Severe in vitro inhibition of erythropoiesis and transient stimulation of granulopoiesis after bone-marrow infection with eight different HIV-2 isolates

Pathogenesis and clinical implications of HIV-related anemia in 2013

Anemia is a common feature of HIV-related disease and has been uniformly demonstrated to be an independent predictor of morbidity and mortality. Although anemia often responds to combination antiretroviral therapy, many patients remain anemic despite therapy and such persistent anemia continues to negatively affect prognosis regardless of drug response. Anemia is also a common feature of normal aging. We postulate that the pathophysiology of anemia in HIV, especially that which persists in the face of combination antiretroviral therapy, is a reflection of underlying proinflammatory pathways that are also thought to contribute to anemia in the elderly, as well as other age-related chronic diseases such as cardiovascular disease and chronic obstructive pulmonary disease. This suggests that HIV induces inflammatory pathways that are associated with a pattern of accelerated aging and that anemia is a biomarker of these processes. A better understanding of the pathophysiology of HIV-related anemia may provide important entry points for improving the chronic manifestations of HIV-related disease.

A polymorphism in the leptin gene promoter is associated with anemia in patients with HIV disease

To study factors associated with anemia and its effect on survival in HIV-infected persons treated with modern combined antiretroviral therapy (cART), we characterized the prevalence of anemia in the Veterans Aging Cohort Study (VACS) and used a candidate gene approach to identify proinflammatory gene single nucleotide polymorphisms (SNPs) associated with anemia in HIV disease. The study comprised 1597 HIV(+) and 865 HIV(-) VACS subjects with DNA, blood, and annotated clinical data available for analysis. Anemia was defined according to World Health Organization criteria (hemoglobin < 13 g/dL and < 12 g/dL in men and women, respectively). The prevalence of anemia in HIV(+) and HIV(-) subjects was 23.1% and 12.9%, respectively. Independent of HIV status, anemia was present in 23.4% and 8% in blacks and whites, respectively. Analysis of our candidate genes revealed that the leptin -2548 G/A SNP was associated with anemia in HIV(+), but not HIV(-), patients, with the AA and AG genotypes significantly predicting anemia (P < .003 and P < .039, respectively, logistic regression). This association was replicated in an independent cohort of HIV(+) women. Our study provides novel insight into the association between genetic variability in the leptin gene and anemia in HIV(+) individuals.

The HIV-1 Tat protein selectively enhances CXCR4 and inhibits CCR5 expression in megakaryocytic K562 cells

The hematopoietic compartments act as long-term reservoirs for human immunodeficiency virus type-1 (HIV-1). Although hematopoietic progenitor cells (HPCs) are rarely infectable, HPCs committed to the megakaryocytic lineage can be infected and support a productive infection by both the X4 and R5 strains of HIV-1. Indeed, in contrast to the CD34+ progenitors, the lineage-committed HPCs express high levels of the HIV-1 co-receptors, CXCR4 and CCR5. The HIV-1 transactivator (Tat) protein has been shown to alter co-receptor expression in T lymphocytes and macrophages. We hypothesized that Tat may regulate co-receptor expression in lineage-specific HPCs as well. We have monitored the effects of Tat protein on co-receptor expression and on lineage-specific differentiation, using the HPC cell line, K562. Butyric acid (BA)-induced erythroid differentiation in K562 cells was suppressed by 1-100 ng/ml of Tat, as evident from a 70-80% decrease in hemoglobin (Hb) production and a 10-30-fold decrease in glycophorin-A expression. However, Tat treatment enhanced phorbol myristate acetate (PMA)-induced megakaryocytic differentiation, as evident from a 180-210% increase in 3H-serotonin uptake and a 5-12-fold increase in CD61 expression. Tat did not significantly alter co-receptor expression in erythroid cells. However, Tat co-treatment profoundly effected both CXCR4 and CCR5 gene expression and protein levels in megakaryocytic cells. In PMA-stimulated cells, Tat increased CXCR4 and decreased in CCR5 expression, this was potentiated in cells chronically exposed to Tat. In conclusion, Tat protein suppresses erythroid and facilitates megakaryocytic differentiation of K562 cells. In megakaryocytic cells, Tat differentially effected CXCR4 and CCR5 expression. Because megakaryocytes may play a crucial role in HIV-1 infectivity in viral reservoirs, our findings implicate a role for Tat protein in dictating co-receptor usage in lineage-committed HPCs.

HIV influence on hematopoiesis at the initial stage of infection

Alterations in the parameters responsible for the characteristic anemic condition of AIDS patients who are at the final stage of infection have already been established. However, the development of these alterations at the initial stage of infection, where no opportunistic infections occur, needs further study. The goal of this study was to verify whether laboratory alterations observed on patients at the final stages of the disease could already be seen at the beginning of HIV infection, or were the result of opportunistic infections. To that end, HIV-seropositive patients identified by the ELISA test and confirmed by immunofluorescence were screened by infectologist doctors and classified as per the Walter Reed Army Institute System. Results showed that thrombocytopenia occurred at an early stage during HIV infection. The number of leukocytes and erythrocytes diminished progressively as the disease advanced, and levels of hemoglobin, transferrin and serum iron were also diminished with the progression of the disease. These results indicate that the laboratory alterations observed in HIV-seropositive patients during the initial stages were, probably, due to virus infection, because these patients did not present opportunistic infections.

In vitro study of Seraspenide on HIV-induced inhibition of granulopoiesis

Soluble(s) factor(s) produced by HIV-infected cells have been implicated in bone marrow dysfunction observed in AIDS patients. We have shown previously that infected macrophage but not CBMC-derived conditioned medium inhibited the differentiation of purified CD34+ cells, suggesting that accessory cells play a crucial role in granulopoiesis inhibition induced indirectly by HIV. In order to prevent this inhibition we tested the potential protective effect of Seraspenide, a reversible inhibitor of hematopoietic progenitors. We showed that 20 h pretreatment of mononuclear cells with Seraspenide at 10(-10) mol/l prevents CFU-GM inhibition induced by HIV-infected cell-derived conditioned medium.

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.

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.

Involvement of HIV nef protein in abnormal hematopoiesis in AIDS: in vitro study on bone marrow progenitor cells

In previous studies (1-4), we described disrupted hematopoiesis in long-term human bone marrow cultures infected with HIV. Conditioned medium (CM) from HIV-1 non-productively infected liquid cultures inhibits the proliferation of granulo-monocytic progenitor cells (CFU-GM) in clonogenic assays. A growth-inhibitory soluble factor was therefore suspected and we report here that this factor has been identified as the nef gene product. These nef-containing supernatants are specifically neutralized by anti-nef antibodies and recombinant nef has the same growth inhibitory properties. We used a nef-deficient virus to confirm that nef protein is responsible for the in vitro growth inhibition of CFU-GM.

Impaired ability of bone marrow cells from immunodeficient mice to establish long-term cultures

Haemopoiesis is often depressed in patients suffering from acquired immune deficiency syndrome (AIDS). Although several mechanisms have been postulated to be responsible for depressed haemopoiesis in AIDS patients, the aetiology of this disorder is still unknown. We hypothesized that failure of the stromal microenvironment may account for part of the haemopoietic defect observed in patients with AIDS. We therefore studied a murine model of AIDS (MAIDS) caused by infection with LP-BM5 virus to determine the ability of bone marrow cells from immunodeficient mice to establish long-term stromal cultures. In addition, normal and MAIDS mice received AZT (2 mg/ml) in their drinking water for up to 1 month to determine the effects of AZT treatment in vivo on the ability of bone marrow cells to support haemopoiesis in long-term cultures. Decreased numbers of non-adherent cells were observed in long-term bone marrow cultures (LTBMC) of MAIDS mice when compared to cultures derived from normal mice. Decreased numbers of non-adherent cells were observed in cultures of bone marrow cells from AZT-treated normal mice, when compared to untreated normal controls. Cells from AZT-treated MAIDS mice produced the smallest number of non-adherent cells. BFU-E and CFU-G/M were decreased in cultures of MAIDS mice when compared to those of normal mice. AZT-treatment further decreased the number of colony-forming cells in both MAIDS mice and normal cultures. Stromal cell function of MAIDS mice was also assessed by inoculating non-adherent cells from normal mice onto confluent irradiated MAIDS LTBMC. Stroma from MAIDS mice was unable to support haemopoietic function of normal bone marrow cells. Polymerase chain reaction (PCR) analysis of steady state levels of cytokine mRNAs of cells from confluent cultures revealed that levels of interleukin-6 mRNA were unchanged in MAIDS mice, as compared to normal controls, but the levels of GM-CSF were decreased in MAIDS mice. These data suggest that LP-BM5 MuLV infection alters the functioning of the haemopoietic stroma and that one mechanism of this depression in haemopoiesis may be via alterations of cytokine production.

Standardized nested polymerase chain reaction-based assay for detection of human immunodeficiency virus type 1 DNA in whole blood lysates

The routine detection of human immunodeficiency virus type 1 (HIV-1) proviral DNA in clinical samples requires a standardized, simple, and sensitive test. To identify the HIV-1 proviral DNA in blood, we used a solid-phase assay based on the affinity capture and the gamma counting of the amplified product after a nested polymerase chain reaction (AMPLICIS test). In order to simplify the general process, whole-blood lysates rather than peripheral blood mononuclear cell lysates were used for the amplifications. The solid-phase capture and counting of the final amplified products allowed us to define precise interpretive criteria to determine the positivity level of the test. Three new primer sets located in the gag and pol structural genes and in the tat regulatory gene of HIV-1 were studied. The results obtained in 54 seropositive and 120 seronegative individuals demonstrated the ability of the AMPLICIS test to be used for HIV-1 provirus detection: 53 of 54 of the seropositive specimens were found to be positive with at least two primer sets. We also assessed the usefulness of this test for the estimation of the HIV-1 DNA load by the end point dilution method with serial dilutions of blood lysates from 26 HIV-1-seropositive patients.