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Biomedical subjects

M S Meltzer

Publications and source records attributed to M S Meltzer.

At least 19 recordsLinked to original sources
PubMed1992

Cytotoxic activity and production of toxic nitrogen oxides by macrophages treated with IFN-gamma and monoclonal antibodies against the 73-kDa lipopolysaccharide receptor.

The hamster IgM mAb 5D3 is specific for an 73-kDa LPS receptor on murine leukocytes. This mAb inhibits binding of radiolabeled LPS to splenocytes and acts as an agonist for induction of LPS-mediated changes in macrophage function. Resident peritoneal macrophages treated with IFN-gamma and mAb 5D3 developed potent cytotoxic activity against tumor cells. Cells treated with IFN-gamma or mAb 5D3 alone were inactive. Macrophage cytotoxic activity induced by IFN-gamma and mAb 5D3 was inhibited by NGMMLA and coincident with high levels of NO2-released into culture fluids. These data show that mAb 5D3 serves as an effective trigger signal for induction of cytotoxic activity with IFN-gamma-primed macrophages. Indeed, mAb 5D3 exactly mimicked the effects of LPS in these same systems. Unlike LPS, effects of mAb 5D3 on induction of macrophage cytotoxic activity and production of nitrogen oxides was abrogated after boiling, and not affected by addition of polymyxin B. The effects of LPS and mAb 5D3 as a trigger signal for IFN-gamma-primed macrophages were associated with production of TNF activity in culture fluids and inhibited by mAb against rTNF-alpha. Expression of class II MHC on macrophages induced by IFN-gamma treatment was suppressed by both LPS and mAb 5D3. These suppressive effects of LPS and mAb 5D3 were not affected by NGMMLA or mAb against rTNF-alpha. Finally, macrophages treated with LPS or mAb 5D3 before exposure to IFN-gamma and LPS or mAb 5D3 did not develop cytotoxic activity or high levels of NO2- in the culture fluids. These same cells developed both effector activities after addition of rTNF-alpha. These results in toto identify the 73-kDa protein as a receptor that mediates LPS-induced changes in macrophage effector function. The mAb 5D3 serves as a specific and defined reagent agonist for analysis of LPS receptor-linked change.

Animals↗
PubMed1992

Enhanced HIV-1 replication in retinoid-treated monocytes. Retinoid effects mediated through mechanisms related to cell differentiation and to a direct transcriptional action on viral gene expression.

Vitamin A and other retinoids have profound effects on macrophage differentiation and function. Such effects could alter interactions between HIV and tissue macrophages, a principal target cell and reservoir for virus during HIV disease. Indeed, retinoids are used to treat various symptoms associated with HIV infection. We show that levels of virus replication in monocytes cultured 7 days before and continuously after HIV infection in 1 to 10 microM retinoic acid were 10- to 20-fold greater than those of control cells. No direct toxicity (detachment from substrate or cell death) was evident in infected or control monocytes treated with less than or equal to 10 microM retinoic acid. Maximum effects of retinoic acid (50% maximum effect was at 0.8 +/- 0.1 microM) required 5 to 7 days treatment before infection and persisted without additional treatment through more than 4 wk. RT activity in cultures of retinoic acid-treated monocytes reached maximum levels much earlier than those of control cultures, but the minimum tissue culture infectious doses for retinoic acid-treated and untreated monocytes were comparable. Retinoic acid treatment did not affect susceptibility of monocytes to HIV infection. Further, the frequency of infected cells in retinoic acid-treated and control cultures were also comparable: about 20% of cells in each culture expressed HIV proteins or RNA 2 wk after infection. In contrast, levels of HIV-specific RNA and DNA were 3- to 5-fold higher in the retinoic acid-treated over control monocytes 1 wk after infection. That retinoic acid increased levels of HIV gene expression in monocyte cultures without affecting the number of infected cells per culture suggested a transcriptional mechanism for the effect. This was confirmed in the U937 myeloid cell line transfected with HIV LTR linked to a chloramphenicol acetyl transferase reporter gene. Chloramphenicol acetyl transferase activity in lysates of retinoic acid-treated cells were 20-fold higher than that of control cells. These data show that retinoic acid significantly increased HIV replication in monocytes through mechanisms related to cell differentiation and to a direct transcriptional effect on viral gene expression.

Cell Differentiation↗
PubMed1992

Induction of IFN-alpha in peripheral blood mononuclear cells by HIV-infected monocytes. Restricted antiviral activity of the HIV-induced IFN.

PBMC cocultured with HIV-infected monocytes for 12 to 48 h released high levels of IFN activity. IFN titers were directly dependent upon time after virus infection and level of HIV replication in infected cells. IFN induction in PBMC was evident with HIV-infected monocytes and PBMC and with myeloid and lymphoblastoid cell lines with at least three different HIV strains. In HIV-infected cell line pairs in which virus infection occurs in both productive and restricted forms, IFN induction in PBMC occurred only with productive infection. IFN activity was acid stable and completely neutralized by antibodies against IFN-alpha. Induction of IFN required cell-cell contact between HIV-infected cells and PBMC, but was independent of MHC compatibility. With PBMC co-cultured with autologous HIV-infected monocytes, IFN induction was highly selective: IL-1 beta, IL-6, or TNF-alpha activity and mRNA were not detected. Cell surface determinants on HIV-infected monocytes that induced IFN in PBMC remained active after fixation in 4% paraformaldehyde. Both adherent and nonadherent PBMC produced IFN after coculture with HIV-infected monocytes. Ability to produce IFN by PBMC was not affected by depletion of T cell, NK cell, B cell, or monocyte subpopulations. The IFN activity produced by PBMC cocultured with HIV-infected cells was about 20-fold less active than equal quantities of rIFN-alpha 2b for inhibition of HIV replication in monocytes and at low concentrations enhanced virus growth. Clinical studies with HIV-infected patients and parallel findings in animal lentivirus disease suggest an adverse role for IFN in disease progression. Conditions for induction of IFN in the culture system described in this report may mimic those in the HIV-infected patient. Defining the molecular basis for IFN induction, the cells that produce IFN, and the altered biologic activity of this important cytokine may provide insight into the pathogenesis of HIV disease.

Cells, Cultured↗
PubMed1992

Interactions between HIV-infected monocytes and the extracellular matrix: increased capacity of HIV-infected monocytes to adhere to and spread on extracellular matrix associated with changes in extent of virus replication and cytopathic effects in infected cells.

Monocytes express cell surface receptors for extracellular matrix (ECM) proteins of basement membranes. These receptors are engaged during extravasation of cells through capillary endothelium into tissue. The number of human immunodeficiency virus (HIV)-infected monocytes that adhered to ECM over 2 h was threefold higher than that of uninfected control cells. This difference was ECM specific and was not observed with a bovine serum albumin substrate. Enhanced adhesion to ECM was evident in monocytes by 4 days after HIV infection and increased through 10 days. Monocytes exposed to a T cell-tropic HIV strain that binds to but does not replicate in monocytes showed no changes in adherence to ECM. Thus, productive infection of monocytes by HIV induces a significant increase in the capacity of these cells to interact with ECM. Enhanced adhesion of HIV-infected monocytes to ECM was associated with increased spreading: at 12 h, sixfold more HIV-infected monocytes were spread on ECM than were uninfected control cells. Cell processes of HIV-infected monocytes formed a complex network on ECM: many of these cells expressed HIV proteins as detected by indirect immunofluorescence. HIV-associated cytopathic effects and levels of virion-associated reverse transcriptase activity depended on the substrate to which monocytes were attached. Virus replication and cytopathic effects in monocytes adhered to ECM, fibronectin, or plastic alone were comparable. In contrast, HIV-infected monocytes attached to laminin showed a significant increase in virus replication and in extent of cytopathic effects through 2 weeks after infection. The lowest levels of HIV replication and cytopathic effects were in monocytes attached to collagen IV. Interactions between monocytes and ECM profoundly affect the manner in which these cells control HIV infection: HIV infection changes the capacity of infected monocytes to attach and spread on ECM; attachment to ECM alters the extent of virus replication in infected cells.

Cell Adhesion↗
PubMed1992

Interactions between HIV-infected monocytes and the extracellular matrix: HIV-infected monocytes secrete neutral metalloproteases that degrade basement membrane protein matrices.

The frequency of human immunodeficiency virus (HIV)-infected monocytes that spread on a model basement membrane was about twofold greater than that of an equal number of uninfected control cells through the initial 12 to 18 h of culture. By 24 h, virtually all HIV-infected and uninfected control cells spread on the basement membrane gel. The frequency of spread cells in the uninfected control population was less than 10% of total cells by 12 days. In contrast, 30 to 40% of HIV-infected monocytes remained spread through this time interval and formed a dense interdigitated network of cell processes on and into the gel matrix. Invasion of the basement membrane matrix by HIV-infected monocytes suggested increased secretion of proteases able to digest the gel. Indeed, levels of neutral protease activity in culture fluids from HIV-infected monocytes were significantly higher than those from equal numbers of uninfected control cells. High levels of protease activity in culture fluids of HIV-infected monocytes required productive virus infection and were not observed with cells exposed to T cell-tropic HIV isolates. The predominant protease activity in these cultures was a 92-kd neutral metallogelatinase. HIV-induced changes in monocyte metalloprotease activity may be important for extravasation of infected cells to tissue or for the development of AIDS-associated neuropathology, carcinogenesis, and opportunistic infection.

Basement Membrane↗
PubMed1992

Mononuclear phagocytes as targets, tissue reservoirs, and immunoregulatory cells in human immunodeficiency virus disease.

We have presented evidence in this review for the following: 1. Macrophages are likely the first cell infected by HIV. Studies document recovery of HIV into macrophages in the early stages of infection in which virus isolation in T cells is unsuccessful and detectable levels of antibodies against HIV are absent. 2. Macrophages are major tissue reservoirs for HIV during all stages of infection. Unlike the lytic infection of T cells, many HIV-infected macrophages show little or no virus-induced cytopathic effects. HIV-infected macrophages persist in tissue for extended periods of time (months) with large numbers of infectious particles contained within intracytoplasmic vacuoles. 3. Macrophages are a vector for the spread of infection to different tissues within the patient and between individuals. Several studies suggest a "Trojan horse" role for HIV-infected macrophages in dissemination of infectious particles. The predominant cell in most bodily fluids (alveolar fluid, colostrum, semen, vaginal secretions) is the macrophage. In semen, for example, the numbers of macrophages exceed those of lymphocytes by more than 20-fold (Wolf and Anderson 1988). 4. Macrophages are major regulatory cells that control the pace and intensity of disease progression in HIV infection. Macrophage secretory products are implicated in the pathogenesis of CNS disease and in control of viral latency in HIV-infected T cells. This litany of events in which macrophages participate in HIV infection in man parallels similar observations in such animal lentivirus infections as visna-maedi or caprine arthritis-encephalitis viruses. HIV interacts with monocytes differently than with T cells. Understanding this interaction may more clearly define both the pathogenesis of HIV disease and strategies for therapeutic intervention.

Antigens, Differentiation, Myelomonocytic↗
PubMed1992

Interferons in the persistence, pathogenesis, and treatment of HIV infection.

Interferon (IFN) plays an important role in the treatment and pathogenesis of HIV disease. Recent studies show beneficial effects of IFN alpha in the treatment of HIV-associated Kaposi's Sarcoma and early HIV-infection. Moreover, cell culture studies support these beneficial effects. HIV infection of monocytes is blocked by IFN alpha administered at the time of viral challenge. The IFN alpha-treated cells show no evidence of HIV infection. Viral gene products produced in monocytes infected with HIV then treated with IFN alpha gradually decrease to baseline. Large quantities of proviral DNA are seen in the HIV-infected IFN alpha-treated cells with little evidence for viral transcription suggesting true microbiological latency. While most viral infections of cells result in IFN production, HIV is a notable exception. Indeed, HIV does not induce monocytes to produce IFN alpha and blocks its production following poly(I).poly(c) stimulation. This allows HIV yet another mechanism to evade an important host antiviral response. Paradoxically, the appearance of IFN activity in sera of HIV-infected patients is associated with disease progression, not resolution. Recent observations showing that the interaction between HIV-infected monocytes and PBMC results in the production of IFN alpha s with reduced anti-HIV activity may help explain this paradox. Thus, IFN alpha plays an important but complex role in HIV disease. The elucidation of cellular factors that regulate the antiretroviral effects of IFN alpha may lead to the development of novel therapeutic strategies for HIV infection.

Animals↗
PubMed1992

No direct neuronotoxicity by HIV-1 virions or culture fluids from HIV-1-infected T cells or monocytes.

Macrophages and microglia are the principal target cells for human immunodeficiency virus (HIV) in brain, and as such, are likely participants in the neuropathology of HIV infection. In a model system for this process, we found that fluids from human monocyte cultures enhanced survival and differentiation of the neurons in fetal rat brain explants. In contrast, fluids from HIV-infected monocyte cultures were strongly toxic to neurons and paradoxically enhanced the proliferation of glial cells. Further, neuronotoxic activity in these fluids was mediated through activation of NMDA binding receptors on the neurons and was inhibited by any of several different NMDA antagonists. Neuronotoxic activity was directly related to contamination of the HIV virus stock with Mycoplasma arginini and M. hominis. Pure cultures of mycoplasma, bacterial lipopolysaccharide (LPS), or murine recombinant tumor necrosis factor alpha (rTNF alpha) each induced neuronotoxicity which exactly mirrored that induced by the contaminated HIV stock. It is likely that mycoplasma or components of the mycoplasma plasma membrane stimulate TNF alpha production by the glial cells in the brain explants. Indeed, careful depletion of glial cells in these explants prevented mycoplasma or LPS-mediated neuronotoxicity. No neuronotoxicity was evident with HIV-1 virus stock, HIV-1 gp120, or culture fluids from HIV-infected T cells or monocytes when these preparations were free of contamination by mycoplasma and LPS. These findings suggest caution in interpretation of those experiments in which similar contamination has not been rigorously excluded.

Animals↗
PubMed1992

Loss of infectivity by progeny virus from alpha interferon-treated human immunodeficiency virus type 1-infected T cells is associated with defective assembly of envelope gp120.

Levels of human immunodeficiency virus (HIV) DNA, RNA, or p24 antigen and reverse transcriptase activity in T-cell cultures treated with 500 IU of recombinant alpha interferon (rIFN alpha) per ml were comparable to those in control cultures. Radioimmunoprecipitation analysis of proteins in lysates of IFN-treated T cells documented a marked accumulation of HIV proteins. Localization of gp120 by immunofluorescence showed a diffuse pattern in IFN-treated cells quite distinct from the ring pattern in untreated control cells. That large quantities of gp120 in aberrant cell compartments might affect HIV morphogenesis was confirmed in infectivity studies: virions from IFN-treated cells were 100- to 1,000-fold less infectious than an equal number of virions from control cells. Direct examination of IFN-treated and control HIV-infected cells by transmission electron microscopy showed little difference in the number or distribution of viral particles. However, quantitation of gp120 by immunogold particle analysis revealed a marked depletion of envelope glycoprotein in virions released from IFN-treated cells. This defect in gp120 assembly onto mature viral particles provides a molecular basis for this loss of infectivity.

Cells, Cultured↗
PubMed1992

Interferon alpha (IFN)-macrophage interactions in human immunodeficiency virus (HIV) infection: role of IFN in the tempo and progression of HIV disease.

Components of the host immune response that constrain virus replication and affect long-lasting antiviral immunity following HIV infection are incompletely defined. IFNs are critical participants in host antiviral processes. While IFN induces significant anti-retroviral activities, they also serve as harbingers for poor clinical outcomes. Moreover, monocytes, a major cellular source of IFN and HIV in man, are poor producer cells for IFN following HIV infection. Indeed, HIV infection of monocytes results in a diminished production and induction of IFN. IFN is only produced during cell to cell contact between HIV-infected cells and uninfected PBMC. Analysis of the biologic activity of HIV-induced IFN(s) shows that it poorly restricts HIV replication. Thus, the role of IFN in HIV disease is complex and seemingly paradoxical. The diminished capacity of HIV-infected monocytes to produce IFN and the production of defective IFNs likely reflect specific viral adaptive mechanisms for persistent infection.

HIV↗
PubMed1991

Epidermal Langerhans cells are not principal reservoirs of virus in HIV disease.

Several reports implicate Langerhans cells of skin as susceptible targets, reservoirs, and vectors for transmission of HIV: 1) numbers of Langerhans cells in skin of HIV-infected patients were decreased about 50% of that in control skin; 2) as many as 30% of Langerhans cells in the skin of HIV-infected patients were morphologically abnormal; 3) viral particles typical for HIV were identified in or around 2 to 5% of these cells; and 4) infectious HIV was isolated from skin biopsies of infected patients. These results were consistent with similar observations of HIV-infected macrophages in such tissues as brain, lung, and lymph node. Despite these findings, other investigators find no evidence for virus infection in the epidermis of HIV-infected patients by any of several immunohistochemical or ultrastructural criteria. To address this controversy, we obtained skin from 28 HIV-seropositive subjects at various clinical stages by full thickness biopsy or suction blister. Samples were analyzed by transmission electron microscopy for presence of HIV virions, by immunofluorescent staining for viral proteins, by in situ hybridization for HIV-specific mRNA, by polymerase chain reaction amplification of virus-specific DNA, and by direct virus isolation by coculture of epidermis onto monocyte target cells. By any of these techniques, demonstration of HIV in the epidermis of infected patients was equivocal and even then, infrequent. In contrast, viral DNA was detected from the dermis of the same skin samples (26 of 28 samples). Moreover, the number and morphology of Langerhans cells in skin of infected patients were within normal limits, regardless of stage of disease. These studies in toto suggest that a role for Langerhans cells as a principal viral reservoir or vector of transmission is highly unlikely.

Aged↗
PubMed1991

Binding of recombinant HIV coat protein gp120 to human monocytes.

Inasmuch as the exact level of CD4 Ag expression on macrophages is controversial and because HIV may interact with macrophages in a manner different from that on T cells, we analyzed the binding of gp120 to freshly isolated and cultured monocytes. rgp120 was iodinated using the lactoperoxidase method to a sp. act. of 600 Ci/mmol. Highly purified monocytes (greater than 90%) were isolated from the leukapheresed blood of normal volunteers by Ficoll-Hypaque sedimentation followed by countercurrent centrifugal elutriation and cultured 7 days in DMEM supplemented with 1000 U/ml macrophage CSF in 10% human serum. Whereas MOLT/4 cells consistently bound freshly prepared 125I-rgp120 at 80% specificity with 5100 +/- 700 mol/cell, MCSF cultured monocytes bound rgp120 at only 0 to 20% specificity and 420 +/- 200 mol/cell. Most of the radioactivity bound by these cells could not be blocked by the addition of unlabeled rgp120. In contrast, the U937 myeloid cell line bound rgp120 with 50% specificity and about 2500 mol/cell. Whereas the antibody OKT4a (anti-CD4) blocked 80% of the binding on MOLT/4 cells and 50% on U937 cells, binding was only inhibited on the average of 6% on cultured monocytes. When soluble rCD4 was used as an inhibitor, binding to MOLT/4 cells was blocked by 80%. In contrast, binding to cultured monocytes was inhibited by 28%. HIV infectivity was blocked by similar concentrations of OKT4a. These observations suggest that although most binding of gp120 to cultured monocytes is not to the CD4 determinant, several hundred molecules do bind to a CD4-like molecule which promotes virus entry and replication.

Binding, Competitive↗
PubMed1991

Enhanced HIV replication in macrophage colony-stimulating factor-treated monocytes.

Monocytes cultured 7 to 10 days in recombinant human macrophage CSF (MCSF) were greater than 400-fold more susceptible to HIV infection than an equal number of cells cultured in medium alone. Levels of reverse transcriptase activity and p24 Ag in culture fluids of monocytes treated with MCSF 1 wk before and continuously after HIV infection were significantly greater than those of control cells cultured without MCSF. HIV-induced cytopathic effects in the MCSF-treated cultures also increased in both frequency and extent. At any given viral inoculum, the frequency of HIV-infected cells, the level of HIV mRNA/infected cell, and the level of proviral DNA/infected culture in MCSF-treated monocyte cultures were dramatically greater than those in control cultures. These differences were directly related to MCSF concentration to a maximum between 750 and 1000 U/ml MCSF, and were evident at all time points examined through 5 wk. None of the preceding effects was observed when MCSF was added at the time of or 1 wk after HIV infection. These data suggest that the predominant effect of MCSF for control of HIV infection is on the monocyte itself, not the virus. If these in vitro observations extend to the HIV-infected patient, then the variable levels of MCSF in tissue or blood may determine both the susceptibility of macrophages to virus infection and the extent of virus replication in infected cells.

Cells, Cultured↗
PubMed1991

Inhibition of human immunodeficiency virus infection in monocytes by monoclonal antibodies against leukocyte adhesion molecules.

CD4 is the surface receptor for HIV envelope. Some evidence exists, however, that other cell surface receptors may be involved in viral entry subsequent to the initial binding of gp120 to CD4. Antibodies to leukocyte integrin LFA-1, a major component of intercellular adhesive interactions, have been shown to inhibit HIV-induced syncytia formation. Using a stringent system for in vitro HIV infection of human leukocytes, we examine the ability of some monoclonal antibodies (mAb) against various adhesion-related molecules to block or partially inhibit productive viral replication. HIV-1 infection of target monocytes or T cells by cell-free virus was blocked completely or partially by some mAb that prevent cell-cell interactions (CD4, HLA-DR, LFA-1, LFA-3), but not by others (ICAM-1, MAC-1, gp150.95, CD2, CD3, CD14). The capacity for mAb to block HIV infection appears to be epitope-specific, and does not relate to the ability to block homotypic adhesion. HIV transmission from infected cells was more difficult to block than was infection by cell-free virus. Adhesion molecules may be involved in facilitating early stages of HIV infection, following gp120/CD4 binding but prior to viral integration, in a manner distinct from cell-cell adhesion.

Antibodies, Monoclonal↗
PubMed1991

Tumor necrosis factor.

Tumor necrosis factor is important in systemic and cutaneous defense, homeostasis, and many disease states. The numerous and diverse effects of tumor necrosis factor are best understood when considered as concentration-dependent, with normal homeostasis progressing to defense followed by toxic effects. Understanding tumor necrosis factor is important for the dermatologist as more studies appear in our literature and potential clinical uses of tumor necrosis factor (and possible anti-tumor necrosis factor agents) are realized.

Communicable Diseases↗