Infection of granulocyte/monocyte progenitor cells with HIV1

Effects of human immunodeficiency virus on the erythrocyte and megakaryocyte lineages

Anaemia and thrombocytopenia are haematological disorders that can be detected in many human immunodeficiency virus (HIV)-positive patients during the development of HIV infection. The progressive decline of erythrocytes and platelets plays an important role both in HIV disease progression and in the clinical and therapeutic management of HIV-positive patients. HIV-dependent impairment of the megakaryocyte and erythrocyte lineages is multifactorial and particularly affects survival, proliferation and differentiation of bone marrow (BM) CD34+ haematopoietic progenitor cells, the activity of BM stromal cells and the regulation of cytokine networks. In this review, we analyse the major HIV-related mechanisms that are involved in the genesis and development of the anaemia and thrombocytopenia observed in HIV positive patients.

Ultrastructure of the polymorphonuclear leucocytes in human immunodeficiency virus infection

The ultrastructure of polymorphonuclear leucocytes (PMNL) was studied in 16 patients infected with the human immunodeficiency virus (HIV). PMNL were isolated from HIV-infected patients with CD4+ lymphocytes counts > 200/mm3 (without signs of active infection) (n = 12) (group 1), or < 200/mm3 (n = 4) (group 2), and from 16 healthy volunteers (group 3). Immunoelectron microscopy staining using an anti-beta 2 integrin antibody (anti-CD18) was performed on PMNL from three individuals of group 2 and of three individuals of group 3, before and after incubation with N-formyl-methionyl-leucylphenylalanine (f-MLP). The radical oxygen intermediates (ROI) production of PMNL was investigated by luminol-mediated chemiluminescence. A number of ultrastructural abnormalities in PMNL were found in a higher proportion in HIV-infected patients. These were: (a) an increase in the size of the Golgi apparatus and in the number of mitochondria, and in the quantity of endoplasmic reticulum; (b) some dysplastic features including large cytoplamic vacuoles, whorl of myelin, and nuclear pockets; (c) an increase prevalence of multivesicular bodies compared with control PMNL; (d) some cylindrical confronting cisternae and tubuloreticular structures. After anti-CD18 staining, gold particles were seen on the plasma membrane and more rarely inside the cytoplasm of PMNL from each group but no decrease in this staining was noted in HIV PMNL. Incubation with f-MLP similarly increased the immunostaining of the PMNL in each group. In vitro ROI production was significantly depressed for HIV PMNL compared with control PMNL. Some ultrastructural abnormalities observed in this study could support the possibility that one of the mechanisms underlying the qualitative functional defects of PMNL from HIV-infected patients may be related to some cytopathic effect.

Mechanism of gamma sigma T-cell-mediated inhibition of stem cell differentiation in vitro: possible relevance for myelosuppression in HIV-infected individuals

We investigated whether gamma delta T cells contribute to the suppression of myelopoiesis in HIV infection. Freshly isolated gamma delta T cells from HIV seropositive patients suppressed CFU-GM growth in vitro. Preactivation of gamma delta T cells with IL-2 and/or IL-15 further reduced the number of CFU-GM. Natural killer cells and to a lower extent CD4+ and CD8+ cells also inhibited CFU-GM growth. In contrast to gamma delta T cells, this effect was not dependent on IL-15 or IL-2 preactivation. Moreover, no enhanced inhibitory effect of CD56+ and CD4+ cells was observed in HIV+ subjects compared to HIV- donors. The myelosuppressive effect of supernatants of gamma delta T cells could be inhibited by antibodies against IFN-gamma or TNF-alpha. Accordingly, we found increased numbers of TNF-alpha or IFN-gamma-secreting CD8+ gamma delta T cells in HIV+ patients. We conclude that the increased fraction of activated gamma delta T cells producing myelosuppressive cytokines might contribute to the dyshematopoiesis frequently observed in HIV-infected individuals.

Gamma delta-T cell-receptor-positive lymphocytes inhibit human hematopoietic progenitor cell growth in HIV type 1-infected patients

In severe HIV infection, the majority of patients exhibit signs of hematopoietic deficiency including anemia, leukopenia, and thrombocytopenia. Besides other pathophysiological mechanisms, the disturbed helper/suppressor ratio of T-lymphocytes suggests that alterations within T cell subpopulations may have a suppressive effect on HIV-associated hematopoiesis. Since a delta TCS-1- and mostly CD-8-positive subpopulation of cytotoxic T-lymphocytes expressing the gamma delta-receptor is increased in peripheral blood and bone marrow of HIV-infected persons, it was the aim of this study to investigate the role of gamma delta-positive cells in HIV-associated bone marrow deficiency. The number of bone marrow-derived pluripotent colony-forming units (CFU-GEMM), burstforming units-erythrocyte (BFU-E), and colony-forming units-granulocyte-monocyte (CFU-GM) of HIV-1-positive patients was significantly (p < 0.05) increased after depletion of CD-8-positive, gamma delta-positive, and delta TCS-1-positive T-lymphocytes. In contrast, the depletion of these subpopulations had no stimulatory effect in healthy controls. Further experiments identified direct cellular contact between effector and hematopoietic progenitor cells and the production of interferon-gamma and tumor necrosis factor-alpha as the mechanisms mediating the suppressive effect of the delta TCS-1-positive cells in HIV-positive patients.

Effect of human immunodeficiency virus infection on haematopoiesis

The pathogenesis of peripheral blood cytopenias in AIDS patients is clearly multifactorial. Among the various contributing mechanisms, those involving a direct role of HIV-1 have been actively investigated in the past few years. It has now been convincingly demonstrated that HIV can impair the survival/proliferative capacity of purified haematopoietic progenitor cells. Although a subset of haematopoietic progenitor cells are perhaps susceptible to HIV-1 infection, both in vitro and in vivo, the suppressive effect does not require either active or latent infection and is probably mediated by the interaction of viral or virus-associated proteins with the cell membrane of haematopoietic progenitor cells. Both the viral load and the biological characteristics of the virus play an important role in suppression, since different isolates displayed different inhibitory activity. Haematosuppression is not a specific property of monocytotropic versus lymphocytotropic or low-replicating versus high-replicating isolates, and it will be important to exactly establish which viral component is crucial to suppression of haematopoietic progenitor cells. Since the haematopoietic stem cell is the common progenitor to both the myeloid and lymphoid lineages, the capacity of HIV to impair the growth of early haematopoietic progenitor cells could contribute not only to the frequent occurrence of anaemia, granulocytopenia and thrombocytopenia in AIDS patients, but also to the inability of the bone marrow to reconstitute a functional pool of mature CD4+ T-cells. It is also possible that haematopoietic progenitor cells committed to the T-lymphoid lineage are impaired by HIV in their differential pathway within the thymus (Bonyhadi et al, 1993). Infection of megakaryocytes could result in underproduction of platelets and possibly represents a major pathogenetic mechanism of HIV-related thrombocytopenia. Infection of monocytes and T-lymphocytes leads in vitro and probably also in vivo to deranged cytokine production. In the first stages of the disease, increased cytokine production, consequent to a chronic immune activation, is probably responsible for the myelodysplastic/hyperplastic alterations observed at the bone marrow level. In more advanced stages of the disease, the general decline in immune function, the consequent imbalance in cytokine production, and the increase in viral burden, may contribute to dysregulated haematopoiesis and peripheral blood cytopenias.

Mechanisms of cytopenia in human immunodeficiency virus infection

Human immunodeficiency virus (HIV) infection often has effects on the hematopoietic system which can be distinguished from the concurrent effects of medications or opportunistic infections. Exactly how the virus mediates these effects remains uncertain, but both in vivo and in vitro studies have pointed up possible direct and indirect modes of hematopoietic suppression. Whether a significant fraction of CD34+ cells in vivo are infected with HIV remains controversial, but most studies using in situ polymerase chain reaction techniques would suggest not. Other more indirect modes of hematopoietic cell suppression such as production of autoantibodies, production of other humoral inhibitory factors, T-cell mediated suppression of hematopoiesis, or production of inhibitory or stimulatory cytokines may also be contributory. It is probable that several of these mechanisms may occur simultaneously, and an increased understanding of their role may lead to improved strategies to correct the cytopenias which often accompany HIV disease.

In vitro improvement of bone marrow-derived hematopoietic colony formation in HIV-positive patients by alpha-D-tocopherol and erythropoietin

The majority of patients with progressive HIV infection develop a severe hematopoietic failure which is aggravated by the hematotoxic effect of azidothymidine (AZT) treatment. Since it was shown in a mouse model that alpha-D-tocopherol (vitamin E derivative) antagonizes the inhibitory influence of AZT on the growth of burst-forming units-erythrocyte (BFU-E), it was the aim of this study to investigate whether alpha-D-tocopherol and high dosages of erythropoietin (EPO) increase the hematopoietic colony-forming capacity of bone marrow cells from patients with progressive HIV disease and especially if they reverse the inhibitory effects of AZT. The data demonstrate that tocopherol (1-100 mumol/l) significantly increases the growth of BFU-E and colony-forming units granulocyte-monocyte (CFU-GM) from HIV-infected patients. This stimulatory effect is dose-dependent (maximum at 30-100 mumol/l) and only occurs when the agent is present from the beginning of the cultures. EPO (5-10 U/ml) also augments the numbers of BFU-E from HIV-infected patients. Tocopherol equally ameliorates the growth of BFU-E and CFU-GM from the HIV-positive cohort in the presence of AZT (10-100 mumol/l). For healthy controls, no such increase was observed, either with tocopherol or with higher dosages of EPO. In conclusion, both tocopherol and EPO partially reverse the myelosuppressive action of AZT in HIV-positive patients.

Human immunodeficiency virus type 1 (HIV-1) and human hematopoietic progenitor cells

Besides a progressive depletion of CD4+ T-lymphocytes, other peripheral blood cytopenias, (granulocytopenia, anemia and thrombocytopenia) are frequently observed in HIV-1 seropositive individuals, especially in patients with overt AIDS. Various experimental evidences suggest that HIV-1 could play a direct role in the pathogenesis of HIV-1 related peripheral blood cytopenias, affecting the survival/proliferation capacity of hematopoietic progenitors. CD34+ human hematopoietic progenitors, however, are substantially not susceptible to HIV-1 infection either in vitro and in vivo and their defects seem rather related to an alteration of bone marrow and peripheral blood microenvironments due to the presence of soluble HIV-1 specific products.

The effects of human immunodeficiency virus infection on macrophage phagocytosis of Candida

The effects of infection by human immunodeficiency virus (HIV) on phagocytic function towards Candida pseudotropicalis were tested using monocytotropic and nonmonocytotropic HIV strains on peripheral blood monocytes. There were no differences in either quantitative phagocytic activity or efficacy between the two infected and control mock-infected monocytes. Immunofluorescence for cytoplasmic p24 antigen and in situ hybridization for detection of HIV-specific RNA sequences revealed that very few cells (10(-4)) exhibit productive infection. Occasional cells with active infection as defined by microscopically detectable fluorescence labelling contained phagocytized yeasts.

Decreased haematopoietic colony growth in long-term bone marrow cultures of HIV-positive patients

Deficiencies in bone marrow stromal cells, i.e. fibroblasts, macrophages, endothelial cells and adipocytes, are considered to play a pathophysiological role in HIV-associated haematopoietic failure. Long-term bone marrow cultures (LTBMC) enable the longitudinal investigation of haematopoietic progenitor cell and bone marrow stromal growth. Therefore, in this study, the haematopoietic colony growth of bone marrow from patients with severe HIV infection was compared to that from healthy controls in LTBMC. The total cumulated number of colony-forming units/granulocyte-macrophage (CFU-GM) was 6.7-fold higher (293.6% vs. 44.0%, p < 0.01), that of colony-forming units/granulocyte-erythrocyte-macrophage-megakaryocyte (CFU-GEMM) was 3.5-fold higher (28.7% vs 8.3%), and that of burst-forming units/erythrocyte (BFU-E) was 31.1-fold higher (68.4% vs 2.2%) than that from HIV-positive patients, respectively (colony number before LTBMC = 100%). In contrast, the cumulated cell number at the end of LTBMC from HIV-positive patients was not reduced (cell numbers in percent of initially seeded cells: HIV-positive 418.4%, HIV-negative 397.1%). The significantly reduced colony-forming capacity over a significantly shorter time span, without reduction in the absolute cell number, in LTBMC from patients with severe HIV-infection as compared to healthy controls, suggests that uncoupling between cell proliferation and differentiation is a pathophysiological mechanism in HIV-dependent haematopoietic failure.

Influence of human recombinant interferon-alpha and interferon-gamma on bone marrow progenitor cells of HIV-positive individuals

As a result of a pathophysiologically unexplainable bone marrow failure, most patients with progressive stages of human immunodeficiency virus (HIV) infection develop anemia, leukopenia, and thrombocytopenia. Besides the possibility of immune-mediated cytolysis or of direct viral infection of hemopoietic progenitor cells, the inhibitory influence of cytokines, for example interferon-alpha (IFN-alpha) and IFN-gamma, on hemopoiesis of HIV-infected patients might be considered as one parameter that contributes to myelosuppression. Therefore, progenitor cells from the bone marrow of HIV+ and HIV- persons were exposed to increasing concentrations of recombinant human IFN-alpha and IFN-gamma in methylcellulose assays. The colony formation of pluripotent (CFU-GEMM), erythroid (BFU-E), and granulocyte-macrophage (CFU-GM) progenitor cells was inhibited by both interferons. The 50% inhibitory doses (ID50) of IFN-alpha were 125.6 U/mL and 131.5 U/mL for BFU-E from HIV-infected persons and normal controls, respectively; the corresponding ID50 of IFN-alpha for CFU-GM growth was 1095.8 U/ml and above 3000 U/ml. When IFN-gamma was studied the ID50 was 341.7 and 2794.6 U/ml for BFU-E from HIV-infected and healthy individuals, respectively, while the ID50 for CFU-GM was above the highest dose levels in both groups (greater than 3000 U/ml). The ID50 for CFU-GEMM was below the lowest dose levels of IFN alpha and IFN gamma tested in both groups (less than 10 U/ml). The inhibitory effects could be specifically neutralized by monoclonal antibodies against IFN-alpha and IFN-gamma, thus confirming that the suppressive effects were due to the cytokines used.

Effect of recombinant human transforming growth factor beta and tumor necrosis factor alpha on bone marrow progenitor cells of HIV-infected persons

With progressive disease, the majority of patients with human immunodeficiency virus (HIV) infection develop bone marrow failure with anemia, leukopenia, and thrombocytopenia, the cause of which has not yet been clarified. Besides direct infection of bone marrow progenitor cells and immune-mediated cytolysis, the action of inhibitory cytokines, like transforming growth factor beta (TGF-beta) and tumor necrosis factor alpha (TNF-alpha), has to be discussed with regard to their pathophysiological role in HIV-induced bone marrow failure. Therefore, the influence of recombinant human TGF-beta and TNF-alpha on colony growth of pluripotent (CFU-GEMM), erythroid (BFU-E), and granulocyte-macrophage (CFU-GM) progenitor cells from the bone marrow of HIV-1-infected persons and normal controls was assessed in methylcellulose cultures. Both cytokines inhibited the colony formation of hematopoietic progenitor cells from HIV-positive persons. When added to unseparated bone marrow cells from HIV-infected persons and normal controls, the 50% inhibition (ID50) of BFU-E by TGF-beta occurred at 1.3 ng/ml and 3.7 ng/ml, respectively, while the ID50 of CFU-GM occurred at 15.5 ng/ml and 142.7 ng/ml. Concentrations of TNF-alpha, causing 50% inhibition of colony formation by bone marrow cells from HIV-infected or noninfected individuals were 6.3 U/ml and 17.0 U/ml for BFU-E, and 24.4 U/ml and greater than 3,000 U/ml for CFU-GM, respectively. The ID50 of the CFU-GEMM growth was below the lowest concentration of both cytokines tested. The suppressive effects were specifically abolished by antibodies against TGF-beta and TNF-alpha, thus confirming that the inhibitory activities were due to the cytokine preparation used.