Increased Bone Marrow Interleukin-7 (IL-7)/IL-7R Levels but Reduced IL-7 Responsiveness in HIV-Positive Patients Lacking CD4+ Gain on Antiviral Therapy

Background: The bone marrow (BM) cytokine milieu might substantially affect T-lymphocyte homeostasis in HIV-positive individuals. Interleukin-7 (IL-7) is a bone marrow-derived cytokine regulating T-cell homeostasis through a CD4+-driven feedback loop. CD4+ T-lymphopenia is associated with increased free IL-7 levels and reduced IL-7R expression/function, which are only partially reverted by highly active antiretroviral therapy (HAART). We investigated the BM production, peripheral expression and signaling (pStat5+ and Bcl-2+ CD4+/CD8+ T cells) of IL-7/IL-7Ra in 30 HAART-treated HIV-positive patients who did not experience CD4+ recovery (CD4+ #200/ml) and who had different levels of HIV viremia; these patients included 18 immunological nonresponders (INRs; HIV-RNA#50), 12 complete failures (CFs; HIV-RNA.1000), and 23 HIVseronegative subjects. Methods: We studied plasma IL-7 levels, IL-7Ra+CD4+/CD8+ T-cell proportions, IL-7Ra mRNA expression in PBMCs, spontaneous IL-7 production by BM mononuclear cells (BMMCs), and IL-7 mRNA/IL-7Ra mRNA in BMMC-derived stromal cells (SCs). We also studied T-cell responsiveness to IL-7 by measuring the proportions of pStat5+ and Bcl-2+ CD4+/CD8+ T cells. Results: Compared to HIV-seronegative controls, CFs and INRs presented elevated plasma IL-7 levels and lower IL-7Ra CD4+/CD8+ cell-surface expression and peripheral blood production, confirming the most relevant IL-7/IL-7R disruption. Interestingly, BM investigation revealed a trend of higher spontaneous IL-7 production in INRs (p = .09 vs. CFs) with a nonsignificant trend toward higher IL-7-Ra mRNA levels in BMMC-derived stromal cells. However, upon IL-7 stimulation, the proportion of pStat5+CD4+ T cells did not increase in INRs despite higher constitutive levels (p = .06); INRs also displayed lower Bcl-2+CD8+ T-cell proportions than controls (p = .04). Conclusions: Despite severe CD4+ T-lymphopenia and a disrupted IL-7/IL-7R profile in the periphery, INRs display elevated BM IL-7/IL-7Ra expression but impaired T-cell responsiveness to IL-7, suggesting the activity of a central compensatory pathway targeted to replenish the CD4+ compartment, which is nevertheless inappropriate to compensate the dysfunctional signaling through IL-7 receptor

Immunodysregulation of HIV disease at bone marrow level

Hernatological abnormalities frequently occur in patients infected with HTV-1. Increasing evidence indicates that bone marrow (BM) suppression results from viral infection of accessory cells, with impaired stromal function and alteration of hematopoietic growth factor network. We investigated the effects of antiretroviral therapy on cytokine and chemokine production by BM cells and stromal cells, in a group of HIV-I-infected subjects before and during treatment. Compared with uninfected controls, an altered cytokine and chemokine production by BM cells has been observed before treatment, characterised by decreased IL-2 and elevated TNF-alpha, MIP-1 alpha, MIP-1 beta, and RANTES levels, along with a defective BM clonogenic activity. Antiretroviral therapy determined an amelioration of stem cell activity; a restoration of stromal cell pattern and functions, and an increased IL-2 production at BM level and a decrease of Fas expression on progenitor cells, in parallel with the diminution of TNF-alpha levels. HIV-1 protease inhibitors (PIs) may improve hematopoietic functions owing to their direct effects on the BM progenitor cells. Ritonavir and indinavir increased the colony growth of BM obtained either from HIV-1-infected patients or from normal individuals, in parallel with the normalization of functional and morphologic characteristics of stromal cells. (c) 2005 Elsevier B.V. All rights reserved

HIV type 1 protease inhibitors enhance bone marrow progenitor cell activity in normal subjects and in HIV type 1-infected patients

HIV- 1 protease inhibitors ( PIs) may improve hematopoietic functions owing to their direct effects on bone marrow ( BM) progenitor cells. In this study we investigated this hypothesis evaluating the effect of adding ritonavir ( RTV) and indinavir ( IND) on hematopoietic colony formation assays by colony- forming cell ( CFC) and long- term culture- initiating cell ( LTC- IC) assays, on apoptosis, on cytokine production and stromal cells, in subjects with HIV- 1 infection, and in seronegative controls. After PI addition, CFC and LTC- IC assays in HIV- 1- infected patients showed levels of colony growth significantly higher than those observed at baseline; the same PI activity on colony formation was observed in healthy subjects. No significant modifications on Fas, the membrane form of Fas ( mFas) and Fas- ligand ( FasL) expression, and on cytokine production were observed at BM level after the addition of PIs. At baseline, in HIV- 1- infected patients, the majority of the stromal cells appeared as large and rounded, whereas after the addition of RTV or IND the stromal cells exhibited a " fibroblast- like" morphology and produced higher stem cell factor ( SCF) and lower MIP- 1alpha levels when compared with the stromal production without the addition of IND. RTV and IND increased colony growth of BM obtained either from HIV- 1- infected patients or from normal individuals, in parallel with the normalization of functional and morphological characteristics of stromal cells

Decreased apoptosis of bone marrow progenitor cells in HIV-1-infected patients during highly active antiretroviral therapy

Impaired haematopoiesis during HIV-1 infection may be caused by the overproduction of inflammatory cytokines by immune cells at the bone marrow level inducing Fas-mediated apoptosis of stem progenitors. In this study, we evaluated the effects of highly active antiretroviral therapy on apoptosis of CD34+ stem cells derived from the bone marrow of HIV-I-infected patients, and observed decreased Fas expression on progenitor cells, in parallel with the diminution of TNF-α levels and the amelioration of clonogenic parameters

T-cell homeostasis alteration in HIV-1 infected subjects with low CD4 T-cell count despite undetectable virus load during HAART

Objective: To investigate the pathogenesis of low CD4 T-cell count in subjects who are immunological non responders (InR) to HAART. Design: Thirty-five HIV-positive subjects on HAART for at least I year, all with undetectable HIV-11 RNA, were studied. Patients were defined as InR according to a CD4 cell increase 20% from baseline and a CD4 cell count > 200/mu l were defined as immunological responders (IR). We performed a comprehensive study to characterize the immune response of InR. Methods: The immunological phenotype of peripheral blood mononuclear cells, thymic naive T cells, T-cell receptor V beta repertoire, serum concentration of interleukin (IL)-7, the expression of IL-7R alpha on naive and memory CD4 and CD8 T cells, and regulatory T cells (T-reg) were studied. Results: In InR a significant reduction (P < 0.0001) of naive and thymic naive CD4 T cells was associated with a reduced expression of IL-7R alpha in both cell subsets, with an increased serum concentration of IL-7 was observed. Furthermore, an increased immune activation with a reduced Treg frequency and increased number of expansions of VP families was observed. Conclusions: The reduced expression of IL-7Ru associated with the persistent immune activation and the alteration of T-reg frequencies in part explains the low level of CD4 T cells observed in InR. (c) 2006 Lippincott Williams & Wilkin