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Biomedical subjects

A Burny

Publications and source records attributed to A Burny.

At least 199 records · Page 11Linked to original sources
PubMed1988

Mode of insertion into a lipid membrane of the N-terminal HIV gp41 peptide segment.

The complete amino-acid sequence of the gp160 polyprotein of HIV (strain WMJ1) has been analyzed by the Eisenberg procedure. The region surrounding the cleavage site between the gp120 and the gp41 subunit contains a receptor-like region immediately followed by a transmembrane-like region containing approximately 13 residues. These two regions are separated by the cleavage site between gp120 and gp41. Since the same arrangement exists in some paramyxoviruses (unpublished observation) and since the effective cleavage between a receptor-like region and the transmembrane-like region is required in paramyxoviruses to generate fusogenic segment (located at the N-terminal sequence of the transmembrane-like region), we have focused our analysis on the conformational properties of the N-terminal peptide segment of HIV gp41. This peptide segment, which consists of a helical structure according to Garnier prediction, was oriented at the lipid-water interface using a theoretical analysis method that we recently developed. Analysis of the transmembrane peptide determined by Eisenberg method shows that the helical segment orients itself in the lipid monolayer obliquely with respect to the lipid-water interface. Since this rather unusual orientation for a membrane segment of a protein is also found in the fusogenic peptide of the Newcastle Disease Virus (Virus Genes, in press) and seems to possess membrane destabilizing properties, it is in agreement with previous reports suggesting a fusogenic role for the N-terminal part of gp41.

HIV↗
PubMed1988

Expression in bacteria of beta-galactosidase fusion proteins carrying antigenic determinants of the two X gene products of bovine leukemia virus.

A cDNA corresponding to the bovine leukemia virus post-envelope region (X gene) was subcloned into the lambda gt11 expression vector. Two large protein fragments corresponding respectively to the long and short open reading frames of the X region were expressed as beta-galactosidase fusion proteins. These products were specifically recognized by sera from bovine leukemia virus-infected cattle.

Animals↗
PubMed1988

Experimental transmission of enzootic bovine leukosis to sheep: latency period of the tumoral disease.

In the field of viral oncogenesis the latency period is the interval between detectable establishment of infection and appearance of a tumor. Between 1969 and 1985, a total of 60 sheep died with lymphosarcoma. They were inoculated with BLV-positive blood from various donor cows, by various routes, at various ages, etc. A statistical analysis was performed trying to find a correlation between the length of the latency period and, on the other hand, one or more factors, such as sex, family lineage, identity of the dam, age at inoculation, route of inoculation, or origin of the inoculum. None of the above mentioned parameters has a significant effect on the length of the latency period. In two series of sheep inoculated with decreasing number of lymphocytes from BLV-positive donor cows, hematological disorders and tumors appeared at first in recipient animals inoculated with the higher doses of infectious blood. Thus, the inoculated dose has an effect upon the length of the latency period; the higher the dose inoculated, the shorter the latency period. This finding suggests an explanation to the natural occurrence of multiple case herds as opposed to no-tumor case herds. A multiple case herd fulfills two conditions: the presence of a good donor and an efficient route of transmission allowing the transfer to the recipient of the optimal amount of infected blood.

Animals↗
PubMed1987

Cloning of a Nicotiana plumbaginifolia protoplast-specific enhancer-like sequence.

We have isolated a 1.5-kb plant DNA fragment (called insert 7) from Nicotiana plumbaginifolia DNA that contains a protoplast-specific enhancer-like sequence. The presence of this sequence on a plasmid carrying a chimeric nos-npt-II gene conferring kanamycin resistance to plant cells, produces an overexpression of the npt-II gene during at least eight days after protoplast transformation. This effect on the expression of the nos promoter was independent of the orientation and was observed both on circular and linearized plasmids. On the contrary, insert 7 had no influence when present on another plasmid (in trans) in cotransformation experiments. The overexpression of the nos-npt-II gene due to the presence of insert 7 on the transforming plasmid is correlated with a higher level of synthesis of the corresponding RNA. Insert 7 did not affect the level of expression of the nos-npt-II gene in stably transformed calli, or in regenerated plants. However, the overexpression was again detected in protoplasts prepared from leaves of stably transformed plants. This 1.5-kb plant DNA fragment contains highly repetitive DNA sequences, specific to N. plumbaginifolia. However, the enhancer-like activity is localized on a 600-bp unique sequence of insert 7. Insert 7 had no detectable effect on the transient expression of another gene, the nopaline synthase gene present at a longer distance on the same plasmid.

Journal Article↗
PubMed1987

The bovine leukemia virus p34 is a transactivator protein.

Recombinant Moloney murine retroviruses containing the BLV post-envelope long open reading frame were constructed and transfected into the psi 2 packaging cell line. They were shown to encode and to express a 34-kd protein able to transactivate the BLV long terminal repeat-directed gene expression in the respective transfected cells. These data demonstrate that the BLV X-LOR gene encodes a p34 transactivator product. Furthermore, the different cell lines produced infectious recombinant retroviruses capable of transferring X-LOR genes into recipient cells. The availability of the BLV transactivator protein should allow us to understand the role of the transactivator protein in BLV-induced leukemogenesis.

Animals↗
PubMed1987

Evaluation of the use of monoclonal antibodies to hemagglutinin and fusion glycoproteins of Newcastle disease virus for virus identification and strain differentiation purposes.

Monoclonal antibodies detect evident antigenic variations in NDV HN and F protein. However, the A/PMV-1 viruses can be identified by HI test using a preparation made of the combination of two different monoclonals. A primary evaluation of the pathogenicity of the isolated viruses can be made by HI test using monoclonal antibodies but needs always confirmation using conventional pathogenicity tests.

Antibodies, Monoclonal↗
PubMed1987

The hemagglutinin-neuraminidase (HN) gene of Newcastle disease virus strain Italien (ndv Italien): comparison with HNs of other strains and expression by a vaccinia recombinant.

A cDNA library was constructed with poly(A+) mRNA from cells infected with the virulent Italien NDV strain. A clone that hybridized to the HN gene mRNA was sequenced. A long open reading-frame encodes for a protein of 571 amino acids, with a calculated molecular weight of 61,900, including 13 cysteine residues and six potential glycosylation sites. To define the sequence changes that occurred in the avian paramyxovirus hemagglutinin-neuraminidase (HN) during the evolution of virulence, we have studied the HNs of the virulent Italien NDV strain, the mesovirulent Beaudette strain and the nonvirulent Hitchner strain. The majority of amino acid variations are conservative changes but they cluster at 4 preferential sites in the putative head of HN. The clusters of amino acid substitutions are intimately associated or overlap with regions of HN rich in charged amino acid residues and in cysteines. The latter are conserved not only between HNs from all 3 NDV strains but also between HNs of 4 different paramyxoviruses, NDV, SV 5, Sendai and PI 3. The HN coding sequence was inserted into the genome of vaccinia virus under the control of vaccinia P 7.5 K transcriptional regulatory sequences. Expression of native HN proteins at the surface of recombinant HN vaccinia-infected cells was demonstrated by indirect immunofluorescence with 2 anti-HN monoclonals.

Amino Acid Sequence↗
PubMed1987

Expression at the cell surface of native fusion protein of the Newcastle disease virus (NDV) strain Italien from cloned cDNA.

A cDNA library was constructed with poly(A)+-mRNAs from NDV-Italien infected BHK-21 cells. A clone, that hybridized to the F gene mRNA, was sequenced. A long open reading frame encodes for a protein of 553 amino acids, with a calculated molecular weight of 59,153, consisting of twelve cysteine residues and six potential glycosylation sites. The protein sequence contains a hydrophobic region at the N-terminus of F1 and a presumptive long transmembrane fragment near the C-terminus. Comparison of the F proteins from NDV strains Italien and Australia-Victoria shows that the sequences are very similar, with conservation of most cysteine residues and of the potential glycosylation sites. The F coding sequence was inserted into the genome of vaccinia virus under the control of vaccinia P7.5 transcriptional regulatory sequences. Expression of F protein was demonstrated by indirect immunofluorescence with five anti-F monoclonal antibodies known to react with conformational epitopes.

Amino Acid Sequence↗
PubMed1987

Expression of a cDNA clone corresponding to the long open reading frame (XBL-I) of the bovine leukemia virus.

Nucleotide sequence analysis of a cDNA clone corresponding to the XBL-I open reading-frame of bovine leukemia virus (BLV) revealed that the AUG initiation codon was located 44 bases downstream from that of the env gene and was part of the p34x mRNA splice donor. . .ATGG/GTAA at the end of the pol gene sequence. RNA from this clone was synthesized in vitro by the SP6 RNA polymerase and translated into a 34,000 mol wt protein in rabbit reticulocyte lysates. The protein (p34x) is recognized in Western blots by most sera of BLV-infected sheep and tumor-bearing cattle, by an anti-synthetic peptide rabbit serum, and by the serum of a rabbit immunized by XBL-I RNA programmed reticulocyte lysates. Both sera react with a 34,000 mol wt protein present in nuclei of BLV-infected cells.

Base Sequence↗
PubMed1987

Experimental transmission of enzootic bovine leukosis to cattle, sheep and goats: infectious doses of blood and incubation period of the disease.

A group of 49 BLV-free recipient animals (24 cattle, 15 sheep and 10 goats) were inoculated intradermally with serial dilutions of blood collected on two BLV-positive donor cows. One donor had a high lymphocytosis and high antibody titers to gpBLV antigens; these two parameters were low for the second donor. The number of lymphocytes which induced BLV infection in recipient animals varied widely with the donor. The high infectivity of a donor seemed to be correlated with high lymphocytosis and high antibody titers to gpBLV antigens. Identification and removal of infectious animals would reduce or stop the spread of the infection in a herd, and could be used in the strategy to eradicate the disease. A given inoculum can be infectious in sheep and, at the same time, harmless in cattle. The incubation periods, apparently shorter in sheep, were generally in the range from 2 to 5 weeks for the three species, and exceptionally above.

Animals↗
PubMed1987

Absence of antibodies to HIV-2/HTLV-4 in six central African nations.

We studied 1508 individuals from Zaire, Burundi, Tanzania, Zambia, Kenya, and Cameroon for antibodies to HIV-2/HTLV-4. AIDS, ARC, other disease or tumor patients and healthy people were sampled from 1984-1986. By radioimmunoprecipitation and SDS/PAGE analysis and/or Western blot we failed to find any samples with specific antibodies to HIV-2/HTLV-4 indicative of infection. In contrast, 363 of these 1508 individuals demonstrated antibodies to HIV-1/HTLV-3B by the same serologic assays. HIV-2/HTLV-4 infection appears to be quite rare in Central Africa. AIDS and related syndromes in this study were exclusively correlated with HIV-1 infection. Studies in West Africa have shown high rates of infection with HIV-2/HTLV-4 where cases of AIDS are still relatively uncommon. These results indicate that HIV-2/HTLV-4 has a distinct geographic distribution from that of HIV-1 in Africa. Further studies are necessary to better define the pathogenicity and natural history of this distinct new virus, HIV-2/HTLV-4.

Antibodies, Viral↗
PubMed1987

Pathogenicity of antigenic variants of Newcastle disease virus Italian strain selected with monoclonal antibodies.

Antigenic variants of the Italian strain of NDV were selected using monoclonal antibodies directed against the HN and F proteins of Italian virus. Antigenic mapping of the HN and F proteins using variant viruses in cross neutralization tests revealed the presence of at least two different epitopes on HN and four epitopes on F protein. Immunoselected variant viruses were demonstrated to have different intravenous pathogenicity index than the parental Italian virus.

Antibodies, Monoclonal↗
PubMed1987

Bovine leukemia virus: isolation and characterization of nonproducer cell clones.

Several single-cell clones were isolated from a fetal lamb kidney cell line (FLK) persistently infected with bovine leukemia virus (BLV). The majority of isolated cell clones were virus productive, several were nonproductive based on the determination of the activity of reverse transcriptase and production of 3H-uridine labeled virus particles. Two nonproductive clones, NP-1 and NP-2, were further characterized in comparison with the virus productive cells. All clones contained three integrated BLV proviruses in the nonproducer cells. The virus specific mRNAs were expressed both in the virus productive and nonproductive cells. The virus-specific protein products were found different in the nonproducing cells. The gag pol precursor Pr145 was missing in NP-1 cells, in NP-2 its Mr was 120 only. In NP-2 cells the precursors Pr70gag and Pr45gag were absent. The env precursor gPr72 and both of the two glycoproteins were detected. The nonproductive cells NP-2 produced mainly env gene products, therefore they were tested as a potential material for anti-BLV vaccine. The NP-2 cells after inoculation to rats and cattle were able to induce formation of neutralizing antibodies directed against the env gene products.

Animals↗
PubMed1987

Provirus integration of bovine leukemia virus into DNA of infected human myeloma cells.

Sixty clones of bovine leukemia virus-infected B-human myeloma ARH77 cells were isolated. The DNAs of all clones were examined for BLV provirus integration by Southern blotting analysis. Proviral sequences were found in DNAs of two clones. One of them (clone I B3) contained one proviral copy with a deletion of approximately 5.5 kb; the other one (clone I F9) carried three integrated proviruses. Viral proteins of 70,000, 42,000 and 35,000 M. W. were found in extracts of clone I F9. In clone I B3 only the 70,000 M.W. protein was detected.

Cell Line↗
PubMed1987

Bovine leukaemia: facts and hypotheses derived from the study of an infectious cancer.

Bovine leukaemia virus (BLV) is the aetiological agent of a chronic lymphatic leukaemia/lymphoma in cows, sheep and goats. Infection without neoplastic transformation has also been demonstrated in pigs, rhesus monkeys, chimpanzees and rabbits and observed in capybaras and water buffaloes. Structurally and functionally, BLV is a relative of human T lymphotropic viruses 1 and 2 (HTLV-I and HTLV-II) since all three viruses show clear-cut sequence homologies. The pathology of the BLV-induced disease, most notably the absence of chronic viraemia, a long latency period and lack of preferred proviral integration sites in tumours, is similar to that of adult T-cell leukaemia/lymphoma induced by HTLV-I. The most striking feature of the three naturally transmitted leukaemia viruses is the X region located between the env gene and the long terminal repeat (LTR) sequence. The X region contains several overlapping long open reading frames, one of which, designated XBL-1, encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and is most probably involved in genetic instability of BLV-infected cells of the B-cell lineage. The 'genetic instability' may put the cell into a state of fragility, ready to move along a number of stages towards full malignancy. Little is known about these events and their causes and we present some theoretical possibilities. BLV infection has a worldwide distribution. In temperate climates the virus spreads mostly through iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by haematophagous insects, there are indications of insect-borne propagation of the virus.

Animals↗