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

HIV infection of thymocytes inhibits IL-7 activity without altering CD127 expression

Abstract Background Thymic function is altered in HIV infection and characterized by dysregulation of the thymic epithelial network, reduced thymic output and ultimately an impaired naïve T-cell pool. The IL-7/IL-7 receptor (IL-7R) signalling pathway is critical for the maturation and differentiation of thymocytes. HIV infection is associated with a decrease in IL-7Rα (CD127) expression and impaired CD127 signalling in circulating CD8+ T-cells; however, little is known about the effect of HIV on CD127 expression and IL-7 activity in the thymus. Therefore, the effect of in vitro HIV infection on CD127 expression and IL-7-mediated function in thymocytes was investigated. Findings In vitro HIV infection of thymocytes did not affect CD127 expression on either total thymocytes or on single positive CD4 or single positive CD8 subsets. However, HIV infection resulted in a decrease in the level of IL-7-induced STAT-5 phosphorylation and Bcl-2 expression in unfractionated thymocytes. Conclusion These findings indicate that HIV infection alters IL-7 responsiveness of thymocytes by a mechanism other than CD127 downregulation and potentially explain the disruption in thymopoiesis observed in HIV infection

CD8+ T-Cell Interleukin-7 Receptor Alpha Expression as a Potential Indicator of Disease Status in HIV-Infected Children

Background: Initiation and modification of antiretroviral therapy in HIV-infected children depend on viral load and CD4+ T-cell count. However, these surrogates have limitations, and complementary immunological markers to assess therapeutic response are needed. Our aim was to evaluate CD8+ T-cell expression of CD127 as a marker of disease status in HIV-infected children, based on adult data suggesting its usefulness. We hypothesized that CD127 expression on CD8+ T-cells is lower in children with more advanced disease. Methods: In a cross-sectional evaluation, we used flow cytometry to measure CD127+ expression on CD8+ T-cells in whole blood from HIV-infected children with varying disease status. This was compared with expression of CD38 on this subset, currently used in clinical practice as a marker of disease status. Results: 51 HIV-infected children were enrolled. There was a strong positive correlation between CD127 expression on CD8+ T-cells and CD4+ T-cell count, and height and weight z-scores, and a strong negative correlation between CD127 expression and viral load. In contrast, we found no association between CD38 expression and these disease status markers. Conclusions: CD8+ T-cell CD127 expression is significantly higher in children with better HIV disease control, and may have a role as an immunologic indicator of disease status. Longitudinal studies are needed to determine the utility of this marker as a potential indicator of HIV disease progression

Development of a Quantitative Bead Capture Assay for Soluble IL-7 Receptor Alpha in Human Plasma

IL-7 is an essential cytokine in T-cell development and homeostasis. It binds to the IL-7R receptor, a complex of the IL-7Rα (CD127) and common γ (CD132) chains. There is significant interest in evaluating the expression of CD127 on human T-cells as it often decreased in medical conditions leading to lymphopenia. Previous reports showed the usefulness of CD127 as a prognostic marker in viral infections such as HIV, CMV, EBV and HCV. A soluble CD127 (sCD127) is released in plasma and may contribute to disease pathogenesis through its control on IL-7 activities. Measuring sCD127 is important to define its role and may complement existing markers used in lymphopenic disease management. We describe a new quantitative assay for the measurement of sCD127 in plasma and report sCD127 concentrations in healthy adults.We developed a quantitative bead-based sCD127 capture assay. Polyclonal CD127-specific antibodies were chosen for capture and a biotinylated monoclonal anti-CD127 antibody was selected for detection. The assay can detect native sCD127 and recombinant sCD127 which served as the calibrator. The analytical performance of the assay was characterized and the concentration and stability of plasma sCD127 in healthy adults was determined. The assay's range was 3.2–1000 ng/mL. The concentration of plasma sCD127 was 164±104 ng/mL with over a log variation between subjects. Individual sCD127 concentrations remained stable when measured serially during a period of up to one year.This is the first report on the quantification of plasma sCD127 in a population of healthy adults. Soluble CD127 plasma concentrations remained stable over time in a given individual and sCD127 immunoreactivity was resistant to repeated freeze-thaw cycles. This quantitative sCD127 assay is a valuable tool for defining the potential role of sCD127 in lymphopenic diseases

Dimensions for a taxonomy of dynamic and hazardous work environments

Abstract OnlyPeer reviewed: YesNRC publication: Ye

STABILON, a Novel Sequence Motif That Enhances the Expression and Accumulation of Intracellular and Secreted Proteins

The dynamic balance of transcriptional and translational regulation together with degron-controlled proteolysis shapes the ever-changing cellular proteome. While a large variety of degradation signals has been characterized, our knowledge of cis-acting protein motifs that can in vivo stabilize otherwise short-lived proteins is very limited. We have identified and characterized a conserved 13-mer protein segment derived from the p54/Rpn10 ubiquitin receptor subunit of the Drosophila 26S proteasome, which fulfills all the characteristics of a protein stabilization motif (STABILON). Attachment of STABILON to various intracellular as well as medically relevant secreted model proteins resulted in a significant increase in their cellular or extracellular concentration in mammalian cells. We demonstrate that STABILON acts as a universal and dual function motif that, on the one hand, increases the concentration of the corresponding mRNAs and, on the other hand, prevents the degradation of short-lived fusion proteins. Therefore, STABILON may lead to a breakthrough in biomedical recombinant protein production