Suppression of in vitro haematopoiesis following human immunodeficiency virus infection

Increased Risk of Anemia, Neutropenia, and Thrombocytopenia in People With Human Immunodeficiency Virus and Well-Controlled Viral Replication

BACKGROUND

Prior to the introduction of combination antiretroviral therapy (cART), cytopenias were common in people with human immunodeficiency virus (PWH), but it is unknown if well-controlled HIV infection is a risk factor for cytopenia. In this study we aimed to determine if HIV infection is an independent risk factor for anemia, neutropenia, lymphocytopenia, and thrombocytopenia.

METHODS

PWH with undetectable viral replication and absence of chronic hepatitis infection (n = 796) were recruited from the Copenhagen Comorbidity in HIV Infection (COCOMO) study and matched uninfected controls from the Copenhagen General Population Study (n = 2388). Hematology was analyzed in venous blood samples. Logistic regression analyses adjusted for age, sex, ethnicity, smoking status, alcohol, and high-sensitivity C-reactive protein were performed to determine possible associations between HIV and cytopenias.

RESULTS

PWH had a higher prevalence of anemia (6.9% vs 3.4%, P < .001), neutropenia (1.3% vs 0.2%, P < .001), and thrombocytopenia (5.5% vs 2.7%, P < .001) compared with uninfected controls. HIV was independently associated with anemia-adjusted odds ratio (aOR) of 2.0 (95% confidence interval [CI], 1.4-3.0); neutropenia aOR, 6.3 (95% CI, 2.0-19.6); and thrombocytopenia aOR, 2.7 (95% CI, 1.8-4.2). No association was found between HIV and lymphocytopenia.

CONCLUSIONS

Cytopenia is rare in people with well-controlled HIV, but HIV remains a risk factor for anemia, neutropenia, and thrombocytopenia and requires ongoing attention and monitoring.

HIV-1 infection depletes human CD34+CD38- hematopoietic progenitor cells via pDC-dependent mechanisms

Chronic human immunodeficiency virus-1 (HIV-1) infection in patients leads to multi-lineage hematopoietic abnormalities or pancytopenia. The deficiency in hematopoietic progenitor cells (HPCs) induced by HIV-1 infection has been proposed, but the relevant mechanisms are poorly understood. We report here that both human CD34+CD38- early and CD34+CD38+ intermediate HPCs were maintained in the bone marrow (BM) of humanized mice. Chronic HIV-1 infection preferentially depleted CD34+CD38- early HPCs in the BM and reduced their proliferation potential in vivo in both HIV-1-infected patients and humanized mice, while CD34+CD38+ intermediate HSCs were relatively unaffected. Strikingly, depletion of plasmacytoid dendritic cells (pDCs) prevented human CD34+CD38- early HPCs from HIV-1 infection-induced depletion and functional impairment and restored the gene expression profile of purified CD34+ HPCs in humanized mice. These findings suggest that pDCs contribute to the early hematopoietic suppression induced by chronic HIV-1 infection and provide a novel therapeutic target for the hematopoiesis suppression in HIV-1 patients.

HIV-1 infection of hematopoietic progenitor cells in vivo in humanized mice

HIV infection has been associated with defective hematopoiesis since the earliest days of the HIV/AIDS epidemic. Generation of all hematopoietic lineages suffers in the face of infection. The mechanisms by which HIV impairs normal blood cell development remain unclear, and direct infection of intermediate hematopoietic progenitors has not been established as a source of HIV-associated hematopoietic pathology. Here, we demonstrate infection of multiple subsets of highly purified intermediate hematopoietic progenitors by wild-type HIV both in vitro and in vivo. Although direct infection is clearly cytotoxic, we find that some infected progenitors can survive and harbor proviral DNA. We report intermediate hematopoietic progenitors to be a novel target of infection and their permissivity to infection increases with development. Further, the nonobese diabetic severe combined immunodeficiency common γ chain knockout-bone marrow-liver-thymus humanized mouse provides a unique model for studying the impact of HIV infection on bone marrow-based human hematopoiesis.

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.

Preferential depletion of CD2(low) plasmacytoid dendritic cells in HIV-infected subjects

Plasmacytoid dendritic cells (pDCs) are decreased in number and are functionally impaired in HIV act reasons for pDCs depletion are still unknown. It was recently reported that pDCs can be divided into two functionally distinct populations based on their CD2 expression level. To determine how the CD2(high) and CD2(low) populations are affected by HIV infection, we analyzed their frequencies in the peripheral blood of HIV-infected subjects and healthy controls. We found that the CD2(low) pDC subset was preferentially depleted in infected individuals. The frequency of CD2(low) pDCs correlated with the CD4(+) T-cell count but not with the plasma viral load. This finding furthers our understanding of the causes and consequences of pDC depletion during HIV infection.

Infection with Anaplasma phagocytophilum induces multilineage alterations in hematopoietic progenitor cells and peripheral blood cells

Infection with Anaplasma phagocytophilum, a gram-negative, lipopolysaccharide (LPS)-negative, obligate intracellular bacterium, results in multiple peripheral blood cytopenias. We hypothesized that infection with this organism would result in decreased bone marrow (BM) function and shifts in hematopoietic progenitor cells (HPCs) and lineage-committed cells in a well-established murine model of infection. HPCs and lineage-committed progenitors were enumerated in the BM and spleen during acute infection. BM cytokine production and BM CXCL12 expression were determined. Infection resulted in peripheral blood bicytopenia, marked decreases in the number of lineage-committed HPCs in the BM along with concurrent increases in the number of lineage-committed HPCs in the spleen, and a mixed, predominantly myelosuppressive BM cytokine environment. There was significant downregulation of CXCL12 in BM cells that may have been partially responsible for changes in HPC trafficking observed. Changes occurred in the absence of direct pathogen infection of BM cells. Hematopoietic lineage assessment demonstrated that there was loss of erythrocytes and B lymphocytes from the BM along with increased granulopoiesis. These changes were accompanied by splenomegaly due to lymphoid hyperplasia and increased hematopoiesis, most notably erythropoiesis. These changes largely mimic well-described inflammation and endotoxin-mediated effects on the BM and spleen; however, the numbers of peripheral blood neutrophils appear to be independently modulated as granulocytic hyperplasia does not result in neutrophilia. Our findings highlight a well-conserved series of events that we demonstrate can be instigated by an LPS-negative pathogen in the absence of an endotoxin-mediated acute proinflammatory response.

Epidemiology of thrombocytopenia in HIV inlection

Thrombocytopenia is a known complication of human immunodeficiency virus Type-1 (HIV-1) infection, and more data need to be collected on its frequency, severity, and clinical sequelae. We determined the frequency of thrombocytopenia and its relationship to other HIV infection characteristics from a review of records of 1004 HIV-infected patients attending two outpatient clinics in Washington, D.C. The self-reported sources of HIV-1 exposure were male homosexual activity (68%), bisexual activity (10%), heterosexual activity (6%), and intravenous drug use (15%). Fifty-nine percent of the individuals were white, 37% were black and 94% were male. Fifteen percent had AIDS. Thrombocytopenia occurred more frequently in subjects with AIDS (21.2%) than in HIV-infected individuals who did not fit clinical criteria for AIDS (9.2%) (p less than 0.001). Patients with few CD4-positive cells and an advanced stage of disease were more likely to have low platelet counts: 30% with an absolute CD4 cell count lower than 200/mm3 vs 8% with CD4 counts between 200 and 500 (p less than 0.00001), and 18.5% with Stage IV disease compared to 7.6% in Stage II (p less than 0.001) had platelet counts less than 150,000/mm3. Thrombocytopenia was more frequent in white males and older subjects. Although subjects infected by heterosexual exposure had a lower frequency of thrombocytopenia, intravenous drug users and homosexual men exhibited similar frequencies of thrombocytopenia. Of all subjects with platelet counts less than 50,000/mm3, 40% reported bleeding and 1 died of an intracranial hemorrhage. Thrombocytopenia occurs frequently in HIV-infected people, primarily in those with AIDS, low CD4 cell numbers, and advanced stages of diseases.

Characterization of quantitative and functional innate immune parameters in HIV-1-infected Colombian children receiving stable highly active antiretroviral therapy

BACKGROUND

The immunological benefits of highly active antiretroviral therapy (HAART) in HIV-1-infected children include reconstitution of CD4+ T-cell count and functional activity. The effect of HAART on innate immune cells has not been well established.

AIM

To characterize innate immune responses in HAART-treated HIV-1-infected children.

PATIENTS AND METHODS

23 HIV-1-infected children on stable HAART and 23 uninfected children were evaluated. The frequency of innate immune cells in peripheral blood was determined by flow cytometry and functional activity was evaluated using Toll-like receptor agonists.

RESULTS

Compared with uninfected children, HAART-treated HIV-1-infected children exhibited a significant decrease in the frequency of plasmacytoid dendritic cells and natural killer and T-cell receptor (TCR)-invariant CD1d-restricted T cells. This deficiency of innate immune cells was observed mainly in children with detectable viral load. We also compared the magnitude of the quantitative restoration of those cells comparing HIV-1-infected children with HIV-1-infected adults and found a partial effect of HAART on immune restoration that was independent of age. In both pediatric and adult subjects Toll-like receptor agonists induced expression of costimulatory molecules and production of proinflammatory cytokines by dendritic cells. Peripheral blood mononuclear cells of HIV-1-infected children produced significantly reduced amounts of interferon-alpha compared with uninfected children.

CONCLUSIONS

HAART administration to HIV-1-infected children does not lead to a complete increase of circulating innate immune cells, particularly in patients with incomplete suppression of HIV.

The treatment of HIV associated thrombocytopenia in haemophiliacs

HIV associated thrombocytopenia occurs in 5-10% of asymptomatic individuals, and 25-45% of people with AIDS. A variety of treatments are available but the inherited bleeding disorder in addition to the thrombocytopenia makes management in haemophiliacs a special problem. The management of this double coagulopathy is described in seven patients. IV gammaglobulin and steroids were useful only in the short term; zidovudine produced a good response, could be taken orally, had anti-HIV activity and was well tolerated in asymptomatic HIV positive patients. Interferon was an alternative when zidovudine was ineffective or produced intolerable side-effects. Splenectomy was considered only after failure of other treatments because of the increased risks of bleeding.

Early bone marrow hematopoietic defect in simian/human immunodeficiency virus C2/1-infected macaques and relevance to advance of disease

To clarify hematological abnormalities following infection with human immunodeficiency virus (HIV), we examined the hematopoietic capability of bone marrow by using cynomolgus monkeys infected with pathogenic simian/human immunodeficiency virus (SHIV) strain C2/1, an animal model of HIV infection. The relationship between the progress of the infection and the CD4/CD8 ratio of T lymphocytes or the amount of SHIV C2/1 viral load in the peripheral blood was also investigated. A colony assay was performed to assess the hematopoietic capability of bone marrow stem cells during the early and advanced phases of the infection. Colonies of granulocytes-macrophages (GM) were examined by PCR for the presence of the SIVmac239 gag region to reveal direct viral infection. There was a remarkable decrease in the CFU-GM growth on days 1 and 3 postinoculation, followed by recovery on day 56. During the more advanced stage, the CFU-GM growth decreased again. There was minimal evidence of direct viral infection of pooled cultured CFU-GM despite the continuously low CD4/CD8 ratios. These results indicate that the decrease in colony formation by bone marrow stem cells is reversible and fluctuates with the advance of the disease. This decrease was not due to direct viral infection of CFU-GM. Our data may support the concept that, in the early phase, production of inhibitory factors or deficiency of a stimulatory cytokine is responsible for some of the bone marrow defects described in the SHIV C2/1 model.

Basic fibroblast growth factor (bFGF) and its receptor expression (bek and flg) In bone marrow stroma of murine AIDS

Murine acquired immunodeficiency disease (MAIDS) induced by LPBM5 MuLV is characterized by a late-stage lymphoma and hematopoietic cytopenias similar to those observed in human AIDS. The pathogenesis of MAIDS-related lymphoma/cytopenia is unknown but it has been postulated to involve a defective marrow microenvironment or stroma. The basic Fibroblast Growth Factor (bFGF) of stromal origin is an important stimulator for hematopoietic progenitors of several lineages. Long-term bone marrow cultures (LTBMCs) were established and pure stromal cell cultures were used for in vitro infection hematopoietic reconstitution studies. Reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze bFGF gene expression in stromal cells derived from either viral-infected marrow or uninfected marrow. RT-PCR analysis showed a 40% reduction in the expression of bFGF transcript expression from viral-infected stromal cells, however, the levels of bek and flg bFGF receptors remained unchanged indicating virus-infection only inhibited bFGF gene expression in stromal cells. Viral infection was associated with a progressive decrease in bFGF transcript expression 35% of control at day 7, 50% of control at day 14 and 60% of control at day 21 compared to the mock-infected cultures. In addition, for bek and flg the transcript expression in, in vitro-infected primary cultures were comparable to the mock-infected cultures and remained essentially unchanged throughout culture period. Western blot analysis revealed viral-infected stromal cells produced a 45% decrease in bFGF protein production. Reduction of bFGF protein was confirmed by indirect immunofluorescent staining. We report MuLV infection reduces bFGF transcript expression but not its surface-receptors (bek and flg) in infected stromal cells. Impaired hematopoiesis consistently exhibited from MuLV-infected stromal cultures was restored by exogenous bFGF; therefore, bFGF was responsible in restoration of normal marrow stromal support function. These results suggest a role for bFGF deficiency in the pathogenesis of MAIDS-related marrow failure.

Simian Immunodeficiency Virus Infection of Hematopoietic Stem Cells and Bone Marrow Stromal Cells

Using a well-characterized fetal rhesus monkey model, simian immunodeficiency virus (SIV) infection of hematopoietic stem cells (HSCs) and stromal cells was investigated to characterize bone marrow abnormalities in SIV-infected animals in vivo. Fetuses (n = 4) were inoculated in utero with pathogenic SIVmac251 using established techniques at 65 days; gestation (early second trimester), then harvested for tissues 65 days after inoculation (late third trimester), and compared with findings from controls of a comparable age (n = 11). Sorted bone marrow CD34CD38, CD34CD38, and marrow stromal cells were analyzed for the SIV genome. Results indicate that CD34CD38 HSCs were not infected, whereas the SIV genome was detected in the CD34CD38 hematopoietic cell population by PCR analysis. The SIV proviral sequence was not detected in stromal cells from SIV-infected fetuses, although SIVmac251 was found to readily infect these cells when assessed in vitro. Flow cytometric analysis revealed that stromal cells express low levels (1 in 600 total cells) of CD4 and CCR5 viral receptors, whereas CXCR4 expression was not observed. These data suggest the following: (1) SIV infection of HSCs requires some degree of differentiation for viral entry similar to findings for humans infected with HIV type 1, and (2) SIV can infect bone marrow stromal cells that express CD4 and CCR5 in vitro, but infected stromal cells are not readily found in vivo.

Highly active antiretroviral therapy corrects hematopoiesis in HIV-1 infected patients: interest for peripheral blood stem cell-based gene therapy

OBJECTIVES

To study, in asymptomatic HIV-1-infected (HIV+) patients, whether peripheral blood hematopoietic progenitor/stem cells (PBPC) mobilized by granulocyte colony stimulating factor (G-CSF), can be used as a source of cells for retroviral gene therapy.

DESIGN

PBPC from two groups of HIV+ patients (treated or untreated by highly active antiretroviral therapy) and from seronegative donors were mobilized with G-CSF.

METHODS

PBPC collected by leukapheresis were enriched for CD34 cells, immunophenotypically and functionally characterized, cultured and infected with retroviral vectors. HIV proviral integration was studied on fresh and cultured cells.

RESULTS

G-CSF moderately and transiently increased the viral load in untreated patients only, and induced in both groups of HIV+ patients mobilization of percentages and numbers of CD34 cells comparable to those of seronegative volunteers. The most immature CD34 cell subset, the clonogenic progenitor and long-term culture initiating cells were significantly decreased in leukapheresis products and CD34-enriched fractions from untreated HIV+ patients but not in those from treated HIV+ patients. Cell cycle activation and growth factor responses of CD34 cells from both groups of HIV+ patients were not different from those of the control group. Culture and retroviral infection of CD34 cells from HIV+ patients did not enhance HIV replication, and yielded transduction levels similar to those obtained using CD34 cells from seronegative donors.

CONCLUSIONS

G-CSF-mobilized PBPC can be safely used for HIV retroviral gene therapy in asymptomatic treated patients while highly active antiretroviral therapy would control the G-CSF-induced increase in viral load and correct the defective hematopoiesis observed in untreated patients, without inhibiting the retroviral transduction of PBPC.

Recovery of hematopoietic activity in bone marrow from human immunodeficiency virus type 1-infected patients during highly active antiretroviral therapy

The mechanisms responsible for the hematopoietic failure in human immunodeficiency virus type 1 (HIV-1)-infected patients are still unknown. Several findings indicate that the in vitro proliferative potential of precursor cells from AIDS patients is reduced. The changes seen in bone marrow (BM) morphology and the defective BM functions associated with cytopenias have both been proposed as potential explanations. In patients treated with highly active antiretroviral therapy (HAART) an immune reconstitution associated with increased whole blood cell counts has been described. We have investigated the effects of HAART on the number of colony-forming cells (CFCs) and long-term culture-initiating cells (LTC-ICs), using long-term BM cell cultures (LTBMC) in a group of subjects with HIV-1 infection enrolled in an open study to evaluate the mechanisms of immune reconstitution during HAART. In each patient, the increase in colony growth was homogeneous, regardless of the type of hematopoietic progenitor cells assayed; in four subjects an increase in the most primitive progenitor cells (LTC-ICs) was observed. These findings were associated with the in vivo data showing increased numbers of BM mononuclear cells (BMMCs) after HAART and with a rise in peripheral CD4(+) T cell counts and decreased levels of plasma HIV-1 RNA. A decreased number of hematopoietic progenitor cells and/or a defective modulation of progenitor cell growth might be the cause of the hematological abnormalities in AIDS patients. Controlling HIV-1 replication by HAART could determine a restoration of stem cell activity, probably because of the suppression of factors that inhibit normal hematopoiesis.

Chemotherapy consisting of doxorubicin, bleomycin, vinblastine, and dacarbazine with granulocyte-colony-stimulating factor in HIV-infected patients with newly diagnosed Hodgkin's disease: a prospective, multi-institutional AIDS clinical trials group study (ACTG 149)

To ascertain the results of standard ABVD chemotherapy (doxorubicin, bleomycin, vinblastine, dacarbazine) in HIV-infected patients with newly diagnosed Hodgkin's disease (HD), a nonrandomized, prospective, multiinstitutional clinical trial was conducted by the AIDS Clinical Trials Group (ACTG), in HIV-infected patients with Hodgkin's disease. All patients received the standard ABVD regimen, with granulocyte-colony-stimulating factor (G-CSF). Antiretroviral therapy was not used. Between May, 1992 and August, 1996, 21 patients were added to the study and treated. The median CD4 count was 113 cells/mm3, and 29% had a history of a clinical AIDS-defining condition before diagnosis of HD. Systemic "B" symptoms were present in 90% at diagnosis. Stage IV HD was present in 67%, with bone marrow involvement in 12 (57%). Nodular sclerosis HD was present in 38%, with mixed cellular disease in 31%. Among all patients entered and treated, complete remission (CR) was attained in 9 (43%; 90% confidence interval [CI], 24%-63%), whereas partial response occurred in 4 (19%), leading to an overall objective response rate of 62% (90% CI, 42%-79%). Despite routine use of G-CSF, 10 patients (47.6%) experienced life-threatening neutropenia, with absolute neutrophil counts <500 cells/mm3. In all, nine opportunistic infections occurred in 6 patients (29%) during the study or shortly thereafter. Median survival was 1.5 years. Results of this study suggest that alternative treatment strategies should be explored, including use of chemotherapy together with antiretroviral therapy.

Pathogenesis of HIV-1 infection within bone marrow cells

Mononuclear phagocytic cells and CD4+ T lymphocytes represent the major targets for infection by HIV-1 in vivo. The most severe pathogenic features associated with HIV-1 infection can be attributed to malfunction or premature death of these cells that are of hematopoietic origin. Patients with acquired immunodeficiency syndrome (AIDS), suffer from many hematologic disorders, particularly those persons with long-term infection of HIV-1. These disorders include anemia, lymphocytopenia, thrombocytopenia and neutropenia. The mechanisms that lead to the induction of these disorders are multi-factorial. However, sufficient evidence has accumulated which suggests that HIV-1 infection of cells within the microenvironment of the bone marrow can lead to the induction of hematopoietic deficits. Most studies indicate that marrow-derived hematopoietic stem cells cannot be infected by HIV-1 until they undergo modest differentiation in order to express the appropriate receptors to enable virus entry and subsequent replication. Some cells within the mixed environment of the marrow stroma appear to support HIV-1 replication however. These cells include marrow microvascular endothelial cells, sometimes referred to as blanket cells, stromal fibroblasts, as well as mononuclear phagocytes. Our recent experiments suggest that the HIV-1 accessory protein, Vpr, plays some role in the activation of marrow-derived mononuclear phagocytes which appears to result in premature phagocytosis of non-adherent marrow cells present in the in vitro cultures. This phenomenon could account, in part, for the induction of cytopenias that are typical of individuals infected by HIV-1.

Neutropenia, neutrophil dysfunction, and bacterial infection in patients with human immunodeficiency virus disease: the role of granulocyte colony-stimulating factor

Neutropenia frequently complicates infection due to human immunodeficiency virus (HIV). The etiology of neutropenia in this setting includes bone marrow infection or infiltration, myelosuppressive therapies, the presence of antibodies to HIV, and accelerated apoptosis. Protection against microbial invaders by neutrophils is further compromised by impaired chemotaxis and phagocytosis, production of toxic oxygen species, and expression of cellular adhesion molecules. Neutropenia is a significant risk factor for bacterial infection in HIV-infected patients. Endogenous cytokines, such as granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor, regulate neutrophil count and function. Treatment with recombinant human methionyl G-CSF (filgrastim) has lessened neutropenia in patients with HIV infection. Clinical trials have shown that the incidence of bacterial infections and the number of consequent days of hospitalization for HIV-infected patients receiving filgrastim therapy are lower. Filgrastim treatment also allows administration of larger doses of myelosuppressive agents.

Gastrointestinal epithelium is an early extrathymic site for increased prevalence of CD34(+) progenitor cells in contrast to the thymus during primary simian immunodeficiency virus infection

The objective of this study was to determine the effects of primary simian immunodeficiency virus (SIV) infection on the prevalence and phenotype of progenitor cells present in the gastrointestinal epithelia of SIV-infected rhesus macaques, a primate model for human immunodeficiency virus pathogenesis. The gastrointestinal epithelium was residence to progenitor cells expressing CD34 antigen, a subset of which also coexpressed Thy-1 and c-kit receptors, suggesting that the CD34(+) population in the intestine comprised a subpopulation of primitive precursors. Following experimental SIVmac251 infection, an early increase in the proportions of CD34(+) Thy-1(+) and CD34(+) c-kit+ progenitor cells was observed in the gastrointestinal epithelium. In contrast, the proportion of CD34(+) cells in the thymus declined during primary SIV infection, which was characterized by a decrease in the frequency of CD34(+) Thy-1(+) progenitor cells. A severe depletion in the frequency of CD4-committed CD34(+) progenitors was observed in the gastrointestinal epithelium 2 weeks after SIV infection which persisted even 4 weeks after infection. A coincident increase in the frequency of CD8- committed CD34(+) progenitor cells was observed during primary SIV infection. These results indicate that in contrast to the primary lymphoid organs such as the thymus, the gastrointestinal epithelium may be an early extrathymic site for the increased prevalence of both primitive and committed CD34(+) progenitor cells. The gastrointestinal epithelium may potentially play an important role in maintaining T-cell homeostasis in the intestinal mucosa during primary SIV infection.

Suppression of rat bone marrow cells by Friend murine leukemia virus envelope proteins

In a retroviral rat model, we have investigated the nontransforming effects of murine leukemia virus FB29 on the bone marrow. Upon intraperitoneal inoculation with murine leukemia virus FB29 of either neonatal or adult rats, bone marrow cells became massively infected within the first 12 days postinoculation. In neonatally inoculated rats, a persistent productive bone marrow infection was established, whereas in rats inoculated as adults, no infected bone marrow cells could be detected beyond 12 days postinoculation. Retroviral infection was most likely cleared by an antiviral immune response (Hein et al., 1995, Virology 211, 408-417). Exposure to virus irreversibly decreased numbers of bone marrow cells staining with monoclonal antibody OX7 by 10-30%. Reduction of OX7+ bone marrow cells by 20% was also observed in vitro, after bone marrow cells from uninfected adult rats had been co-incubated with virus. FB29-envelope proteins were sufficient alone to reduce numbers of OX7+ bone marrow cells, both in vivo and in vitro. According to results on incorporation of propidium iodide, decreased numbers of OX7+ cells were due to cell death. By flow cytometric analyses OX7+ bone marrow cells as well as monocytes/macrophages were identified to be major target cells for infection with FB29 within the bone marrow. Thus, the mechanism(s) responsible for death of OX7+ bone marrow cells might be due to direct toxicity of viral envelope proteins and/or to interactions of viral envelope proteins with cells of the monocytic lineage.

Neither Human Immunodeficiency Virus-1 (HIV-1) nor HIV-2 Infects Most-Primitive Human Hematopoietic Stem Cells as Assessed in Long-Term Bone Marrow Cultures

Attempts to clarify the pathophysiology of human immunodeficiency virus (HIV)-mediated bone marrow (BM) dysfunction have yielded inconsistent results regarding the susceptibility of BM progenitors to the viral infection. To specifically address this question, we exposed highly purified subpopulations of human BM progenitor cells to various HIV-1 and HIV-2 strains and assessed (pro)viral gene presence and expression in more-committed (CD34+CD38+) as well as most-primitive (CD34+CD38−) cells in long-term BM cultures. Quantitative analysis of long-term culture-initiating cells (LTCIC) failed to demonstrate adverse effects of exposing hematopoietic stem cells to HIV. Our results show that HIV-2, similar to HIV-1, does not infect hematopoietic stem cells in vitro with any significant frequency and infected cells are not present within LTCICs. Cytofluorometric analysis of CD34+ cells for surface molecules that facilitate HIV entry was consistent with the functional assay in that expression of virus receptors was predominantly on the more-committed subsets of BM progenitors. The failure to detect productive or latent HIV in the most-primitive human BM progenitor and stem cells has important implications for future therapeutic strategies, including those dealing with transduction of these cells with protective genes as a treatment modality for AIDS.

Neither Human Immunodeficiency Virus-1 (HIV-1) nor HIV-2 Infects Most-Primitive Human Hematopoietic Stem Cells as Assessed in Long-Term Bone Marrow Cultures

Attempts to clarify the pathophysiology of human immunodeficiency virus (HIV)-mediated bone marrow (BM) dysfunction have yielded inconsistent results regarding the susceptibility of BM progenitors to the viral infection. To specifically address this question, we exposed highly purified subpopulations of human BM progenitor cells to various HIV-1 and HIV-2 strains and assessed (pro)viral gene presence and expression in more-committed (CD34+CD38+) as well as most-primitive (CD34+CD38−) cells in long-term BM cultures. Quantitative analysis of long-term culture-initiating cells (LTCIC) failed to demonstrate adverse effects of exposing hematopoietic stem cells to HIV. Our results show that HIV-2, similar to HIV-1, does not infect hematopoietic stem cells in vitro with any significant frequency and infected cells are not present within LTCICs. Cytofluorometric analysis of CD34+ cells for surface molecules that facilitate HIV entry was consistent with the functional assay in that expression of virus receptors was predominantly on the more-committed subsets of BM progenitors. The failure to detect productive or latent HIV in the most-primitive human BM progenitor and stem cells has important implications for future therapeutic strategies, including those dealing with transduction of these cells with protective genes as a treatment modality for AIDS.

Filgrastim prevents severe neutropenia and reduces infective morbidity in patients with advanced HIV infection: results of a randomized, multicenter, controlled trial. G-CSF 930101 Study Group

OBJECTIVE

To assess the effect of filgrastim treatment on the incidence of severe neutropenia in patients with advanced HIV infection, and the effect of initial filgrastim treatment on prevention of infectious morbidity.

DESIGN

Randomized, controlled, open-label, multicenter study.

SETTING

Outpatient centers and physician offices.

PATIENTS

Men and women aged > 13 years, who were HIV antibody-positive, and had a CD4 cell count < 200 x 10(6)/l, absolute neutrophil count (ANC) 0.75-1.0 x 10(9)/l, and platelet count > or = 50 x 10(9)/l within 7 days of randomization were eligible. Two hundred and fifty-eight patients entered and 201 completed the study.

INTERVENTION

Daily filgrastim (starting at 1 microg/kg daily, adjusted up to 10 microg/kg daily) or intermittent filgrastim (starting at 300 microg daily one to three times per week to a maximum of 600 microg daily 7 days weekly) was administered to maintain an ANC between 2 and 10 x 10(9)/l. Patients in the control group received filgrastim if severe neutropenia developed.

MAIN OUTCOME MEASURES

Incidence of severe neutropenia (ANC < 0.5 x 10(9)/l) or death, incidence of bacterial and fungal infections, duration of hospitalization and intravenous antibacterial use, and safety.

RESULTS

The primary endpoint of severe neutropenia or death was less frequent in patients who received daily (12.8%) or intermittent (8.2%) filgrastim compared with control patients (34.1%; P<0.002 and P<0.0001 for comparison with daily and intermittent groups, respectively). Filgrastim-treated patients developed 31% fewer bacterial infections and 54% fewer severe bacterial infections than control patients, required 26% less hospital days including 45% fewer hospital days for bacterial infections, and needed 28% fewer days of intravenous antibacterials. Filgrastim was not associated with an increase in HIV-1 plasma RNA level in a subset of patients in whom this was measured or any new or unexpected adverse events.

CONCLUSION

Filgrastim was safe and effective in preventing severe neutropenia in patients with advanced HIV infection, and may reduce the incidence and duration of bacterial infections, incidence of severe bacterial infections, duration of hospital days for infections, and days of intravenous antibacterial agents.

Secondary colony formation after long-term bone marrow culture using peripheral blood and bone marrow of HIV-infected patients

OBJECTIVE

To determine if defective bone marrow function in HIV infection is associated with decreased numbers of progenitor cells or defective stromal cell function.

DESIGN

Defective bone marrow function may in part be responsible for the cytopenias so frequently seen in patients with AIDS. Although a number of investigators have reported impaired growth of committed hematopoietic progenitor cells in HIV-1-infected patients, few studies have examined the most primitive hematopoietic stem cells. Our study was designed to determine the function and quality of the most immature hematopoietic progenitor and stem cells in the peripheral blood and bone marrow of HIV-1-infected patients and to assess stromal cell function.

METHODS

For quantification of these cells we used a modified long-term culture-initiating cell (LTCIC) assay in which the number of secondary colony-forming cells after 5 weeks of stromal culture served as a measure of LTCIC. Stromal cells from normal controls and HIV-1-infected patients were used for cross-matching experiments. Normal CD34+ cells or those derived from HIV-infected patients were plated and colony growth assessed.

RESULTS

We found that HIV-1-infected patients had a mean of 0.8 secondary colony-forming cells/10(5) peripheral blood mononuclear cells (PBMC), whereas normal controls showed 1.2 secondary colony-forming cells/10(5) PBMC (P = not significant) after long-term culture. Asymptomatic patients showed well preserved numbers of secondary colony-forming cells after long-term culture of PBMC, but a significant reduction was seen in patients with a history of opportunistic infections (P < 0.01), low CD4+ cell count (< 200 x 10(6)/l; P < 0.05), or leukopenia (P < 0.05). Decreased numbers of secondary colony-forming cells have also been found in bone marrow of HIV-1-infected patients with advanced disease. When normal CD34+ cells were cultured on stromal layers from bone marrow of HIV-1-infected patients or normal controls, no differences in the numbers of surviving progenitor cells were found.

CONCLUSIONS

Our data indicate that the hematopoietic defect in HIV-1 infection involves the most immature hematopoietic cells and becomes evident in advanced disease. Stromal function of HIV-infected patients appears normal.

Suppression of Megakaryocyte Colony Growth by Plasma From Foals Infected With Equine Infectious Anemia Virus

Foals infected with equine infectious anemia virus become thrombocytopenic 7 to 20 days after virus inoculation, and within a few days following the onset of detectable viremia. The thrombocytopenia is associated with suppression of platelet production. Possible mediators of suppression of thrombopoiesis include tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β), cytokines that are released during inflammation. To assess effects of plasma or serum from infected foals on megakaryocyte (MK) growth and maturation in vitro, equine low-density bone marrow cells were cultured for clonogenic and ploidy assays. Neutralizing antibodies to TNF-α and TGF-β were added to cultures to determine the contribution of these cytokines to suppression of thrombopoiesis. Plasma from the immediately pre-thrombocytopenia (Pre-Tp) period significantly reduced MK colony numbers. This suppression was partially reversed upon antibody neutralization of plasma TNF-α, TGF-β, or both. There were no differences in ploidy distribution of MK grown in the presence of preinfection serum compared with those grown in the presence of Pre-Tp serum. These results indicate that TNF-α and TGF-β may contribute to suppression of MK proliferation and represent likely factors in the pathogenesis of thrombocytopenia.

Suppression of Megakaryocyte Colony Growth by Plasma From Foals Infected With Equine Infectious Anemia Virus

Foals infected with equine infectious anemia virus become thrombocytopenic 7 to 20 days after virus inoculation, and within a few days following the onset of detectable viremia. The thrombocytopenia is associated with suppression of platelet production. Possible mediators of suppression of thrombopoiesis include tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β), cytokines that are released during inflammation. To assess effects of plasma or serum from infected foals on megakaryocyte (MK) growth and maturation in vitro, equine low-density bone marrow cells were cultured for clonogenic and ploidy assays. Neutralizing antibodies to TNF-α and TGF-β were added to cultures to determine the contribution of these cytokines to suppression of thrombopoiesis. Plasma from the immediately pre-thrombocytopenia (Pre-Tp) period significantly reduced MK colony numbers. This suppression was partially reversed upon antibody neutralization of plasma TNF-α, TGF-β, or both. There were no differences in ploidy distribution of MK grown in the presence of preinfection serum compared with those grown in the presence of Pre-Tp serum. These results indicate that TNF-α and TGF-β may contribute to suppression of MK proliferation and represent likely factors in the pathogenesis of thrombocytopenia.

Infection of Human Marrow Stroma by Human Immunodeficiency Virus-1 (HIV-1) Is Both Required and Sufficient for HIV-1–Induced Hematopoietic Suppression In Vitro: Demonstration by Gene Modification of Primary Human Stroma

Patients with human immunodeficiency virus-1 (HIV-1) infection often present with bone marrow (BM) failure that may affect all hematopoietic lineages. It is presently unclear whether this failure reflects a direct viral impairment of the CD34+ hematopoietic progenitor cells or whether the virus affects the BM microenvironment. To study the effects of HIV-1 on the BM microenvironment, we examined the stromal cell monolayers in long-term BM culture (LTBMC), which are the in vitro equivalent of the hematopoietic microenvironment. We assessed the hematopoietic support function (HSF ) of human stromal layers by determining the cellular proliferation and colony-forming ability of hematopoietic progenitors from BM cells grown on the stromal layers. We show that the HSF is reduced by in vitro infection of the human stromal cell layer by a monocytotropic isolate of HIV-1 (JR-FL). There is no loss of HSF when the stromal cell layer is resistant to HIV-1 replication, either using murine stromal cell layers that are innately resistant to HIV-1 infection or using human stromal cells genetically modified to express a gene that inhibits HIV-1 replication (an RRE decoy). Decreased HSF was seen using either human or murine hematopoietic cells, if the stromal cells were human cells that were susceptible to HIV-1 infection. These in vitro studies implicate HIV-1 replication in the stroma as the essential component causing decreased hematopoietic cell production in HIV-1 infection.

Severity of AIDS and the response to EPO in uremia

To determine the factors that govern their response to erythropoietin (EPO), we conducted a cross-sectional study of all patients in four outpatient hemodialysis facilities in Brooklyn, NY, who had end-stage renal disease (ESRD) and human immunodeficiency virus (HIV) infection and were receiving recombinant EPO. We also compared the hematocrit and EPO requirements of these patients to those of a control group of hemodialysis patients without HIV infection. We documented known duration of HIV infection, and total CD4 count was measured once. In both groups, hematocrit was measured weekly for 5 weeks and a mean value calculated for each subject. Transferrin saturation was measured twice and a mean value calculated for each subject. Intensity of hemodialysis was assessed by measuring both percent reduction of urea and serum albumin concentration twice; mean values were calculated for each subject. Twenty-nine (88%) of 33 study subjects had acquired immunodeficiency syndrome. Mean known duration of HIV infection was 49 +/- 32.5 months (median, 48 months), and mean total CD4 count was 143 +/- 152.4 cells/mm3 (median, 72 cells/mm3). Mean hematocrit in the study subjects was 27.4% +/- 4.7% compared with 27.6% +/- 3.7% in the controls (P = 0.69). Mean thrice-weekly EPO dose was higher in the study subjects (90 +/- 52 U/kg body weight) than in the controls (62 +/- 36 U/Kg body weight) (P = 0.001). Among the study subjects, hematocrit had direct univariate correlations with serum albumin concentration (r = 0.43; P = 0.02), transferrin saturation (r = 0.4; P = 0.03), and percent reduction of urea (r = 0.4; P = 0.02), but not with total CD4 count (r = -0.05; P = 0.8) or known duration of HIV infection (r = -0.11; P = 0.55). There was an inverse correlation between hematocrit and dose of EPO (r = -0.5; P = 0.003). Multiple regression analysis showed that transferrin saturation (P = 0.01) and percent reduction of urea (P = 0.003) had direct correlations with hematocrit after adjustment for other factors. There was an inverse relationship between hematocrit and dose of EPO (P = 0.0006). We conclude that in patients with ESRD and HIV infection receiving hemodialysis, the response to EPO (hematocrit) is modulated by the dose of EPO, quantity of hemodialysis, and transferrin saturation, but not by the severity of HIV disease. Hemodialysis patients infected with HIV receive a higher dose of EPO than those without HIV infection.

Virus-induced transient bone marrow aplasia: major role of interferon-alpha/beta during acute infection with the noncytopathic lymphocytic choriomeningitis virus

The hematologic consequences of infection with the noncytopathic lymphocytic choriomeningitis virus (LCMV) were studied in wild-type mice with inherent variations in their interferon (IFN)-alpha/beta responder ability and in mutant mice lacking alpha/beta (IFN-alpha/beta R0/0) or gamma IFN (IFN-gamma R0/0) receptors. During the first week of infection, wild type mice demonstrated a transient pancytopenia. Within a given genetic background, the extent of the blood cell abnormalities did not correlate with the virulence of the LCMV isolate but variations were detected between different mouse strains: they were found to depend on their IFN-alpha/beta responder phenotype. Whereas IFN-gamma R0/0 mice were comparable to wild-type mice, IFN-alpha/beta R0/0 mice exhibited unchanged peripheral blood values during acute LCMV infection. In parallel, the bone marrow (BM) cellularity, the pluripotential and committed progenitor compartments were up to 30-fold reduced in wild type and IFN-gamma R0/0, but remained unchanged in IFN-alpha/beta R0/0 mice. Viral titers in BM 3 d after LCMV infection were similar in these mice, but antigen localization was different. Viral antigen was predominantly confined to stromal BM in normal mice and IFN-gamma R0/0 knockouts, whereas, in IFN-alpha/beta R0/0 mice, LCMV was detected in > 90% of megakaryocytes and 10-15% of myeloid precursors, but not in erythroblasts Although IFN-alpha/beta efficiently prevented viral replication in potentially susceptible hematopoietic cells, even in overwhelming LCMV infection, unlimited virus multiplication in platelet and myeloid precursors in IFN-alpha/beta R0/0 mice did not interfere with the number of circulating blood cells. Natural killer (NK) cell expansion and activity in the BM was comparable on day 3 after infection in mutant and control mice. Adaptive immune responses did not play a major role because comparable kinetics of LCMV-induced pancytopenia and transient depletion of the pluripotential and committed progenitor compartments were observed in CD8(0/0) and CD4(0/0) mice, in mice depleted of NK cells, in lpr mice, and in perforin-deficient (P0/0) mice lacking lytic NK cells. Thus, the reversible depression of hematopoiesis during early LCMV infection was not mediated by LCMV-WE-specific cytotoxic T lymphocyte, cytolysis, or secreted IFN-gamma from virally induced NK cells but was a direct effect of IFN-alpha/beta.

Effect of HIV type 1 Tat protein on butyric acid-induced differentiation in a hematopoietic progenitor cell line

The trans-activator protein (Tat) of HIV-1 plays an important role in viral pathogenesis. Since Tat has been shown to alter expression of a number of host cellular genes, we have investigated the role of Tat in modulating gene expression and differentiation in hematopoietic progenitor cells. Tat protein was introduced in K562 cells, a human hematopoietic progenitor cell line, by either scrape-loading onto HeLa (HL)-tat cells or direct electroporation of an affinity-purified glutathione S-transferase (GST)-Tat fusion protein. Under these conditions, butyric acid-induced hemoglobin production in K562 cells was suppressed by 65 and 52%, respectively. However, coculturing with wild-type HeLa cells or electroporation with the control GST protein did not decrease hemoglobin production. To confirm the presence of bioactive Tat protein within K562 cells, the cells were transiently transfected with a pHIV/LTR-CAT prior to the introduction of Tat. A 30- to 40-fold induction in CAT gene expression was observed in the transfected K562 cells, which were either cocultured with HL-tat or were electroporated with GST-Tat. Simultaneous transient transfection of K562 cells with a TAR expression plasmid, to compete for the availability of Tat protein, significantly downregulated the HIV LTR trans-activation by Tat. In addition, overexpression of the TAR RNAs in K562 cells was able to downregulate the suppressive effect of Tat on butyric acid-induced differentiation. RT-PCR analysis of the total RNAs isolated from these cells demonstrated that Tat protein suppressed the butyric acid-induced gamma-globin gene expression by an average of 54% without affecting the level of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNAs. These data indicate that the viral Tat protein plays a significant role in abrogating erythroid differentiation in K562 cells.

Lack of in vivo effect of granulocyte-macrophage colony-stimulating factor on human immunodeficiency virus type 1

Neutropenia complicates HIV disease or its treatment in a large proportion of patients. Hematopoietic growth factor support has been tested in a number of clinical settings in HIV disease and has been demonstrated to be of benefit for specific parameters. One consideration regarding the use of hematopoietic growth factors in HIV disease is their potential effect on HIV viral burden, since alterations in HIV expression have been documented with certain cytokines in vitro. It has also been reported that some cytokines, notably GM-CSF, potentiate the antiviral properties of thymidine analogs such as zidovudine (AZT) in vitro. We tested these observations in vivo. Twelve HIV-positive patients with a CD4 cell count < or = 200/mm3 or HIV plasma viremia who were receiving a stable dose of zidovudine were enrolled into three dose cohorts of yeast-derived GM-CSF at 50, 125, or 250 micrograms/m2 daily by subcutaneous self-injection for 28 days. Measurements of HIV activity included serum acid-dissociated HIV p24 antigen levels, plasma and peripheral blood mononuclear cell (PBMC) limiting dilution HIV culture, and plasma HIV quantitative competitive polymerase chain reaction (PCR). Serum and intracellular zidovudine levels were measured as well as hematologic, immunologic, and toxicity parameters. Virologic measures showed neither significant upregulation nor downregulation of serum acid-dissociated HIV p24 antigen, plasma and PBMC HIV culture, or PCR in association with GM-CSF administration. A trend toward increased intracellular AZT levels was noted, but this did not achieve statistical significance (p = 0.073). CD4 and CD8 lymphocytes were essentially unaffected while absolute neutrophil counts increased with GM-CSF administration as expected. These data suggest that administration of GM-CSF does not perturb HIV activity or immunologic parameters in patients receiving AZT for advanced HIV disease. No potentiation of AZT antiviral effect was demonstrated.

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.

In vitro potency of inhibition by antiviral drugs of hematopoietic progenitor colony formation correlates with exposure at hemotoxic levels in human immunodeficiency virus-positive humans

Inhibition of in vitro colony formation of human hematopoietic progenitors (CFU-granulocyte-macrophage, burst-forming unit-erythroid) by the antiviral nucleoside drugs alovudine, zalcitabine, zidovudine, ganciclovir, stavudine, didanosine, lamivudine, and acyclovir was measured. Significant correlations between in vitro 50% inhibitory concentrations and the daily human exposures (area under the concentration-time curve from 0 to 24 h; in micromolar.hour) of these chronically administered drugs in human immunodeficiency virus-positive patients that induced neutropenia or anemia were demonstrated by both linear regression and Spearman rank-order analyses. These quantitative correlations allow estimation of the exposure at which bone marrow toxicity may occur with candidate compounds.

Impaired cytokine production by bone marrow stromal cells of immunodeficient mice

The aetiology of the bone marrow suppression in HIV-infected patients is unknown. We have demonstrated previously that the ability of bone marrow cells, derived from mice made immunodeficient by infection with the retrovirus LP-BM5, to establish long-term stromal cultures is impaired. In this study we determined the ability of bone marrow stromal cells from these immunodeficient mice to produce cytokines important in haemopoiesis. Neither SCF, IL-3, GM-CSF nor TNF alpha were found in conditioned media of long-term bone marrow cultures (LTBMC) of normal or MAIDS mice. We failed to detect mRNA for TNF or IL-1 alpha, by reverse transcription polymerase chain reaction (RT-PCR), in cultures derived from either normal or immunodeficient mice. Steady-state levels of transcripts for IL-6 were equal in cells from normal and MAIDS mice. Steady-state levels of mRNA for TGF beta 1, a known inhibitor of haemopoiesis, were decreased in cultures derived from MAIDS mice at late stages of infection. The mRNA level of the multipotent haemopoietic regulator stem cell factor was also decreased in MAIDS cultures as compared with normals. Transcripts encoding the transmembrane form of the growth factor were almost absent. Addition of soluble GM-CSF and SCF only transiently increased the production of CFUs (BFUE and CFU-G/M) in MAIDS LTBMC. These findings suggest that derangements in cytokine production in stromal cells of immunodeficient mice may contribute to the suppression of haemopoiesis observed in this disease. One mechanism of HIV-induced depression of haemopoiesis may be via alterations of the haemopoietic microenvironment.

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.

HIV Tat protein potentiates in vitro granulomonocytic progenitor cell growth

The direct involvement of hematopoietic progenitor cells in AIDS which results in dysregulated hematopoiesis, probably due to regulatory factors yet to be determined, has been reported by us and others. In this study we demonstrate that the HIV-2 Tat gene product is released in supernatant of HIV-2-infected long-term bone marrow cultures (LTBMC). These Tat-containing supernatants specifically enhanced growth of CFU-GM in agar culture system and this promoting activity was specifically neutralized with anti-Tat antibodies. The use of different recombinant Tat proteins confirmed that Tat has been responsible for enhanced in vitro growth of CFU-GM after HIV-2 infection of LTBMC. Moreover, limiting dilution analysis showed that Tat acts directly on the CD34+ cell population in which it increases the frequency of IL3-responding cells.

Dysplastic haemopoiesis following orthotopic liver transplantation: comparison with similar changes in HIV infection and primary myelodysplasia

To validate scientifically our prior empiric observations that patients develop significant haemopoietic dysplasia following solid organ transplantation, we developed a quantitative lineage-specific scoring system to evaluate dysplastic features of bone marrow aspirates and core biopsies. We used this scoring system to compare retrospectively randomly selected bone marrow aspirates and core biopsies from 19 patients undergoing orthotopic liver transplantation (OLT), 21 with a known history of human immunodeficiency virus (HIV) infection, and 18 with primary or chemotherapy-related myelodysplastic syndromes (MDS). Our results show that the OLT patient group developed significant but milder haemopoietic dysplastic changes than the HIV or MDS groups, and that the MDS group developed more severe dysplasia of the myeloid lineage than the other groups. The possible roles for drugs and infectious agents in the pathophysiology of dysplastic changes are discussed.

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.

Revisited indications for bone marrow examinations in HIV-infected patients

We reviewed the indications for and the results of bone marrow examination (BME) from HIV-infected patients as an attempt to improve its diagnostic yield. One-hundred-and-eight bone marrow specimens from 90 patients during a 3-year period were examined. A cytological, histological and microbiological study was carried out on the specimens. Forty-three evaluable examinations (40% of total) performed for cytopenia showed normo- or hypercellularity in 33 (77%). Fifty bone marrow specimens were cultured for mycobacteria with a yield of 42% when the indication was persistent fever. Positive cultures yielded Mycobacterium avium complex in 8 out of 12 patients. Twenty-seven patients had both culture and biopsy; granulomas were associated with all the positive (10/10) and with 1 out of 17 negative cultures (chi-square test: p < 0.001). A bone marrow involvement with lymphoma was found in 2 out of 6 patients with previously diagnosed lymphoma, and biopsy revealed a lymphoma in 2 patients. Morphological bone marrow examination should be associated with other techniques in order to appreciate bone marrow production. Bone marrow biopsy is useful for the investigation of persistent fever since granulomas suggestive of disseminated mycobacteria are frequent and allow a treatment to be initiated before microbiological confirmation and antibiotic susceptibility test.