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Biomedical subjects

H Tsiang

Publications and source records attributed to H Tsiang.

At least 55 records · Page 3Linked to original sources
PubMed1986

Membrane carbohydrate requirement for rabies virus binding to chicken embryo related cells.

The involvement of cellular carbohydrates in the interaction of rabies virus with chicken embryo related cell receptors was investigated. Two different methodological approaches were employed: specific glycosidases were used to treat the cells before infection, and specific lectins were used to compete with the viral binding. The results indicate the participation of sialic acid, galactose, mannose, and N-acetyl-glucosamine but not fucose in the cellular requirements for rabies virus infection.

Animals↗
PubMed1985

Effect of concanavalin A on the early events of rabies virus infection of CER cells.

The effect of concanavalin A on rabies virus infection of CER cells was investigated. Pretreatment of CER cells with concanavalin A inhibited cellular susceptibility to rabies virus infection. The lectin also was found to be inhibitory when applied after the viral binding step. Moreover, the lectin had a direct inhibitory effect on the infectivity of the virion. These lectin-mediated inhibitions could be reversed by alpha-D-methyl-mannopyranoside. These complex effects are discussed with regard to the mechanism of rabies virus entry into CER cells.

Animals↗
PubMed1985

Gangliosides in early interactions between vesicular stomatitis virus and CER cells.

In the present report an attempt was made to elucidate the role of gangliosides in early interactions between vesicular stomatitis virus (VSV) and CER cells. Research was carried out to test the ability of gangliosides from mammal brains and from CER cells to inhibit viral attachment to susceptible cells. The incubation of VSV in the presence of gangliosides decreased the subsequent infection of CER cells by the virus. When similar experiments were performed with gangliosides inserted in liposomes the inhibition of infection was enhanced. Since carbohydrate moieties could participate to rhabdovirus binding as a part of a glycolipid receptor, CER cells were subjected to the action of glycosidases and these produced a fall in the viral attachment. Deglycosilated CER cells reacquired their susceptibility to virus infection after coating with gangliosides immediately after enzyme treatment. Results obtained show the participation of gangliosides in the receptorial structure for vesiculovirus of susceptible CER cells.

Animals↗
PubMed1984

Role of phospholipids in rhabdovirus attachment to CER cells. Brief report.

The effect of phospholipases on rhabdovirus attachment to CER cells and the competitive binding of phospholipids and viruses to cells were studied. Results obtained indicate that, although to a different extent, some phospholipids represent a binding site for both Vesicular Stomatitis Virus (VSV) and rabies virus.

Animals↗
PubMed1984

Mechanism of rabies virus entry into CER cells.

The early steps of rabies virus (CVS) infection in vitro were studied in chicken embryo-related (CER) cells. The infection was monitored by looking for specific intracytoplasmic viral inclusions using anti-rabies fluorescein isothiocyanate at 24 h after the addition of virus. The attachment of rabies virus to CER cells was shown to be inhibited by pretreatment of the cells with neuraminidase. These cells recovered their susceptibility to rabies virus infection 6 h after removal of the enzyme. Treatment of CER cells with neuraminidase after the viral attachment step did not inhibit infection. The subsequent delivery of infectious virions into acid prelysosomal vacuoles or lysosomes was studied using lysosomotropic agents. Ammonium chloride and chloroquine were used to prevent the virus fusion step thus preventing infection. Both drugs were shown to inhibit the early steps of infection, NH4Cl having a much earlier effect than chloroquine. The two drugs had no effect on the attachment step nor did NH4Cl inhibit virus multiplication. The use of metabolic inhibitors (2-deoxy-D-glucose and sodium azide) shows that the entry of rabies virus into CER cells does not require the involvement of cellular energy processes. In electron microscopy studies, the presence of rabies virus particles was detected in coated pits and coated vesicles as well as in uncoated vesicles, and later in lysosomes. These data indicate that the mechanism by which rabies virus enters CER cells is probably through adsorptive endocytosis and does not require the participation of cellular metabolic active processes.

Adsorption↗
PubMed1984

Distribution of rabies virus, interferon and interferon-mediated enzymes in the brains of virus-infected rats.

The distribution of rabies virus, interferon and interferon-mediated enzymes, pppA(2'p5'A)n synthetase (2-5A synthetase) and poly(rI) . poly(rC)-Sepharose-bound protein kinase, was studied in different regions of the brains of rabies virus-infected rats. A broad range of virus infectivity was found in the brain stem, cerebellum, cortex, hippocampus and striatum. Similarly, the levels of interferon were variable (2500 to 60 000 units/mg protein in tissue extracts) in the different brain regions studied but were unrelated to the corresponding infectivities . The level of 2-5A synthetase and protein kinase was enhanced several-fold in the individual brain regions and the degree of such enhancement was correlated with the level of interferon.

2',5'-Oligoadenylate Synthetase↗
PubMed1983

An in vivo and in vitro study of rabies virus infection of the rat superior cervical ganglia.

In the attempt to develop a homogeneous neuronal model to study rabies pathogenesis in vivo and in vitro, the superior cervical ganglia (SCG) were chosen because of their unique features. In vivo infection of the SCG was attempted by inoculation of fixed rabies virus into the anterior eye chamber. However, viral by this route as well as intracerebrally failed to infect this neuronal organ in adult rats whereas the infection was poorly efficient in 24 hours newborn rats. Dissociated cell cultures from the rat embryo SCG were infected in vitro and examined for the presence of rabies specific antigen and release of virus particles in the supernatant. Despite the presence of rabies nucleoprotein in the cytoplasm and the presence of typical Negri bodies, neurons from the rat SCG produced few particles as observed by electron microscopy and no increase in virus yields could be detected by titration of viral infectivity during the infectious cycle. Our observations indicate that although rabies virus is neurotropic as shown in previous studies, all neuronal tissues are not equally susceptible to this viral infection. The resistance of the SCG to rabies virus infection in vivo does not seems to be a lack of accessibility of this organ to infection since other authors had shown that it could be infected by herpes virus. Both in vitro and in vivo experiments show that although neurons from the SCG are susceptible to rabies virus infection, infected cells do not produce rabies infectious virions efficiently.

Animals↗
PubMed1983

Neurotropism of rabies virus. An in vitro study.

The relative susceptibility of neurons and glia, grown as monolayers in vitro, to rabies virus infection was explored. Established cell lines of neuronal or glial phenotype and primary cultures of cells derived from mouse dorsal root ganglia (DRC) or brain were used as homologues of the targets of rabies virus in the nervous system. Fixed rabies virus (CVS) strain was used in most experiments; other fixed rabies strains (PV, HEP, ERA) and a street rabies virus isolate were used in some. Virus-cell tropism was determined by immunofluorescence assay for rabies nucleocapsid antigen and cell permissivity was assessed by titration of virus yields. Neuronal cells always exhibited a much greater susceptibility to infection and a greater propensity to sustain viral growth. By immunofluorescence, 90-100% of neurons commonly had viral inclusion bodies, while doses of the virus three to four orders of magnitude higher still left greater than 99% of astrocytes, in brain cell cultures and 90 +/- 5% of the non-neuronal cells in DRG cultures without any obvious signs of rabies virus. Neuroblastoma cells (95 +/- 5% with viral antigens) produced viral yields about four orders of magnitude higher than glioma cells (10 +/- 5% with viral antigens). Though the overall infectivity of street virus was lower than that of fixed virus strains, a significantly higher viral tropism for neurons than for glia was maintained. Thus, primary neuronal cultures offer a means of exploring molecular events in rabies virus infection and their role in pathogenesis.

Animals↗
PubMed1983

Protein synthesis in VSV infected CNS, neuroblastoma and BHK cell lines.

The protein synthesis of VSV infected CNS of mice was analysed by SDS-PAGE. Cellular and viral protein synthesis in the CNS were also compared to VSV infected neuroblastoma cells (clone NS 20) and fibroblasts (BHK21). Inhibition of host protein synthesis was observed in the three systems tested. However, this inhibition was shown to occur faster in neuroblastoma cells than in BHK cells, whereas it proceeded progressively in the brain. Thus the shut off of host cell protein synthesis by VSV seems to be a general phenomenon that occurs in vivo as well as in vitro. VSV protein from the CNS, or from neuroblastoma cells and fibroblasts were found to migrate similarly in SDS-PAGE. The viral L protein synthesis was found to be particularly active in the CNS, with respect to that observed in NS20 and BHK cells. The viral glycoprotein failed to be detected in the VSV infected mouse brain in our experimental conditions. The results show that VSV infection in vivo occurs with some difference with that of non neuronal cells, and that in vivo studies suggest the existence of cellular modulation that should be taken in account in the pathogenesis of this rhabdovirus.

Animals↗
PubMed1982

[Molecular and cellular aspects of the pathogenesis of rabies].

The true causes of the beginning of the symptoms and the eventual mortality of rabies are not very well known. Immunopathological factors certainly intervene, but they only complete a process of neuronal alteration. Contrary to other viruses which lyse the infected cells, the rabies virus does not necessarily destroy the neurones which are the preferential target cells. On the contrary, RNA synthesis is stimulated during CNS infection by the rabies virus. Synthesis is not stimulated by the multiplication of the rabies virus in the cell lines of fibroblastic or neuronal origin, which suggests the existence of regulations on neuronal level functions in the CNS. Nevertheless, the protein virus synthesis seemed equally submitted to specific neuron regulations or neuronal populations. The traces of a neuronal dysfunction during infection by the rabies virus have been investigated, using as a probe, variations of muscarinic acetyl choline receptors in the CNS. The presence of these receptors is revealed by the use of an antagonistic ligand of acetyl choline, quinuclidinyl benzylate. We were able to show that as regards the rat, the appearance of the first signs of paralysis is correlated with the diminution of the receptor binding. Thus, it seems that the presence of the virus in the CNS provokes neuronal alteration which can in itself condition the viral multiplication and eventually modulate the viral pathogenesis expression.

Animals↗
PubMed1982

Neuronal function impairment in rabies-infected rat brain.

In homogenates of rabies-infected rat brain the specific binding of a tritium-labelled antagonist of muscarinic acetylcholine (mACh) varied during the course of infection. A small increase in the binding of the antagonist, quinuclidinyl benzylate (QNB), during the first days after infection was followed by a marked decrease as the symptoms of rabies appeared. Measurements of 3H-labelled QNB binding in dissected brain regions, i.e. brain stem, caudatus nucleus, cortex, hippocampus, cerebellum and medulla, showed that the decrease in binding was greater in the hippocampus than in any other brain region. We conclude that in the central nervous system (CNS) of the rabies-infected rat neuronal impairment may be one manifestation of rabies pathogenesis.

Animals↗
PubMed1981

Presence of specific antigens in neuronal cells infected with fixed and street rabies virus strains.

The presence of rabies specific antigens is investigated after infection with different rabies virus strains in neural cell lines and in the central nervous system of laboratory rodents. In fixed rabies infected cells, the rabies glycoprotein is found to be present 48 h after infection, whereas in hamsters this protein was found 5 days after an intracerebral inoculation. In contrast, rabies glycoprotein was not detectable in any of the street rabies-infected cell system by the fluorescent antibody test, although nucleoprotein was present, showing that infection occurred in these cells. Rabies glycoprotein was also undetectable in the central nervous system (CNS) of athymic nude mice which is known to be very sensitive to street rabies infection and to contain large quantities of viral material. Our results suggest that the smaller amount of rabies glycoprotein synthesized during street rabies infection are of consequence for the pathogenesis of rabies disease. The immunopathology of street rabies virus infection is certainly modulated by the failure of the viral glycoprotein to be present in large quantities on the surface of the infected cellular membrane as in the case of fixed rabies.

Animals↗
PubMed1981

BCG modulation of delayed type hypersensitivity, humoral response and acquired resistance after rabies vaccination.

The immunopotentiating action of BCG was evaluated in rabies. The maximum enhancing effect on delayed type hypersensitivity (DTH) was obtained 14 days after rabies immunization when different BCG vaccination schedules were tested in mice. A stable form of specific sensitization to rabies antigen under the modulation of BCG pretreatment was obtained. High concentrations of rabies antigen were found to be inhibitory for the DTH reaction. Levels of protection were evaluated in rabies vaccination after BCG modulation. One single injection of rabies vaccine in BCG pretreated mice was as effective as two injections of rabies vaccine in normal mice. However, in the latter, increase of protection was correlated with the levels of neutralizing antibody. On the other hand, the BCG pretreated mice, protection was not associated with a significant increase in antibody. Pretreatment with BCG alone influenced the outcome of fixed rabies as well as street rabies by enhancing the natural resistance to rabies infection.

Animals↗
PubMed1980

In vivo detection of specific cell-mediated immunity in street rabies virus infection in mice.

In street rabies-infected mice, in vivo expression of delayed type hypersensitivity (DTH) measured by the footpad test was revealed by challenge with inactivated fixed rabies virus (RV). The use of BCG as an adjuvant cell-mediated immunity (CMI) was necessary for the production of significant DTH levels. Typical DTH kinetics were obtained, with a maximum at 24 h after the challenge. DTH was also found to be at highest levels 4 days after infection with street rabies virus. DTH could also be revealed with street rabies virus in RV immunized mice. Adoptive transfer of lymphoid cells from a street rabies infected donor to normal recipient mice was performed and DTH was tested with RV. Susceptibility of DTH to immunosuppression by cyclophosphamide treatment was also assayed in street rabies virus-infected mice and in adoptively-sensitized recipient mice. These results and the relationship between DTH and CMI in rabies infection and immunization are discussed.

Adjuvants, Immunologic↗
PubMed1979

Evidence for an intraaxonal transport of fixed and street rabies virus.

Colchicine was used to inhibit axonal transport and to demonstrate that rabies virus spread from the peripheral inoculation site to the CNS by the retrograde axoplasmic flow. Colchicine was applied by the mean of elastomer implants around the sciatic nerve of young rats in order to obtain higher local concentrations of the drug. This procedure avoided the systemic effects of colchicine encountered with the usual treatment. To confirm the efficiency of the axoplasmic flow inhibition by colchicine, 125I-tetanus toxin was used as a marker. Uptake of colchicine by the sciatic nerve was monitored by the use of 3H-labelled colchicine. Interruption of the retrograde axoplasmic flow resulted in prevention of fixed and street rabies virus propagation. Moreover, the centrifugal spread of rabies could be inhibited using this experimental procedure.

Animals↗