| long-term visna virus infection of sheep choroid plexus cells: initiation and preliminary characterization of the carrier cultures. | two sheep choroid plexus cell cultures were maintained and propagated for 413 days since being infected with strain k796 visna virus. the majority of the cells in these cultures contained visna virus-specific antigen on days 93 and 105 after infection. reverse transcriptase-like activity similar to that present in visna virus preparations was obtained from these cultures when very little plaque-forming virus was being synthesized. the persistently infected cultures are resistant to the cytopathi ... | 1975 | 47311 |
| rna-instructed dna polymerase activity in a cytoplasmic particulate fraction in brains from guamanian patients. | nervous system tissues from a number of patients with idiopathic neurological disorders were examined for biochemical evidence of rna tumor virus infection. rnase-sensitive dna polymerase activity was found in a cytoplasmic particulate fraction from two patients with guamanian amyotrophic lateral sclerosis (als) but not in brains from two normal u.s. individuals. the buoyant density of the enzyme-containing fraction was 1.16-1.18 g/ml and could be converted to a denser region of the gradient ( ... | 1975 | 49390 |
| the slow infection caused by visna virus. | | 1975 | 56255 |
| [comparative study of rna-dependent dna polymerases (revertases) of avian myeloblastosis virus and visna virus]. | | 1976 | 61846 |
| ovine cells: their long-term cultivation and susceptibility to visna virus. | sheep choroid plexus (scp) cells have been subcultured more than 120 times and have undergone over 300 cell generations. these fibroblastic-appearing scp ii-b cells contain ovine-specific antigens, have an absolute plating efficiency of 23 to 28% and are as susceptible to visna virus infection and virus-induced cytopathology as their low passage level counterparts. cultures of low, relatively high and high passage level scp cells produced equivalent amounts of visna virus at similar rates when i ... | 1977 | 68914 |
| infection of human cell cultures with bovine visna virus. | fibroblastoid cell cultures derived from leukaemic bone marrow were successfully infected with bvv. after 2 months of subcultivation the cultures showed the appearance of foci of altered cells, suggestive of malignant transformation. such foci were absent in non-inoculated cultures. both control and inoculated cultures had a limited life span, i.e. neither of them could be developed into continuous transformed cell lines. the presence of at least some bvv genome functions in the inoculated cells ... | 1978 | 75246 |
| evidence for two forms of rna-dependent dna polymerase in visna virus. | the visna viral rna-dependent dna polymerase has been resolved into two forms by affinity chromatography. glycerine gradient centrifugation of the two forms showed that one form sedimented at 6.9 s corresponding to an apparent molecular weight of 135 000 and the other at 6.3 s corresponding to 118 000. sodium dodecyl sulfate (sds)-polyacrylamide gel electrophoresis of the two forms indicated that the 6.9 s enzyme is composed of 2 molecules of 68 000 mol. wt. chain and the 6.3 s is a single chain ... | 1979 | 85464 |
| [immunologic aspects of preparation of antiserum to the reverse transcriptase from avian myeloblastosis virus]. | after immunization of rabbits the antiserum was prepared against purified reverse transcriptase (revertase) from avian myeloblastosis virus (amv). the antiserum demonstrated enzymeneutralizing antibody activity that was associated with ummunoglobulin g fraction but not with igm. the high antigenicity of amv revertase for rabbits was shown. the active antiserum was obtained after 4 immunizations of rabbit with approximately 20 microgram of the enzyme. non-specific revertase inhibitors were found ... | 1976 | 88006 |
| phosphonoformate inhibition of visna virus replication. | phosphonoformate (pfa) inhibits multiplication of visna virus in sheep choroid plexus cells; a 50% reduction of virus yield was obtained by 20 to 80 microm pfa. morphological changes, such as syncytial formation and cell degeneration, could be reversibly prevented by pfa. cell growth was not significantly affected at 500 microm pfa, although prolonged treatment with 2 mm pfa did arrest cell growth. cell-free reverse transcriptase activity primed with various synthetic template-primers was inhibi ... | 1979 | 90168 |
| phosphonoformate inhibits reverse transcriptase. | the new antiviral substance phosphonoformate (pfa) has been tested in a cell-free system for its effect on reverse transcriptases from an avian retrovirus (avian myeloblastosis virus, amv) and from mammalian retroviruses (rauscher leukaemia virus, rmulv; bovine leukaemia virus; baboon endogenous virus; simian sarcoma virus; visna virus). the observed inhibitory effect of pfa has been compared with that of a structurally related substance, phosphonoacetate (paa). phosphonoformate, at a concentrat ... | 1979 | 94344 |
| zwoegerziekte virus, the causative agent for progressive interstitial pneumonia (maedi) and meningo-leucoencephalitis (visna) in sheep. | the final results of experimental infections with virus recovered from the lungs of sheep suffering from progressive interstitial pneumonia (=zwoegerziekte=maedi) are reported. the virus could be reisolated from blood samples of all experimentally infected sheep. every animal produced antibodies against the virus. the neutralising, complement-fixing and precipitating antibodies remained present in the blood for six years. fourteen out of 21 intrapulmonarily infected sheep developed clinical and/ ... | 1975 | 164056 |
| comparative studies of visna and maedi viruses as antigens. | rabbits were immunized with purified visna and maedi viruses, using complete freund adjuvant, in footpad and intramuscular sites. the resulting antisera and their isolated immunoglobulin g (igg) and m (igm) classes were evaluated by tanned-cell passive hemagglutination (pha), complement fixation, gel diffusion, and virus neutralization tests. early, intermediate, and late bleedings showed increasingly high antibody activities by the pha, complement fixation, and gel diffusion tests. the activiti ... | 1975 | 164409 |
| proceedings: characterization of dna polymerase from visna virus. | | 1975 | 166334 |
| virus-like particles in buffy coat cells of normal goats and goats infected with progressive pneumonia virus. | by electron microscopy, virus-like particles (vlp) were seen in neutrophils and lymphocytes from buffy coats prepared from 5 goats inoculated with progressive pneumonia virus (ppv) and 3 noninoculated goats. the vlp were 80 to 120 nm in diameter, limited by a unit membrane, and resembled ppv, visna virus, and other members of the oncornavirus family. some vlp seemed to have electron-dense nucleoids and external spikes. in neutrophils, vlp were observed budding into vacuoles; rarely, intravacuola ... | 1975 | 167620 |
| genomic complexities of murine leukemia and sarcoma, reticuloendotheliosis, and visna viruses. | the genetic complexities of several ribodeoxyviruses were measured by quantitative analysis of unique rnase t1-resistant oligonucleotides from 60-70s viral rnas. moloney murine leukemia virus was found to have an rna complexity of 3.5 x 10(6) daltons, whereas moloney murine sarcoma virus had a significantly smaller genome size of 2.3 x 10(6). reticuleondotheliosis and visna virus rnas had complexities of 3.9 x 10(6), respectively. analysis of rnase a-resistant oligonucleotides of rous sarcoma vi ... | 1976 | 176429 |
| infectivity of visna virus dna. | | 1976 | 176812 |
| tumor incidence in visna virus inoculated mice. | mice (female swiss albino) inoculated when newborn with visna virus had tumors in 77% of cases when examined 8-12 months later. the tumors were mainly of the mammary carcinoma type. the tumor incidence in non-infected control animals was only 20%. in contrast, no increased incidence of tumors was observed among visna virus-inoculated inbred mice (balb/c, cba and dba) with low incidence of spontaneous mammary carcinoma. | 1976 | 178528 |
| antigenic analysis of isolated polypeptides from visna virus. | the antigenic activity of 10 visna polypeptides separated by gel filtration in the presence of 6 m guanidine hydrochloride (guhcl) was examined with rabbit antisera made specific for visna virus. the results showed that the first (guhcl 1) and the ninth (guhcl 9) polypeptide peak reacted with the antisera when examined in immunodiffusion, passive hemagglutination, and complement fixation tests. whole virus, guhcl 1, and guhcl 9, when tested with the antisera, appeared to be immunologically ident ... | 1976 | 184045 |
| pathogenesis of visna. i. sequential virologic, serologic, and pathologic studies. | a total of 56 icelandic sheep were infected with visna virus by intracerebral injection of strain 1514 and the course of infection was followed for 12 months. virus was isolated from more than 90 per cent of the animals, primarily from central nervous system and lymphoid tissues. however, titers of free infectious virus were minimal and virus isolation often required the use of tissue explants. all sheep raised serum-neutralizing and complement-fixing antibodies beginning 1 to 3 months after inf ... | 1976 | 185458 |
| membrane changes associated with assembly of visna virus. | | 1976 | 185798 |
| [electron microscopic observation of the infectious cycle of visna virus in sheep choroid plexus cells at temperatures under 37 degrees c]. | electron microscope study of viral penetration at 4 degrees c shows that viral particles first attach to cells. the attachment sites are invaginations which later fuse to form phagocytic cytoplasmic vacuoles. some virus particles with altered envelopes can be seen in the cytoplasm. after ten days of incubation at 29 degrees c, filamentous inclusions and mature viral particles are seen in the cytoplasm. the cellular membrane budding process and virus release observed at 37 degrees c have disappea ... | 1976 | 186212 |
| pathogenesis of visna. ii. effect of immunosuppression upon early central nervous system lesions. | it was hypothesized that the lesions of visna might represent an immunopathologic process. to test this hypothesis, a 1-month schedule of immunosuppressive treatment was devised, using horse anti-sheep thymocyte serum. in hampshire sheep, this regime was shown to protect against experimental allergic encephalomyelitis, to inhibit development of tuberculin hypersensitivity, to retard rejection of skin homografts by 3 weeks, and to markedly reduce the number and mitogenic responsiveness of periphe ... | 1976 | 186661 |
| pathogenesis of visna. iii. immune responses to central nervous system antigens in experimental allergic encephalomyelitis and visna. | experimental allergic encephalomyelitis (eae) was induced in sheep in pursuit of the hypothesis that an immune response against central nervous system antigens might play a role in the pathogenesis of visna. nine to 12 days after sensitization with whole sheep brain and complete freund's adjuvant, approximately 50% of sheep developed a fulminating lethal form of eae. following a second sensitization, another 20% of animals developed eae whereas a residual 30% failed to develop any signs or histo ... | 1976 | 186662 |
| isolation and characterization of a virus associated with progressive pneumonia (maedi) of sheep. | a virus with growth and morphologic characteristics of progressive pneumonia (maedi-visna) virus was isolated from the lungs of sheep with typical clinical and postmortem changes of chronic progressive pneumonia. the virus grew slowly in cultures of embryonic ovine lung cells, causing syncytial formation and degeneration. syncytia developed much slower and involved fewer cells than reported for other similar viruses isolated from sheep. as seen with the electron microscope, the virus reproduced ... | 1976 | 187087 |
| slow persistent infection caused by visna virus: role of host restriction. | proviral dna has been demonstrated by in situ hybridization in foci of cells of a lamb infected with the rna slow virus visna. a few of these cells also contain the major virion structural antigen p30. this restriction in virus gene expression in the infected animal provides a mechanism for persistence of virus in this chronic infection. | 1977 | 188133 |
| complexity and polyadenylic acid content of visna virus 60-70s rna. | the genomic complexity of visna virus was measured by quantitative analysis of 18 rnase t1-resistant oligonucleotides from 60-70s rna. t1-resistant oligonucleotides were separated by two-dimensional polyacrylamide gel electrophoresis. visna virus had a genomic complexity of 3.6 x 10(6) daltons, very close to the size of a single 30-40s rna subunit. it was therefore concluded that the visna virus genome is largely polyploid. visna virus 60-70s rna polyadenylic acid segment was purified by t1 rnas ... | 1977 | 189072 |
| the ultrastructure of early visna lesions. | the ultrastructure of visna, a slowly progressive menigo-encephalomyelitis of sheep, was studied in animals sacrificed one month after intracerebral inoculation of visna virus. the major pathological changes, representative of those seen during the first year after infection, consist of inflammation and minor focal destructive lesions of grey and white matter. the inflammatory infiltrates, both subependymal and perivascular as well as of the choroid plexus, were composed mainly of lymphocytes an ... | 1977 | 192037 |
| slow virus infection: replication and mechanisms of persistence of visna virus in sheep. | the influence of the age and immune status of the host on the slow replication and persistence of visna virus in sheep was studied. twenty-five randomly bred fetal american lambs were inoculated intracerebrally with visna virus. eight of these fetuses were immunosuppressed by thymectomy and antiserum to lymphocytes before inoculation. fetuses were sacrificed sequentially, and tissues were processed for viral quantitation. no exponential increase of virus occurred in either the normal or immunosu ... | 1977 | 192812 |
| characterization of visna virus envelope neuraminic acid. | visna virus particles inhibit influenza virus hemagglutination in an assay for neuraminic acid-containing viruses. pretreatment of visna virus with neuraminidase abolished hemagglutination inhibition activity but did not significantly affect attachment, infectivity, or virus-induced cell fusion in sheep choroid plexus cell monolayers. | 1977 | 195094 |
| antigenic shift of visna virus in persistently infected sheep. | visna viruses isolated from persistently infected sheep were antigenically distinct from the plaque-purified virus used for inoculation. the selection of antigenic variants under antibody pressure, thought to occur in vivo, was reproduced in sheep cell cultures inoculated with plaque-purified visna virus and maintained in antibody. antigenic shift may be a mechanism for persistence of virus in slow or recurrent viral infections. | 1977 | 195339 |
| visna virus rna synthesis. | visna is a classical slow infection in which virus characteristically persists in the face of the host immune response. the agent of this disease belongs to the retravirus group. the persistence of infection and the slow spread of virus are at least in part a consequence of restriction of the expression of virus genetic information in tissues of an infected animal (a. t. haase et al., science 195:175-177, 1977), but the point at which the virus life cycle is interrupted in vivo and the mechanism ... | 1977 | 198587 |
| [ultrastructural aspects of the cell fusion induced by visna virus on sheep choroid plexus cell in culture]. | sheep choroid plexus cells infected with low multiplicities of infection of visna virus were stellate and had long and thin processes containing filaments and forming cytoplasmic bridges between adjacent cells. enlargement of the bridges resulted in the formation of multinucleated cells. some glycoproteins were clustered on filaments outside the cell. the cytoplasmic changes showed : an intensive protein synthesis; numerous mitochondria closely associated with filaments and some lysosomes and nu ... | 1977 | 199372 |
| protein a-peroxidase: a valluable tool for the localization of antigens. | protein a of staphylococcus aureus has been conjugated to horseradish peroxidase and used in an indirect immunolabeling technique to visualize membrane and viral antigens. the same protein a-peroxidase conjugate was used with antisera from five different species. using this indirect test, membrane markers for t and b lymphocytes were labeled with a greater specificity than when peroxidase conjugated anti-immunoglobulin was used in the second step. viral antigens on cells infected with measles, v ... | 1977 | 199666 |
| the infection caused by visna virus. a model for the study of slow degenerative diseases of the central nervous system. | | 1977 | 199878 |
| polyacrylamide gel electrophoresis of visna virus polypeptides isolated by agarose gel chromatography. | the proteins of visna are separated into nine major peaks by agarose gel chromatography in 6 m guanidine hydrochloride (guhcl). the polypeptides in eack peak were isolated by acid precipitation and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (sds-page). the patterns of sds-page show that the excluded material from the guhcl column contains an aggregate of 10 non-glycosylated polypeptides. it is shown that this aggregate represents virus substructures that are not comple ... | 1978 | 202737 |
| lack of maedi viral related rna in pulmonary carcinoma of sheep (jaagsiekte). | molecular hybridisation with radioactively labelled dna complementary to the rna of the maedi virus was used to probe for homologous rna in the polysome fraction of pulmonary carcinomas (jaagiekte) of awassi sheep. no sequence homology was detected, which suggests that maedi (or visna) virus is not implicated in the aetiology of pulmonary carcinoma of sheep. | 1978 | 203989 |
| [bioligical aspects of cell fusion induced in vitro by sheep visna virus]. | visna virus induced cell fusion of sheep choroid plexus cells was explored in vitro. fusion is early rapid, and of exogenous origin for multiplicities of infection equal to or greater than 2 ufp per cell; whereas fusion is slow, late-occurring and of endogenous origin for multiplicities of infection less than or equal to 0.75 ufp per cell. | 1978 | 210900 |
| [kinetics and ultrastructure of sheep fibroblast fusion induced by polyethylene glycol. comparison with endogenous cell fusion induced by visna virus]. | the authors compare the fusion of sheep fibroblasts induced by low multiplicities of infection using visna virus and by high concentrations of polyethylene-glycol. in the case of visna virus cell fusion is of the endogenous type, while fusion induced by polyethylene-glycol is of the exogenous type. the ultrastructural features are discussed for each type of cell fusion. the main differences between the two systems involve the intracellular microfilaments and golgi apparatus. | 1978 | 210901 |
| [comparison of various serological methods for the demonstration of maedi/visna virus antibodies]. | | 1978 | 212904 |
| resistance of visna virus to interferon. | visna is a slow infection of sheep caused by a retrovirus. the persistence of virus despite the immune response of the host is best explained by restricted genetic expression of the virus and consequently prolonged periods of residence inside cells. the purpose of this investigation was to determine whether the restriction in genetic expression of visna virus is mediated by interferon. sheep interferon induced by polyriboinosinic-polyribocytidylic acid in fetal lambs inhibited the growth of herp ... | 1978 | 213502 |
| virus mutation during 'slow infection': temporal development and characterization of mutants of visna virus recovered from sheep. | visna virus could be recovered from peripheral blood leukocytes of sheep for years after intracerebral inoculation. viruses recovered from sheep prior to and several months after development of antibody were antigenically identical to the parental strain used for inoculation. subsequently, mutant viruses which were not neutralized by the animals' sera were obtained. longitudinal studies of leukocyte viruses collected from two infected sheep showed that more than one strain of virus could co-exis ... | 1978 | 214521 |
| absence of circularly permuted and largely redundant sequences in the genome of visna virus. | a previous study of the infectivity of visna virus proviral dna suggested that the genetic information of the virus is distributed over at least two of the rna subunits. because the genetic complexity of visna virus corresponds to the size of one subunit, this result may imply that sequence redundancies exist within each subunit. in the present article we have examined this question by constructing a map of the large rnase t1-resistant oligonucleotides of the viral genome. our principal results ... | 1978 | 214577 |
| detection of viral sequences of low reiteration frequency by in situ hybridization. | the sensitivity of in situ hybridization has been increased at least 10-fold by hybridizing in cdna excess, by increasing the diffusion of the cdna through the cells, by hybridizing at optimum temperature, and by stabilizing hybrids during autoradiography. saturation of intracellular rna with [3h]cdna has been achieved. the assay is quantitative. in situ hybridization has been used to detect and quantitate visna virus rna in infected cells. by using [3h]cdna with specific activity of 2 x 10(8) d ... | 1978 | 216014 |
| specificity of response to viral proteins in horses infected with equine infectious anemia virus. | three structural proteins of equine infectious anemia virus were purified, labeled with 125i, and utilized in radioimmunoassays with horse sera and antisera to heterologous retroviruses. whereas radioimmunoassay titers for the major protein, p25, were 500- to 1,000-fold higher than titers in immunodiffusion, for clinical purposes these two procedures were equivalent. antibodies to two low-molecular-weight proteins, p12 and p10, were also found in infected horses, but with a lower frequency and l ... | 1979 | 217831 |
| cell surface changes associated with mutation of visna virus in antibody-treated cell cultures. | | 1979 | 218349 |
| precipitation of visna viral proteins by immune sera of rabbits and sheep. | eighteen polypeptides equivalent to 1.2 x 10(6) daltons of visna virus were specifically precipitated by immune sera from rabbits and sheep. the hyperimmunized rabbit antisera contained high concentrations of antibodies against p25 and p14, whereas the sera from sheep actively infected with visna virus showed a large quantity of anti-gp115 antibody. the results indicate that almost all the polypeptides reported previously (f. h. lin, j. virol. 25:207--214, 1978) are virus-specific components of ... | 1979 | 219247 |
| pathogenesis of visna. iv. spinal fluid studies. | visna is a persistent retrovirus infection of sheep which produces a chronic progressive paralytic disease after an incubation period lasting from months to years. the cerebrospinal fluid (csf) was repeatedly sampled in a group of icelandic sheep which were infected intracerebrally and followed up to 42 months. minimal levels of infectious virus were isolated from the cerebrospinal fluid (csf) up to 4 months after infection after which csf neutralizing antibodies appeared in many sheep. these an ... | 1979 | 220394 |
| sera and cerebrospinal fluids from normal uninfected sheep contain a visna virus inhibiting factor. | | 1979 | 220542 |
| the synthesis and structure of visna virus dna. | | 1979 | 222046 |
| [comparison of exogenous cell fusion induced by a wild and two mutant strains of sheep visna virus]. | exogen cell fusion induced in vitro by a wild strain of visna virus of sheep is compared with two mutant strains isolated from the precedent. one of them produces large plaques in vitro (strain lpf), and the other produces small plaques (strain spf). these strains behave in different ways according to infection multiplicity, type of cells, temperature and timing of fusing activity. taking the wild strain k 796 as a base of reference, the strain spf seems to have a higher rate fusing activity and ... | 1979 | 222497 |
| visna virus-induced fusion of nerve cells in vitro. | | 1979 | 224264 |
| isolation of a glycoprotein and two structural proteins of maedi-visna virus. | | 1979 | 224577 |
| [in vitro fusion ability of agents causing slow diseases of the central nervous system]. | the authors study cell fusion in vitro induced by two kinds of slow viruses : visna virus of sheep and scrapie of mouse and creutzfeldt-jakob disease of man agents. cell-fusion induced by visna virus is either slow and late occuring (fusion from within) or early and rapid (fusion from without) according to experimental conditions. whereas, cell-fusion induced by spongiform encephalopathies agents is only of slow appearance, looking an endogenous phenomenon. | 1979 | 226238 |
| antigenic variation in visna virus. | two antigenic variants of visna virus were isolated sequentially from a single sheep inoculated with a plaque-purified strain of virus designated 1514. the genetically stable variants, lv1-1 and lv1-4, are of two classes: lv1-1 is partially neutralized by antibody to the inoculum strain 1514, while lv1-4 is not neutralized by antibody to 1514. the genetic mechanism responsible for generating the antigenic variants was investigated by comparing the chymotryptic and tryptic maps of the envelope gl ... | 1979 | 227603 |
| characterization of visna virus mrna. | visna virus is a retrovirus responsible for a classical slow infection of the central nervous system of sheep. in the present work we focused our attention on the viral mrna's. we found that, during the acute infection in vitro, (i) viral mrna's amount to only 0.1% of the total cytoplasmic rna, (ii) 20% of the total cytoplasmic viral rna is found in polyribosomes, and (iii) three viral mrna's can be identified by sucrose gradient sedimentation or polyacrylamide gel electrophoresis. their sedimen ... | 1979 | 228056 |
| myelin lesions in the rabbit eye model as a bystander effect of herpes simplex and visna virus sensitization. | rabbits were immunized with herpes simplex and visna virus in complete freund's adjuvant. uv-inactivated herpes virus and the purified visna virus protein p25 injected intraocularly into these rabbits elicited a moderate inflammatory cell infiltration in the epiretinal myelinated nerve fiber bundles accompanied by signs of demyelination. it is therefore apparent that also viral antigen can induce myelin lesions as a so-called "bystander effect" of a cell-mediated immune response (bystander demye ... | 1979 | 230691 |
| [evidence for the production of a fusion factor during in vitro infection of sheep choroid plexus cells by visna virus]. | one of the most important early events during the infection of sheep choroïd plexus cells in culture by visna virus is the synthesis by these cells of a fusion factor distinct from the virus. the cell fusion activity of this factor does not seem transmissible. it promotes cell shape changes and a migration of the nucleus towards the cell wall. | 1979 | 230888 |
| detection of antibodies against glycoprotein of maedi-visna virus released as soluble antigen in cell cultures. | | 1979 | 232343 |
| the demonstration of maedi/visna virus in sheep in great britain. | a virus indistinguishable from that causing maedi/visna has been isolated from a sheep flock in great britain. the virus was identified in cell cultures using immunofluorescent and electron microscopical techniques. the complement fixation test and the agar gel immunodiffusion test were used to assess the proportion of serological reactors within the flock. there has been no evidence of clinical disease in the flock into which foreign imports were introduced in the years prior to 1976. | 1979 | 233278 |
| adenosine triphosphatase activity during fusion of cultured sheep choroid plexus cells induced by either visna virus or polyethylene glycol. | | 1978 | 233847 |
| an ultrastructural study of the cerebrospinal fluid in visna. | an electron microscopic examination was done on 8 samples of cerebrospinal fluid (csf) from icelandic sheep infected by the intracerebral route with visna virus. the specimens were collected 1 month, 2 months, and 4 years after infection. a differentail cell count done on low-power electron micrographs showed that the cellular exudate was composed of mononuclear cells mainly macrophages and lymphocytes with a few plasma cells. macrophages were with one exception more numerous than lymphocytes an ... | 1979 | 506689 |
| [studies on the epizootiology of maedi/visna in sheep (author's transl)]. | the transmission of maedi/visna from a severely infected flock to their progeny was studied. at birth, the lambs were divided at random in four groups of approximately forty animals each, which were exposed to the parent flock for zero hours, ten hours, six weeks and one year respectively. although more than 80 percent of the ewes were affected with maedi, lambs which were separated from the ewes immediately after birth continued to be free from maedi/visna virus infection during an eight years ... | 1979 | 516037 |
| immune reactivity of visna virus-inoculated mice. | visna virus inoculation of mice before immunization with unrelated antigens caused suppression of humoral and cell-mediated immune responses. the immunosuppressive effect was dependent on the virus dose and time of administration. the number of "background" antibody-producing spleen cells increased slightly after inoculation of visna virus. heat treatment of visna virus abolished its immunosuppressive effect. replication of visna virus in mice seemed to be a prerequisite for its immunomodulating ... | 1978 | 669804 |
| maedi-visna virus infection in rams in nova scotia. | | 1978 | 688172 |
| distinct subsets of retroviruses encode dutpase. | the nonprimate lentiviruses feline immunodeficiency virus, equine infectious anemia virus, visna virus, and caprine encephalitis virus contain a gene segment in the polymerase gene that is lacking in the primate lentiviruses. a related sequence has been noted in other retroviruses, most notably the type d retroviruses. computer searches have indicated a relatedness between this unique gene segment, termed proteaselike element and elements of both the aspartate proteinase and the dutpase enzyme f ... | 1992 | 1310783 |
| a simplified method for the detection of maedi-visna virus rna by in situ hybridization. | a simplified in situ hybridization method for the detection of maedi-visna virus (mvv) rna in cultured cells using 35s-labelled dna probes is described. the protocol currently used in this laboratory for the in situ detection of mvv rna involves paraformaldehyde fixation followed by extensive cellular pretreatment prior to hybridization. it was found that substitution of paraformaldehyde fixation with brief acetone treatment and the removal of subsequent pretreatment steps gave a similar level o ... | 1992 | 1313037 |
| structural and functional analysis of the visna virus rev-response element. | the distantly related lentiviruses human immunodeficiency virus type 1 (hiv-1) and visna virus each encode a posttranscriptional regulatory protein, termed rev, that is critical for expression of the viral structural proteins. we genetically mapped the cis-acting target sequence for visna virus rev, the visna virus rev-response element or rre-v, to a complex 176-nucleotide rna stem-loop structure that coincides with sequences encoding the n terminus of the transmembrane component of envelope. th ... | 1992 | 1316470 |
| molecular mechanisms of visna virus tat: identification of the targets for transcriptional activation and evidence for a post-transcriptional effect. | visna virus is a pathogenic lentivirus of sheep that is distantly related to the primate lentiviruses, including the human immunodeficiency virus type 1 (hiv-1). replication of hiv-1 in cell culture requires the expression of a virus-encoded protein, tat, which is a potent trans-activator of viral gene expression. visna virus encodes an analogous tat protein that greatly increases gene expression directed by the visna viral ltr. this report uses a stable vero cell line that constitutively expres ... | 1992 | 1316669 |
| expression of maedi-visna virus major core protein, p25: development of a sensitive p25 antigen detection assay. | the gene for the major core protein, p25, of maedi-visna virus (mvv) was cloned using a pcr (polymerase chain reaction) strategy employing primers designed for the insertion of the gene directly into yeast ty-vlp expression vectors. in this system p25 is expressed as a fusion protein which self-assembles into virus-like particles (vlps) due to interaction of the ty a fusion partner. high levels (50-60 mg/l) of p25 fusion protein were produced, and p25 was recovered in soluble and highly pure for ... | 1992 | 1321836 |
| identification and subcellular localization of the q gene product of visna virus. | the genome of the sheep visna lentivirus contains an open reading frame, q, which has a coding potential of 230 amino acid residues. this paper reports the identification and the subcellular localization of the q orf-encoded protein detected in lysates of visna virus-infected sheep choroid plexus cells. sera from sheep either experimentally or naturally infected with visna virus reacted with the bacterially synthesized q protein indicating that the in vivo expressed q product is immunogenic. ant ... | 1992 | 1322597 |
| involvement of fos and jun in the activation of visna virus gene expression in macrophages through an ap-1 site in the viral ltr. | gene expression of visna virus is highly restricted in monocytes, but is induced when monocytes differentiate into macrophages. a previous study on differential regulation of visna virus gene expression revealed that a specific ap-1 site in the long terminal repeat of the viral dna is required for phorbol-ester-induced gene expression in macrophages (gabuzda, hess, small, and clements, mol. cell. biol., 9, 2728-2733). in the present investigation, we examined the association of two dna binding p ... | 1992 | 1326822 |
| pathogenesis of central nervous system lesions in visna: cell-mediated immunity and lymphocyte subsets in blood, brain and cerebrospinal fluid. | there are several indications that central nervous system (cns) lesions in visna are immune-mediated and that cell-mediated immunity (cmi) may be of importance in the initiation of the lesions. to study the role of cmi in the pathogenesis of cns lesions, five sheep were infected by intracerebral inoculation with visna virus and observed for 1 year. the following parameters were monitored at regular intervals: (1) neutralizing and elisa antibodies; (2) visna virus-specific stimulation of lymphocy ... | 1992 | 1334965 |
| spatial visualization of progressive states of maturing lentivirus. | progressive states of maturing lentivirus: maedia visna virus (mvv) and human immunodeficiency virus (hiv), respectively, have been visualized by 2-d electron microscopy and by 3-d electron microscopic tomography. a major fraction of mvv and a low percentage of hiv appear as immature particles 4 to 5 days post virus infection. upon budding the gag-precursor material is densely packed inside the external envelope. after virus release the major portion of precursors is assembled within an approxim ... | 1992 | 1336244 |
| genomic heterogeneity of small ruminant lentiviruses detected by pcr. | in order to detect a large spectrum of small ruminant lentiviruses, primers for pcr were chosen in conserved parts of the ltr and gag genes of icelandic visna virus 1514 and of the pol gene of caprine arthritis-encephalitis virus. this set of primers was tested in six different caprine arthritis-encephalitis virus (caev)- and maedi-visna virus isolates of dutch, american and swiss origin. the ltr primers allowed the detection of the corresponding fragments of all isolates. the gag primers allowe ... | 1992 | 1336245 |
| characteristics of the t cell-mediated immune response to maedi-visna virus. | virus-specific t cell-mediated immunity was investigated in healthy sheep persistently infected with the ruminant lentivirus maedi-visna. visna-specific lymphocyte proliferation was demonstrated in response to both purified virions and recombinant p25, the major core protein of maedi-visna virus. the responding t cell population in this assay was mainly of the cd4+ phenotype, although in some individuals cd8+ t cells were also shown to respond to visna antigen in this system. | 1992 | 1360179 |
| characterisation of visna virus reverse transcriptase: a micro scale reverse transcriptase assay adapted for use with an automated cell harvester. | the reverse transcriptase of the sheep lentivirus visna/maedi virus has been characterised. optima for magnesium ion concentration (5-10 mm), potassium ion concentration (150 mm) and ph (8.25) for this enzyme are very similar to those previously described for the human immunodeficiency viruses. the assay used for this work makes use of a cell harvester to speed up the processing of multiple samples. it is small scale, requiring 15 microliters of sample, is rapid, and is able to detect virus at t ... | 1992 | 1372910 |
| analysis of antibody response to ovine lentivirus by using viral gene products expressed in a prokaryotic system. | the polymerase chain reaction (pcr) was used to amplify, clone, and express eight dna fragments encoding p25, p16, reverse transcriptase (rt) core, c'-terminal rt, n'- and c'-terminals of external (gp70), and transmembrane (gp40) envelope proteins from visna virus infectious recombinant dna. efforts were focused on characterizing the nature of the humoral immune response of ovine progressive pneumonia (opp) virus infected animals and identifying the conserved and prime-reactive antigenic determi ... | 1992 | 1384477 |
| phenotypic analysis of lymphocyte populations in the lungs and regional lymphoid tissue of sheep naturally infected with maedi visna virus. | we have analysed the phenotype of lymphocytes in lung and regional lymph node of symptomatic and asymptomatic sheep infected with the ovine lentivirus, maedi visna virus (mvv). compared to equivalent tissues from age-matched, non-infected controls, mvv-infected sheep show increased numbers of lymphocytes in the lung, both in the bronchus-associated lymphoid tissue (balt) and in the alveolar septae. both cd8+ and cd4+ t lymphocyte numbers in alveolar septae were increased, particularly in animals ... | 1992 | 1385026 |
| [suspicion of visna in a sheep from graubünden canton]. | a lentivirus belonging to the group of retroviridae causes a chronic progressive interstitial pneumopathy (maedi) or a demyelinating encephalo-myelitis (visna) in sheep and goats. pulmonary lesions of maedi as well as sero-positive, clinically healthy animals can be observed in switzerland; visna, which even in countries with endemic infection does not occur frequently, is extremely rare. the head and cervical spine of an ewe with severe nervous troubles suspected of scrapie were submitted for p ... | 1992 | 1439707 |
| clinicopathological investigation of primary, uncomplicated maedi-visna virus infection. | maedi-visna virus infection in a flock of sheep in scotland was associated with respiratory disease, neurological disease, mastitis and lameness. the major clinical signs were dyspnoea (particularly on exercise), progressive fore- and hindlimb ataxia and balance defects, mammary induration and multilimb lameness, occasionally with enlarged carpal joints. pathological examinations revealed lesions in the lungs, central nervous system, mammary glands and joints which were consistent with those ind ... | 1992 | 1466120 |
| conserved functional organization of the human immunodeficiency virus type 1 and visna virus rev proteins. | visna virus encodes a posttranscriptional regulatory protein that is functionally analogous to the rev trans activator of human immunodeficiency virus type 1. here, we demonstrate that the known functional organization of the human immunodeficiency virus type 1 rev trans activator is shared by the distantly related visna virus rev protein. in particular, both rev proteins contain an n-terminal domain marked by a highly basic core motif that determines rna sequence specificity, as well as a secon ... | 1991 | 1645796 |
| isolation, identification, and partial cdna cloning of genomic rna of jaagsiekte retrovirus, the etiological agent of sheep pulmonary adenomatosis. | the genome of the jaagsiekte (js) retrovirus (jsrv), the etiological agent of sheep pulmonary adenomatosis (jaagsiekte), has been identified, isolated, and partly cloned. the jsrv genome is ca. 8.7 kb long. cdna of the genomic rna was synthesized and cloned. a clone, js 46.1, was isolated and characterized. it has an insert of 2.1 kb which hybridizes to the same 8.7-kb rna in all the jsrv-infected sheep lung washes tested but does not hybridize to maedi-visna virus, a sheep lentivirus often foun ... | 1991 | 1651422 |
| nucleotide sequence of ev1, a british isolate of maedi-visna virus. | we have isolated a maedi-visna-like virus from the peripheral blood mononuclear cells of a british sheep displaying symptoms of arthritis and pneumonia. after brief passage in fibroblasts this virus (designated ev1) was used to infect choroid plexus cells. cdna clones of the virus were prepared from these cells and sequenced. gaps between non-overlapping clones were filled using gene amplification by the polymerase chain reaction. the genome structure is similar to that described for visna virus ... | 1991 | 1651983 |
| identification of a putative cellular receptor for the lentivirus visna virus. | one mechanism by which viral tropism may be controlled is by the expression of a specific virus receptor on the cell surface. this paper reports the identification of a putative cellular receptor for visna virus, the prototype virus of the family lentiviridae. using a virus overlay protein blot assay we identified a group of polypeptides of apparent mr 30k to 33k which interacts with visna virus and is present on permissive but not non-permissive cells. a rat polyclonal anti-ovine major histocom ... | 1991 | 1651984 |
| expression in escherichia coli and sequencing of the coding region for the capsid protein of dutch maedi-visna virus strain zzv 1050: application of recombinant protein in enzyme-linked immunosorbent assay for the detection of caprine and ovine lentiviruses. | maedi-visna in sheep and caprine arthritis-encephalitis in goats are caused by two closely related and widespread lentiviruses. the infections are characterized by life-long virus persistence and slow induction of antiviral antibodies. the diagnosis is based on the detection of antiviral antibodies. we have used the polymerase chain reaction (pcr) to amplify a part of the gag gene coding for the entire capsid protein and for parts of the matrix and nucleocapsid proteins. sequencing of the pcr fr ... | 1991 | 1653261 |
| identification of cell membrane proteins that bind visna virus. | visna virus infects cells of ovine origin by attaching to a cell surface receptor via its envelope glycoprotein. the identity of the visna virus receptor is not known. to identify the molecule responsible for binding the virus to target cells, virus overlay protein blot assays were used to examine the molecular weights of cell surface molecules which bind purified virus. molecules on the surface of goat synovial membrane (gsm) cells and sheep choroid plexus (scp) cells of approximately 15, 30, a ... | 1991 | 1656089 |
| identification of the fusion domain in the visna virus transmembrane protein. | visna virus, a lentivirus of sheep, causes fusion of susceptible cells. fusion has previously been shown to be mediated by the viral envelope glycoprotein. the transmembrane protein of visna virus contains a hydrophobic region at its amino terminus. this region is similar to the fusion epitopes of the orthomyxoviruses and paramyxoviruses. this region is located in a position similar to that of the fusion epitopes in the transmembrane proteins of hiv-1 and siv. to determine the role of this hydro ... | 1991 | 1656602 |
| rna pseudoknots downstream of the frameshift sites of retroviruses. | rna pseudoknot structural motifs could have implications for a wide range of biological processes of rnas. in this study, the potential rna pseudoknots just downstream from the known and suspected retroviral frame-shift sites were predicted in the rous sarcoma virus, primate immunodeficiency viruses (hiv-1, hiv-2, and siv), equine infectious anemia virus, visna virus, bovine leukemia virus, human t-cell leukemia virus (types i and ii), mouse mammary tumor virus, mason-pfizer monkey virus, and si ... | 1991 | 1663382 |
| immune reactions and immunopathologic changes induced in ovine fetuses and lambs by maedi-visna virus. | seventy- to 80-day fetuses of merino ewes were inoculated intramuscularly in utero and 2-week-old lambs of the same breed intratracheally with 10(6.3) tcid50/0.1 ml of maedi-visna virus strain k1512 isolated in iceland. while no precipitins appeared in the serum of fetuses, such antibodies were demonstrable in the lambs from postinoculation (pi) day 30. indirect immunofluorescence (iif) revealed the presence of antibodies in samples from both fetuses and lambs; the detectability of these antibod ... | 1991 | 1664651 |
| in situ amplification of visna virus dna in tissue sections reveals a reservoir of latently infected cells. | maedi and visna are, respectively, the pulmonary and neurological manifestations of slowly progressive infections of sheep caused by retroviruses of the lentivirus subfamily. lentivirus infections are also persistent infections in which host defenses are generally not successful in eliminating the infectious agent because of restricted viral gene expression in many infected cells. in this report, we describe a method for amplifying and detecting viral dna in tissue sections which has made it pos ... | 1991 | 1665538 |
| [double infection with maedi virus and adenomatosis virus in merino sheep]. | this is the first report of the simultaneous occurrence of sheep pulmonary adenomatosis and lymphoid interstitial pneumonia (maedi) in the same animal in the federal republic of germany. seven adult sheep of the merino landrace were tested by immunodiffusion-assay for antibodies against maedi/visna-virus. five of them originating from three different flocks had a positive reaction. in all pulmonary foci, which were examined by light microscopy, we found proliferations of the alveolar epithelium ... | 1991 | 1665601 |
| neurobiology of simian and feline immunodeficiency virus infections. | experimental and clinical evidence indicates that all lentiviruses of animals and humans are neurotropic and potentially neurovirulent. the prototypic animal lentiviruses, visna virus in sheep and caprine arthritis encephalitis virus in goats have been known for decades to induce neurologic disease. more recently, infection of the brain with the human immunodeficiency virus (hiv) has been linked to an associated encephalopathy and cognitive/motor complex. while the visna virus and caprine arthri ... | 1991 | 1669709 |
| retroviral arthritis: phenotypic analysis of cells in the synovial fluid of sheep with inflammatory synovitis associated with visna virus infection. | a phenotypic analysis on synovial fluid cells from the carpal and tarsal joints of sheep with visna virus-induced inflammatory synovitis was performed. the results showed increased representation of cells bearing lymphocyte, macrophage, and dendritic cell markers compared to equivalent synovial fluid cells from normal uninfected age-matched controls. in infected sheep, cd8+ t cells tended to predominate over cd4+ cells, while the numbers of gamma delta t cells varied from being absent in some sa ... | 1991 | 1675163 |
| human and ovine lentiviral infections compared. | maedi-visna virus (mvv) of sheep was the first lentivirus to be isolated. the genomic organization of mvv is very similar to that of human immunodeficiency virus (hiv) with several genes regulating the expression of the viral genome. viral replication is severely restricted in the host and some cells apparently contain the genetic information in a dna provirus form with little or no expression of viral antigens. this seems to be a major factor in causing the "slowness" of lentiviral infections a ... | 1991 | 1684142 |
| antibody to reverse transcriptase of human retroviruses in multiple sclerosis. | htlv-1, hiv-1 and hiv-2 western blot analysis of sera from patients with multiple sclerosis (ms), from patients with other neurological diseases and from blood donors, revealed a rather frequent cross-reactivity with retroviral proteins in the ms group, though no patient was positive with the corresponding specific elisa serology. statistical analysis revealed a significant difference between the ms group and the two control groups for hiv-1 and hiv-2 reverse transcriptase fragments and for htlv ... | 1991 | 1724334 |
| effect of maedi-visna virus infection on lamb growth. | | 1991 | 1759347 |
| genetic structure of the pol-env region of the caprine arthritis-encephalitis lentivirus genome. | the nucleotide sequence of the pol-env intergenic region of two isolates of caprine arthritis-encephalitis virus (caev) was determined. two open reading frames (orfs) were identified, designated q and s by homology with visna virus. caev orf s is a single exon encoding a deduced 87-amino acid gene product sharing 36 amino acid identities with the visna trans-acting transcriptional activator (tat). ten of these identities comprise a conserved cgcrlcnpgw sequence similar to a cysteine-rich domain ... | 1991 | 1845832 |
| isolation of replication-competent molecular clones of visna virus. | visna virus is the prototypic member of a subfamily of retroviruses responsible for slow infections of animals and humans. as a part of our investigation of the functions of viral gene products in virus replication, we have isolated three infectious molecular clones and determined the complete nucleotide sequences of two of the clones. we have also characterized the progeny of the biologically cloned viral stocks and of the infectious clones and document considerable heterogeneity in plaque size ... | 1991 | 1847257 |
| comparative features of retroviral infections of livestock. | retroviral infections of livestock have become of increasing importance due to their usefulness as comparative models for human retroviral infections and their effects upon animal health and marketability of animals and animal products nationally and internationally. this paper presents a perspective on the retroviruses of economic concern in veterinary medicine with emphasis on the importance of understanding the modes of virus transmission and the species specificity of the viruses. the retrov ... | 1990 | 1963391 |
| [the occurrence and distribution of maedi-visna virus infection in lower austrian sheep breeding establishments]. | in a period of one year blood samples of 374 sheep of lower austrian flocks were examined in intervals of two months for antibodies against maedi-visna (mv). further on specific attention was paid to the prevalence of mv-infection in the flocks. the antibody-titers were determined by means of agar gel-immunodiffusion test. in 5 (23.8%) of 21 flocks 45 (12.0%) of the sheep were seropositive. seroprevalence varied within the examined breeds: 19 (27.1%) of 70 karakul-sheep, 18 (28.1%) of 64 east-fr ... | 1990 | 1963842 |