Human immunodeficiency virus type 1-induced hematopoietic inhibition is independent of productive infection of progenitor cells in vivo

ISG15-LFA1 interactions in latent HIV clearance: mechanistic implications in designing antiviral therapies

Interferon types-I/II (IFN-αβ/γ) secretions are well-established antiviral host defenses. The human immunodeficiency virus (HIV) particles are known to prevail following targeted cellular interferon secretion. CD4+ T-lymphocytes are the primary receptor targets for HIV entry, but the virus has been observed to hide (be latent) successfully in these cells through an alternate entry route via interactions with LFA1. HIV facilitates its post-entry latency-driven mode of hiding through these interactions to displace or inhibit ISG15 by forming the HIV1-LFA1 complex in lieu of ISG15-LFA1, which would at least transiently halt and bypass type-I IFN secretion. This could explain why the elimination of HIV from cellular hideouts is difficult. Hence, HIV clearance needs to be addressed to reverse its latency in LFA1+ T-lymphocytes and CD34+/CD133+ early progenitor stem cells. In the context of hematopoietic or endothelial stem-progenitor cells (HSPC/ESPC), we discuss the potential role of LFA1 in HIV permissiveness and latency in LFA1-CD34+/CD133+ versus LFA1+CD34+/CD133+ HSPCs/ESPCs. In HIV latency, the viral particles may remain engaged on the naïve-resting cells' LFA1, which are then unable to accommodate the ISG15 molecules owing to conformational changes induced upon occupation by the virus at the ISG15-LFA1 binding or interaction sites through halting of the subsequent downstream type-II IFN secretion. Viral binding to LFA1, including its transfer through activated-naïve cell-cell contacts may be a key step that needs to be addressed to prevent "transient or partial" virus-induced shutdown of type-I IFN secretion. This process allows an alternate viral entry and hideout site via LFA1. The subsequent administration of recombinant ISG15 may ensure sufficient type I/II IFN release to promote, enhance, or sustain the innate immune responses. Thus, combination antiviral therapies could potentially include exogenous ISG15 to maintain or sustain biologically and clinically relevant ISG15-LFA1 interactions. In addition to alternating with co-challenges of PKC-pro-LRA-drug modulators, this is administered post (antiretroviral therapy) and continued with periodic ART until permanent elimination of viral resurgence and latency is achieved in patients with HIV/AIDS. This triple-combination drug regimen is expected to pave the path for systemic virus clearance in vivo.

Contrasting mechanistic susceptibilities of hematopoietic and endothelial stem-progenitor cells in respective pathogeneses of HIV-1 and SARS-CoV-2 infections

The multitude of cellular types can be expected to behave differently when receiving invading pathogens such as mammalian viruses. The nature-dictated causes for such intrinsic cellular diversity become the criteria for the emergence of specific virus-receptor interactions on that particular host cellular surface, in order to accommodate contact with various other living entities whether desirable to the host or not. At present, we are presented with an example of two contrasting behaviours wherein the well-known HIV-1 and the more recently emergent SARS-CoV-2 cause adverse consequences to the differentiation and functions of progenitor stem cells. These include the two different downstream multipotent CD34+ hematopoietic (HSPC) and CD133+ endothelial (ESPC) stem-progenitor cells of their common pluripotent hemangioblast precursors. The two viruses target the respective endothelial and hematopoietic stem-progenitor cells to thrive upon the relevant host cellular surrounded stromal microenvironments by adopting reciprocally-driven mechanistic routes, which incidentally cause pathogenesis either directly of ESPC (SARS-CoV-2), or indirectly of HSPC (HIV-1). HIV-1 utilizes the CD4+ T-lymphocyte receptor thereby advancing pathogenesis indirectly to the CD34+ HSPC. SARS-CoV-2 directly targets the CD133+ ESPC via ACE2 receptor causing cytokine storms of the CD4+ T-lymphocytes. In this manner, these two viruses cause and extend their damage to the other cellular sub/types coexisting in the host cellular microenvironments. The infected individuals require clinical interventions that are efficacious to prevent cellular dysfunction and ultimate cell depletion or death. We infer from these viruses mediated pathogeneses mechanisms a potential common origin of microRNA molecular therapies to address cellular dysfunctions and prevent cell loss.

Benefits and limitations of humanized mice in HIV persistence studies

Significant advances in the treatment of HIV infection have been made in the last three decades. Antiretroviral therapy (ART) is now potent enough to prevent virus replication and stop disease progression. However, ART alone does not cure the infection, primarily because HIV can persist in stable long-term reservoir cells including latently-infected CD4 + T cells. A central goal of the HIV research field is to devise strategies to eliminate these reservoirs and thereby develop a cure for HIV. This requires robust in vivo model systems to facilitate both the further characterization of persistent HIV reservoirs and evaluation of methods for eliminating latent virus. Humanized mice have proven to be versatile experimental models for studying many basic aspects of HIV biology. These models consist of immunodeficient mice transplanted with human cells or tissues, which allows development of a human immune system that supports robust infection with HIV. There are many potential applications for new generations of humanized mouse models in investigating HIV reservoirs and latency, but these models also involve caveats that are important to consider in experimental design and interpretation. This review briefly discusses some of the key strengths and limitations of humanized mouse models in HIV persistence studies.

Hematopoietic Stem/Progenitor Cells and the Pathogenesis of HIV/AIDS

The interaction between human immunodeficiency virus (HIV) and hematopoietic stem/progenitor cells (HSPCs) has been of great interest. However, it remains unclear whether HSPCs can act as viral reservoirs. Many studies have reported the presence of latently infected HSPCs in the bone marrow of HIV-infected patients, whereas many other investigators have reported negative results. Hence, further evidence is required to elucidate this controversy. The other arm of HSPC investigations of HIV infection involves dynamics analysis in the early and late stages of infection to understand the impact on the pathogenesis of acquired immunodeficiency syndrome. Several recent studies have suggested reduced amounts and/or functional impairment of multipotent, myeloid, and lymphoid progenitors in HIV infection that may contribute to hematological manifestations, including anemia, pancytopenia, and T-cell depletion. In addition, ongoing and future studies on the senescence of HSPCs are expected to further the understanding of HIV pathogenesis. This mini review summarizes reports describing the basic aspects of hematopoiesis in response to HIV infection and offers insights into the association of HIV infection/exposure of the host HSPCs and hematopoietic potential.

HIV-1 inhibits haematopoiesis via microRNA secreted by virus-infected CD4+ T cells

INTRODUCTION

HIV-1-infected patients develop haematological disorders such as cytopenias. One possible explanation is the inhibition of haematopoiesis at the level of differentiation of CD34+ haematopoietic progenitor stem cells. Based on our previous studies, we hypothesised that there may be viral encoded, or host cellular factors which participate in the process of inhibition of haematopoiesis.

MATERIALS AND METHODS

Virus-depleted media from infected CD4+ T cells was prepared by filtration and added to CD34+ cell differentiation semisolid medium. We have also used the virus-depleted media to isolate host/viral factors including miRNA. Isolated miRNAs were screened for their haematopoietic inhibitory function using the miRNA mining approach.

RESULTS

Addition of virus-depleted media caused a 40% inhibition of differentiation of CD34+ cells into myeloid and erythroid colony formation. Real-time RT-PCR showed miR-15a and miR-24 from both pIndie-C1 and pNL4.3 HIV-1-infected cells showed a significant differential expression when compared to control media.

CONCLUSION

In this study, we have identified two miRNAs, miR-15a and miR-24 secreted from purified HIV-1-infected CD4+ T cells that inhibited CD34+ haematopoietic progenitor stem cell differentiation into myeloid and erythroid colonies in vitro.

BURDEN OF CYTOPAENIAS AMONG HIV POSITIVE PREGNANT WOMEN AT THE UNIVERSITY COLLEGE HOSPITAL, IBADAN

INTRODUCTION

Few studies have examined cytopaenia among HIV positive pregnant women.

OBJECTIVES

To assess burden of cytopaenia among HIV positive pregnant women.

METHODOLOGY

This cross-sectional study of women on HAART ≤6months, defined anemia as hematocrit <33%, leucopenia as total white blood cell count <3,000 cells/mm3 and thrombocytopenia as absolute platelet count <100,000 cells/mm3. Univariate and bivariate analyses were performed.

RESULTS

Over 8 years, of 1,197 women, the mean age was 29.02(±5.4) years and mean gestational age 25.9(±8.1) weeks. Prevalence of anaemia was 76.8%, leucopaenia 6.9% and thrombocytopenia 4.7%. The mean haematocrit was 28.5%(±4.5); median white blood count 5,500/mm3 ; median platelet count 200,000/mm3 and median CD4 323 cells/mm3. Mean haematocrit was highest (29.7%±5.3) in women in the first trimester but lowest (28.4% ±4.6) in women in second trimester (p=0.04). Compared with earlier trimesters, women in the third trimester had higher median white blood count (5,600 cells/mm3), higher neutrophil (61.0% ±11.2) but lower lymphocytes (28.3%± 9.2) (p=0.18; 0.00, 0.00). Median absolute platelet count was highest (206,000 cells/mm3) in the first trimester but lowest (195,000 cells/mm3) in third trimester (0.04). Women with lower CD4 had higher prevalence of cytopaenias.

CONCLUSION

Cytopaenias are not uncommon in this population especially with lower CD4.

Studies of retroviral infection in humanized mice

Many important aspects of human retroviral infections cannot be fully evaluated using only in vitro systems or unmodified animal models. An alternative approach involves the use of humanized mice, which consist of immunodeficient mice that have been transplanted with human cells and/or tissues. Certain humanized mouse models can support robust infection with human retroviruses including different strains of human immunodeficiency virus (HIV) and human T cell leukemia virus (HTLV). These models have provided wide-ranging insights into retroviral biology, including detailed information on primary infection, in vivo replication and pathogenesis, latent/persistent reservoir formation, and novel therapeutic interventions. Here we describe the humanized mouse models that are most commonly utilized to study retroviral infections, and outline some of the important discoveries that these models have produced during several decades of intensive research.

Prevalence and correlates of cytopenias in HIV-infected adults initiating highly active antiretroviral therapy in Uganda

Background

Cytopenias are the most common HIV-associated hematological abnormality. Cytopenias have been associated with several factors including sex, race/ethnicity, geographical location and comorbidities such as tuberculosis, hepatitis B infection, fever and oral candidiasis. Cytopenias become more prevalent as HIV progresses and are often fatal. Data from resource-limited settings about the prevalence and correlates of cytopenia are limited. Therefore we conducted this cross-sectional study to assess the prevalence and correlates of cytopenia among adult AIDS patients at initiation of HAART in Uganda.

Methods

400 HIV-infected subjects who were HAART-naïve or on HAART for ≤ 6 months were enrolled into the Multivitamins, HAART and HIV/AIDS Trial. Anemia was defined according to WHO guidelines as any hemoglobin concentration < 12 g/dl for non-pregnant females and < 13 g/dl for males. Leucopenia and thrombocytopenia were defined using study site laboratory reference ranges for lack of generally accepted definitions for these 2 cell lines as leucopenia if white blood cell count < 2.75 × 10⁹ cells/litre and thrombocytopenia if platelets < 125 × 10⁹ cells/litre for females and < 156 × 10⁹ cells/litre for males. Univariate and bivariate analyses were done to describe the patient population and log-binomial regression was used to quantify the correlates of cytopenia.

Results

Sixty five percent of the 400 subjects had at least one form of cytopenia. Anemia occurred in 47.8%, leucopenia in 24.3%, thrombocytopenia in 8.3%, bicytopenia in 21.9% and only 2 had a pancytopenia. Cytopenia was more prevalent in females (prevalence ratio [PR]:1.33, 95% confidence interval [CI]:1.12-1.59); CD4 count category 50 to <200 (PR: 0.75, 95% CI: 0.64 -0.88) and CD4 count category 200 to <350 (PR: 0.74, 95% CI: 0.59 - 0.92) compared to CD4 count category <50; normal BMI (PR: 0.82, 95% CI:0.68-1.00) and overweight BMI (PR: 0.64, 95% CI:0.50- 0.82) compared to underweight BMI and those with a history or presence of oral candidiasis.

Conclusions

Cytopenias are a frequent complication in HIV-infected adults at initiation of HAART in Uganda. The presence of any cytopenia was associated with female sex, decreasing CD4 count and decreasing body mass index. Prospective studies in resource-limited settings on the trend in HIV-related cytopenias are needed.

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.

Prevalence of Anemia and Immunological Markers in HIV-Infected Patients on Highly Active Antiretroviral Therapy in Northeastern Nigeria

BACKGROUND

There are conflicting reports on the impact of highly active antiretroviral therapy (HAART) in resolving hematological complications. Whereas some studies have reported improvements in hemoglobin and other hematological parameters resulting in reduction in morbidity and mortality of HIV patients, others have reported no improvement in hematocrit values of HAART-treated HIV patients compared with HAART-naïve patients.

OBJECTIVE

This current study was designed to assess the impact of HAART in resolving immunological and hematological complications in HIV patients by comparatively analyzing the results (immunological and hematological) of HAART-naive patients and those on HAART in our environment.

METHODS

A total of 500 patients participated, consisting of 315 HAART-naive (119 males and 196 females) patients and 185 HAART-experienced (67 males and 118 females) patients. Hemoglobin (Hb), CD4+ T-cell count, total white blood count (WBC), lymphocyte percentage, plateletes, and plasma HIV RNA were determined.

RESULTS

HAART-experienced patients were older than their HAART-naive counterparts. In HAART-naive patients, the incidence of anemia (packed cell volume [PCV] <30%) was 57.5%, leukopenia (WBC < 2.5), 6.1%, and thrombocytopenia < 150, 9.6%; it was, significantly higher compared with their counterparts on HAART (24.3%, 1.7%, and 1.2%, respectively). The use of HAART was not associated with severe anemia. Of HAART-naive patients, 57.5% had a CD4 count < 200 cells/μL in comparison with 20.4% of HAART-experienced patients (P < 0.001). The mean viral load log10 was significantly higher in HAART-naive than in HAART-experienced patients (P < 0.001). Total lymphocyte count < 1.0 was a significant predictor of <CD4 counts < 200 cells/μL in HAART-naïve patients, but this relationship was not observed in HAART-experienced patients.

CONCLUSION

HAART has the capability of reducing the incidence of anemia, other deranged hematological and immunological parameters associated with disease progression, and death in HIV-infected patients. Total lymphocyte count fails to predict CD4 count < 200 cells/μL in our cohort; thus, its use in the management and monitoring of HIV-infected patients in our settings is not reliable.

Predictors of anaemia and iron deficiency in HIV-infected pregnant women in Tanzania: a potential role for vitamin D and parasitic infections

OBJECTIVE

Anaemia is common during pregnancy, and prenatal Fe supplementation is the standard of care. However, the persistence of anaemia despite Fe supplementation, particularly in HIV infection, suggests that its aetiology may be more complex and warrants further investigation. The present study was conducted to examine predictors of incident haematological outcomes in HIV-infected pregnant women in Tanzania.

DESIGN

Prospective cohort study. Cox proportional hazards and binomial regression models were used to identify predictors of incident haematological outcomes: anaemia (Hb < 110 g/l), severe anaemia (Hb < 85 g/l) and hypochromic microcytosis, during the follow-up period.

SETTING

Antenatal clinics in Dar es Salaam, Tanzania.

SUBJECTS

Participants were 904 HIV-infected pregnant women enrolled in a randomized trial of vitamins (1995-1997).

RESULTS

Malaria, pathogenic protozoan and hookworm infections at baseline were associated with a two-fold increase in the risk of anaemia and hypochromic microcytosis during follow-up. Higher baseline erythrocyte sedimentation rate and CD8 T-cell concentrations, and lower Hb concentrations and CD4 T-cell counts, were independent predictors of incident anaemia and Fe deficiency. Low baseline vitamin D (<32 ng/ml) concentrations predicted a 1.4 and 2.3 times greater risk of severe anaemia and hypochromic microcytosis, respectively, during the follow-up period.

CONCLUSIONS

Parasitic infections, vitamin D insufficiency, low CD4 T-cell count and high erythrocyte sedimentation rate were the main predictors of anaemia and Fe deficiency in pregnancy and the postpartum period in this population. A comprehensive approach to prevent and manage anaemia, including micronutrient supplementation and infectious disease control, is warranted in HIV-infected women in resource-limited settings - particularly during the pre- and postpartum periods.

Mesenchymal stem cell derived hematopoietic cells are permissive to HIV-1 infection

BACKGROUND

Tissue resident mesenchymal stem cells (MSCs) are multipotent, self-renewing cells known for their differentiation potential into cells of mesenchymal lineage. The ability of single cell clones isolated from adipose tissue resident MSCs (ASCs) to differentiate into cells of hematopoietic lineage has been previously demonstrated. In the present study, we investigated if the hematopoietic differentiated (HD) cells derived from ASCs could productively be infected with HIV-1.

RESULTS

HD cells were generated by differentiating clonally expanded cultures of adherent subsets of ASCs (CD90+, CD105+, CD45-, and CD34-). Transcriptome analysis revealed that HD cells acquire a number of elements that increase their susceptibility for HIV-1 infection, including HIV-1 receptor/co-receptor and other key cellular cofactors. HIV-1 infected HD cells (HD-HIV) showed elevated p24 protein and gag and tat gene expression, implying a high and productive infection. HD-HIV cells showed decreased CD4, but significant increase in the expression of CCR5, CXCR4, Nef-associated factor HCK, and Vpu-associated factor BTRC. HIV-1 restricting factors like APOBEC3F and TRIM5 also showed up regulation. HIV-1 infection increased apoptosis and cell cycle regulatory genes in HD cells. Although undifferentiated ASCs failed to show productive infection, HIV-1 exposure increased the expression of several hematopoietic lineage associated genes such as c-Kit, MMD2, and IL-10.

CONCLUSIONS

Considering the presence of profuse amounts of ASCs in different tissues, these findings suggest the possible role that could be played by HD cells derived from ASCs in HIV-1 infection. The undifferentiated ASCs were non-permissive to HIV-1 infection; however, HIV-1 exposure increased the expression of some hematopoietic lineage related genes. The findings relate the importance of ASCs in HIV-1 research and facilitate the understanding of the disease process and management strategies.

Abnormalities of erythropoiesis during HIV-1 disease: a longitudinal analysis

BACKGROUND

Impaired erythropoiesis is a key abnormality described in untreated HIV-1 disease. Most of the available data on HIV-associated hematopoietic abnormalities were obtained using unfractionated bone marrow-derived mononuclear cells, thus resulting in significant inter (and intra)-individual variability in the number of cultured precursors. Aim of this study was to assess the erythropoietic capability of purified CD34+ progenitors through a longitudinal analysis of burst-forming units-erythroid (BFU-E) growth before and after antiretroviral therapy (ART).

METHODS

Twelve HIV-infected individuals were studied before and after ART; 31 HIV-uninfected individuals were enrolled as controls. CD34+ progenitors were purified from peripheral blood by immunomagnetic sorting and cultured in methylcellulose-based medium containing stem cell factor, granulocyte-monocyte colony-stimulating factor, interleukin-3, and erythropoietin. Serum levels of iron, transferrin, transferrin saturation index, soluble transferrin receptor, ferritin, and erythropoietin were also evaluated.

RESULTS

Baseline BFU-E levels were increased in untreated HIV-infected individuals when compared with controls but declined significantly after successful ART. In contrast, serum levels of erythropoietin and soluble transferrin receptor increased significantly after ART.

CONCLUSIONS

These findings suggest that, in untreated HIV-infected individuals, chronic inflammation and/or immune activation is associated with defective erythropoiesis and accumulation of erythroid precursors. ART-induced suppression of HIV-1 replication is associated with normalization of BFU-E levels.

The utilization of humanized mouse models for the study of human retroviral infections

The development of novel techniques and systems to study human infectious diseases in both an in vitro and in vivo settings is always in high demand. Ideally, small animal models are the most efficient method of studying human afflictions. This is especially evident in the study of the human retroviruses, HIV-1 and HTLV-1, in that current simian animal models, though robust, are often expensive and difficult to maintain. Over the past two decades, the construction of humanized animal models through the transplantation and engraftment of human tissues or progenitor cells into immunocompromised mouse strains has allowed for the development of a reconstituted human tissue scaffold in a small animal system. The utilization of small animal models for retroviral studies required expansion of the early CB-17 scid/scid mouse resulting in animals demonstrating improved engraftment efficiency and infectivity. The implantation of uneducated human immune cells and associated tissue provided the basis for the SCID-hu Thy/Liv and hu-PBL-SCID models. Engraftment efficiency of these tissues was further improved through the integration of the non-obese diabetic (NOD) mutation leading to the creation of NODSCID, NOD/Shi-scid IL2rγ^-/-, and NOD/SCID β2-microglobulin^null animals. Further efforts at minimizing the response of the innate murine immune system produced the Rag2^-/-γ_c^-/- model which marked an important advancement in the use of human CD34+ hematopoietic stem cells. Together, these animal models have revolutionized the investigation of retroviral infections in vivo.

Stem cell transplantation in HIV-infected patients

Lymphoma remains a leading cause of mortality in HIV-infected patients. In the HIV-negative setting, high-dose therapy with autologous stem cell transplantation has been a long accepted treatment for certain malignancies such as lymphoma and leukemia. Early transplant trials excluded older patients and patients with comorbidities such as HIV infection. The procedure-related mortality of transplantation, however, has decreased both due to the use of peripheral blood stem cells instead of bone marrow and due to the use of new reduced intensity conditioning regimens. During this same era, the treatment of HIV infection has also become more effective. Patients are no longer dying of opportunistic infections and in addition, their hematologic function has improved. With these advances in HIV therapy, it is possible for HIV-infected patients to mobilize an adequate number of stem cells for an autologous transplant. In addition, with appropriate antiretroviral therapy and infection prophylaxis, the HIV-infected patient can tolerate intensive doses of chemotherapy. This review will summarize clinical trials of autologous stem cell transplantation in HIV-positive patients. Furthermore, the field of solid-organ transplantation has grown to also include HIV-positive patients. The challenges in solid-organ transplantation are similar to allogeneic stem cell transplantation, namely that patients require chronic immunosuppression. This article will also review some of the approaches to allogeneic stem cell transplantation in the HIV-positive patient and provide a rationale for the broader use of stem cell transplantation for appropriate HIV-related hematologic malignancies.

Is Nef the elusive cause of HIV-associated hematopoietic dysfunction?

HIV-associated hematological abnormalities involve all lineages of blood cells, thus implying that the virus impairs the function of early HSCs. However, the underlying mechanisms of this defect are unknown, particularly since HSCs are largely resistant to HIV-1 infection. In this issue of the JCI, Prost and colleagues show that the viral accessory protein Negative factor (Nef) plays a potentially critical role in the pathogenesis of HIV/SIV-associated hematopoietic dysfunction by affecting the clonogenic potential of HSCs (see the related article beginning on page 1765). Soluble Nef induces PPARgamma in uninfected HSCs, thereby suppressing the expression of STAT5A and STAT5B, two factors necessary for proper HSC function. The identification of this novel activity of extracellular Nef defines a new mechanism of HIV/SIV pathogenesis and suggests that approaches aimed at increasing STAT5A and STAT5B expression may be considered in HIV-infected individuals with prominent hematological abnormalities. The results also raise the question of whether dysregulation of hematopoiesis by extracellular Nef plays a role in the development of T cell immunodeficiency and the high levels of chronic immune activation associated with AIDS.

Human and simian immunodeficiency viruses deregulate early hematopoiesis through a Nef/PPARgamma/STAT5 signaling pathway in macaques

Infection of primates by HIV-1 and SIV induces multiple hematological abnormalities of central hematopoietic origin. Although these defects greatly contribute to the pathophysiology of HIV-1 infection, the molecular basis for altered BM function remains unknown. Here we show that when cynomolgus macaques were infected with SIV, the multipotent potential of their hematopoietic progenitor cells was lost, and this correlated with downregulation of STAT5A and STAT5B expression. However, forced expression of STAT5B entirely rescued the multipotent potential of the hematopoietic progenitor cells. In addition, an accessory viral protein required for efficient SIV and HIV replication and pathogenicity, "Negative factor" (Nef), was essential for SIV-mediated impairment of the multipotent potential of hematopoietic progenitors ex vivo and in vivo. This newly uncovered property of Nef was both conserved between HIV-1 and SIV strains and entirely dependent upon the presence of PPARgamma in targeted cells. Further, PPARgamma agonists mimicked Nef activity by inhibiting STAT5A and STAT5B expression and hampering the functionality of hematopoietic progenitors both ex vivo and in vivo. These findings have extended the role of Nef in the pathogenicity of HIV-1 and SIV and reveal a pivotal role for the PPARgamma/STAT5 pathway in the regulation of early hematopoiesis. This study may provide a basis for investigating the potential therapeutic benefits of PPARgamma antagonists in both patients with AIDS and individuals with hematopoietic disorders.

Infection of hematopoietic progenitor cells by HIV-1 subtype C, and its association with anemia in southern Africa

Reports from southern Africa, an area in which human immunodeficiency virus type 1 (HIV-1) infection is caused almost exclusively by subtype C (HIV-1C), have shown increased rates of anemia in HIV-infected populations compared with similar acquired immunodeficiency syndrome (AIDS) patients in the United States, an area predominantly infected with subtype B (HIV-1B). Recent findings by our group demonstrated a direct association between HIV-1 infection and hematopoietic progenitor cell health in Botswana. Therefore, using a single-colony infection assay and quantitative proviral analysis, we examined whether HIV-1C could infect hematopoietic progenitor cells (HPCs) and whether this phenotype was associated with the higher rates of anemia found in southern Africa. The results show that a significant number of HIV-1C, but not HIV-1B, isolates can infect HPCs in vitro (P < .05). In addition, a portion of HIV-1C-positive Africans had infected progenitor cell populations in vivo, which was associated with higher rates of anemia in these patients (P < .05). This represents a difference in cell tropism between 2 geographically separate and distinct HIV-1 subtypes. The association of this hematotropic phenotype with higher rates of anemia should be considered when examining anti-HIV drug treatment regimens in HIV-1C-predominant areas, such as southern Africa.

HIV-1 negatively affects the survival/maturation of cord blood CD34(+) hematopoietic progenitor cells differentiated towards megakaryocytic lineage by HIV-1 gp120/CD4 membrane interaction

To investigate the mechanisms involved in the human immunodeficiency virus type 1 (HIV-1)-related thrombocytopenia (TP), human umbilical cord blood (UCB) CD34(+) hematopoietic progenitor cells (HPCs) were challenged with HIV-1(IIIb) and then differentiated by thrombopoietin (TPO) towards megakaryocytic lineage. This study showed that HIV-1, heat-inactivated HIV-1, and HIV-1 recombinant gp120 (rgp120) activated apoptotic process of megakaryocyte (MK) progenitors/precursors and decreased higher ploidy MK cell fraction. All these inhibitory effects on MK survival/maturation and platelets formation were elicited by the interaction between gp120 and CD4 receptor on the cell membrane in the absence of HIV-1 productive infection. In fact, in our experimental conditions, HPCs were resistant to HIV-1 infection and no detectable productive infection was observed. We also evaluated whether the expression of specific cytokines, such as TGF-beta1 and APRIL, involved in the regulation of HPCs and MKs proliferation, was modulated by HIV-1. The specific protein and mRNA detection analysis, during TPO-induced differentiation, demonstrated that HIV-1 upregulates TGF-beta1 and downregulates APRIL expression through the CD4 engagement by gp120. Altogether, these data suggest that survival/differentiation of HPCs committed to MK lineage is negatively affected by HIV-1 gp120/CD4 interaction. This long-term inhibitory effect is also correlated to specific cytokines regulation and it may represent an additional mechanism to explain the TP occurring in HIV-1 patients.

Natural Killer Cell Receptor NKG2A/HLA-E Interaction Dependent Differential Thymopoiesis of Hematopoietic Progenitor Cells Influences the Outcome of HIV Infection

HIV infection and its outcome is complex because there is great heterogeneity not only in clinical presentation, incomplete clinical information of markers of immunodeficiency and in measurements of viral loads. Also, there many gene variants that control not only viral replication but immune responses to the virus; it has been difficult to study the role of the many AIDS restricting genes (ARGs) because their influence vary depending on the ethnicity of the populations studies and because the cost to follow infected individuals for many years. Nevertheless, at least genes of the major histocompatibility locus (MHC) such as HLA alleles have been informative to classify infected individuals following HIV infection; progression to AIDS and long-term-non-progressors (LTNP). For example, progressors could be defined as up to 5 years, up to 11 years or as we describe in this report up to 15 years from infection, and LTNP could be individuals with normal CD4+ T cell counts for more than 15 years with or without high viral loads. In this review, we emphasized that in the studies of ARGs the HLA alleles are important in LTNP; HLA-B alleles influencing the advantage to pathogens to produce immune defense mediated by CD8+ T cells (cognate immunuity). Our main point we make in this report is that contrary to recent reports claiming that this dominant effect was unlikely due to differences in NK activation through ligands such as HLA-Bw4 motif, we believe that cognate immunity as well as innate immunity conferred by NK cells are involved. The main problem is that HLA-Bw4 alleles can be classified according the aminoacid in position 80. Isoleucine determines LTNP, which is a ligand for 3DS1. Such alleles did not include HLA-B*44. B*13 and B*27 which have threonine at that position. The authors have not considered the fact that in addition to the NK immunoglobulin receptors, NK receptors can be of the lectin like such as NKG2A/HLA-E to influence the HIV infection outcome. HLA-Bw4 as well as HLA-Bw6 alleles can be classified into those with threonine or methionine in the second position of their leader peptides. These leader peptides are ligands for NKG2A in which methionine influences the inhibitory role of NKG2A for killing infected targets. Functional studies have not been done as well as studies of these receptors in infected individuals. However, analyses of the leader peptides of HLA-B alleles in published reports, suggested that threonine in the second position can explain the importance of HLA-B*57, B*13, B*44 as well as certain Bw6 alleles in LNTP. In addition, we analyzed the San Francisco database that was reported and found that the association of HLA-B alleles with LNTP or with progressors can be due to the presence of threonine or methionine in their second position. Therefore, studies of outcome of HIV infection should include not only mechanisms of cognate immunity mediated by peptides and CD8+ T cells but also, NK receptors of two types, NKG2A as well as 3DSI. We propose that the SCID mouse should be used to understand mechanisms mediated by many of the ARGs especially the importance of thymus derived cells as well as NK receptor interactions with their ligands in this experimental animal transplanted with human stem cells, thymus or NK cells obtained from individuals of known HLA genotypes.

Lower hemoglobin levels in human immunodeficiency virus-infected patients with a positive direct antiglobulin test (DAT): relationship with DAT strength and clinical stages

BACKGROUND

There are conflicting opinions regarding the effect of positive direct antiglobulin test (DAT) on hemoglobin (Hb) levels in human immunodeficiency virus-infected (HIV+) patients.

STUDY DESIGN AND METHODS

A total of 166 samples from HIV+ outpatients were studied. The DAT was performed with the tube test and column agglutination technology (CAT).

RESULTS

The DAT was positive in 18.67 percent with the tube method and 33.73 percent with the CAT. Patients with DAT-positive results showed lower Hb levels than DAT-negative patients, 12.3 g per dL versus 14.3 g per dL (p = 0.0002). The univariate logistic regression enabled us to study the phenomenon better and fit the probability of having a DAT-positive result on the basis of the Hb levels. The relationship between the CAT and the tube test when washing the red blood cells (RBC) at 4 degrees C was stronger than when washing these at room temperature (phi = 0.8156; p = 0.000). The Hb levels were significantly lower in the positive DATs of Stage C (acquired immune deficiency syndrome [AIDS]) and Stage B (symptomatic non-AIDS patients), which showed decreasing Hb values for increasing agglutination strengths (p = 0.000). Anemia was related with the DAT results (odds ratio [OR], 8.005; p = 0.000) but not to the AIDS condition (OR, 1.741; p = 0.221).

DISCUSSION

Our study indicates that the DAT-positive results may be specifically related to lower Hb levels in HIV+ patients. The immunologic RBC clearance could be part of the anemic multifactorial condition in HIV+ patients.

Hematopoietic stem cell–engrafted NOD/SCID/IL2Rγnull mice develop human lymphoid systems and induce long-lasting HIV-1 infection with specific humoral immune responses

Critical to the development of an effective HIV/AIDS model is the production of an animal model that reproduces long-lasting active replication of HIV-1 followed by elicitation of virus-specific immune responses. In this study, we constructed humanized nonobese diabetic/severe combined immunodeficiency (NOD/SCID)/interleukin-2 receptor γ-chain knockout (IL2Rγnull) (hNOG) mice by transplanting human cord blood–derived hematopoietic stem cells that eventually developed into human B cells, T cells, and other monocytes/macrophages and 4 dendritic cells associated with the generation of lymphoid follicle–like structures in lymphoid tissues. Expressions of CXCR4 and CCR5 antigens were recognized on CD4+ cells in peripheral blood, the spleen, and bone marrow, while CCR5 was not detected on thymic CD4+ T cells. The hNOG mice showed marked, long-lasting viremia after infection with both CCR5- and CXCR4-tropic HIV-1 isolates for more than the 40 days examined, with R5 virus–infected animals showing high levels of HIV-DNA copies in the spleen and bone marrow, and X4 virus–infected animals showing high levels of HIV-DNA copies in the thymus and spleen. Furthermore, we detected both anti–HIV-1 Env gp120– and Gag p24–specific antibodies in animals showing a high rate of viral infection. Thus, the hNOG mice mirror human systemic HIV infection by developing specific antibodies, suggesting that they may have potential as an HIV/AIDS animal model for the study of HIV pathogenesis and immune responses.

Impaired in-vitro growth of megakaryocytic colonies derived from CD34 cells of HIV-1-infected patients with active viral replication

OBJECTIVE

To address the mechanisms of the thrombocytopoietic dysfunction that may follow HIV infection and to compare peripheral blood and bone marrow as sources of CD34 progenitor cells in HIV-infected patients.

METHODS

The study used CD34 progenitor cells from 20 previously untreated HIV-infected individuals, 20 HIV-infected individuals treated with antiretroviral therapy and a control group of 20 HIV-uninfected healthy individuals to examine in-vitro megakaryocytopoiesis. There were no hematological abnormalities at baseline in the study groups. CD34 progenitor cells derived from peripheral blood and bone marrow were purified and cultured in medium containing thrombopoietin, interleukin-3, and interleukin-6. HIV-1 plasma viral load was determined by b-DNA technique. Expression of receptors for thrombopoietin, interleukin-3, and interleukin-6 was assessed on CD34 cells by flow cytometry, and numbers of receptors per single cell were calculated by Quanticalc software.

RESULTS

Growth of megakaryocytopoietic colony-forming units (CFU-MK) were impaired in untreated HIV-infected individuals despite normal platelet counts. Viral load levels inversely correlate with CFU-MK growth and platelet counts. Antiretroviral drug-treated individuals showed normal megakaryocyte development. Similar results were obtained whether the CD34 progenitor cells derived from peripheral blood or bone marrow.

CONCLUSIONS

These findings suggest that megakaryocyte differentiation is impaired before the onset of overt thrombocytopenia in HIV-infected patients and provide evidence for a direct link between viral replication and perturbed megakaryocytopoiesis, which appears to be prevented and/or restored by antiretroviral therapy. The results indicate that peripheral blood represents a suitable source of CD34 hematopoietic progenitors for studies of megakaryocytopoiesis in HIV disease.

Aetiological factors related to a positive direct antiglobulin test result in human immunodeficiency virus-infected patients

BACKGROUND AND OBJECTIVES

The aim of this study was to examine the clinical importance and causes of a positive result in the direct antiglobulin test (DAT) in human immunodeficiency virus-infected (HIV(+)) patients. We therefore studied haematological parameters in outpatient samples, and also analysed the impact of highly active anti-retroviral therapy (HAART) on the DAT results.

STUDY DESIGN AND METHODS

Haematological parameters, clinical stages, chemo-antibiotic treatments and HAART treatment were studied to determine any relationships with DAT results in 115 consecutive HIV(+) patients.

RESULTS

Significantly lower haemoglobin (Hb) levels were detected in patients with HIV who had a positive DAT result. Hepatitis C virus (HCV) co-infection (odds ratio 2.529) and trimethoprim-suphamethoxazfole (TMP-SMX) prophylaxis (odds ratio 3.751) had a significant association with DAT positivity. Patients receiving HAART were less likely to have a positive DAT [odds ratio (OR) 0.383; P = 0.035]. Among the patients treated with TMP-SMX, those with a positive DAT had lower Hb levels (11.9 g/dl) than those with a negative DAT (14.2 g/dl; P = 0.04). HCV antibody positivity and TMP-SMX prophylaxis showed a cumulative effect on positive DATs (OR 4.533). The surface exploratory analysis indicated the distribution of the positive DATs in relationship with the CD4(+) count and Hb levels.

CONCLUSIONS

Significantly lower Hb levels were detected in DAT-positive HIV(+) patients. HCV co-infection and TMP-SMX prophylaxis appear to confer an increased risk of DAT positivity. The presence of red blood cell autoantibodies may be associated with anaemia in HIV disease in the absence of overt haemolysis.

The HIV-1 Tat protein enhances megakaryocytic commitment of K562 cells by facilitating CREB transcription factor coactivation by CBP

The human immunodeficiency virus type 1 (HIV-1) Tat protein regulates transcription factor functions and alters cellular gene expression. Because hematopoietic progenitor cell (HPC) differentiation requires activation of lineage-specific transcription factors, Tat may affect hematopoiesis in HIV-1-infected micro-environments. We have monitored the molecular effects of Tat on megakaryocytic differentiation in the HPC line, K562. Flow cytometry analysis of CD61 indicated that phorbol myristate acetate (PMA) (16 nM) stimulated megakaryocytic commitment of K562 cells was increased (3- to 4-fold) following exposure to Tat (1-100 ng/ml). Activation of the megakaryocytic transcription factor cAMP regulatory element binding protein (CREB) and its coactivation by the CREB binding protein (CBP) was subsequently monitored. CREB phosphorylation and DNA binding were measured by Western immunodetection and electrophoretic mobility shift assays (EMSA), respectively. Within 2 hrs after stimulation, Tat increased both CREB phosphorylation and DNA binding by 7- to 10-fold. Transient cotransfection with CREB reporter and CBP expression plasmids demonstrated that Tat treatment increases (3- to 4-fold) both PMA-stimulated and CBP-mediated transcription via the cAMP regulatory element. Histone acetyl transferase (HAT) activity was increased (8- to 10-fold) in Tat-stimulated cells, which suggested increased chromosomal accessibility of transcription factors. Two-hybrid cotransfection assays using reporter plasmid containing the GAL4 DNA-binding domain and expression plasmid coding for the GAL4-CBP fusion protein, showed that Tat increases (2-fold) CBP-mediated coactivation of CREB. Both reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis showed that Tat treatment increases CBP gene expression (7- to 9-fold) and protein levels (5- to 7-fold) within 6-12 hrs after stimulation. Our findings indicated that Tat treatment increases both CREB function and CREB coactivation by CBP, which may facilitate megakaryocytic commitment of K562 cells. Induction of this molecular signaling by HIV-1 Tat protein may have relevance in understanding the HIV-induced hematologic manifestations and possibly in regulation of viral infectivity parameters in progenitor cell reservoirs.

Chimeric SCID-hu Model as a Human Hematopoietic Stem Cell Host That Recapitulates the Effects of HIV-1 on Bone Marrow Progenitors in Infected Patients

The chimeric small animal model system wherein the severe combined immunodeficient mouse is transplanted with human fetal thymus and liver tissues (SCID-hu Thy/Liv) has been used in different areas of experimental research [1]. A living model system offers the advantage that studies of longer duration than in vitro can be performed. Here we discuss the importance of experimental in vivo studies and how well the data generated using this model system correlates with epidemiological studies from HIV-positive humans. Patients with HIV-1 infection often suffer from cytopenias, with thrombocytopenia typically having an earlier onset than anemia and neutropenia. The cytopenias in patients may be caused by virus effects at the stem cell level, or the mature blood cell level, or by other factors like medications used to treat the infection. Several studies preformed in SCID-hu animals show that the function of human hematopoietic progenitor stem cells are indirectly affected by HIV-1 infection. Colony forming activity (CFA) assays on hematopoietic progenitor cells derived from SCID-hu animals and human bone marrow have been performed as a measure of progenitor cellular function, and HIV-1 infection decreased CFA in multiple lineages that include megakaryoid, erythroid and myeloid types. Highly active antiretroviral therapy (HAART) partially and transiently reduces the inhibition of multilineage CFA and data suggest that HIV-1 indirectly affects stem cell differentiation into multiple lineages. The cojoint human hematopoietic organ of this small animal model system recapitulates the inhibitory effects of HIV-1 infection on the function of progenitor cells of the human bone marrow. Thus the SCID-hu (Thy/Liv) model is a useful in vivo system for preclinical translational research towards development of stem cell therapies in HIV infection.

Stem Cells in Aging: Influence of Ontogenic, Genetic and Environmental Factors

Aging is a genetically programmed decline in the functional effectiveness of the organism. It is manifested by a collective group of changes in cells or organs that occur over the course of a lifespan, limiting the duration of life. Longevity usually refers to long-lived members of a population within species. Organs develop and can involute according to specific timetables. Such timetables correlate with a preordained proliferative capacity of cells mediated by cell and organ clocks. In this review, we discuss different aspects related to genetic and environmental factors that are involved in determining life span. We discuss the influence of ontogenic, genetic and environmental factors in aging. The genetic factors can be studied in embryonic stem cells (ESC) and in niches (microenvironments) of stem cells (SC) using cellular or experimental animal models. We discuss molecular mechanisms involving genes and proteins associated with death pathways, niches, or hubs, on longevity. Moreover, we also discuss genes and proteins, associated with death pathways, on longevity. Unraveling these mechanisms may further our understanding of human aging leading to development of therapeutic interventions with the potential of prolonging life.

Impact of bone marrow hematopoiesis failure on T-cell generation during pathogenic simian immunodeficiency virus infection in macaques

Experimental infection of macaques with pathogenic strains of simian immunodeficiency virus (SIV) represents one of the most relevant animal models for studying HIV pathogenesis. In this study, we demonstrated a significant decrease in the generation of CD4+ T cells from bone marrow (BM) CD34+ progenitors in macaques infected with SIVmac251. This decrease appears to result from changes in the clonogenic potential of BM progenitors of both the myeloid and lymphoid lineages. We also demonstrated a significant decrease in the numbers of the most immature long-term culture-initiating cells (LTC-ICs). Hematopoietic failure occurred as early as primary infection, in the absence of CD34+ BM cell infection and was not related to plasma viral load. No major change was observed in the phenotype of BM CD34+ cells from infected macaques, including apoptosis markers such as annexin V staining and BcL-2 expression, but a significantly higher that normal proportion of cells were in the G0/G1 phase. This is the first demonstration that failure of BM hematopoiesis results in impaired T-cell production, which may contribute to the disruption of T-lymphocyte homeostasis characteristic of pathogenic lentiviral infections in primates.

Targeting c-Mpl for revival of human immunodeficiency virus type 1-induced hematopoietic inhibition when CD34+ progenitor cells are re-engrafted into a fresh stromal microenvironment in vivo

The inhibition of multilineage hematopoiesis which occurs in the severe combined immunodeficiency mouse with transplanted human fetal thymus and liver tissues (SCID-hu Thy/Liv) due to human immunodeficiency virus type 1 (HIV-1) infection is also accompanied by a severe loss of c-Mpl expression on these progenitor cells. Inhibition of colony-forming activity (CFA) of the CD34(+) progenitor cells is partially revived to about 40% of mock-infected Thy/Liv implants, following reconstitution of the CD34(+) cells that were exposed to HIV-1 infection, in a new Thy/Liv stromal microenvironment of irradiated secondary SCID-hu recipients at 3 weeks post-re-engraftment. In addition, in these reconstituted animals, the proportion of c-Mpl(+) CD34(+) cells relative to c-Mpl(-) CD34(+) cells increased by about 25%, to 35% of mock-infected implants, suggesting a reacquirement of c-Mpl phenotype by the c-Mpl(-) CD34(+) cells. These results suggest a correlation between c-Mpl expression and multilineage CFA of the human CD34(+) progenitor cells that have experienced the effects of HIV-1 infection. Treatment of the secondary-recipient animals with the c-Mpl ligand, thrombopoietin (Tpo), further increased c-Mpl expression and CFA of re-engrafted CD34(+) cells previously exposed to virus in the primary implants to about 50 to 70% over that of those re-engrafted CD34(+) cells derived from implants of untreated animals. Blocking of c-Mpl with anti-c-Mpl monoclonal antibody in vivo by injecting the SCID-hu animals resulted in the reduction or loss of CFA. Thus, inhibition, absence, or loss of c-Mpl expression as in the c-Mpl(-) CD34(+) subset of cells is the likely cause of CFA inhibition. Further, CFA of the CD34(+) cells segregates with their c-Mpl expression. Therefore, c-Mpl may play a role in hematopoietic inhibition during HIV-1 infection, and control of its expression levels may aid in hematopoietic recovery and thereby reduce the incidence of cytopenias occurring in infected individuals.

Impact of Highly Active Antiretroviral Therapy on Anemia and Relationship Between Anemia and Survival in a Large Cohort of HIV-Infected Women

BACKGROUND

Anemia is common in HIV-infected individuals and may be associated with decreased survival.

OBJECTIVE

To ascertain the impact of highly active antiretroviral therapy (HAART) on anemia and the relationship between anemia and overall survival in HIV-infected women.

METHODS

A prospective multicenter study of HIV-1 infection in women. Visits occurred every 6 months, including a standardized history, physical examination, and comprehensive laboratory evaluation. The setting was a university-affiliated clinic at 6 sites in the United States. Participants were 2056 HIV-infected women from the Women's Interagency HIV Study (WIHS). The outcome measure was anemia, defined as hemoglobin (Hb) <12 g/dL. Survival analysis was based on overall mortality during the follow-up period.

RESULTS

Among HIV-infected women who were not anemic at baseline, 47% became anemic by 3.5 years of follow-up. On multivariate analysis, the use of HAART was associated with resolution of anemia even when used for only 6 months (odds ratio [OR] = 1.45; P < 0.05). In the multivariate model, a CD4 cell count <200 cells/microL (OR = 0.56; P < 0.001); HIV-1 RNA level > or =50,000 copies/mL (OR = 0.65; P < 0.001), and mean corpuscular volume (MCV) value <80 fL (OR = 0.40; P < 0.001) were also associated with an inability to correct anemia. Similarly, use of HAART for 12 months or more was associated with a protective effect against development of anemia (OR = 0.71; P < 0.001). Among HIV-infected women, anemia was independently associated with decreased survival (hazard ratio [HR] = 2.58; P < 0.001). Other factors associated with decreased survival included a CD4 cell count <200 cells/microL (HR = 5.83; P < 0.001), HIV-1 RNA level > or = 50,000 copies/mL (HR = 2.12; P < 0.001), and clinical diagnosis of AIDS (HR = 2.83; P < 0.001).

CONCLUSIONS

Anemia is an independent risk factor for decreased survival among HIV-infected women. HAART therapy for as little as 6 months is associated with resolution of anemia.

Stem cells and immune reconstitution in AIDS

The hematopoietic system generally has reserve sufficient to tolerate significant insult and regenerative capacity to overcome most damage due to infectious agents. However, HIV infection results in a progressive decline in hematopoietic function and even in the context of potent, anti-retroviral therapy is able to only incompletely reconstitute immune function. The ability of the immune system to respond to HIV itself remains compromised, a defect that leaves infected individuals with a lifelong dependence on medications. The capability of stem cells and the thymus to restore function and their limitations in the context of HIV infection are discussed in this review.

The CCR5 and CXCR4 coreceptors--central to understanding the transmission and pathogenesis of human immunodeficiency virus type 1 infection

In this review, we will discuss what is known, what is suspected, and what still remains obscure about the central role played by coreceptor expression and usage in the transmission and pathogenic consequences of human immunodeficiency virus type 1 (HIV-1) infection. An emphasis will be on the HIV-1 phenotypic variants that are defined by their usage of the CCR5 or CXCR4 coreceptors, and how the different cellular tropism of these variants influences how and where HIV-1 replicates in vivo. We will also review what might happen when coreceptor antagonists are used clinically to treat HIV-1 infection.

Treatment of human immunodeficiency virus-related lymphoma with haematopoietic stem cell transplantation

The advent of highly active antiretroviral therapy (HAART) and its co-administration with chemotherapy in patients with human immunodeficiency virus (HIV)-related lymphoma has lead to the exploration of potentially curative combination chemotherapy and myeloablative therapy followed by autologous haematopoietic stem cell transplantation (ASCT). Applying the same principles used for patients with HIV-negative aggressive lymphoma, in 1998 we developed a program of high-dose therapy and ASCT at City of Hope for patients with HIV-related lymphoma and Hodgkin's disease. Our studies have primarily included patients with chemosensitive lymphoma in relapse or first remission with poor-risk features at diagnosis. Filgrastim (G-CSF)-primed peripheral blood stem cell mobilization and apheresis have been successful while patients were receiving HAART and chemotherapy. To date, ASCT has been performed in 19 patients with HIV-related lymphoid malignancies, representing the largest single-institution experience reported to date. Most patients received a chemotherapy-based conditioning regimen consisting of high-dose carmustine, etoposide and cyclophosphamide. Early infections, namely bacteremias and neutropenic fever were similar to those observed in the HIV-negative transplant setting. Opportunistic infections were rare and easily treatable. There were three early deaths, two from relapsed lymphoma and one from multi-organ failure in an older patient. The remaining 16 patients are alive and in remission. In summary, ASCT is well tolerated, can result in long-term remissions, and is potentially curative in selected HIV-related lymphoma patients with chemosensitive relapse and high-risk disease in first remission defined by the age-adjusted International Prognostic Index criteria (i.e., two or three of the following: elevated LDH, advanced stage, and poor performance status). Acquisition of resistance to HAART remains as a potential problem for HIV-positive patients who are cured of their lymphoma.

Human T-cell leukemia virus type 1 tax oncoprotein suppression of multilineage hematopoiesis of CD34+ cells in vitro

Human T-cell leukemia virus type 1 (HTLV-1) and HTLV-2 are highly related viruses that differ in disease manifestation. HTLV-1 is the etiologic agent of adult T-cell leukemia and lymphoma, an aggressive clonal malignancy of human CD4-bearing T lymphocytes. Infection with HTLV-2 has not been conclusively linked to lymphoproliferative disorders. We previously showed that human hematopoietic progenitor (CD34(+)) cells can be infected by HTLV-1 and that proviral sequences were maintained after differentiation of infected CD34(+) cells in vitro and in vivo. To investigate the role of the Tax oncoprotein of HTLV on hematopoiesis, bicistronic lentiviral vectors were constructed encoding the HTLV-1 or HTLV-2 tax genes (Tax1 and Tax2, respectively) and the green fluorescent protein marker gene. Human hematopoietic progenitor (CD34(+)) cells were infected with lentivirus vectors, and transduced cells were cultured in a semisolid medium permissive for the development of erythroid, myeloid, and primitive progenitor colonies. Tax1-transduced CD34(+) cells displayed a two- to fivefold reduction in the total number of hematopoietic clonogenic colonies that arose in vitro, in contrast to Tax2-transduced cells, which showed no perturbation of hematopoiesis. The ratio of colony types that developed from Tax1-transduced CD34(+) cells remained unaffected, suggesting that Tax1 inhibited the maturation of relatively early, uncommitted hematopoietic stem cells. Since previous reports have linked Tax1 expression with initiation of apoptosis, lentiviral vector-mediated transduction of Tax1 or Tax2 was investigated in CEM and Jurkat T-cell lines. Ectopic expression of either Tax1 or Tax2 failed to induce apoptosis in T-cell lines. These data demonstrate that Tax1 expression perturbs development and maturation of pluripotent hematopoietic progenitor cells, an activity that is not displayed by Tax2, and that the suppression of hematopoiesis is not attributable to induction of apoptosis. Since hematopoietic progenitor cells may serve as a latently infected reservoir for HTLV infection in vivo, the different abilities of HTLV-1 and -2 Tax to suppress hematopoiesis may play a role in the respective clinical outcomes after infection with HTLV-1 or -2.

Should HIV-positive patients with lymphoma be offered stem cell transplants?

Advances in effective antiretroviral therapy for HIV infection have made high-dose therapy and autologous stem cell transplantation possible in patients with HIV-associated lymphomas. Regimen-related toxicity is not significantly increased when antiretroviral therapy is combined with high-dose chemoradiotherapy. Durable engraftment can be seen with autologous stem cell rescue. Infectious complications can be managed with a combination of surveillance and prophylaxis. Long-term remissions of these high-risk lymphomas can be achieved with this approach. This suggests that patients with HIV-associated lymphomas should be considered for autologous transplantation in a manner similar to HIV-negative lymphoma patients.

HIV-1 replication and pathogenesis in the human thymus

How HIV replicates and causes destruction of the thymus, and how to restore thymic function, are among the most important questions of HIV-1 pathogenesis and therapy in adult as well as pediatric patients. The thymus appears to function, albeit at reduced levels, throughout the life of adults, to respond to T cell depletion induced by HIV and to be suppressed by HIV. In this review, we summarize recent findings concerning HIV replication and pathogenesis in the human thymus, focusing on mechanistic insights gleaned from studies in the SCID-hu Thy/Liv mouse and human fetal-thymus organ culture (HF-TOC) models. First, we discuss HIV viral determinants and host factors involved in the replication of HIV in the thymus. Second, we consider evidence that both viral factors and host factors contribute to HIV-induced thymocyte depletion. We thus propose that multiple mechanisms, including depletion and suppression of progenitor cells, paracrine and direct lytic depletion of thymocytes, and altered thymocyte selection are involved in HIV-induced pathology in the thymus. With the SCID-hu Thy/Liv mouse and HF-TOC models, it will be important in the coming years to further clarify the virological, cell biological, and immunological mechanisms of HIV replication and pathogenesis in human thymus, and to correlate their significance in HIV disease progression.

Immune reconstitution in HIV infection and its relationship to cancer

HIV infection results in formidable immune dysfunction, widely affecting the immune system, but typified by T lymphopenia. This dysfunction includes a perturbed immune response to several persistent viruses that have a propensity to cause tumors. Effective control of HIV replication by highly active antiretroviral therapy (HAART) results in regeneration of the damaged immune system, and recent advances have allowed this immune reconstitution to be better defined. This article describes the immunodeficiency caused by HIV and the response of the immune system to HAART, with specific reference to the immune response to cancers associated with HIV infection.

HIV type 1 infection alters cytokine mRNA expression in thymus

We and others have previously shown that HIV infection of human thymus/liver implants in severe combined immunodeficient (SCID-hu Thy/Liv) mice results in a loss of CD4(+) thymocytes and a decreased recovery of human myeloid and erythroid colony-forming activity. Furthermore, our previous studies have shown that this decrease in colony-forming potential is due to indirect effects, rather than to massive loss of CD34(+) hematopoietic progenitor cells, suggesting that HIV infection might alter expression of hematopoietic cytokines. Herein we have investigated potential HIV-1-induced perturbations of hematolymphoid microenvironments by determining the effect of HIV-1 infection on levels of cytokine mRNAs in human stroma and thymocytes, using the reverse transcription-polymerase chain reaction (RT-PCR). The levels of interleukin 6 (IL-6), interferon gamma (IFN-gamma), and IL-2 RNAs increased and macrophage inflammatory protein 1beta (MIP-1beta) RNA decreased significantly in infected thymocytes. IL-6 RNA levels in stroma also increased somewhat with infection; however, expression of stromal cell-derived factor 1 (SDF-1) by stromal elements was not affected. IL-4 RNA levels were unaffected by infection in both stroma and thymocytes. Antiretroviral drug treatment of the infected animals, which results in restoration of colony-forming potential, tends to restore the cytokine mRNA levels in HIV-1-infected implants to those of mock-infected implants. These results indicate that HIV-1 infection can greatly distort the cytokine profiles in Thy/Liv implants, and suggest that cytokine perturbation could be involved in virus-induced inhibition of hematopoiesis.

The effects of different HIV type 1 strains on human thymic function

Studies of HIV-1-infected humans indicate that the thymus can be infected by HIV-1. In some of these patients, there is a significant CD4(+) T cell decline and a faster disease progression. This phenomenon is more evident in pediatric patients who depend heavily on their thymus for generation of new T cells. We hypothesize that HIV-1 causes T cell regenerative failure within the thymus, which has a profound impact on disease progression. Building on our established human thymopoiesis model, we include dynamic interactions between different HIV-1 strains (R5 and X4) and thymocytes. Our results predict that thymic infection with different HIV-1 strains induces thymic dysfunction to varying degrees, contributing to differences in disease progression as observed in both HIV-1-infected children and adults. Thymic infection in children is more severe than in adults, particularly during X4 infection. This outcome is likely due to both a higher viral load and a more active thymus in pediatric patients. Our results also indicate that a viral strain switch from R5 to X4 induces further deterioration in thymopoiesis. We predict that both viral and host factors play key roles in controlling thymic infection, including strain virulence and health status of the thymus.

Toward cellular-based therapies for HIV infection

Infection with HIV-1 progressively erodes immune function, leading ultimately to multiple hematopoietic cytopenias. In advanced HIV disease, anemia, neutropenia, and thrombocytopenia occur in a large fraction of patients and are reflective of a striking inability of the bone marrow to accomplish a compensatory increase in production. No failure of compensatory production is greater than that of the T lymphoid system, where despite apparently effective control of HIV replication, restoration of anti-HIV immunity does not occur. Recent technical developments have provided considerable insight into hematopoietic dysfunction in HIV disease and, in particular, in vivo T cell generation. This article will review some of the mechanisms participating in immune regeneration, the stakes involved in effectively accomplishing full reconstitution, and potential approaches to enhance the limited endogenous regenerative process.

Hematologic Aspects of HIV/AIDS

This review addresses various aspects of HIV infection pertinent to hematology, including the consequences of HIV infection on specific aspects of hematopoiesis and an update on the current biologic, epidemiologic and therapeutic aspects of AIDS-related lymphoma and Hodgkin's disease. The results of the expanding use of progenitor cell transplantation in HIV infected patients are also reviewed. In Section I, Dr. Scadden reviews the basis for HIV dysregulation of blood cell production, focusing on the role of the stem cell in HIV disease. T cell production and thymic function are discussed, with emphasis placed upon the mechanisms of immune restoration in HIV infected individuals. Results of clinical and correlative laboratory studies are presented. In Section II, Dr. Levine reviews the recent epidemiologic trends in the incidence of lymphoma, since the widespread availability of highly active anti-retroviral therapy (HAART). The biologic aspects of AIDS-lymphoma and Hodgkin's disease are discussed in terms of pathogenesis of disease. Various treatment options for these disorders and the role of concomitant anti-retroviral and chemotherapeutic intervention are addressed. Drs. Zaia and Krishnan will review the area of stem cell transplantation in patients with AIDS related lymphoma, presenting updated information on clinical results of this procedure. Additionally, they report on the use of gene therapy, with peripheral blood CD34+ cells genetically modified using a murine retrovirus, as a means to treat underlying HIV infection. Results of gene transfer experiments and subsequent gene marking in HIV infected patients are reviewed.

Early and persistent bone marrow hematopoiesis defect in simian/human immunodeficiency virus-infected macaques despite efficient reduction of viremia by highly active antiretroviral therapy during primary infection

The hematological abnormalities observed in human immunodeficiency virus (HIV)-infected patients appear to be mainly due to bone marrow dysfunction. A macaque models of AIDS could greatly facilitate an in vivo approach to the pathogenesis of such dysfunction. Here, we evaluated in this model the impact of infection with a pathogenic simian/human immunodeficiency virus (SHIV) on bone marrow hematopoiesis. Three groups of macaques were inoculated with 50 50% median infective doses of pathogenic SHIV 89.P, which expresses env of dual-tropic HIV type 1 (HIV-1) 89.6 primary isolate. During the primary phase of infection, animals were treated with either a placebo or highly active antiretroviral therapy (HAART) combining zidovudine, lamivudine, and indinavir, initiated 4 or 72 h postinfection (p.i.) and administered twice a day until day 28 p.i. In both placebo-treated and HAART-treated animals, bone marrow colony-forming cells (CFC) progressively decreased quite early, during the first month p.i. One year p.i., both placebo- and HAART-treated animals displayed decreases in CFC to about 56% of preinfection values. At the same time, a dramatic decrease (greater than 77%) of bone marrow CD34(+) long-term culture-initiating cells was noted in all animals were found. No statistically significant differences between placebo- and HAART-treated monkeys were found. These data argue for an early and profound alteration of myelopoiesis at the level of the most primitive CD34(+) progenitor cells during SHIV infection, independently of the level of viremia, circulating CD4(+) cell counts, or antiviral treatment.