Publications (6) View all
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Article: Differential expression and function of α-mannosidase I in stimulated naive and memory CD4+ T cells.
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ABSTRACT: N-linked protein glycosylation represents an important cellular process for modifying protein properties. It resembles a cascade of various enzymatic reactions, in which class I α-mannosidases play a central role. We and others have recently shown that N-glycosylation plays a major role for immune functions. We now analyzed the expression and function of α-mannosidase I in CD4(+) naive and memory T cells studying human and murine T cells. Alpha-mannosidase I function was altered by (i) treatment with Kifunensine, a specific inhibitor class I α-mannosidases, (ii) synthetic inhibitory RNA, and (iii) overexpression by retroviral gene transfer. T-cell activation was evaluated by CD69 expression, cytokine production and proliferation. Our results demonstrate (i) that α-mannosidase I transcription is transiently downregulated after T-cell activation with either polyclonal anti-CD3/CD28 antibodies or allogeneic CD19(+) B cells, and (ii) that α-mannosidase I exerts an inhibitory effect on T-cell activation. It is interesting to note that the inhibitory effect was restricted to naive CD4(+) T cells in both systems, human T cells and murine transgenic CD4(+)OT-II cells, whereas human memory T cells and primed CD4(+)OT-II cells remained unaffected. Alpha-mannosidase I inhibition reduced the activation threshold for naive but not already primed CD4(+)OT-II cells as the cells were able to respond to lower ovalbumin peptide concentrations and increased the rejection potential of alloreactive T cells in vivo. Thus, complex N-glycans generated by enzymes such as α-mannosidase I inhibit the activation of naive T cells. These findings could be used to improve the ex vivo priming of naive T cells for adaptive T-cell therapies.Journal of immunotherapy (Hagerstown, Md.: 1997) 06/2011; 34(5):428-37. · 3.20 Impact Factor -
Article: Prevalence of transmitted drug resistance and impact of transmitted resistance on treatment success in the German HIV-1 Seroconverter Cohort.
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ABSTRACT: The aim of this study is to analyse the prevalence of transmitted drug resistance, TDR, and the impact of TDR on treatment success in the German HIV-1 Seroconverter Cohort. Genotypic resistance analysis was performed in treatment-naïve study patients whose sample was available 1,312/1,564 (83.9% October 2008). A genotypic resistance result was obtained for 1,276/1,312 (97.3%). The resistance associated mutations were identified according to the surveillance drug resistance mutations list recommended for drug-naïve patients. Treatment success was determined as viral suppression below 500 copies/ml. Prevalence of TDR was stable at a high level between 1996 and 2007 in the German HIV-1 Seroconverter Cohort (N = 158/1,276; 12.4%; CI(wilson) 10.7-14.3; p(for trend) = 0.25). NRTI resistance was predominant (7.5%) but decreased significantly over time (CI(Wilson): 6.2-9.1, p(for trend) = 0.02). NNRTI resistance tended to increase over time (NNRTI: 3.5%; CI(Wilson): 2.6-4.6; p(for trend)= 0.07), whereas PI resistance remained stable (PI: 3.0%; CI(Wilson): 2.1-4.0; p(for trend) = 0.24). Resistance to all drug classes was frequently caused by singleton resistance mutations (NRTI 55.6%, PI 68.4%, NNRTI 99.1%). The majority of NRTI-resistant strains (79.8%) carried resistance-associated mutations selected by the thymidine analogues zidovudine and stavudine. Preferably 2NRTI/1PIr combinations were prescribed as first line regimen in patients with resistant HIV as well as in patients with susceptible strains (susceptible 45.3%; 173/382 vs. resistant 65.5%; 40/61). The majority of patients in both groups were treated successfully within the first year after ART-initiation (susceptible: 89.9%; 62/69; resistant: 7/9; 77.8%). Overall prevalence of TDR remained stable at a high level but trends of resistance against drug classes differed over time. The significant decrease of NRTI-resistance in patients newly infected with HIV might be related to the introduction of novel antiretroviral drugs and a wider use of genotypic resistance analysis prior to treatment initiation.PLoS ONE 01/2010; 5(10):e12718. · 4.09 Impact Factor -
Article: Time trends of syphilis and HSV-2 co-infection among men who have sex with men in the German HIV-1 seroconverter cohort from 1996-2007.
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ABSTRACT: Numbers of newly diagnosed HIV infections among men who have sex with men (MSM) in Germany increased after the year 2000. We sought to explore trends in STI co-infections around the time of HIV seroconversion in patients from the German HIV-1 seroconverter cohort from 1996-2007. MSM from the cohort were included for secondary analysis, if seroconversion occurred between 1996 and 2007 and if a blood sample taken within 2 y after HIV infection was available for further testing. Samples were tested for antibodies against Treponema pallidum and HSV-2. A classification system was developed to assign the chronology of syphilis and HIV-1 infection. Data of 1052 MSM were eligible for analysis. Overall seroprevalence of syphilis markers was 26%, increasing from 10% (1996-1999) to 35% (2005). Among HIV seroconverters with positive syphilis antibodies, 32% (n=88) were rated as having had coincident infections with HIV and syphilis. Coincident syphilis infection at HIV diagnosis increased substantially (p<0.001) from 2.3% in 2000 to 16.9% in 2003; and thereafter declined to 4.3% in 2007. Mean HSV-2 antibody prevalence was 40.5%, mean anti-HSV-2 IgM prevalence was 11.2%, with no significant change over time. We found a stable prevalence of HSV-2 infection and increasing prevalence of syphilis infection around the time of HIV acquisition among MSM in Germany. Time course and rate of co-infections suggest that a re-emerging syphilis co-epidemic among MSM after 2000 could have contributed to an increase of HIV incidence by enhancing HIV transmission probability.Sexually transmitted infections 10/2010; 86(5):331-6. · 2.18 Impact Factor -
Article: Generation of HCMV-specific T-cell lines from seropositive solid-organ-transplant recipients for adoptive T-cell therapy.
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ABSTRACT: Chronically immunosuppressed patients, like solid-organ-transplant (SOT) recipients, are at increased risk for severe human cytomegalovirus (HCMV) infection. Despite the availability of effective antiviral drugs, lasting control of remaining viruses is dependent on an effective T-cell immunity. So in some patients conventional antiviral therapy cannot control the infection and prolonged virostatic therapy is limited by its side effects and the development of viral resistance. Selective reconstitution of cellular immunity by adoptive transfer of HCMV-specific T cells derived from healthy donors is a safe and effective approach in hematopoietic stem cell transplant recipients. The aim of this study was to determine whether functional HCMV-specific T cells can also be generated from chronically immunosuppressed patients. Autologous CD4+/8+ T-cell lines directed against the HCMV protein IE-1 were generated from the peripheral blood of SOT patients using a recently developed modular protocol easily applicable to good-manufacturing-practice conditions. T-cell lines from SOT patients showed similar features as cells from healthy donors regarding phenotype, functionality (HCMV-specific killing, gene expression pattern, and cytokine secretion), IE-1 epitope recognition, and dominance of distinct T-cell receptor V beta families. Most importantly, this protocol also allowed the generation of T-cell lines from immunosuppressed patients with HCMV infection/chronic HCMV disease. Our data suggest the potential of this autologous approach for the treatment of SOT recipients suffering from HCMV infection/disease poorly responding to virostatic therapy.Journal of immunotherapy (Hagerstown, Md.: 1997) 10/2009; 32(9):932-40. · 3.20 Impact Factor -
Article: Expression of tolerance associated gene-1, a mitochondrial protein inhibiting T cell activation, can be used to predict response to immune modulating therapies.
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ABSTRACT: Immune modulating therapies gain increasing importance in treatment of patients with autoimmune diseases such as psoriasis. None of the currently applied biologics achieves significant clinical improvement in all treated patients. Because the therapy with biologics is cost intensive and sometimes associated with side effects, noninvasive diagnostic tools for early prediction of responders are of major interest. We studied the effects of Alefacept (LFA3Ig), an approved drug for treatment of psoriasis, on leukocytes in vitro and in vivo to identify gene markers predictive for treatment response and to further investigate its molecular mechanisms of action. In an open-label study, 20 psoriasis patients were treated weekly with 15 mg Alefacept over 12 wk. We demonstrate that transcription of the tolerance-associated gene (TOAG-1) is significantly up-regulated whereas receptor for hyaluronic acid mediated migration (RHAMM) transcription is down-regulated in PBMCs of responding patients before clinical improvement. TOAG-1 is exclusively localized within mitochondria. Overexpression of TOAG-1 in murine T cells leads to increased susceptibility to apoptosis. Addition of Alefacept to stimulated human T cells in vitro resulted in reduced frequencies of activated CD137(+) cells, increased TOAG-1 but reduced RHAMM expression. This was accompanied by reduced proliferation and enhanced apoptosis. Inhibition of proliferation was dependent on enhanced PDL1 expression of APCs. Thus, peripheral changes of TOAG-1 and RHAMM expression can be used to predict clinical response to Alefacept treatment in psoriasis patients. In the presence of APCs Alefacept can inhibit T cell activation and survival by increasing expression of TOAG-1 on T cells and PDL1 on APCs.The Journal of Immunology 09/2009; 183(6):4077-87. · 5.79 Impact Factor
