Marianne Wallace

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.

Gamma/delta T lymphocytes in viral Infections

T lymphocyte progenitors differentiate into two distinct T cell lineages. Although the αβ and γδ T cell lineages resemble each other phenotypically and functionally, there are some striking differences. Some γδ T cells recognize, similarly to αβ T cells, peptides presented by major histocompatibility complex (MHC) proteins or MHC‐like molecules. However, there are γδ T cells that recognize MHC molecules in a fundamentally different manner in comparison with αβ T cells. Also in contrast to aLβ T lymphocytes, many γδ T cells are capable of recognizing nonpeptide antigens. Most responses of γδ T cells appear to be directed against microbial pathogenic agents including bacteria, parasites, and viruses. In particular, the potent cytotoxic responses of γδ T cells against cells infected with, for example, herpesviruses or lentiviruses may be essential for the overall antiviral defense of vertebrates. The analysis of antiviral immunosurveillance by γδ T cells is crucial for understanding the unique biological role of this lymphocyte subset.

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.

FUNCTIONAL GAMMA DELTA T-LYMPHOCYTE DEFECT ASSOCIATED WITH HUMAN IMMUNODEFICIENCY VIRUS INFECTIONS

BackgroundAntiviral cellular immune responses may influence immunological homeostasis in HIV-infected persons. Recent data indicate that Vγ9/Vδ2 T lymphocytes display potent cytotoxic activities against human cells infected with certain viruses including HIV. Understanding the role of γδ T cells in the course of HIV infection may be helpful for designing novel treatment strategies for HIV-associated disorders.Materials and MethodsThe constitutive recognition of Daudi cells and monoethyl pyrophosphate (Etpp) by peripheral blood Vγ9/Vδ2 T cells was assessed using a proliferation assay. The cytotoxicity of Daudi-stimulated lymphocyte populations was measured by chromium release assays. The HIV infectivity for γδ T cell clones was determined by measuring the levels of HTV p24 in cell supernatants. The effect of in vitro HIV-infection on cytokine mRNA production by γδ T cell clones was assessed by PCR.ResultsThe constitutive proliferative responses of peripheral blood Vγ9/Vδ2 T cells and the lytic functions of Daudi-expanded lymphoid cells from HTV+ persons were substantially diminished in comparison with those of HlV-seronegative persons. These alterations were present in asymptomatic HIV+ persons prior to substantial αβ CD4+ T cell loss. Productive fflV infection of γδ T cells in vitro had no measurable effect either on their proliferative response to Daudi stimuli or on the expression of cytokine mRNAs for IFN-γ, IL-2, IL-4, IL-5, IL-6, IL-10, and IL-13.ConclusionsThe constitutive responsiveness of Vγ9/Vδ2 T lymphocytes to Daudi and Etpp is severely altered in HIV+ persons. HTV infection of γδ T cells in vitro does not substantially change their cytokine expression or antigenic response.

Innate T-Cell Immunity in HIV Infections: The Role of Vg9Vd2 T Lymphocytes

There is growing interest in the use of innate immune reactions in the therapy and prophylaxis of various diseases. Natural T (NT) lymphocytes that recognize infected cells or microbial compounds without the classical genetic restriction by polymorphic MHC molecules are crucial components of innate immunity. NT cells bearing the Vgamma9Vdelta2 T-cell receptor (TCR) are broadly reactive against intracellular pathogens, can lyse human immunodeficiency virus (HIV) infected cells, and release cytokines capable of regulating HIV replication. The potent antiviral activities of Vgamma9Vdelta2 T cells may help to contain viral spread during acute HIV infection and/or to prevent the establishment of viral persistence. Substantial changes in the composition and function of circulating gammadelta T-cell pools occur in HIV-infected patients. These changes a) may contribute to the etiopathogenesis of opportunistic infections and neoplasms, and b) are partly reversed by highly active anti-retroviral therapy (HAART). In addition to direct antiviral activities, activated gammadelta T cells influence dendritic cell maturation and the adaptive alphabeta T-cell response. Vgamma9Vdelta2 T cells can be stimulated in vivo and in vitro by various nonpeptidic antigens (NpAgs) and recent animal experimental data suggest that activated Vgamma9Vdelta2 T cells may help to control SIV replication. Currently, NpAgs are being assessed as potential therapeutic agents in AIDS, tuberculosis and certain cancers susceptible to Vgamma9Vdelta2 T-cell effector mechanisms.

Vγ9Vδ2 T cell-mediated non-cytolytic antiviral mechanisms and their potential for cell-based therapy

Abstract In healthy adult Homo sapiens, the most frequent circulating γδ T cells (Vγ9Vδ2) respond to pyrophosphomonoesters, alkylamines (together referred to as non-peptidic antigens, NpAgs) and nitrogen-containing bisphosphonates. The seemingly very low toxicity of bisphosphonate and pyrophosphomonoester drugs in vivo, may allow novel approaches to the immunotherapy of viral infections. For example, these drugs can be used to stimulate Vγ9Vδ2 T cells to release antiviral molecules that directly suppress virus replication without destroying the virus-replicating cells. In addition, the soluble molecules released by γδ T cells could boost the antiviral potency of cytotoxic T lymphocytes (CTLs) and promote antigen presentation. The relative therapeutic value of drug-induced direct antiviral and immunoregulatory activities may depend on the infecting virus as well as on the nature of protective immune responses.

The effects of interleukin-15 on human γδ T cell responses to Plasmodium falciparum in vitro

We observed that the gammadelta T cell subset expands when human peripheral blood mononuclear cells (PBMC) from malaria-naive donors are cultured with Plasmodium falciparum lysate in the presence of IL-2 or IL-15, cytokines that utilize two common IL-2 receptor subunits. IL-15 induced the expansion of the gammadelta T cell subset at all levels tested, whereas IL-2 was not stimulatory at high levels. Flow cytometric analysis of apoptosis using the TUNEL assay indicated that the percentage and absolute number of gammadelta T cells undergoing apoptosis were greater in cultures stimulated with antigen and IL-2 than in cultures stimulated with either antigen and IL-15 or control erythrocyte lysate and IL-2. The ability of IL-15 to enhance gammadelta T cell function was also assessed; the results suggest that IL-15 can function with IL-2 to enhance the capacity of gammadelta T cells to inhibit parasite replication. Together these data indicate that IL-2 and IL-15, which both bind to IL-2Rbeta and IL-2R(gamma)c, enhance gammadelta T cell function, but they appear to have different effects on proliferation and survival.

Antiviral activity of primate γδ T lymphocytes isolated by magnetic cell sorting

The exposure of human or rhesus monkey peripheral blood mononuclear cells (PBMCs) to interleukin 2 (IL‐2) in vitro resulted in a selective outgrowth of γδ lymphocytes. Using positive selection by monoclonal antibodies and magnetic beads, γδ T lymphocytes were isolated from these cultures. Without priming by viral antigens, the purified γδ T lymphocytes lyse immunodeficiency virus‐infected cells substantially better than the uninfected counterparts.

A Randomized Phase II Trial Evaluating Different Schedules of Zoledronic Acid on Bone Mineral Density in Patients With Prostate Cancer Beginning Androgen Deprivation Therapy

OBJECTIVE To assess the effects of timing and schedule of zoledronic acid (ZA) administration on bone mineral density (BMD) in patients beginning androgen deprivation therapy (ADT) for the treatment of recurrent prostate cancer. PATIENTS AND METHODS In this randomized, 3-arm trial, we evaluated changes in BMD after 3 different ZA administration schedules in men with recurrent prostate cancer who were beginning ADT. Forty-four patients were enrolled and randomized to receive a single dose of ZA given 1 week before beginning ADT (arm 1), a single dose of ZA given 6 months after beginning ADT (arm 2), or monthly administration of ZA starting 6 months after beginning ADT, for a total of 6 doses (arm 3). RESULTS Patients who received ZA before ADT had a significant improvement in BMD at the total proximal femur and trochanter after 6 months compared with the other groups. In addition, only patients in the arm that received multiple doses improved lumbar spine BMD while on ADT, with these findings persisting to 24 months. However, this group also experienced more grade 1 adverse events. CONCLUSIONS Analysis of these data suggests that ZA administration before initiation of ADT was superior to treatment 6 months after starting ADT in maintaining BMD. In addition, monthly ZA administration can increase BMD above baseline but is associated with more adverse events. Further study is needed to examine whether the timing and frequency of ZA therapy in patients on ADT can reduce fracture risk.

Gamma/delta T cells: From bench to bedside

Abstract Protection from exogenous invaders and elimination of endogenous aberrations are the main contributions of T cells to homeostasis. T cells with Vγ9Vδ2-encoded T-cell receptors (TCRs) have a unique ability to interact with a plethora of phosphoantigens in a major histocompatibility complex (MHC)-unrestricted manner. The biological function of this recognition is largely unclear. However, since Vγ9Vδ2 T cells are potent cytotoxic effectors capable of killing tumor cells and target cells infected with numerous viruses including human immunodeficiency virus (HIV), simian immunodeficiency virus (SIV), herpes viruses and many others, it is likely that they are involved in antitumor and antiviral immunosurveillance. The observations of tumor-infiltrating γδ T cells with cytotoxic properties and profound quantitative and functional changes in γδ T cells associated with various infectious diseases (including those caused by viruses) are compatible with this hypothesis. For example, the most frequent human peripheral blood γδ T-cell subset expressing Vγ9Vδ2 TCRs is functionally disabled and numerically decreased in some HIV-infected persons. The nonresponsiveness of Vγ9Vδ2 T cells is accompanied by their decreased IFNγ and TNFα production. The overall level of γδ T-cell activation at different stages of HIV infection may be clinically relevant. At an initial stage of HIV infection, the extremely potent antiviral cytotoxic activities of Vγ9Vδ2 T cells may limit the viral spread. At later stages of disease, Vγ9Vδ2 T-cell dysfunction may contribute to the loss of resistance to opportunistic pathogens (such as atypical mycobacteria) and neoplasms (e.g., lymphomas) frequently associated with HIV infections. The activity of Vγ9Vδ2 T cells both in vivo and can be regulated by nonpeptidic antigens. These molecules are being assessed as potential therapeutic vaccines in acquired immunodeficiency syndrome (AIDS) and certain cancers susceptible to the Vγ9Vδ2 T-cell attack.