Federico Martini

Phosphoantigen-Reactive Vγ9Vδ2 T Lymphocytes Suppress In Vitro Human Immunodeficiency Virus Type 1 Replication by Cell-Released Antiviral Factors Including CC Chemokines

Vgamma9Vdelta2 T lymphocytes are broadly reactive against various intracellular pathogens and display both lytic and proliferative responses to human immunodeficiency virus (HIV)-infected cells. HIV infection of peripheral blood mononuclear cell cultures led to absolute increases in Vgamma9Vdelta2 T cells accompanied by decreased p24 levels. Strong gammadelta T cell activation with nonpeptidic mycobacterial phosphoantigens (TUBAg1 extract or synthetic isopentenyl pyrophosphate) resulted in potent inhibition of HIV replication through soluble released factors. Subsequent analyses showed that phosphoantigen-activated gammadelta T cells produced substantial amounts of beta-chemokines (macrophage inflammatory protein [MIP]-1alpha, MIP-1beta, and regulated-on-activation, normal T-cell-expressed and -secreted beta-chemokine [RANTES]), which represent the natural ligand for the CCR5 HIV coreceptor. Accordingly, anti-beta-chemokine antibodies neutralized the inhibition of monocytotropic HIV strains by gammadelta T cell-released factors. Moreover, a T-tropic HIV strain using the CXCR4 coreceptor for virus entry was potently inhibited. Together, these data reveal that phosphoantigen-activated gammadelta T cells are an important source of CC chemokines and may suppress HIV replication through cell-released antiviral factors.

Cutting Edge: TGF-β1 and IL-15 Induce FOXP3+ γδ Regulatory T Cells in the Presence of Antigen Stimulation

Several subsets of αβ regulatory T cells (Tregs) have been described and studied intensively, but the potential regulatory role of γδ T cells remains largely unclear. Lymphocytes expressing γδ TCR are involved in both innate and adaptive immune responses, and their major adult human peripheral blood subset (Vγ9Vδ2) displays a broad reactivity against microbial agents and tumors. In this study we report that γδ T lymphocytes with regulatory functions (Vδ2 Tregs) are induced in vitro in the presence of specific Ag stimulation and cytokines (TGF-β1 and IL-15). These cells express FOXP3 and, similarly as αβ Tregs, suppress the proliferation of anti-CD3/anti-CD28 stimulated-PBMC. Phenotypic and functional analyses of Vδ2 Tregs will very likely improve our understanding about the role of γδ T cells in the pathogenesis of autoimmune, infectious, and neoplastic diseases.

Antiviral reactivities of γδ T cells

Abstract The complex antiviral immune mechanisms involve both adaptive and innate reactions mediated by γδ T lymphocytes, whose unique immunosurveillance contributions are analyzed here in different clinical and experimental settings. It is beyond any doubt that the fast, potent, cytotoxic as well as non-cytolytic antiviral activities of γδ T cells are critical in protecting the host against diverse viral pathogens.

γδ T Cells Cross-Link Innate and Adaptive Immunity in Mycobacterium tuberculosis Infection

Protective immunity against mycobacterial infections such as Mycobacterium tuberculosis is mediated by interactions between specific T cells and activated antigen presenting cells. To date, many aspects of mycobacterial immunity have shown that innate cells could be the key elements that substantially may influence the subsequent adaptive host response. During the early phases of infection, innate lymphocyte subsets play a pivotal role in this context. Here we summarize the findings of recent investigations on γδ T lymphocytes and their role in tuberculosis immunity.

Association of Profoundly Impaired Immune Competence in H1N1v-Infected Patients with a Severe or Fatal Clinical Course

BACKGROUND Pandemic A/H1N1v influenza is characterized by a mild clinical course. However, a small subset of patients develops a rapidly progressive course caused by primary viral pneumonia or secondary bacterial infections that, in many cases, lead to death due to respiratory failure. The aim of the present study was to analyze the involvement of the immune response in the clinical presentation of H1N1v influenza. METHODS The differentiation and functional capability of T cells from H1N1v-infected patients presenting with either mild disease (n=22) or severe or fatal disease (n=6) were compared. Moreover, plasma cytokines and chemokines were quantified. RESULTS T cells from H1N1v-infected patients presenting with a severe clinical course resulted in impaired effector cell differentiation and failed to respond to mitogenic stimulation. T cell anergy was strictly associated with a severe acute phase of infection, but T cells could be restored in patients able to recover. Of interest, massive expression of CD95 marker was found on anergic T cells, suggesting an apoptosis-related mechanism. Finally, lower plasma levels of interferon-alpha and monocyte chemoattractant protein-1 were found in patients with a worse clinical course of influenza, suggesting impaired production of these cytokines. CONCLUSIONS Our results show a strict association between host immune competence and the severity of the clinical course of H1N1v infection. By monitoring host functional response, patients with an enhanced risk of developing influenza-associated severe complications could be identified in a timely manner.

Acute human immunodeficiency virus replication causes a rapid and persistent impairment of Vγ9Vδ2 T cells in chronically infected patients undergoing structured treatment interruption

T cells expressing Vgamma9Vdelta2 display lytic and proliferative responses against human immunodeficiency virus (HIV)-infected cells and release antiviral soluble factors. Chronic HIV-positive patients have deep changes in the composition and function of the circulating gammadelta T cell pool that are restored by highly active antiretroviral therapy (HAART). gammadelta T cells were analyzed during the rapid plasma HIV RNA rebound in HIV-infected patients undergoing structured treatment interruption (STI). A loss in circulating Vgamma9Vdelta2 T cells was observed, indicating that acute HIV replication may influence Vgamma9Vdelta2 homeostasis. These cells were lost among CD45RA(-)CD27(-) Vgamma9Vdelta2 T cell effectors, and a significant unresponsiveness, measured as antigen-driven interferon-gamma production, was observed during STI. After HAART resumption and consequent inhibition of HIV replication, Vgamma9Vdelta2 T cell reactivity was restored both quantitatively and functionally. These observations indicate that Vgamma9Vdelta2 T cells are activated early after active HIV replication but are rapidly lost when viremia is not controlled.

HIV-mediated γδ T cell depletion is specific for Vγ2+ cells expressing the Jγ1.2 segment

Circulating Vγ2/Vδ2+ T cells, normally constituting 3-6% of all CD3+ T cells in blood, are severely depleted after HIV infection. The mechanism(s) for Vγ2/Vδ2+ T cell depletion are unknown, partly because these cells are CD4- and resistant to HIV infection. To determine whether this cell depletion was general for all Vγ2+ cells or specific for an individual subset, we analyzed the Vγ2 repertoire and found consistent differences between HIV+ and uninfected control samples. The change in Vγ2 repertoire was the result of preferentially depleting only those Vγ2 cells that express the Jγ1.2 segment. The specific loss of Vγ2-Jγ1.2+ cells was polyclonal, as the Vγ subset retained normal diversity even after HIV infection, and loss occurred without significant changes in the paired chain (Vδ2) repertoire, or in the alternate Vδ1 chain repertoire. Specific depletion of Vγ2-Jγ1.2/Vδ2 T cells is the first evidence of a common, T cell receptor-dependent cell loss in HIV disease and it provides a clear example of byst...

Zoledronic acid and interleukin-2 treatment improves immunocompetence in HIV-infected persons by activating Vγ9Vδ2 T cells.

Objective:γδ T cells bearing the Vγ9Vδ2 T-cell receptor exert many antiviral effector functions in humans, including release of anti-HIV factors and direct cytotoxicity against virus-infected cells. Moreover, they are known to activate dendritic cells, improving antigen presentation function. After HIV infection, Vγ9Vδ2 T-cell number and reactivity are rapidly affected and they decrease upon disease progression. Bisphosphonate drugs such as zoledronic acid (Zol), used to treat bone diseases, have been shown to induce in vivo, in combination with interleukin-2, Vγ9Vδ2 T-cells’ activation. The aim of this work was to verify whether the administration of Zol in combination with interleukin-2 in HIV-infected patients might improve Vγ9Vδ2 T-cell function, including immune adjuvancy mediated by γδ-dendritic cell cross-talk. Design and methods:In HIV patients naive to antiretroviral therapy, we analyzed the effect of combined Zol and interleukin-2 treatment, in comparison to Zol alone, on Vγ9Vδ2 T-cell number, maturation and function, on dendritic cell activation and on HIV-specific CD8 T-cell response. Results:Zol and interleukin-2-combined treatment induced in-vivo Vγ9Vδ2 T-cell expansion and maturation. Paralleling Vγ9Vδ2 T-cell activation, increased dendritic cell maturation and HIV-specific CD8 T-cell responses were found. Conclusion:The specific modulation of Vγ9Vδ2 T-cell number and responsiveness after HIV infection may be at least transiently restored in vivo by Zol and interleukin-2 treatment. In this way, the immune effector mechanisms, secondary to Vγ9Vδ2 T-cell activation, were improved, suggesting a possible adjuvancy role of Zol and interleukin-2 treatment in restoring innate and specific competence in HIV-infected persons.

HLA-E up-regulation induced by HIV infection may directly contribute to CD94-mediated impairment of NK cells.

Alterations in NK cell numbers and function have been repeatedly shown during HIV infection. In this study, NK cell number and MHC class I expression on CD4+ T cells were studied in HIV patients at different stages of disease progression. An increased expression of HLA-E was seen on CD4+ T cells. In parallel, a reduced number of CD94+ NK cells was observed in advanced disease stages. Moreover, a decline in CD94 expression on NK cells was observed at the HIV replication peak in patients undergoing antiretroviral treatment interruption, suggesting a role of viral replication on NK cells alterations. In vitro HIV infection induced a rapid down-regulation of HLA-A,B,C expression, paralleled by an increased expression of HLA-E surface molecules, the formal ligands of CD94 NK receptors. HIV-infected HLA-E expressing cells were able to inhibit NK cell cytotoxicity through HLA-E expression, since cytotoxicity was restored by antibody masking experiments. These data indicate that the CD94/HLA-E interaction may contribute to NK cell dysfunction in HIV infection, suggesting a role of HIV replication in this process.

Activated Vγ9Vδ2 T cells trigger granulocyte functions via MCP-2 release

Vγ9Vδ2 T cells display a broad antimicrobial activity by directly killing infected cells and by inducing an effective adaptive immune response. The activation of Vγ9Vδ2 T cells by aminobisphosphonate drugs such as zoledronic acid (ZOL) results in a massive release of cytokines and chemokines that may induce a bystander activation of other immune cells. The aim of this work was to evaluate the ability of soluble factors released by ZOL-activated Vγ9Vδ2 T cells to induce granulocyte activation. We showed that soluble factors released by ZOL-stimulated Vγ9Vδ2 T cells activate granulocytes by inducing their chemotaxis, phagocytosis, and α-defensins release. Proteomic analysis allowed us to identify a number of cytokines and chemokines specifically released by activated Vγ9Vδ2 T cells. Moreover, MCP-2 depletion by neutralizing Ab revealed a critical role of this chemokine in induction of granulocyte α-defensins release. Altogether, these data show a Vγ9Vδ2-mediated activation of granulocytes through a bystander mechanism, and confirm the wide ability of Vγ9Vδ2 T-lymphocytes in orchestrating the immune response. In conclusion, an immune modulating strategy targeting Vγ9Vδ2 T cells may represent a key switch to induce an effective and well-coordinated immune response, and can be proposed as a way to strengthen the immune competence during infectious diseases.