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Burkhard Ludewig

Publications and source records attributed to Burkhard Ludewig.

34 records · Page 2Linked to original sources
PubMed2004

Molecular characterization of virus-induced autoantibody responses.

Here we present a comprehensive molecular mapping of virus-induced autoimmune B cell responses obtained by serological identification of antigens by recombinant expression cloning analysis. Immunoscreening of cDNA expression libraries of various organs (lung, liver, and spleen) using sera from mice infected with cytopathic (vaccinia virus [VV]) or noncytopathic (lymphocytic choriomeningitis virus [LCMV]) viruses revealed a broad specificity of the elicited autoantibody response. Interestingly, the majority of the identified autoantigens have been previously described as autoantigens in humans. We found that induction of virus-induced autoantibodies of the immunoglobulin G class largely depends on the CD40-CD40L-mediated interaction between T and B cells. Furthermore, antibody titers against a number of autoantigens were comparable to the concomitantly induced antiviral antibody response. Comparison of serum reactivity against a selected panel of autoantigens after infection with VV, LCMV, or vesicular stomatitis virus showed that the different virus infections triggered distinct autoantibody responses, suggesting that virus infections may leave specific "autoantibody fingerprints" in the infected host.

Algorithms↗
PubMed2004

Immunopathogenesis of atherosclerosis.

Recent clinical studies indicate that the number of microbial infections (the "pathogen burden") critically determines the development and progression of atherosclerotic disease. Viruses or bacteria with a specific tropism for cells of the vascular wall may contribute to the initial vascular injury via direct cytopathic effects or via the induction of genuine autoimmune responses. Immunopathological processes such as molecular mimicry, epitope spreading, or bystander activation of self-reactive lymphocytes most likely fuel the chronic inflammatory process in the vascular wall. Recognition of atherogenesis as a pathogen-driven, immunopathological process makes this disease amenable to new treatment strategies such as vaccination or immunomodulation.

Animals↗
PubMed2004

Determining control parameters for dendritic cell-cytotoxic T lymphocyte interaction.

Dendritic cells (DC) are potent immunostimulatory cells facilitating antigen transport to lymphoid tissues and providing efficient stimulation of T cells. A series of experimental studies in mice demonstrated that cytotoxic T lymphocytes (CTL) can be efficiently induced by adoptive transfer of antigen-presenting DC. However, the success of DC-based immunotherapeutic treatment of human cancer, for example, is still limited because the details of the regulation and kinetics of the DC-CTL interaction are not yet completely understood. Using a combination of experimental mouse studies, mathematical modeling, and nonlinear parameter estimation, we analyzed the population dynamics of DC-induced CTL responses. The model integrates a predator-prey-type interaction of DC and CTL with the non-linear compartmental dynamics of T cells. We found that T cell receptor avidity, the half-life of DC, and the rate of CTL-mediated DC-elimination are the major control parameters for optimal DC-induced CTL responses. For induction of high avidity CTL, the number of adoptively transferred DC was of minor importance once a minimal threshold of approximately 200 cells per spleen had been reached. Taken together, our study indicates that the availability of high avidity T cells in the recipient in combination with the optimal application regimen is of prime importance for successful DC-based immunotherapy.

Animals↗
PubMed2004

Phenotype and functional analysis of human monocyte-derived dendritic cells loaded with biodegradable poly(lactide-co-glycolide) microspheres for immunotherapy.

Dendritic cells (DC) are increasingly explored as cellular vaccines for tumor immunotherapy. In most reported DC-based cancer vaccine trials, DC have been pulsed with soluble tumor antigen-derived peptide ligands of MHC molecules. Considering that the half-life of peptide/MHC complexes on the cell surface is relatively short and that soluble exogenous protein antigens cannot be efficiently processed via the MHC class I-processing pathway, the current vaccination procedure is not optimal for the induction of strong T cell responses aiming at tumor rejection. Recently, we have shown that antigen presentation can be prolonged when synthetic peptides were encapsulated in biodegradable poly(D,L-lactide-co-glycolide) (PLGA) microspheres (MS) for uptake by DC. In the present study, we investigated the phenotypic and functional consequences of MS uptake by human monocyte-derived dendritic cells (MoDC) in vitro. We found that immature MoDC that were prepared in serum free media suitable for clinical application were able to phagocytose high numbers of MS, while matured MoDC showed a reduced capacity for phagocytosis of MS. The ingestion of MS did not change the cell surface expression of CD80, CD83, CD86 and HLA-DR of immature and mature DC, suggesting that MS uptake did not induce DC maturation but that maturation by cytokines or LPS was unaltered in the presence of MS. Furthermore, MS-loaded mature MoDC expressed normal levels of the chemokine receptor CCR7 and migrated as efficiently towards CCL19 or CCL21 as unloaded MoDC. DC viability and the secretion of TNF-alpha and IL-12 was not significantly changed by MS loading. Taken together, our data indicate that PLGA-MS loading has no negative effects on the pivotal properties of MoDC in vitro. It should therefore be feasible to further develop this antigen loading strategy for clinical use in immunotherapy against viral infections and tumors.

Absorbable Implants↗
PubMed2004

Immunopathological basis of virus-induced myocarditis.

Heart diseases are an important cause of morbidity and mortality in industrialized countries. Dilated cardiomyopathy (DCM), one of the most common heart diseases, may be the consequence of infection-associated myocardits. Coxsackievirus B3 (CVB3) can be frequently detected in the inflamed heart muscle. CVB3-induced acute myocarditis is most likely the consequence of direct virus-induced myocyte damage, whereas chronic CVB3 infection-associated heart disease is dominated by its immunopathological sequelae. Bona fide autoimmunity, for example, directed against cardiac myosin, may favor chronic destructive immune damage in the heart muscle and thereby promote the development of DCM. The immunopathogenesis of myocarditis and subsequent DCM induced either by pathogens or autoantigens can be investigated in well-established animal models. In this article, we review recent studies on the role of viruses, with particular emphasis on CVB3, and different immunological effector mechanisms in initiation and progression of myocarditis.

Animals↗
PubMed2004

Rapid identification of coronavirus replicase inhibitors using a selectable replicon RNA.

A previously unknown coronavirus (CoV) is the aetiological agent causing severe acute respiratory syndrome (SARS), for which an effective antiviral treatment is urgently needed. To enable the rapid and biosafe identification of coronavirus replicase inhibitors, we have generated a non-cytopathic, selectable replicon RNA (based on human CoV 229E) that can be stably maintained in eukaryotic cells. Most importantly, the replicon RNA mediates reporter gene expression as a marker for coronavirus replication. We have used a replicon RNA-containing cell line to test the inhibitory effect of several compounds that are currently being assessed for SARS treatment. Amongst those, interferon-alpha displayed the strongest inhibitory activity. Our results demonstrate that coronavirus replicon cell lines provide a versatile and safe assay for the identification of coronavirus replicase inhibitors. Once this technology is adapted to SARS-CoV replicon RNAs, it will allow high throughput screening for SARS-CoV replicase inhibitors without the need to grow infectious SARS-CoV.

Animals↗
PubMed2004

Underwhelming the immune response: effect of slow virus growth on CD8+-T-lymphocyte responses.

The speed of virus replication has typically been seen as an advantage for a virus in overcoming the ability of the immune system to control its population growth. Under some circumstances, the converse may also be true: more slowly replicating viruses may evoke weaker cellular immune responses and therefore enhance their likelihood of persistence. Using the model of lymphocytic choriomeningitis virus (LCMV) infection in mice, we provide evidence that slowly replicating strains induce weaker cytotoxic-T-lymphocyte (CTL) responses than a more rapidly replicating strain. Conceptually, we show a "bell-shaped" relationship between the LCMV growth rate and the peak CTL response. Quantitative analysis of human hepatitis C virus infections suggests that a reduction in virus growth rate between patients during the incubation period is associated with a spectrum of disease outcomes, from fulminant hepatitis at the highest rate of viral replication through acute resolving to chronic persistence at the lowest rate. A mathematical model for virus-CTL population dynamics (analogous to predator [CTL]-prey [virus] interactions) is applied in the clinical data-driven analysis of acute hepatitis B virus infection. The speed of viral replication, through its stimulus of host CTL responses, represents an important factor influencing the pathogenesis and duration of virus persistence within the human host. Viruses with lower growth rates may persist in the host because they "sneak through" immune surveillance.

Acute Disease↗
PubMed2003

CCL19/CCL21-triggered signal transduction and migration of dendritic cells requires prostaglandin E2.

The control of dendritic cell (DC) migration is pivotal for the initiation of cellular immune responses. When activated with inflammatory stimuli, the chemokine receptor CCR7 is up-regulated on DCs. Activated DCs home to lymphoid organs, where the CCR7 ligands CCL19 and CCL21 are expressed. We previously found that human monocyte-derived DCs (MoDCs) exclusively migrated to CCL19 and CCL21 when matured in the presence of prostaglandin (PG) E2. Because PGE2 did not alter CCR7 cell surface expression, we examined whether PGE2 may exert its effect by coupling CCR7 to signal transduction modules. Indeed, stimulation with CCR7 ligands led to enhanced phosphatidylinositol-3-kinase-mediated phosphorylation of protein kinase B when MoDCs were matured in the presence of PGE2. Moreover, CCL19/CCL21-induced intracellular calcium mobilization in MoDCs occurred only when PGE2 was present during maturation. MoDC migration to CCL19 and CCL21 was dependent on phospholipase C and intracellular calcium flux but not on phosphatidylinositol-3 kinase. Hence, our data provide insight into CCL19/CCL21-triggered signal transduction pathways and identify a novel function for PGE2 in controlling the migration of mature MoDCs by facilitating CCR7 signal transduction.

Blotting, Western↗
PubMed2003

Autoimmunity seen through the SEREX-scope.

Autoantibodies can be detected in autoimmune diseases with a long prodromal phase and may serve as early indicators of disease activity. Autoantibody-based screening methods are therefore potent tools for the identification of target antigens. The SEREX method (serological identification of antigens by recombinant expression cloning) has been developed for the serological definition of immunogenic tumor antigens. Recent studies indicate that the SEREX approach may also be utilized for the analysis of complex immune responses involved in autoimmune diseases.

Animals↗
PubMed2003

Dendritic cell homeostasis in the regulation of self-reactivity.

Dendritic cells (DC) are known for their remarkable ability to induce specific T cell responses. However, the existing views on the role of DC in maintaining tolerance to self-antigens and induction of autoimmunity are somewhat controversial especially when the basic physiology of DC migration, function and homeostasis is considered. This review attempts to provide a comprehensive overview on these topics with particular emphasis on DC homeostasis and presents implications for the generation of pathological autoimmune T cell responses. Furthermore, we advocate the need for a conceptual characterization of the immune system operating in vivo. With particular focus on the contribution of DC, we suggest that a 'spatiotemporal' view of the rules for T cell responses (antigen dose and availability, duration and mode of antigen presentation) permits a better understanding of the relevant factors contributing to the pathogenesis of autoimmune diseases.

Animals↗
PubMed2002

Smooth muscle cells in transplant atherosclerotic lesions are originated from recipients, but not bone marrow progenitor cells.

BACKGROUND: Smooth muscle cell (SMC) accumulation in the intima of vessels is a key event in the pathogenesis of transplant atherosclerosis. The traditional hypothesis that SMCs in the lesion are derived from the media of the donor vessel has been challenged by recent observations, but the cell origin is still not well established. METHODS AND RESULTS: Here, we use a simplified model of artery allografts in transgenic mice to clearly identify the source of SMCs in transplant atherosclerosis. Aortic segments donated by BALB/c mice allografted to ROSA26 (C57B/6) mice expressing beta-galactosidase (gal) in all tissues showed that neointimal cells derived exclusively from host cells. It was also demonstrated that SMCs of neointimal and atherosclerotic lesions in vessels allografted to mice expressing beta-gal only in SMCs (SM-LacZ) or to apoE-deficient/SM-LacZ mice originated from the recipient, and not donor vessels. Interestingly, bone marrow transplantation of SM-LacZ beta-gal-expressing cells into aortic allograft recipients revealed completely negative beta-gal staining of neointimal and atherosclerotic lesions. However, a population of beta-gal-positive cells in lesions of allografts was observed in chimeric mice with ROSA26 beta-gal-expressing marrow cells. When bone marrow cells from both ROSA26 and SM-LacZ mice were cultured and stimulated with platelet-derived growth factor-BB, alpha-actin and beta-gal double-positive cells were found, suggesting that bone marrow cells have an ability to differentiate into SMCs. CONCLUSIONS: Thus, we provide strong evidence that SMCs of neointimal and atherosclerotic lesions in allografts are derived from the recipients and that non-bone marrow-derived progenitor cells are a possible source of SMCs in atherosclerotic lesions.

Actins↗
PubMed2002

Antiviral immune responses in the absence of organized lymphoid T cell zones in plt/plt mice.

The paucity of lymph node (LN) T cells (plt) mutation in mice results in strongly reduced T cell numbers in LNs and homing defects of both dendritic cells (DCs) and naive T cells. In this study, we investigated the functional significance of the plt phenotype for the generation of antiviral immune responses against cytopathic and noncytopathic viruses. We found that DC-CD8(+) T cell contacts and the initial priming of virus-specific T cells in plt/plt mice occurred mainly in the marginal zone of the spleen and in the superficial cortex of LNs. The magnitude of the initial response and the maintenance of protective memory responses in plt/plt mice was only slightly reduced compared with plt/+ controls. Furthermore, plt/plt mice mounted rapid neutralizing antiviral B cell responses and displayed normal Ig class switch. Our data indicate that the defective homing of DCs and naive T cells resulting from the plt/plt mutation results in a small, but not significant, effect on the induction of protective antiviral T and B cell immunity. Overall, we conclude that the spatial organization of secondary lymphoid T cell zones via the CCR7-CC chemokine ligand 19/CC chemokine ligand 21 pathway is not an absolute requirement for the initial priming and the maintenance of protective antiviral T and B cell responses.

Animals↗
PubMed2002

Arterial inflammation and atherosclerosis.

Arterial inflammation is a significant component of atherosclerotic disease and it has been suggested that specific immune responses directed against autoantigens or pathogen-derived antigens presented in the vascular wall could initiate and/or maintain atherosclerotic processes. Atherogenic cofactors such as altered cholesterol metabolism may not only impact locally on inflammatory responses in atherosclerotic lesions, but may also alter general immune-responsiveness. The evidence to date suggests that the mutual chronic perpetuation of immune mediated vascular inflammation and cholesterol-induced atherosclerosis is a key step in atherogenesis.

Animals↗
PubMedDate not supplied

Towards a coronavirus-based HIV multigene vaccine.

Human immunodeficiency virus (HIV) infection represents one of the major health threats in the developing world. The costly treatment of infected individuals with multiple highly efficient anti-HIV drugs is only affordable in industrialized countries. Thus, an efficient vaccination strategy is required to prevent the further spread of the infection. The molecular biology of coronaviruses and particular features of the human coronavirus 229E (HCoV 229E) indicate that HCoV 229E-based vaccine vectors can become a new class of highly efficient vaccines. First, the receptor of HCoV 229E, human aminopeptidase N (hAPN or CD13) is expressed mainly on human dendritic cells (DCs) and macrophages indicating that targeting of HCoV 229E-based vectors to professional antigen presenting cells can be achieved by receptor-mediated transduction. Second, HCoV 229E structural genes can be replaced by multiple transcriptional units encoding various antigens. These virus-like particles (VLPs) containing HCoV 229E-based vector RNA have the ability to transduce human DCs and to mediate heterologous gene expression in these cells. Finally, coronavirus infections are associated with mainly respiratory and enteric diseases, and natural transmission of coronaviruses occurs via mucosal surfaces. In humans, HCoV 229E causes common cold by infecting the upper respiratory tract. HCoV 229E infections are mainly encountered in children and re-infection occurs frequently in adults. It is thus most likely that pre-existing immunity against HCoV 229E will not significantly impact on the vaccination efficiency if HCoV 229E-based vectors are used in humans.

AIDS Vaccines↗