pathogenicity in domestic dogs and wildlife. Of most concern are reports of CDV infection and disease in non-human primates raising the possibility of zoonosis. In this article we review the global occurrence of CDV and PDV, and present both historical and genetic information relating to these viruses crossing species barriers.

Marine Morbilliviruses: Diversity and Interaction with Signaling Lymphocyte Activation Molecules

Epidemiological reports of phocine distemper virus (PDV) and cetacean morbillivirus (CeMV) have accumulated since their discovery nearly 30 years ago. In this review, we focus on the interaction between these marine morbilliviruses and their major cellular receptor, the signaling lymphocyte activation molecule (SLAM). The three-dimensional crystal structure and homology models of SLAMs have demonstrated that 35 residues are important for binding to the morbillivirus hemagglutinin (H) protein and contribute to viral tropism. These 35 residues are essentially conserved among pinnipeds and highly conserved among the Caniformia, suggesting that PDV can infect these animals, but are less conserved among cetaceans. Because CeMV can infect various cetacean species, including toothed and baleen whales, the CeMV-H protein is postulated to have broader specificity to accommodate more divergent SLAM interfaces and may enable the virus to infect seals. In silico analysis of viral H protein and SLAM indicates that each residue of the H protein interacts with multiple residues of SLAM and vice versa. The integration of epidemiological, virological, structural, and computational studies should provide deeper insight into host specificity and switching of marine morbilliviruses.

Neglected Hosts of Small Ruminant Morbillivirus

Eradication of small ruminant morbillivirus (PPRV) is targeted for 2030. PPRV lineage IV is found in much of Asia and Africa. We used PPRV lineage IV strain Kurdistan/2011 in transmission trials to investigate the role of pigs, wild boar, and small ruminants as PPRV reservoirs. Suids were a possible source of infection.

Neuronal and astrocytic involvement in striped dolphins (Stenella coeruleoalba) with morbilliviral encephalitis

Dolphin morbillivirus (DMV), a highly pathogenic agent, may cause peculiar, "brain-only" forms of infection (BOFDI), in which viral antigen and/or genome is found exclusively in the brain from striped dolphins (Stenella coeruleoalba). These BOFDIs show morphopathological similarities with subacute sclerosing panencephalitis and old dog encephalitis (ODE) in measles virus-infected patients and in canine distemper virus-infected dogs, respectively. The brain tissue from 3 BOFDI-affected striped dolphins was investigated by means of double labelling-indirect immunofluorescence (DL-IIF) and ultrastructurally, in order to characterize the DMV-targeted neuronal and non-neuronal cell populations, along with the associated submicroscopic findings. Viral colonization of calbindin-immunoreactive (IR) and nitric oxide synthase-IR neurons was detected in the cerebral parenchyma from the 3 DMV-infected dolphins under study, associated with nuclear (chromatin) and cytoplasmic (mitochondrial) ultrastructural changes. Furthermore, a limited viral targeting of brain astrocytes was found in these animals, all of which exhibited a prominent astrogliosis/astrocytosis. To the best of our knowledge, those herein reported should be the first submicroscopic pathology and neuropathogenetic data about BOFDI in striped dolphins. In this respect, the marked astrogliosis/astrocytosis and the low viral colonization of brain astrocytes in the 3 DMV-infected dolphins under investigation are of interest from the comparative pathology and viral neuropathogenesis standpoints, when compared with ODE-affected dogs, in whose brain a non-cytolytic, astrocyte-to-astrocyte infectious spread has been recently documented. Further studies aimed at characterizing the complex DMV-host interactions in BOFDI-affected striped dolphins are needed.

Sequential conformational changes in the morbillivirus attachment protein initiate the membrane fusion process

Despite large vaccination campaigns, measles virus (MeV) and canine distemper virus (CDV) cause major morbidity and mortality in humans and animals, respectively. The MeV and CDV cell entry system relies on two interacting envelope glycoproteins: the attachment protein (H), consisting of stalk and head domains, co-operates with the fusion protein (F) to mediate membrane fusion. However, how receptor-binding by the H-protein leads to F-triggering is not fully understood. Here, we report that an anti-CDV-H monoclonal antibody (mAb-1347), which targets the linear H-stalk segment 126-133, potently inhibits membrane fusion without interfering with H receptor-binding or F-interaction. Rather, mAb-1347 blocked the F-triggering function of H-proteins regardless of the presence or absence of the head domains. Remarkably, mAb-1347 binding to headless CDV H, as well as standard and engineered bioactive stalk-elongated CDV H-constructs treated with cells expressing the SLAM receptor, was enhanced. Despite proper cell surface expression, fusion promotion by most H-stalk mutants harboring alanine substitutions in the 126-138 "spacer" section was substantially impaired, consistent with deficient receptor-induced mAb-1347 binding enhancement. However, a previously reported F-triggering defective H-I98A variant still exhibited the receptor-induced "head-stalk" rearrangement. Collectively, our data spotlight a distinct mechanism for morbillivirus membrane fusion activation: prior to receptor contact, at least one of the morbillivirus H-head domains interacts with the membrane-distal "spacer" domain in the H-stalk, leaving the F-binding site located further membrane-proximal in the stalk fully accessible. This "head-to-spacer" interaction conformationally stabilizes H in an auto-repressed state, which enables intracellular H-stalk/F engagement while preventing the inherent H-stalk's bioactivity that may prematurely activate F. Receptor-contact disrupts the "head-to-spacer" interaction, which subsequently "unlocks" the stalk, allowing it to rearrange and trigger F. Overall, our study reveals essential mechanistic requirements governing the activation of the morbillivirus membrane fusion cascade and spotlights the H-stalk "spacer" microdomain as a possible drug target for antiviral therapy.

Morbillivirus infections: an introduction

Research on morbillivirus infections has led to exciting developments in recent years. Global measles vaccination coverage has increased, resulting in a significant reduction in measles mortality. In 2011 rinderpest virus was declared globally eradicated - only the second virus to be eradicated by targeted vaccination. Identification of new cellular receptors and implementation of recombinant viruses expressing fluorescent proteins in a range of model systems have provided fundamental new insights into the pathogenesis of morbilliviruses, and their interactions with the host immune system. Nevertheless, both new and well-studied morbilliviruses are associated with significant disease in wildlife and domestic animals. This illustrates the need for robust surveillance and a strategic focus on barriers that restrict cross-species transmission. Recent and ongoing measles outbreaks also demonstrate that maintenance of high vaccination coverage for these highly infectious agents is critical. This introduction briefly summarizes the most important current research topics in this field.

The Entangled History of Sadoka (Rinderpest) and Veterinary Science in Tanzania and the Wider World, 1891-1901

Scholarship on the Tanzanian Rinderpest epizootic of the 1890s has assumed that German colonizers understood from the start that they were confronting the same disease that had afflicted Eurasia for centuries. Outward indicators of the epizootic, known locally as sadoka, especially wildlife destruction, were unknown in Europe, leading German veterinarians to doubt that the African disease was Rinderpest. Financial constraints and conflicting development agendas, especially tension between ranching and pastoralism, deterred early colonial applications of veterinary science that might have led to an early diagnosis. European veterinarians, guarding their authority against medical researchers, opposed inoculation therapies in the case of Rinderpest in favor of veterinary policing despite recent breakthroughs in vaccine research. The virus was not identified before reaching South Africa in 1896, but this breakthrough had little influence on policy in East Africa. Yet emergent international disease conventions directed at bubonic plague entangled with veterinary policy in East Africa.

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.

The tumor-associated marker, PVRL4 (nectin-4), is the epithelial receptor for morbilliviruses

PVRL4 (nectin-4) was recently identified as the epithelial receptor for members of the Morbillivirus genus, including measles virus, canine distemper virus and peste des petits ruminants virus. Here, we describe the role of PVRL4 in morbillivirus pathogenesis and its promising use in cancer therapies. This discovery establishes a new paradigm for the spread of virus from lymphocytes to airway epithelial cells and its subsequent release into the environment. Measles virus vaccine strains have emerged as a promising oncolytic platform for cancer therapy in the last ten years. Given that PVRL4 is a well-known tumor-associated marker for several adenocarcinoma (lung, breast and ovary), the measles virus could potentially be used to specifically target, infect and destroy cancers expressing PVRL4.

Morbillivirus v proteins exhibit multiple mechanisms to block type 1 and type 2 interferon signalling pathways

Morbilliviruses form a closely related group of pathogenic viruses which encode three non-structural proteins V, W and C in their P gene. Previous studies with rinderpest virus (RPV) and measles virus (MeV) have demonstrated that these non-structural proteins play a crucial role in blocking type I (IFNα/β) and type II (IFNγ) interferon action, and various mechanisms have been proposed for these effects. We have directly compared four important morbilliviruses, rinderpest (RPV), measles virus (MeV), peste des petits ruminants virus (PPRV) and canine distemper virus (CDV). These viruses and their V proteins could all block type I IFN action. However, the viruses and their V proteins had varying abilities to block type II IFN action. The ability to block type II IFN-induced gene transcription correlated with co-precipitation of STAT1 with the respective V protein, but there was no correlation between co-precipitation of either STAT1 or STAT2 and the abilities of the V proteins to block type I IFN-induced gene transcription or the creation of the antiviral state. Further study revealed that the V proteins of RPV, MeV, PPRV and CDV could all interfere with phosphorylation of the interferon-receptor-associated kinase Tyk2, and the V protein of highly virulent RPV could also block the phosphorylation of another such kinase, Jak1. Co-precipitation studies showed that morbillivirus V proteins all form a complex containing Tyk2 and Jak1. This study highlights the ability of morbillivirus V proteins to target multiple components of the IFN signalling pathways to control both type I and type II IFN action.

Virucidal activity of a scorpion venom peptide variant mucroporin-M1 against measles, SARS-CoV and influenza H5N1 viruses

Outbreaks of SARS-CoV, influenza A (H5N1, H1N1) and measles viruses in recent years have raised serious concerns about the measures available to control emerging and re-emerging infectious viral diseases. Effective antiviral agents are lacking that specifically target RNA viruses such as measles, SARS-CoV and influenza H5N1 viruses, and available vaccinations have demonstrated variable efficacy. Therefore, the development of novel antiviral agents is needed to close the vaccination gap and silence outbreaks. We previously identified mucroporin, a cationic host defense peptide from scorpion venom, which can effectively inhibit standard bacteria. The optimized mucroporin-M1 can inhibit gram-positive bacteria at low concentrations and antibiotic-resistant pathogens. In this investigation, we further tested mucroporin and the optimized mucroporin-M1 for their antiviral activity. Surprisingly, we found that the antiviral activities of mucroporin-M1 against measles, SARS-CoV and influenza H5N1 viruses were notably increased with an EC₅₀ of 7.15 μg/ml (3.52 μM) and a CC₅₀ of 70.46 μg/ml (34.70 μM) against measles virus, an EC₅₀ of 14.46 μg/ml (7.12 μM) against SARS-CoV and an EC₅₀ of 2.10 μg/ml (1.03 μM) against H5N1, while the original peptide mucroporin showed no antiviral activity against any of these three viruses. The inhibition model could be via a direct interaction with the virus envelope, thereby decreasing the infectivity of virus. This report provides evidence that host defense peptides from scorpion venom can be modified for antiviral activity by rational design and represents a practical approach for developing broad-spectrum antiviral agents, especially against RNA viruses.

Infection and direct injury in human hepatocyte explants and a hepatoblastoma cell line due to hepatiticomimetic (non-hepatitis) viruses

Hepatitis is caused by hepatitis viruses, but hepatitis or hepatocellular enzyme abnormalities is sometimes associated with infection by the hepatiticomimetic viruses. The direct and indirect effects of infection with hepatiticomimetic viruses were examined in two human hepatocyte systems. Poliovirus, adenovirus, and herpes simplex virus (HSV) induced cytopathology in Hep G2 cells. Measles virus caused no change in hepatocytes. Poliovirus infection did not affect cellular protein synthesis, and the peak of hepatocellular enzyme release coincided with the peak of virus release. The increase in adenovirus protein synthesis correlated with the decrease of transferrin synthesis, and enzyme release was not prominent. HSV induced viral protein synthesis with enhanced processing and inhibition of synthesis of alpha1-antitrypsin. The peak of enzyme release was later than the peak of virus release. In primary hepatocytes, poliovirus, adenovirus, and induced extensive cytopathology and enzyme release, and VZV caused cytopathology and significant but minute enzyme release. The ratio of lactate dehydrogenase to aspartate aminotransferase release was larger in poliovirus infection in both hepatocytes than in HSV or VZV infection. Although poliovirus and adenovirus are released by cytolysis and HSV and VZV are secreted by exocytosis of cytoplasmic vacuoles, enzyme release was independent of the type of virus release. Adenovirus showed strong cytotoxicity but did not modify the membrane nor cause enzyme release. Enzyme release was associated with modification of the surface membrane due to apoptosis with poliovirus and necrosis with HSV. Consequently hepatocellular injury by viral infection did not reflect the amount or pattern of hepatocellular enzyme release.

Infected Cell Carriers: A New Strategy for Systemic Delivery of Oncolytic Measles Viruses in Cancer Virotherapy

Attenuated measles viruses (MVs) propagate selectively in human tumor cells, and phase I clinical trials are currently underway to test their oncolytic activity. A major theoretical impediment to systemic MV application is the presence of pre-existing antiviral immunity. We hypothesized that autologous MV-infected cells might be a more reliable vehicle than cell-free virions to deliver the infection to tumor cells in subjects with neutralizing titers of anti-measles antibodies. Our in vitro studies, using a dual-color fluorescent model, demonstrated efficient cell-to-cell transfer of infection via heterofusion. In contrast to infection by naked virions, heterofusion between infected cell carriers and tumor cells was more resistant to antibody neutralization. Infected monocytic, endothelial, or stimulated peripheral blood cells could deliver oncolytic MV to tumor lesions in vivo, after intravenous (i.v.) or intraperitoneal (i.p.) administration. Single or repeated i.p. injections of monocytic carriers significantly improved survival of animals bearing human ovarian cancer xenografts. Systemic or i.p. injection of MV-infected cells successfully transferred infection by heterofusion to Raji lymphomas or hepatocellular carcinoma tumors in the presence of neutralizing antibodies. These results suggest a novel strategy for systemic delivery of oncolytic virotherapy in cancer patients that can "bypass" the pre-existing humoral immunity against MV.

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.

[The morphology of the micro-capsulated polyacrylic acid-based formulation of measles vaccine]

The morphology and virus localization were studied in the microcapsulated measles vaccine formulation involving polyacrylic acid (PAA) copolymers as a matrix. Transmission electron microscopy and phosphotungsic staining at a pH value of 2 to 7 showed that the morphology of microparticles was related to the value of pH and to the concentration of a polymer in the matrix. In the neutral medium, the microcapsules had the sizes of 0.5 to 10 microm, which were optimal for transport through the intestinal wall when immunization was orally used. Immunocytochemistry revealed measles virus antigen within the microparticles. The specific activity of the microcapsulated formulation of measles virus was as high as 3.36 and 4.31 lg of TCD50/0.5 ml for the samples containing 1 and 0.1% polymer, respectively. The findings suggest that the microparticles of the vaccine contain live measles virus.

Measles Metapopulation Dynamics: A Gravity Model for Epidemiological Coupling and Dynamics

Infectious diseases provide a particularly clear illustration of the spatiotemporal underpinnings of consumer-resource dynamics. The paradigm is provided by extremely contagious, acute, immunizing childhood infections. Partially synchronized, unstable oscillations are punctuated by local extinctions. This, in turn, can result in spatial differentiation in the timing of epidemics and, depending on the nature of spatial contagion, may result in traveling waves. Measles epidemics are one of a few systems documented well enough to reveal all of these properties and how they are affected by spatiotemporal variations in population structure and demography. On the basis of a gravity coupling model and a time series susceptible-infected-recovered (TSIR) model for local dynamics, we propose a metapopulation model for regional measles dynamics. The model can capture all the major spatiotemporal properties in prevaccination epidemics of measles in England and Wales.

Morbillivirus downregulation of CD46

There is evidence that CD46 (membrane cofactor protein) is a cellular receptor for vaccine and laboratory-passaged strains of measles virus (MV). Following infection with these MV strains, CD46 is downregulated from the cell surface, and consequent complement-mediated lysis has been shown to occur upon infection of a human monocytic cell line. The MV hemagglutinin (H) protein alone is capable of inducing this downregulation. Some wild-type strains of MV fail to downregulate CD46, despite infection being prevented by anti-CD46 antibodies. In this study we show that CD46 is also downregulated to the same extent by wild-type, vaccine, and laboratory-passaged strains of rinderpest virus (RPV), although CD46 did not appear to be the receptor for RPV. Expression of the RPV H protein by a nonreplicating adenovirus vector was also found to cause this downregulation. A vaccine strain of peste des petits ruminants virus caused slight downregulation of CD46 in infected Vero cells, while wild-type and vaccine strains of canine distemper virus and a wild-type strain of dolphin morbillivirus failed to downregulate CD46. Downregulation of CD46 can, therefore, be a function independent of the use of this protein as a virus receptor.

Susceptibility of cats to equine morbillivirus

OBJECTIVE

To assess the susceptibility of cats to equine morbillivirus (EMV) by direct administration of the virus by subcutaneous, intra-nasal or oral routes, and following exposure to infected cats.

DESIGN

A disease transmission study, with controls, using ten cats.

PROCEDURE

Groups of cats were given the virus by the designated methods and assessed for evidence of infection by clinical examination, plus pathological and virological tests.

RESULTS

All cats administered the virus by subcutaneous, intra-nasal or oral routes became infected and developed the disease within 4 to 8 days. One of two cats in contact with affected cats also developed the disease, but two cats kept near to affected cats did not become infected. The virus was isolated from a range of tissues collected from the infected cats, and the lesions observed in affected cats were similar to those previously observed in horses naturally and experimentally infected with the virus.

CONCLUSION

This is the first demonstration that animals can be infected with EMV by non-parenteral means, that the virus can transmit naturally between animals and confirms other reports of the similarity of EMV disease in horses and cats.