PubMed Health⌕ Search

Biomedical subjects

J A Levy

Publications and source records attributed to J A Levy.

At least 19 recordsLinked to original sources
PubMed1992

Human immunodeficiency virus (HIV) type 1 can superinfect HIV-2-infected cells: pseudotype virions produced with expanded cellular host range.

In studies on viral interference, cloned T-cell lines chronically infected with human immunodeficiency virus (HIV) type 1 or HIV-2 were inoculated with several strains of these two AIDS retrovirus subtypes. HIV-2UC1-infected cells, which still express the CD4 receptor, could be superinfected with a variety of HIV-1 and HIV-2 strains. This event was accompanied by cytopathic effects in the cells and production of pseudotype virions with an expanded cellular host range. HIV-1- or HIV-2-infected clonal cell lines, which did not express CD4, could not be superinfected by any HIV strains but were coinfected after transfection of molecular clones into the persistently infected cells. These observations indicate that viral interference with HIV occurs at the cell surface and involves a down-modulation of the CD4 molecule. If the CD4 protein is expressed, superinfection can take place, and phenotypically mixed virus particles are produced. Since HIV-1 and HIV-2 dually infected individuals have been detected, these in vitro observations may have relevance to the in vivo state.

B-Lymphocytes↗
PubMed1992

HIV-1 expression in chimpanzees can be activated by CD8+ cell depletion or CMV infection.

CD8+ cell antiviral activity and cytomegalovirus (CMV) were investigated in vivo as possible cofactors influencing the outcome of HIV-1 infection. The role of CD8+ cell suppression of HIV replication was evaluated by depleting CD8+ cells in two infected chimpanzees by inoculation with monoclonal anti-CD8 antibodies. Two other infected animals were injected with chimpanzee CMV (CCMV)-infected human fibroblasts to determine if exposure to this virus would induce HIV replication. Treatment with anti-CD8 antibody resulted in recovery of virus from the CD4+ lymphocytes of one animal at 1, 4, and 6 months, and from a second animal at 1 month postinoculation. In contrast, virus had been recovered only once or not at all from these infected chimpanzees for 4 years prior to treatment. Similarly, HIV was recovered from the CD4+ cells of the two animals 2 to 3 months after inoculation of CCMV-infected fibroblasts but not after inoculation of control uninfected fibroblasts. These studies suggest that CD8+ cell-mediated suppression and the presence of other viruses (such as CMV) could act as cofactors in influencing the extent of HIV-1 replication in vivo and, possibly, progression to disease.

Animals↗
PubMed1979

Apolipoprotein is responsible for neutralization of xenotropic type C virus by mouse serum.

We have shown that the circulating lipoproteins of the mouse contain a potent inhibitor of infectivity of the xenotropic type C virus. This virus neutralization does not involve immunoglobulins or complement. After fractionation of the lipoproteins on the basis of particle size, flotation properties, and electrostatic charge, virus neutralizing activity is found primarily in the triglyceride-rich lipoproteins (predominantly the chylomicrons) and in the HDL(2) subfraction of the high density lipoproteins. In fasted animals, activity resides chiefly in the high density lipoproteins. Neutralization titers increase strikingly during alimentary lipemia in both the lipoproteins of the rho < 1.006 g/cm(3) fraction and the high density lipoproteins. Increased activity persists in the high density lipoproteins after the lipemia recedes. Virus neutralizing activity is completely eliminated in all fractions by antiserum against high density lipoproteins and, in the triglyceride-rich fractions, by antiserum to murine apolipoprotein B. Complete removal of lipids markedly reduces the neutralizing activity of both classes of lipoproteins. Apolipoproteins delipidated with tetramethylurea retain some activity, which is enhanced by binding to a phospholipid-stabilized triglyceride emulsion and which is abolished by proteolytic digestion. We have demonstrated in vitro transfer of activity between high density and very low density lipoproteins of the mouse. These data indicate that xenotropic virus neutralization by normal mouse serum depends upon a protein that transfers among lipoprotein particles in a fashion analogous to the C apolipoproteins of other mammalian species.

Animals↗
PubMed1979

Chondrodystrophic myotonia: electromyographic and cardiac features of a case.

TheSchwartz-Jampel syndrome or chondrodystrophic myotonia is a rare disease characterized by dwarfism, diffuse osteoarticular alterations, blepharospasm, perioral muscular contractions and electromyographic alterations. The authors present a case of chondrodystrophic myotonia focusing mainly on facial electromyographic and cardiac findings. The electromyography of the orbicularis oculi muscles showed abundant myotonic discharges like other facial muscles as well as muscles of the members. It was not possible to obtain true electrical silence between myotonic discharges, suggesting that the blepharospasm is a consequence of persistent muscular contraction. No conclusive evidence of myocardiopathy was given by clinical or laboratory cardiac examinations. General characteristics of the syndrome are discussed as well as the treatment with procamide and phenytoin.

Abnormalities, Multiple↗
PubMed1979

Genetics of xenotropic virus expression in mice. I. Evidence for a single locus regulating spontaneous production of infectious virus in crosses involving NZB/B1NJ and 129/J strains of mice.

The extent of infectious xenotropic virus expression in homogenized splenic tissues from the high-virus-expressing NZB/BINJ mice and the non-virus-expressing 129/J mice and their crosses has been examined. The data suggest that a single autosomal "dominant-like" gene controls the spontaneous production and release of infectious xenotropic virus in NZB mice. Analysis of infectious virus production in second-backcross families [(F1 X 129) X 129] confirmed this conclusion. Variations in the amount of X-tropic virus released were evident in all genetic crosses. Virus titers (expressed as focus-forming units per milliliter) of supernatant fluid ranged from high levels in the NZB mice to somewhat lower levels in crosses involving the 129 mice. In the absence of a definite pattern in the titers observed in the genetic crosses studied, the term dominant-like is proposed for the single gene regulating the expression of X-tropic virus in NZB mice.

Animals↗
PubMed1978

Normal human placentas contain RNA-directed DNA polymerase activity like that in viruses.

Extracts from over 100 normal human placentas have been examined for RNA-directed DNA polymerase (DNA nucleotidyltransferase, EC 2.7.7.7) activity. More than 80% of these placentas contained this enzyme activity, which banded at a density of 1.15-1.17 g/ml in sucrose. After heat treatment, this enzyme activity was shifted in density to 1.22-1.24 g/ml. The enzymatic activity was greater with (rC)n.(dG)12-18 than with (dC)n.(dG)12-18 and was not stimulated by (dG)12-18 alone. The product of the endogenous reaction, which was sensitive to RNase, had the characteristics of a small DNA associated with a large RNA by hydrogen bonding. Electron microscopic inspection of the material with a density of 1.15-1.17 g/ml revealed numerous retrovirus-like particles with central electron-dense cores and double-membraned envelopes. The enzyme may be associated with the retrovirus-lik particles noted in the trophoblast layer of some human placentas.

Female↗
PubMed1978

Relationship of endogenous murine xenotropic type C virus production to spontaneous transformation of cultured cells.

Spontaneous production of endogenous xenotropic viruses by clones of New Zealand Black (NZB) embryo cells occurs at a constant level even after several cell transfers. Foci of cell alteration occur spontaneously in some of the clonal lines after 6 to 10 passages. The amount of virus generated does not correlate with spontaneous transformation.. of these NZB cells nor of cells from NIH Swiss or BALB/c mice. The data demonstrate an intracellular regulation of xenotropic virus expression which remains stable over several cell generations and differs from that controlling cell transformation

Animals↗
PubMed1978

FBJ osteosarcoma virus in tissue culture. III. Isolation and characterization of non-virus-producing FBJ-transformed cells.

Hamster and rat cell lines have been established that have been transformed by FBJ murine sarcoma virus (FBJ-MuSV) but that do not produce virus. The hamster cell line originated from an osteosarcoma that appeared in a hamster inoculated at birth with an extract of a CFNo1 mouse FBJ-osteosarcoma. The rat cell line was obtained by transferring the FBJ-MuSV genome to normal rat kidney cells in the absence of the FBJ type C virus (FBJ-MuLV), which, usually in high concentration, accompanies the FBJ-MuSV. Both transformed hamster and rat cell lines contain the FBJ-MuSV genome, which can be rescued by ecotropic and xenotropic murine type C viruses. This rescued genome produces characteristic FBJ-MuSV foci in tissue culture and, in appropriate animal hosts, induces osteosarcomas typical of those induced by FBJ-MuSV. FBJ-MuSV was isolated originally from a parosteal osteosarcoma that occurred naturally in a mouse. Since there was no previous history of passage of the agent through any other animal species, these non-virus-producing hamster and rat cells transformed by FBJ-MuSV should be very helpful in molecular studies examining the origin of spontaneous sarcoma genomes in mice.

Animals↗