Search PubMed⌕ Search

Biomedical subjects

J Orenstein

Publications and source records attributed to J Orenstein.

At least 37 records · Page 2Linked to original sources
PubMed1993

Human immunodeficiency virus infection of the human thymus and disruption of the thymic microenvironment in the SCID-hu mouse.

Infection with the human immunodeficiency virus (HIV) results in immunosuppression and depletion of circulating CD4+ T cells. Since the thymus is the primary organ in which T cells mature it is of interest to examine the effects of HIV infection in this tissue. HIV infection has been demonstrated in the thymuses of infected individuals and thymocytes have been previously demonstrated to be susceptible to HIV infection both in vivo, using the SCID-hu mouse, and in vitro. The present study sought to determine which subsets of thymocytes were infected in the SCID-hu mouse model and to evaluate HIV-related alterations in the thymic microenvironment. Using two different primary HIV isolates, infection was found in CD4+/CD8+ double positive thymocytes as well as in both the CD4+ and CD8+ single positive subsets of thymocytes. The kinetics of infection and resulting viral burden differed among the three thymocyte subsets and depended on which HIV isolate was used for infection. Thymic epithelial (TE) cells were also shown to endocytose virus and to often contain copious amounts of viral RNA in the cytoplasm by in situ hybridization, although productive infection of these cells could not be definitively shown. Furthermore, degenerating TE cells were observed even without detection of HIV in the degenerating cells. Two striking morphologic patterns of infection were seen, involving either predominantly thymocyte infection and depletion, or TE cell involvement with detectable cytoplasmic viral RNA and/or TE cell toxicity. Thus, a variety of cells in the human thymus is susceptible to HIV infection, and infection with HIV results in a marked disruption of the thymic microenvironment leading to depletion of thymocytes and degeneration of TE cells.

Animals↗
PubMed1992

Cell-to-cell spread of HIV-1 occurs within minutes and may not involve the participation of virus particles.

Although virus infections have been classically studied with "cell-free" virion preparations, many animal viruses are able to spread both in vitro and in vivo by inducing cell-cell fusion. An efficient system to monitor the cell-to-cell spread of HIV-1 has been developed employing chronically infected H9 donor cells. Under appropriate conditions of cocultivation with uninfected cells, the synthesis of unintegrated viral DNA, monitored by Southern blot hybridization, occurred between 2 and 4 hr following infection; viral proteins were detected 8 to 12 hr following cocultivation and progeny virions were released into the medium by 16 hr. The use of metabolic inhibitors or specific envelope/receptor antibodies revealed that the cell-to-cell spread of HIV required: (1) gp120-CD4 interaction and (2) reverse transcription. Light and electron microscopy, fluorescent dye redistribution, and soluble CD4 competition experiments all demonstrated that the HIV-induced cell-cell fusion began within 10 to 30 min of cocultivation. Surprisingly, the electron microscopic analyses also suggested that budding or mature virus particles did not participate in this process. Thus the virus-induced cell-cell fusion observed is very likely the result of gp120/gp41 proteins, on the surface of infected cells, interacting with CD4 molecules on uninfected cells. These findings are of immediate importance in understanding the mechanism(s) of HIV-1 transmission in vivo and for the design of effective vaccines and antiviral agents.

Blotting, Western↗
PubMed1992

Dual regulation of silent and productive infection in monocytes by distinct human immunodeficiency virus type 1 determinants.

The regulation of human immunodeficiency virus type 1 infection and replication in primary monocytes was investigated by mutagenesis of recombinant proviral clones containing an env determinant required for the infectivity of monocytes. Virus replication was assayed by determination of reverse transcriptase activity in culture fluids and by recovery of virus from monocytes following cocultivation with uninfected peripheral blood mononuclear cells. Three virus replication phenotypes were observed in monocytes: productive infection, silent infection, and no infection. Incorporation of the monocytetropic env determinant in a full-length clone incapable of infection or replication in primary monocytes (no infection) conferred the capacity for highly efficient virus replication in monocytes (productive infection). Clones with the env determinant but lacking either functional vpr or vpu genes generated lower replication levels in monocytes. Mutation of both vpr and vpu, however, resulted in nearly complete attenuation of virus replication in monocytes, despite subsequent virus recovery from infected monocytes by cocultivation with uninfected peripheral blood mononuclear cells (silent infection). These findings indicate a central role for the "accessory" genes vpu and vpr in productive human immunodeficiency virus type 1 replication in monocytes and indicate that vpu and vpr may be capable of functional complementation.

Amino Acid Sequence↗
PubMed1992

The role of stereotactic biopsy in the management of HIV-related focal brain lesions.

The criteria for brain biopsy in patients with acquired immunodeficiency syndrome (AIDS) remain unclear and without universal acceptance. In order to shed more light on this issue, the authors reviewed the records of 25 AIDS patients with focal cerebral lesions who consecutively underwent stereotactic biopsy between November 1988 and October 1990. The most frequently occurring diagnoses were lymphoma (36%), progressive multifocal leukoencephalopathy (24%), and toxoplasmosis (8%). Patients whose central nervous system disease resulted in their initial presentation (approximately 40%) survived a median of 37 weeks, as opposed to 6 weeks for those who had previous AIDS-related infections. The proportion of biopsies of contrast-enhancing lesions that were diagnostic and thereby contributed to the patients' therapeutic management was 87.5%. On the other hand, only 67% of the biopsies of nonenhancing lesions were diagnostic, and none of these lesions were treatable. All of the lymphoma patients had had AIDS for some time and, despite a reasonable preoperative Karnofsky score and postoperative radiation therapy, their median survival was only 6 weeks; however, biopsy was critical to their therapeutic management. Early brain biopsy, rather than empiric antitoxoplasmosis therapy, appears indicated for aggressive therapy of contrast-enhancing lesions in patients who have had previous manifestations of AIDS. The role for biopsy of nonenhancing lesions is less clear, but it may provide prognostic information.

AIDS Dementia Complex↗
PubMed1989

Human immunodeficiency virus type 1 in spinal cords of acquired immunodeficiency syndrome patients with myelopathy: expression and replication in macrophages.

Spinal cord disease is common in patients infected with human immunodeficiency virus type 1 (HIV-1), and a characteristic vacuolar myelopathy is present at autopsy in approximately one-fourth of acquired immunodeficiency syndrome patients. Pathologic examination of the spinal cord shows vacuolation of white matter and infiltration by macrophages, a process distinct from HIV-1 encephalopathy. To determine the presence and localization of HIV-1 RNA in the spinal cords of acquired immunodeficiency syndrome patients with vacuolar myelopathy, we used the technique of combined in situ hybridization and immunohistochemical staining on the same slide. Spinal cord tissue sections were stained with markers for macrophages, endothelial cells, oligodendroglia, astrocytes, and myelin and then hybridized in situ with HIV-1-specific RNA probes. Combined in situ hybridization and immunohistochemical staining on three spinal cords showed HIV-1 expression in mononuclear and multinucleated macrophages localized mainly to areas of myelopathy in spinal cord white matter. Immunohistochemical staining and electron microscopy showed myelin within macrophages and electron microscopy revealed HIV-1 budding from macrophages. These data suggest a role for HIV-1-infected macrophages locally in the pathogenesis of vacuolar myelopathy and add to the body of evidence that these cells play a role systemically in the development of HIV-1-related disease.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Characterization of a promonocyte clone chronically infected with HIV and inducible by 13-phorbol-12-myristate acetate.

The present study has investigated the effect of PMA, an inducer of monocyte differentiation, on HIV expression in a chronically infected promonocyte clone. After acute HIV infection of U937 cells, clones that constitutively expressed varying levels of HIV were isolated by limiting dilution. One clone (U1) produced low levels of HIV but was found to increase its production 20-fold after PMA induction, as detected by reverse transcriptase or A capture. Further characterization of U1 indicated that PMA could induce cellular differentiation and maturation in the clone similar to that in uninfected U937 cells. In addition, functional studies revealed that superoxide anion production from the U1 clone was not different from that of uninfected U937 cells. Electron microscopic studies of U1 indicated that PMA induced endocytotic vesicles containing many HIV particles. These studies provide a model at the clonal level to 1) examine latency or chronicity of HIV infection in monocytes and 2) delineate the signals required for conversion to high level viral expression.

Cell Differentiation↗