Structure and organization of paramyxovirus particles.

The paramyxovirus family comprises major human and animal pathogens such as measles virus (MeV), mumps virus (MuV), the parainfluenzaviruses, Newcastle disease virus (NDV), and the highly pathogenic zoonotic hendra (HeV) and nipah (NiV) viruses. Paramyxovirus particles are pleomorphic, with a lipid envelope, nonsegmented RNA genomes of negative polarity, and densely packed glycoproteins on the virion surface. A number of crystal structures of different paramyxovirus proteins and protein fragments were solved, but the available information concerning overall virion organization remains limited. However, recent studies have reported cryo-electron tomography-based reconstructions of Sendai virus (SeV), MeV, NDV, and human parainfluenza virus type 3 (HPIV3) particles and a surface assessment of NiV-derived virus-like particles (VLPs), which have yielded innovative hypotheses concerning paramyxovirus particle assembly, budding, and organization. Following a summary of the current insight into paramyxovirus virion morphology, this review will focus on discussing the implications of these particle reconstructions on the present models of paramyxovirus assembly and infection.

Viral research in Brazilian owls (Tyto alba and Rhinoptynx clamator) by transmission electron microscopy / Investigación viral en buhos brasileños (Tyto alba y Rhinoptynx clamator) a través de microscopía electrónica de transmisión

The barn-owl (Tyto Alba) and striped-owl (Rhinoptynx clamator) belong respectively to the families Tytonidae and Strigidae. Avian paramyxoviruses have been isolated from a variety of species of wild and domestic birds wordlwide causing diverse clinical symptoms and signs. Paramyxoviruses belong to the family Paramyxoviridae and Avulovirus genus, including nine serotypes (APMV 1 to 9). The lymphoid leukosis is a retrovirus-induced neoplasia. The avian retroviruses belong to the Retroviridae family and to the Alpharetrovirus genus. Coronaviruses can cause respiratory and enteric disease in several species of birds. They belong to the Coronaviridae family and to the groups 3a e 3c. In this study, we describe the presence of viruses in four owls, two barn owls (Tyto alba) and two striped owls (Rhinoptynx clamator), rescued from tree-lined streets of Sao Paulo, Brazil and sent to the Recovery Center of Wild Animals of the Tietê Ecological Park, where the animals died. Fragments of lung, liver and small intestine of these birds were processed for transmission electron microscopy utilizing negative staining (rapid preparation), immunoelectron microscopy and immunocitochemistry techniques. Under the transmission electron microscopy paramyxovirus particles, pleomorphic, roughly spherical or filamentous, measuring 100 to 500 nm of diameter containing an envelope covered by spikes, an herring-bone helical nucleocapsid-like structure, measuring 15 to 20 nm in diameter, were visualized in the samples of lung, liver and small intestine of all owls. In small intestine samples of the two striped-owl (owls 3 and 4) it was detected pleomorphic coronavirus particles with a diameter of 75-160 nm containing a solar corona-shaped envelope, with projections of approximately 20 nm of diameter. In liver fragments of one striped-owl (owl 4) pleomorphic particles of retrovirus with a diameter of 80-145 nm containing an envelope with short projections and diameter of 9 nm were....

La lechuza (Tyto Alba) y el búho de orejas (Rhinoptynx clamator) pertenecen respectivamente a las familias Strigidae y Tytonidae. El paramixovirus aviario se ha aislado de especies de vida silveste como las aves domésticas por todo el mundo, causando diversos síntomas clínicos. El paramixovirus pertenece a la familia Paramyxoviridae y al Avulovirus genus que incluye nueve serotipos (APMV 1 a 9). La leucosis linfoide es una neoplasia inducida por retrovirus. Los retrovirus aviarios pertenecen a la familia Retroviridae y el género Alpharetrovirus. Los coronavirus pueden causar enfermedades respiratorias y entéricas en varias especies de aves. Ellos pertenecen a la familia Coronaviridae y a los grupos 3a y 3c. En este estudio, se describe la presencia del virus en cuatro búhos, dos lechuzas (Tyto alba) y dos búhos de orejas (Rhinoptynx clamator), rescatados de las calles arboladas de São Paulo, Brasil y enviados al Centro de Recuperación de Animales Silvestres del Parque Ecológico de Tietê, donde hubo murieron los animales. Fragmentos de pulmón, delhígado y del intestino delgado de estas aves fueron procesados para microscopía electrónica de transmisión utilizando tinción negativa (preparación rápida), inmunomicroscopía y técnicas de inmunocitoquímica. Bajo microscopía electrónica de transmisión, partículas de paramixovirus, pleomórficas, aproximadamente esféricas o filamentosas, de 100 a 500 nm de diámetro con un sobre cubierto por espigas, y nucleocápside helicoidal con características de espiga, midiendo 15 a 20 nm de diámetro, fueron visualizadas en las muestras de pulmón, hígado e intestino delgado de todos los búhos. En muestras de intestino delgado de dos búho de orejas (búhos 3 y 4) se detectaron partículas pleomórficas con coronavirus de un diámetro de 75-160 nm con un sobre con forma de corona solar, con proyecciones de aproximadamente 20 nm de diámetro. En el hígado de un búho de orejas (búho 4) se observaron partículas pleomórficas de retrovirus con ...

Characterization of Mapuera virus: structure, proteins and nucleotide sequence of the gene encoding the nucleocapsid protein.

The molecular biology of Mapuera virus was studied at both the protein and nucleic acid levels. Seven virus-encoded proteins were detected in infected Vero cells. The sizes and characteristics of each of the proteins determined from various radiolabelling experiments allowed preliminary identification of the proteins as the large (L; 190 kDa), haemagglutinin neuraminidase (HN; 74 kDa), nucleocapsid (N; 66 kDa), fusion (F0; 63 kDa), phosphoprotein (P; 49 kDa), matrix (M; 43 kDa) and non-structural (V; 35 kDa) proteins. Western blot analysis showed that the HN, N and P proteins were major antigens recognized in the mouse. A cDNA library of total virus-infected cellular mRNA was created and screening of the library resulted in the detection of cDNA sequences representing the N mRNA transcript of Mapuera virus. The N mRNA sequence determined from the clones was 1731 nt in length and contained an ORF that encoded 537 amino acids, the complete 3' untranslated region and part of the 5' non-coding region. The calculated M(r) of the N protein was 59 kDa, which is close to the 66 kDa protein observed by SDS-PAGE.

Possible vaccine-induced canine distemper in a South American bush dog (Speothos venaticus).

Suspected vaccine-induced canine distemper was diagnosed in a captive female bush dog (Speothos venaticus). Macroscopic lesions included mild congestion of the gastric mucosa and focal consolidation of the lung. Histopathological lesions included status spongiosis, gliosis, widespread eosinophilic, intranuclear and intracytoplasmic inclusion bodies in neurons, astrocytes and gitter cells of the cerebral, cerebellar and spinal white matter.

Characterization of a virus associated with turkey rhinotracheitis.

A virus associated with turkey rhinotracheitis was purified and its morphology and structural polypeptides were compared with those of the bovine, human and murine members of the genus Pneumovirus. The isolate possessed surface projections 13 to 14 nm in length and a helical nucleocapsid 14 nm in diameter with a pitch of 7 nm. Approximately seven presumed viral polypeptides were observed. Their apparent molecular weights were 200 x 10(3) (200K), 84K, 54K, 42K, 37K, 31K and 14K; two of these, the 84K and 54K polypeptides, were glycosylated. The virus was shown to possess many features that were similar to established pneumoviruses and can therefore be regarded as a possible member of this genus.

Respiratory disease and wasting in athymic mice infected with pneumonia virus of mice.

Although pneumonia virus of mice (PVM) is ubiquitous among rodent colonies in the United States, it has not been reported to cause clinically apparent disease in euthymic mice. However, PVM has been reported to cause respiratory disease and death in experimentally infected euthymic and athymic mice. A group of nu/nu mice, housed in quarantine in a Trexler-type isolator, had weight loss and dyspnea. Gross necropsy findings included cachexia and diffuse pulmonary edema or lobar consolidation. Histologically there was diffuse interstitial pneumonia. Electron microscopy revealed filamentous virions budding from plasma membranes, and immunohistochemical staining of lung tissue was positive for PVM antigen. PVM was isolated from affected lung tissue in BHK 21 cells and mouse antibody production tests resulted in seroconversion to PVM. Experimental inoculation of athymic mice with lung homogenate from spontaneously infected mice resulted in clinically apparent respiratory disease and histologic lung changes similar to those in naturally infected mice. Inoculation of athymic mice with infected BHK 21 cell culture fluid resulted in pneumonia which was qualitatively similar to, but less severe than, that observed in mice with spontaneous disease. These findings indicate that naturally occurring PVM infection in athymic mice may cause respiratory disease and wasting.

Studies on the nature of fibrillar nuclei. Distinction from viral nucleocapsid.

Despite sufficient evidence to the contrary, fibrillar nuclei continue to be claimed by some to represent paramyxovirus. In a review of the electron-microscopic material, fibrillar nuclei were found in a variety of tissues and situations where a viral etiology is unlikely. Fibrillar nuclei were most often found in postmortem and formalin-fixed material. These nuclei were also experimentally produced in postmortem human lung with formalin fixation followed by a deionized water rinse. It is concluded that fibrillar nuclei do not represent virus, but chromatin, and it is believed that this chromatin appearance is related to cell injury and to tissue processing. It is also believed that fibrillar nuclei occur with much greater frequency than realized. These nuclei are usually ignored during examination of specimens by light and electron microscopy because these specimens are usually being selectively screened for other changes and perhaps because a clear understanding of their significance is still lacking.

Evidence for a viral etiology of Paget's disease of bone.

Ultrastructural studies of the bone cells in patients with Paget's disease of bone have revealed the presence of nuclear and cytoplasmic inclusions that resemble the nucleocapsids of Paramyxoviridae virus. Immunocytologic studies of bone biopsy specimens and cultured bone cells have demonstrated positive responses with antisera against measles virus and/or respiratory syncytial virus. These observations suggest that Paget's disease may be a slow viral infection of bone. The exact nature of the putative viral agent has yet to be established.

Intrinsic fluorescence of some myxo- and paramyxoviruses and of their subviral fractions.

Fluorescence spectra of Sendai and influenza A(H1N1) viruses have different emission maxima; their quantum yield is much lower than that of tobacco mosaic virus. Solubilized envelopes and nucleoproteins of Sendai, influenza and mumps virus have different half-bandwidth and relative quantum yield values of emission, according to the agent used for disruption. Thus emission (as well as excitation and absorption) spectra of Triton X-100-solubilized envelopes show a marked hypsochromic shift as compared with the envelopes obtained by Tween20-disruption. The results are correlated with the different disruption extent achieved with the two agents.

Multiple sclerosis and viruses: an overview.

The evidence for a viral etiology of MS has been reviewed. The strongest evidence favoring a virus is based primarily on epidemiologic considerations. Less convincing evidence comes from pathologic studies, serology, lymphocyte reactivity to viral antigens, and reports of identification of virus in MS tissues. Animal models of viral demyelination exist, which may provide insight into possible etiologic agents and pathogenetic mechanisms. Considering all the data, it is clear that no agent can be convincingly linked to MS at the present time. If a single virus causes the majority of cases of MS, then a morbilliform virus--canine distemper--is a leading contender, because this agent is consistent with the epidemiologic and serologic findings and is highly neurovirulent for animals ranging from mice to primates. Since no virus fulfills the usual criteria for linking an infectious agent to a disease, other possibilities must be considered. If MS is caused by a single virus, it may be a common virus not presently considered as being associated with MS, or an agent as yet unidentified. It is also conceivable that multiple agents, acting alone or in concert, initiate the MS process, perhaps through a common immune-mediated pathway. In this regard, another human demyelinating disease--the Guillain-Barré syndrome--which may in some instances become a chronic remitting and relapsing disorder, is thought to be initiated by multiple infectious agents but to have an immunologic pathogenesis.

Properties of a newly isolated, serologically distinct avian paramyxovirus.

The morphological, bio-physical and growth properties of the isolate duck/Hong Kong/D3/75 (D3/75) were consistent with this virus being a member of the paramyxovirus group. Using haemagglutination inhibition and neuraminidase inhibition tests no serological relationships between D3/75 and other paramyxoviruses could be demonstrated. The structural polypeptides of D3/75 were also typical of paramyxoviruses, consisting of 6--7 polypeptides ranging in molecular weight from 46,000--200,000 under reduced conditions. Two polypeptides were glycosylated.

Ultrastructural studies of perivascular cuffing cells in multiple sclerosis brain.

Perivascular cuffs in brains taken at autopsy from 6 patients with multiple sclerosis (MS) were examined by electron microscopy. Light and electron microscopy of brain revealed acute and chronic types of cuffs. The acute type of cuffs, consisting of many lymphocytes and lymphoid cells and a few lipid-laden macrophages, was usually seen in the nondemyelinated white matter or in the margin of the plaques, and infrequently within a plaque. The chronic type consisted mainly of macrophages, plasmacytoid cells, and plasma cells and was always seen within the plaques. In the parenchymal tissue of the white matter, macrophages participated in phagocytosis of myelin and axons, but no peeling or stripping of myelin sheath by inflammatory cells was observed. So-called paramyxovirus-like fuzzy filaments were observed in the nuclei of the mononuclear cells of perivascular cuffs obtained from 5 patients. The filaments were found predominantly in the acute rather than chronic type of cuffs. Specific antigens of measles and 6/94 viruses and intranuclear RNA corresponding to the filaments could not be demonstrated in the perivascular inflammatory cells by the immunofluorescence technique or acridine orange staining.

Intranuclear "paramyxovirus-like" material in multiple sclerosis, adreno-leukodystrophy and Kuf's disease.

Detailed comparative ultrastructural examination of multiple sclerosis (MS) plaques, inflammatory CNS lesions from adreno-leukodystrophy(A-LD), tissue from a case of chronic granulomatous meningitis, biopsy samples of necrotic cerebral cortex and CNS tissue from a case of Kuf's disease (adult-type ceroid lipofuscinosis), has revealed that the intranuclear filamentous material previously thought to be related to a viral infection in MS is a non-specific finding. These intranuclear strands were, however, found in greatest frequency in the acute lesions of MS and were absent from chronically demyelinated areas. The macrophages, lymphocytes and fibrocytes containing filamentous material in the nuclei were mainly perivascular. In A-LD, some macrophages in active lesions contained similar nuclei, and in Kuf's disease they were present in some glial cells in the cerebral cortex.