Frieder Koszik

Plasmacytoid dendritic cells express TRAIL and induce CD4 T-cell apoptosis in HIV-1 viremic patients

Artificial Toll-like receptor 7/8 (TLR7/8) ligands can endow plasmacytoid dendritic cells (pDCs) with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-dependent lytic properties. Keeping in mind that ssRNA serves as natural TLR7/8 ligand, we searched for TRAIL-expressing cells in persons infected with HIV and identified TRAIL+ pDCs in HIV-1 viremic persons, but not in nonviremic and healthy persons. TRAIL expression on pDCs was directly correlated with individual viral loads. Conversely, HIV-1 viremia was found to be associated with the up-regulation of the apoptosis-transmitting receptor TRAIL R1 on activated CD4+ T cells. As a consequence, the latter became susceptible to TRAIL-dependent pDC-mediated killing. In contrast, initiation of antiretroviral therapy led to the up-regulation of apoptosis-inhibiting TRAIL R4 on CD4+ T cells, which subsequently became resistant against pDC-mediated cellular injury. Definition of pDCs as killers of CD4+ T cells implies a new mechanism of disease progression in HIV infection.

Glucocorticosteroids Modify Langerhans Cells To Produce TGF-β and Expand Regulatory T Cells

Although glucocorticosteroids (GCSs) have been used for many decades in transplantation and (auto)inflammatory diseases, the exact mechanisms responsible for their immunosuppressive properties are not fully understood. The purpose of this study was to characterize the effects of oral GCSs on the cutaneous immune response. We analyzed, by immunofluorescence staining and quantitative RT-PCR, residual skin biopsy material from a clinical study in which we had used oral GCS as positive control for determining the effects of candidate anti-inflammatory compounds on epicutaneous patch tests of Ni-allergic patients. Expectedly, oral GCS treatment led to a reduction of clinical symptoms and infiltrating leukocytes. Notably, we observed increased numbers of dermal FOXP3+CD25+ T cells and epidermal Langerhans cells (LCs) that were associated with upregulated mRNA expression of TGF-β in lesions of GCS-treated Ni-allergic patients. To investigate this phenomenon further, we exposed purified LCs to GCS. They exhibited, in contrast to GCS-nonexposed LCs, 1) a more immature phenotype, 2) higher intracellular amounts of TGF-β, and 3) increased receptor activator for NF-κB expression, conditions that reportedly favor the expansion of regulatory T cells (Tregs). Indeed, we observed an enhancement of functionally suppressive FOXP3+ T cells when CD3+ cells were incubated with GCS-pretreated LCs. The expansion of Tregs was inhibited by TGF-β blockage alone, and their suppressive activity was neutralized by a combination of anti–TGF-β and anti–IL-10 Abs. Our data show that systemically applied GCSs endow LCs with Treg-promoting properties and thus shed new light on the mechanisms of GCS-mediated immunosuppression.

TRAIL+ Human Plasmacytoid Dendritic Cells Kill Tumor Cells In Vitro: Mechanisms of Imiquimod- and IFN-α–Mediated Antitumor Reactivity

Dendritic cells (DCs) not only exhibit the unique capacity to evoke primary immune responses, but may also acquire TLR-triggered cytotoxic activity. We and others have previously shown that TLR7/8- and TLR9-stimulated plasmacytoid DCs (pDCs) isolated from human peripheral blood express the effector molecule TRAIL. The exact mechanisms through which pDCs acquire and elicit their cytotoxic activity are still not clear. We now show that in the absence of costimulators, TRAIL induction on pDCs occurs with agonists to intracellular TLRs only and is accompanied by a phenotypic as well as functional maturation, as evidenced by a comparatively superior MLR stimulatory capacity. pDCs acquired TRAIL in an IFN-α/β–dependent fashion and, notably, TRAIL expression on pDCs could be induced by IFN-α stimulation alone. At a functional level, both TLR7/8- (imiquimod [IMQ]) and TLR9-stimulated (CpG2216) pDCs lysed Jurkat T cells in a TRAIL- and cell contact-dependent fashion. More importantly, IFN-α–activated pDCs acquired similar cytotoxic properties, independent of TLR stimulation and maturation. Both IMQ- and IFN-α–activated pDCs could also lyse certain melanoma cell lines in a TRAIL-dependent fashion. Interestingly, suboptimal doses of IMQ and IFN-α exhibited synergistic action, leading to optimal TRAIL expression and melanoma cell lysis by pDCs. Our data imply that tumor immunity in patients receiving adjuvant IMQ and/or IFN-α may involve the active participation of cytotoxic pDCs.

A quadrivalent HPV vaccine induces humoral and cellular immune responses in WHIM immunodeficiency syndrome.

WHIM-syndrome is an inherited immunodeficiency disorder with abnormal susceptibility to human papillomavirus (HPV) infection and diseases. We determined safety and immunogenicity to a quadrivalent HPV vaccine in WHIM-syndrome by detection of HPV-specific antibodies and lymphoproliferation. In virus-like-particle (VLP)-ELISA, a WHIM patient showed antibody titers up to 400 for HPV-6/11/16/18, whereas immuno-competent controls developed titers of 6400-25,600. In pseudovirion assays, the patients neutralization titers ranged from 20 to 400 to the four HPV vaccine types, while titers of 1600-25,600 were detected in healthy vaccinees. Specific proliferation of PBMC of the WHIM patient to the HPV vaccine was demonstrated. This first report on response to HPV vaccination in WHIM-immunodeficiency highlights that patients with WHIM-syndrome, and probably other immunodeficiencies, may benefit from HPV immunoprophylaxis.

Efalizumab modulates T cell function both in vivo and in vitro

BACKGROUND The anti-CD11a mAb efalizumab has been successfully used in patients with moderate to severe psoriasis. Although peripheral blood leukocytes ubiquitously express LFA-1 (CD11a/CD18), it is assumed that efalizumab exerts its effects primarily on T lymphocytes by blocking migration and by interfering with the immunological synapse. OBJECTIVE To test the latter assumption, we asked whether efalizumab interferes with T cell proliferation induced by qualitatively and quantitatively different stimuli. METHODS We exposed PBMC isolated either from healthy or psoriatic individuals to titrated doses of plate-bound anti-CD3, PHA or allogeneic PBMC. Furthermore we stimulated normal PMBC (i) in the presence of efalizumab and (ii) after preincubation and removal of efalizumab. RESULTS We found that PBMC of efalizumab-treated psoriatics responded perfectly to PHA but were hyporeactive towards allogeneic leukocytes and anti-CD3. Similarly, efalizumab added to cultures of normal PBMC led to impaired proliferation induced by allogeneic leukocytes and by suboptimal, but not optimal concentrations of anti-CD3. To understand the underlying mechanisms we exposed normal PBMC to efalizumab under various conditions and stimulated them thereafter via anti-CD3. Whereas addition of soluble efalizumab to the culture did not modify the reactivity of PBMC to plate-bound anti-CD3, crosslinking of CD11a with efalizumab plus anti-human IgG rendered T cells less reactive to a subsequent anti-CD3 stimulus. CONCLUSION These observations suggest that efalizumab treatment induces a state of T cell hyporesponsiveness and provide an explanation as to why efalizumab is effective in patients with stable psoriasis, but often fails to control disease flares. When maintained over a prolonged period of time the observed T cell hyporeactivity may conceivably put efalizumab recipients at an increased risk of biologically relevant immunosuppression.

Evaluation of modified Interferon alpha mRNA constructs for the treatment of non-melanoma skin cancer

Application of in vitro transcribed (IVT) messenger ribonucleic acid (mRNA) is an increasingly popular strategy to transiently produce proteins as therapeutics in a tissue or organ of choice. Here, we focused on the skin and aimed to test if whole human skin tissue explant technology can be used to evaluate the expression efficacy of different IVT Interferon alpha (IFN-α) mRNA constructs in situ, after biolistic delivery. Skin explants were viable and intact for at least five days based on histologic analysis and TUNEL staining. Using GFP reporter mRNA formulations, we found mostly epidermal expression after biolistic delivery. Two out of five sequence-optimized IFN-α mRNA variants resulted in significantly improved IFN-α protein expression in human skin compared to native IFN-α mRNA transfection. IFN-α secretion analysis of the surrounding culture media confirmed these results. We provide a proof-of-concept that IFN-α mRNA delivery into intact human full thickness skin explants can be utilized to test mRNA sequence modifications ex vivo. This approach could be used to develop novel mRNA-based treatments of common epidermal skin conditions including non-melanoma skin cancer, where IFN-α protein therapy has previously shown a strong therapeutic effect.