miR-146a controls CXCR4 expression in a pathway that involves PLZF and can be used to inhibit HIV-1 infection of CD4+ T lymphocytes

Abstract MicroRNA miR-146a and PLZF are reported as major players in the control of hematopoiesis, immune function and cancer. PLZF is described as a miR-146a repressor, whereas CXCR4 and TRAF6 were identified as miR-146a direct targets in different cell types. CXCR4 is a co-receptor of CD4 molecule that facilitates HIV-1 entry into T lymphocytes and myeloid cells, whereas TRAF6 is involved in immune response. Thus, the role of miR-146a in HIV-1 infection is currently being thoroughly investigated. In this study, we found that PLZF mediates suppression of miR-146a to control increases of CXCR4 and TRAF6 protein levels in human primary CD4 + T lymphocytes. We show that miR-146a upregulation by AMD3100 treatment or PLZF silencing, decreases CXCR4 protein expression and prevents HIV-1 infection of leukemic monocytic cell line and CD4 + T lymphocytes. Our findings improve the prospects of developing new therapeutic strategies to prevent HIV-1 entry via CXCR4 by using the PLZF/miR-146a axis

Exosomes: Potential model for complement-stealth delivery systems

Exosomes are nature's nanocarriers that transport biological information in humans. Their structural properties, origin and functions are making them interesting objects for the diagnosis of diseases, such as cancer, and also, as innovative tools for drug delivery. The interaction of exosomes with the immune system has been one of the focal points of interest; nevertheless their "stealth" properties helping to avoid adverse immune reactions are still not fully understood. In this review, after giving an overview of recent findings on the role of exosomes in disease pathogenesis and physiological functions, we focused on their interaction with the immune system and possibilities for clinical applications. The potential of exosomes of creating stealth nanoparticles that are better tolerated by the immune system than the presently available synthetic drug delivery systems represent a promising new approach in nanomedicine. © 2015 by De Gruyter 2015

Transcellular communication at the immunological synapse: A vesicular traffic-mediated mutual exchange

The cell's ability to communicate with the extracellular environment, with other cells, and with itself is a crucial feature of eukaryotic organisms. In the immune system, T lymphocytes assemble a specialized structure upon contact with antigen-presenting cells bearing a peptide-major histocompatibility complex ligand, known as the immunological synapse (IS). The IS has been extensively characterized as a signaling platform essential for T-cell activation. Moreover, emerging evidence identifies the IS as a device for vesicular traffic-mediated cell-to-cell communication as well as an active release site of soluble molecules. Here, we will review recent advances in the role of vesicular trafficking in IS assembly and focused secretion of microvesicles at the synaptic area in naïve T cells and discuss the role of the IS in transcellular communication

HIV-1-infected cells transiently express lentiviral RNA shuttled by exosomes

Aims: Exosomes are lipid bilayer vesicles of 50-100 nm released by basically all cell types. We recently reported that full-length HIV-1 RNA and lentiviral vector (LV) genome associate with exosomes through similar mechanisms. Here, we investigated the fate of lentiviral RNA shuttled by exosomes in target cells. Material & methods: Exosomes from cells transduced by a LV expressing green fluorescent protein under the control of an heterologous promoter were purified by iodixanol gradients and used to evaluate the LV expression in target cells. Results: The genome of LV incorporated in exosomes can be expressed in HIV-1-infected cells, but not in those that are uninfected, despite apparently similar levels of exosome internalization. The expression disappeared 2-3 days after challenge, and was blocked by pre-treatment with azidothymidine. Conclusion: Lentiviral genome incorporated in exosomes can be expressed in target cells having reverse transcriptase activity

Cell activation and HIV-1 replication in unstimulated CD4+ T lymphocytes ingesting exosomes from cells expressing defective HIV-1

Background: A relevant burden of defective HIV-1 genomes populates PBMCs from HIV-1 infected patients, especially during HAART treatment. These viral genomes, although unable to codify for infectious viral particles, can express viral proteins which may affect functions of host cells as well as bystander ones. Cells expressing defective HIV-1 have a lifespan longer than that of cells producing infectious particles. Hence, their interaction with other cell types, including resting lymphocytes, is expected to occur frequently in tissues where HIV actively replicates. We investigated the effects of the expression of a prototype of functionally defective HIV-1 on bystander, unstimulated CD4(+) T lymphocytes. Results: We observed that unstimulated human primary CD4(+) T lymphocytes were activated and became permissive for HIV-1 replication when co-cultivated with cells expressing a functionally defective HIV-1 (F12/Hut-78 cells). This effect depended on the presence in F12/Hut-78 supernatants of nanovesicles we identified as exosomes. By inspecting the underlying mechanism, we found that ADAM17, i.e., a disintegrin and metalloprotease converting pro-TNF-alpha in its mature form, associated with exosomes from F12/Hut-78 cells, and played a key role in the HIV-1 replication in unstimulated CD4(+) T lymphocytes. In fact, the treatment with an inhibitor of ADAM17 abolished both activation and HIV-1 replication in unstimulated CD4(+) T lymphocytes. TNF-alpha appeared to be the downstream effector of ADAM17 since the treatment of unstimulated lymphocytes with antibodies against TNF-alpha or its receptors blocked the HIV-1 replication. Finally, we found that the expression of Nef(F12) in exosome-producing cells was sufficient to induce the susceptibility to HIV-1 infection in unstimulated CD4(+) T lymphocytes. Conclusions: Exosomes from cells expressing a functionally defective mutant can induce cell activation and HIV-1 susceptibility in unstimulated CD4(+) T lymphocytes. This evidence highlights the relevance for AIDS pathogenesis of the expression of viral products from defective HIV-1 genomes