The role of cross-presentation in tolerance and immunity
„Cross-presentation“ describes a mechanism of antigen-presentation, where exogenous antigen (Ag) is presented via MHC class I molecules to CD8 T cells. This mechanism is thought to be especially important for anti-tumor-responses and tolerance induction of self-reactive CD8 T cells. We have generated transgenic models, where DCs a specifically inhibited in cross-presentation, in order to study the actual role of this mechanism in vivo. CD8 T cell responses to exogenous Ag are largely blunted or absent in these mice (Figure 1).
Figure 1: CD8 T cell proliferation to exogenous Ag is strongly reduced, when cross-pressentation is deficient (left: control; middle: wild type; right: cross-presentation-deficient).
In addition we could demonstrate that DCs defective in cross-presentation are unable to protect certain peripheral tissues from infiltrating self-reactive T cells (Figure 2). The precise mechanisms of these protective DC-functions is a current topic of our research.
Figure 2: Self-reactive CD8 T cells (green) infiltrate skin, when DCs are cross-presentation-incompetent (Luckashenak, Schroeder et al. 2008; Immunity 28:521)
Further research topics are listed below. Current funding for our research is provided by the DFG and the european community.
SFB 455 Viral Function and Immunomodulation (2008 – 2010)Project B14: Analysis of tolerogenic Dendritic Cells
In peripheren lymphoiden Organen präsentieren Dendritische Zellen (DC) MHC-Antigenkomplexe (Ag). Dies führt bei Ag-spezifischen T Zellen entweder zu deren Aktivierung oder funktionellen Inaktivierung (Toleranz). Nach neueren Befunden benötigen DC ein gewisses Maß an „Reife“ zur effektiven Toleranzinduktion, da unreife DC von naiven T Zellen nicht erkannt werden. Die von DC integrierten Signale, die zur effektiven Toleranzinduktion führen, sind noch größtenteils unbekannt. Im vorliegenden Antrag soll DC-Maturierung in vivo genetisch beeinflusst und funktionell analysiert werden.
SFB 456 Target structures for selective tumorintervention (2008-2010)
Projekt B12: The role of steady-state MHC class I - CD8 T cell interaction in proliferative capacity and repertoire diversity
The CD8 T cell avidity for its target cell determines the efficacy of tumorcell- lysis and killing. This avidity is determined by the genetically encoded T cellreceptor (TCR) as well as by immunoregulatory surface molecules expressed by T cells. In this project we will analyse a further level of regulation, the so-called „T cell tuning“, where the threshold of T cell activation seems to be critically determined by the actual T cell environment.
SFB 571 Autoimmune reactions: from manifestations and mechanisms to therapy (2008-2011)
Project B5: On the role of cross-presenting Dendritic Cells in T cell tolerance induction
Autoreactive T cells are purged from the peripheral T cell repertoire by central deletion in the thymus. However, low affinity T cells with specificity for self-antigen (Ag) can escape deletion and must be controlled by peripheral tolerance mechanisms. Up to now the relative importance of peripheral tolerance and its contribution to protection from autoimmunity remains unclear. Dendritic cells (DC) presenting tissue self-Ag via MHC molecules to self-specific T cells seem to be instrumental for peripheral tolerance. Using mice with DC deficient for functions such as Ag-uptake and/or -presentation we will investigate the relative role of peripheral tolerance.
DFG-Project KU2413/1-1 (Co-applicant Dr. Kuipers)
The role of microRNAs in dendritic cell development and function
MicroRNAs are recently discovered non-coding RNA molecules around 22 nucleotides of length that inhibit gene expression. Several hundred different microRNAs have been described up to now in almost all eukaryotes and have been shown to play important roles in various physiological processes ranging from development to metabolism. Dendritic cells (DC) are cells of the immune system specialized in pathogen recognition and activation of the adaptive immune response, which also express microRNAs. Several subsets of DC can be distinguished, differing in phenotype and function, but it is not known what the contribution of microRNAs to differences in DC subset development and function is. In this project we will explore the role of microRNAs in development and function of DC subsets. We have previously identified differences in microRNA expression between different DC subsets using microarray technology. We will change the levels of differentially expressed microRNAs and analyze effects on DC phenotype and function. In parallel, we will analyze DC from mice deficient in all miRNAs using mice lacking an essential miRNA processing component.
Integrated Project "COMPUVAC": Rational design and standardized Evaluation of novel genetic vaccines
Recombinant viral vectors and virus-like particles are considered the most promising vehicles to deliver antigens in prophylactic and therapeutic vaccines against infectious diseases and cancer. Several potential vaccine designs exist but their cost-effective development cruelly lacks a standardized evaluation system. On these grounds, COMPUVAC is devoted to (i) rational development of a novel platform of genetic vaccines and (ii) standardization of vaccine evaluation. COMPUVAC assembles a platform of viral vectors and virus-like particles that are among today’s most promising vaccine candidates and that are backed up by the consortium’s complementary expertise and intellectual property, including SMEs focusing on vaccine development. COMPUVAC recognizes the lack of uniform means for side-by-side qualitative and quantitative vaccine evaluation and will thus standardize the evaluation of vaccine efficacy and safety by using “gold standard” tools, molecular and cellular methods in virology and immunology, and algorithms based on genomic and proteomic information.
“Gold standard” algorithms for intelligent interpretation of vaccine efficacy and safety will be built into COMPUVAC’s interactive “Genetic Vaccine Decision Support System”, which should generate (i) vector classification according to induced immune response quality, accounting for gender and age, (ii) vector combination counsel for prime-boost immunizations, and (iii) vector safety profile according to genomic analysis.
Since one of our “gold standard” antigens is the West Nile virus (WNV) envelope protein, an additional aim of COMPUVAC is to generate a candidate vaccine against WNV. As end products, our vector platform and “gold standard” tools, methods and algorithms will be available to the scientific and industrial communities as a toolbox and interactive database which standardized nature should contribute to cost-effective development of novel vaccines with validated efficacy and safety profiles.
STREP "THOVLEN": Targeted Herpesvirus-derived Oncolytic Vectors for Live Cancer European Network
The overall objective of THOVLEN is to develop safe and efficient herpes simplex virus type 1 (HSV-1)-derived oncolytic vectors, designed to strictly target and eradicate human hepatocellular carcinomas (HCC), the most common liver cancer of adults. HSV-1 is certainly one of the most promising viral platforms for the development of improved oncolytic vectors, as anticipated by the unique biological properties of this virus and confirmed by the encouraging results coming from clinical trials in gliomas. However, the first generations of oncolytic HSV-1 vectors have also shown limitations regarding efficacy and safety. New generations of innovative HSV-1 vectors with improved potency and safety are required before the oncolytic strategy using HSV-1 becomes a standard therapeutic reality against cancer, and this is the goal of THOVLEN. One of the most important innovative contributions of our project concerns the overall approach towards the improvement of HSV-1-based oncolytic viruses. Instead of focusing on the development of vectors carrying deletions in particular virus genes, we will engineer competent, but replication-restricted, HSV-1 vectors, strictly targeted to HCC. These vectors will combine multiple HCC-targeting approaches, both at the level of entry and at the level of gene expression and replication, and will be able to multiply and spread only in HCC, while displaying no virulence in normal healthy tissues. Additionally, an important innovation is related to the ability of the HSV-l vectors to permit a sophisticated and flexible combined approach against HCC. That is, in addition to optimizing the oncolytic properties of HSV-1 vectors, THOVLEN will exploit the very large transgenic capability of HSV-1 to generate vectors that will simultaneously display multiple and multimodal anti-tumour activities acting either locally or systemically, including combined expression of anti-angiogenic, immune-modulatory, and oncolytic proteins.
HEVAR (HErpesvirus-based VAccines against Rotavirus infections) collaborative project funded by the European Union FP 6.
It involves four academic laboratories from four European countries (France, Switzerland, Germany, Italy) and four academic laboratories belonging to three South American countries (Argentine, Brazil, Uruguay).
HEVAR will develop herpes simplex virus type 1 (HSV-1)-based vectors for the generation and analysis of rotavirus-specific expression and display model vaccines.
Our approach is based on the possibility of engineering HSV-1-based vectors expressing and/or displaying rotavirus antigens, either individually or in combination, alone or together with immune-modulator genes.
Our goal is to evaluate the ability of these vectors to elicit protective immune responses against rotavirus infection in normal and transgenic mice, therefore helping to elucidate the contribution of individual rotavirus antigens, and of different components of the immune system, to the architecture of the immune response and to protection upon rotavirus challenge in this animal model.
In addition to contributing to a better understanding of the immune biology of rotavirus infection and of evaluating the feasibility of using HSV-1 vectors as anti-rotavirus vaccines, the main deliverables of HEVAR will be a set of toolboxes containing a large collection of HSV-1-based and DNA-based vectors expressing human and mouse rotavirus antigens that will be evaluated in mice, which will be rendered accessible to any academic team wishing to use them for vaccine development or fundamental research on rotaviruses.
A last set of deliverables will consist in a series of scientific meetings and events required to achieve the transfer of knowledge and complex technology required to generate, produce, and evaluate, the HSV-1-based gene transfer vectors in South America, therefore, improving the human capital and the technological competence of these countries, as well as the reciprocal transfer to European teams of knowledge on the biology of rotavirus and other endemic viruses with high social cost in South America, as a way to strengthen the awareness to, and the understanding of, these neglected diseases.
Diarrhoea caused approximately 2 million deaths per year worldwide in the last decade and was responsible for an estimated 20% of mortality in children aged less than 4 years in developing countries. Rotaviruses are the most common cause of severe dehydrating diarrhoea in young children in these countries, accounting for 20% to 60% of hospitalized cases. Rotavirus infection and disease cannot be controlled by hygiene and sanitation measures and almost all children will be infected with rotavirus in the first years of life. An estimated 140 million diarrhoeal episodes, and a minimum of 450,000-600,000 deaths per year, with immense medical/societal costs, mainly in developing countries, highlights the urgent need for the development and deployment of an effective prophylactic anti-rotavirus vaccine, that would have universal application as part of childhood immunization programs.