Karine Breckpot

Assessing T-cell responses in anticancer immunotherapy: Dendritic cells or myeloid-derived suppressor cells?

Since dendritic cells operate as professional antigen-presenting cells (APCs) and hence are capable of jumpstarting the immune system, they have been exploited to develop a variety of immunotherapeutic regimens against cancer. In the few past years, myeloid-derived suppressor cells (MDSCs) have been shown to mediate robust immunosuppressive functions, thereby inhibiting tumor-targeting immune responses. Thus, we propose that the immunomodulatory activity of MDSCs should be carefully considered for the development of efficient anticancer immunotherapies.

Immune modulation by genetic modification of dendritic cells with lentiviral vectors

Our work over the past eight years has focused on the use of HIV-1 lentiviral vectors (lentivectors) for the genetic modification of dendritic cells (DCs) to control their functions in immune modulation. DCs are key professional antigen presenting cells which regulate the activity of most effector immune cells, including T, B and NK cells. Their genetic modification provides the means for the development of targeted therapies towards cancer and autoimmune disease. We have been modulating with lentivectors the activity of intracellular signalling pathways and co-stimulation during antigen presentation to T cells, to fine-tune the type and strength of the immune response. In the course of our research, we have found unexpected results such as the surprising immunosuppressive role of anti-viral signalling pathways, and the close link between negative co-stimulation in the immunological synapse and T cell receptor trafficking. Here we review our major findings and put them into context with other published work.

Lentiviral vectors and gene therapy

Lentiviral vectors and gene therapy / , Lentiviral vectors and gene therapy / , کتابخانه دیجیتال جندی شاپور اهواز

Myeloid-Derived Suppressor Cells and Cancer

The book starts with an introduction to and history of myeloid-derived suppressor cells (MDSCs), followed by a description of their differentiation, their role in the tumour microenvironment and their therapeutic targeting. It closes with an outlook on future developments. In cancer patients, myelopoiesis is perturbed and instead of generating immunogenic myeloid cells (such as dendritic cells, inflammatory macrophages and granulocytes), there is an increase in highly immature MDSCs. These cells are distributed systemically, resulting in general immunosuppression. They also infiltrate tumours, promoting their progression and metastasis by inhibiting the natural anti-tumour immune response. As these cells also interact with classical anti-neoplastic treatments, they have become major therapeutic targets in the pharmaceutical industry and in oncology research

Dendritic Cells and Lentiviral Vectors: Mapping the Way to Successful Immuno Gene Therapy

Professional antigen presenting cells, in particular dendritic cells (DCs) are central players in the immune response (Steinman & Banchereau 2007). Their function is dual; on the one hand DCs evoke strong immune responses against antigens that are considered hazardous, on the other hand DCs induce tolerance against self-antigens. To that end, DCs need to present antigen-derived peptides in the context of MHC class I or class II molecules to CD8+ and CD4+ T cells, respectively. It is the context in which these peptides are presented that determines the outcome of the immune response, immune activation versus tolerance. Consequently, DCs have become targets for immunotherapy against not only cancer and infectious disease, but also autoimmune diseases and transplantation rejection (Palucka et al.). Key to successful DC-based immunotherapy is the delivery of the antigen of interest, be it cancer, viral or auto-antigens, to DCs, as well as the delivery of molecules that dictate the immune stimulatory capacity of the DCs. Therefore, it is not surprising that much effort has been put in the development of vectors for genetic modification of DCs (Breckpot et al. 2004c). Of these lentiviral vectors (LVs), often derived from human immunodeficiency virus type 1 (HIV-1) are amongst the most efficient gene delivery vehicles, for both in vitro and in vivo modification of DCs (Escors & Breckpot ; Breckpot et al. 2007a). In addition, these LVs were demonstrated to activate the innate immune system through interaction with amongst others Toll-like receptors (TLRs), a characteristic that makes LVs even better suited for immunotherapeutic approaches against cancer and infectious diseases (Breckpot et al. ; Brown et al. 2006a). As immune activation of DCs is critical for the induction of antigenspecific immunity, several strategies have been developed to further strengthen the immune response by introduction of immune modulating molecules or by modulation of wellknown activation pathways such as the nuclear factor-kappaB (NF-κB), mitogen activated protein kinase (MAPK) p38 and MAPK c-Jun N-terminal kinases (JNK) pathways (Breckpot & Escors 2009a). Although LVs inherently activate DCs, they have also been evaluated for their ability to switch of the stimulatory capacity of DCs, thus to generate tolerogenic DCs. The strategies exploited therefore are similar to the strategies employed to activate DCs and include introduction of single inhibitory molecules and modulation of pathways that

Manipulating Immune Regulatory Pathways to Enhance T Cell Stimulation

Cancer immunotherapy aspires to treat malignant disease by activating cancer specific immune responses. It is generally accepted that the latter can only be achieved by an approach in which tumor specific T cells are educated to recognize and kill tumor cells, whilst they are furthermore empowered to overcome immunosuppressive mechanisms present both at peripheral sites and in the tumor environment. Dendritic cells (DCs) have been extensively explored as a cellular vaccine for the stimulation of tumor specific T cells. Several strategies have been devised to manipulate these cells to become strongly activated tumor associated antigen (TAA) presenting cells. Our growing knowledge on the biology of DCs and the costimulatory as well as inhibitory molecules expressed by them, provides us with opportunities to generate DCs that are capable of hyper-activating cytotoxic T lymphocytes (CTLs) whilst they impact on regulatory T cells (Treg), which are now well established to be an important contributor to failure of cancer vaccines. In this chapter, we will focus on the cross talk between DCs and T cells mediated by the CD70/CD27 and PD-L1/PD-1 axis as these have been identified as critical pathways in the regulation of immunity versus tolerance.

Lentiviral Vectors in Immunotherapy

Genetic immunotherapy can be defined as a therapeutic approach in which therapeutic genes are introduced into defined target cell types to modulate immune responses. A major challenge for this therapeutic strategy is the delivery of these genes into target cells in an efficient, stable manner. Possibly one of the best systems to achieve this is the use of lentivi‐ ral vectors (lentivectors) as gene carriers, as they are capable of transducing both dividing and resting cells [1].

Targeted Lentiviral Vectors: Current Applications and Future Potential

About two decades ago recombinant human immunodeficiency virus type 1 (HIV-1) wasproposed as a blueprint for the development of lentiviral vectors (LVs) (Naldini, Blomer etal. 1996). Lentiviral vectors exhibit several characteristics that make them favorable tools forgene therapy, including sustained gene delivery through vector integration, transduction ofboth dividing and non-dividing cells, applicability to different target cell types, absence ofexpression of viral proteins after transduction, delivery of complex genetic elements, lowgenotoxicity and the relative ease of vector manipulation and production (Cattoglio, Facchi‐ni et al. 2007; Bauer, Dao et al. 2008). This is reflected in the numerous applications such as:transgene (tg) overexpression (Lopez-Ornelas, Mejia-Castillo et al. 2011), persistent gene si‐lencing (Wang, Hu et al. 2012), immunization (Breckpot, Emeagi et al. 2008), generation oftransgenic animals (Baup, Fraga et al. 2010), in vivo imaging (Roet, Eggers et al. 2012), induc‐tion of pluripotent cells, stem cell modification (Sanchez-Danes, Consiglio et al. 2012), line‐age tracking and site-directed gene editing (Lombardo, Genovese et al. 2007) as well asmany applications targeting cancer cells (Petrigliano, Virk et al. 2009).Recombinant LVs can be derived from primate as well as non-primate lentiviruses such asHIV-1 and simian immunodeficiency virus (SIV) next to the equine infectious anemia virus,caprine arthritis-encephalitis virus, maedi-visna virus, feline immunodeficiency virus (FIV)and bovine immunodeficiency virus respectively (Escors and Breckpot 2010). They are allmembers of the Retroviridae family with ‘retro’ referring to their capacity to retro-transcribetheir diploid single stranded (ss) RNA genome into a double stranded (ds) DNA copy that is

Clinical Grade Lentiviral Vectors

Thirty years of extensive research culminated in the year 2000 with the publication of the first clearly successful human gene therapy clinical trial. The trial corrected X-linked severe combined immunodeficiency (SCID-X1) in children using a therapeutic γ-retrovirus vector. Soon afterwards, the results of several other trials were published. More recently, lentiviral vectors have been used for the correction of human β-thalassaemia and adrenoleukodystrophy. In this chapter, we discuss the production of clinical grade retro and lentivectors for their application in human therapy.

Human Gene Therapy with Retrovirus and Lentivirus Vectors

The first human gene therapy clinical trial unsuccessfully took place in the 1970s. Despite extensive research and development in this subject, it was only approximately 10 years ago in 2000, that the results from a completely successful human gene therapy trial were published. Severe combined immunodeficiency X1 was corrected by ex vivo transduction of autologous hematopoietic stem cells with a γ-retrovirus vector encoding the therapeutic gene, followed by retransplantation. Since then, several other clinical trials using retro and lentivectors have followed. In this chapter we will briefly describe and discuss these successful trials for the correction of genetic diseases.