High SDF-1 expression in HIV-1 carriers does not correlate with CD8+ T-cell-mediated suppression of viral replication

The altered expression of homing factors in CD34+ hematopoietic stem cells following G-CSF injection and its effects on transplantation quality in ALL patients

Hematopoietic stem cells (HSCs) transplantation is considered a suitable treatment for malignant or nonmalignant hematological diseases. This study aims to investigate the HSCs homing factors in bone marrow (BM) donors of acute lymphoblastic leukemia (ALL) patients following granulocyte colony-stimulating factor (G-CSF) injection, as well as the G-CSF effects on BM transplantation quality in these patients. To mobilize HSCs into peripheral blood, G-CSF was used for ALL patient's BM donors. For HSCs counting, CD34+ cells were evaluated in analogous and autologous donors using flow cytometry. The expression of stem cell homing factors in CD34+ cells and peripheral blood mononuclear cells (PBMCs) were investigated using a real-time polymerase chain reaction. Finally, hematological factors after BM transplantation in ALL patients were assessed. According to our results, after G-CSF injection, the level of CD34+ HSCs was statistically increased. Besides, autologous donors showed a higher level of CD34+ cells compared to analogous donors before and after G-CSF injection. Additionally, a higher number of CD34+ HSCs was achieved in the autologous samples following G-CSF injection. Furthermore, after G-CSF injection, the expression of matrix metalloproteinase (MMP)-2, MMP-9 was increased; while, stromal cell-derived factor 1, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 expression were decreased. Moreover, the expression of C-X-C chemokine receptor type 4, lymphocyte function-associated antigen 1, and very late antigen-4 in CD34+ cells and PBMCs were decreased. BM transplantation on Day 90 also caused an increased level of white blood cells, red blood cells, and platelets as compared to the first day; however, no statistical differences were observed in hemoglobin level. In conclusion, G-CSF by altering the expression of HSCs homing factors in ALL donors improves BM transplantation quality in ALL patients.

The CD8+ T Cell Noncytotoxic Antiviral Responses

The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.

Allo-antigen stimulated CD8+ T-cells suppress NF-κB and Ets-1 DNA binding activity, and inhibit phosphorylated NF-κB p65 nuclear localization in CD4+ T-cells

CD8+ T-cells of asymptomatic HIV-1 carriers (AC) suppress human immunodeficiency virus type 1 (HIV-1) replication in a class I major histocompatibility complex (MHC-I)-restricted and -unrestricted manner. In order to investigate the mechanism of MHC-I-unrestricted CD8+ T-cell-mediated HIV-1 suppression, we previously established allo-antigen stimulated CD8+T-cells from HIV-1-uninfected donors. These allo-antigen stimulated CD8+ T-cells suppressed HIV-1 replication in acutely infected autologous CD4+ T-cells when directly co-cultured. To elucidate the mechanism of HIV-1 replication suppression, we analyzed DNA-binding activity and phosphorylation of transcriptional factors associated with HIV-1 replication by electrophoresis mobility shift assay and Western blotting. When CD4+ T-cells were cultured with allo-antigen stimulated CD8+ T-cells, the reduction of NF-κB and Ets-1 DNA-binding activity was observed. Nuclear localization of NF-κB p65 and Ets-1 was suppressed in CD4+ T-cells. Although NF-κB p65 and Ets-1 are known to be regulated by protein kinase A (PKA), no difference was observed in the expression and phosphorylation of the PKA catalytic subunit in CD4+ T-cells cultured with PHA-treated CD8+ T-cells or allo-antigen stimulated CD8+ T-cells. Cyclic AMP is also known to enter through gap junctions, but the suppression of HIV-1 replication mediated by allo-antigen stimulated CD8+ T-cells was not affected by the gap junction inhibitor. The nuclear transport of phosphorylated NF-κB p65 (Ser276) was inhibited only in CD4+ T-cells cultured with allo-antigen stimulated CD8+ T-cells. Our results indicate that allo-antigen stimulated CD8+ T-cells suppress the transcriptional activity of NF-κB p65 or Ets-1 in an antigen-nonspecific manner, and inhibit the nuclear transport of phosphorylated NF-κB p65 (Ser276).

SDF-1alpha is a potent inducer of HIV-1-Specific CD8+ T-cell chemotaxis, but migration of CD8+ T cells is impaired at high viral loads

Multiple impairments in HIV-1-specific cytotoxic T cells (CTL) have been reported, but derangements in HIV-1-specific CD8+ T-cell chemotaxis have not been described previously. We assessed migration to SDF-1alpha (stromal cell-derived factor 1-alpha) and CX3CL1 in vitro and expression of cognate receptors, CXCR4 and CX3CR1, by flow cytometry in peripheral blood and lymph node CD8+ T cells from HIV-1-seropositive and -seronegative individuals. Compared with seronegative individuals, percentages of CXCR4+CD8+ T cells were reduced (median, 26% versus 74%, p < 0.001) and percentages of CX3CR1+CD8+ T cells were increased (median, 33% versus 15%, p = 0.03) in seropositive individuals. Robust migration of peripheral blood mononuclear cell (PBMC) CD8+ T cells to SDF-1alpha (1 alphag/ml) was observed in both HIV-1-seropositive (median chemotactic index [CI] 4.9) and -seronegative (median CI 2.8) subjects (p = 0.46). CI to SDF-1alpha was not significantly related to percentage of CXCR4+CD8+ T cells or density of CXCR4, but correlated inversely with plasma HIV-1 RNA concentration (r = -0.82, p = 0.03). Little chemotaxis was observed in response to CX3CL1 and it was unrelated to CX3CR1 expression. Lymph node CD8+ T-cell chemotaxis to SDF-1alpha and CX3CL1 in four subjects demonstrated the same patterns observed in PBMC. HIV-1-specific tetramer-staining CD8+ T cells exhibited chemotaxis of similar magnitude as PBMC CD8+ T cells in a subset of subjects. These data suggest that SDF-1alpha is a potent chemoattractant for HIV-1-specific CTL, but that impairments in migration of HIV-1-specific CTL may exist at high viral loads. Improved understanding of the determinants of CTL localization may provide insight into novel therapies to enhance delivery of CTL to sites of HIV-1 replication.

Suppression of HIV-1 Replication by HIV-1-Irrelevant CD8+Cytotoxic T Lymphocytes Resulting in Preservation of Persistently HIV-1-Infected CellsIn Vitro

CD8+ cells of asymptomatic HIV-1 carriers (AC) contain HIV-1-specific cytotoxic T lymphocytes (CTLs) but suppress HIV-1 replication in a class I major histocompatibility complex (MHC-I)-unrestricted manner. In order to selectively investigate the HIV-1-suppressive function of CTLs apart from HIV-1-specific cytotoxicity, HIV-1-irrelevant allo-specific CTLs were established from an HIV-1-uninfected individual and their HIV-1-suppressive activity against autologous CD4+ peripheral blood mononuclear cells (PBMC) was examined. We found that these CTLs significantly suppressed both R5 and X4-HIV-1 replication in either acutely or persistently infected autologous PBMC. Although these CTLs partially killed HIV-1-infected PBMC through Fas ligand, CTLs still suppressed late steps of HIV-1 replication in the presence of neutralizing antibodies to Fas ligand. HIV-1 replication in PBMC that had been suppressed by CTLs was reversible following depletion of CTLs from culture, analogous to the previous observation for CD8+ cell-depleted PBMC of AC. Induction of HIV-1 replication by CTL-depletion was amplified by addition of newly prepared CD4+ cells or activation with staphylococcal enterotoxin B. Our results indicate that CTLs can suppress HIV-1 replication in PBMC in an antigen-nonspecific manner and preserve infected cells in a state capable of restarting HIV-1 replication and transmission.

Elevated plasma stromal cell-derived factor 1 protein level in the progression of HIV type 1 infection/AIDS

Stromal cell-derived factor 1 (SDF-1) is a unique chemokine involved in multiple organogenesis as well as in the regulation of HIV infection. Here we determined the plasma SDF-1 concentrations of 193 HIV-1-infected individuals and 154 normal Japanese volunteers by developing a highly sensitive measurement system based on time-resolved fluoroimmunoassay (SDF-1 TR-FIA). This system is also valid for the mouse model to quantitate circulating SDF-1 concentration in vivo and thereby its correlation with CXCR4 expression level on CD4(+) T cells. Interestingly, plasma SDF-1 concentrations in HIV-1-infected individuals were three times higher than those in a normal control group and plasma SDF-1 protein levels showed an inverse correlation with CD4(+) T cell count and a positive correlation with plasma HIV-1 RNA load. Notably, individuals with later stage HIV-1 infection, who maintained fewer than 200 CD4(+) T cells per cubic milliliter and more than 10,000 copies of HIV-1 RNA per milliliter, showed the highest plasma SDF-1 level among individuals at any stage of HIV-1 infection. These results suggest that endogenous SDF-1 is upregulated by HIV-1 infection, particularly in late-stage HIV-1 infection/AIDS.

Cytokines and HIV-1: interactions and clinical implications

Cytokines play an important role in controlling the homoeostasis of the immune system. Infection with HIV results in dysregulation of the cytokine profile in vivo and in vitro. During the course of HIV-1 infection secretion of T-helper type 1 (Th1) cytokines, such as interleukin (IL)-2, and antiviral interferon (IFN)-gamma, is generally decreased, whereas production of T helper type 2 (Th2) cytokines, IL-4, IL-10, proinflammatory cytokines (IL-1, IL-6, IL-8) and tumour necrosis factor (TNF)-alpha, is increased. Such abnormal cytokine production contributes to the pathogenesis of the disease by impairing cell-mediated immunity. A number of cytokines have been shown to modulate in vitro HIV-1 infection and replication in both CD4 T lymphocytes and cells of macrophage lineage. HIV-inductive cytokines include: TNF-alpha, TNF-beta, IL-1 and IL-6, which stimulate HIV-1 replication in T cells and monocyte-derived macrophages (MDM), IL-2, IL-7 and IL-15, which upregulate HIV-1 in T cells, and macrophage-colony stimulating factor, which stimulates HIV-1 in MDM. HIV-suppressive cytokines include: IFN-alpha, IFN-beta and IL-16, which inhibit HIV-1 replication in T cells and MDM, and IL-10 and IL-13, which inhibit HIV-1 in MDM. Bifunctional cytokines such as IFN-gamma, IL-4 and granulocyte-macrophage colony-stimulating factor have been shown to have both inhibitory and stimulatory effects on HIV-1. The beta-chemokines, macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta and RANTES are important inhibitors of macrophage-tropic strains of HIV-1, whereas the alpha-chemokine stromal-derived factor-1 suppresses infection of T-tropic strains of HIV-1. This review outlines the interactions between cytokines and HIV-1, and presents clinical applications of cytokine therapy combined with highly active antiretroviral therapy or vaccines.