Karim Benihoud

Adenovirus vectors for gene delivery.

Recent endeavors in the development of adenovirus as a gene vector have focused on the modification of virus tropism, the accommodation of larger genes, and the increase in stability and control of transgene expression. Whereas partial or total deletions of viral genes increase the cloning capacity and partly reduce the cellular immune response, control of the humoral response, which often precludes efficient readministration, remains a challenge.

Substitution of Hexon Hypervariable Region 5 of Adenovirus Serotype 5 Abrogates Blood Factor Binding and Limits Gene Transfer to Liver

Liver tropism potentially leading to massive hepatocyte transduction and hepatotoxicity still represents a major drawback to adenovirus (Ad)-based gene therapy. We previously demonstrated that substitution of the hexon hypervariable region 5 (HVR5), the most abundant capsid protein, constituted a valuable platform for efficient Ad retargeting. The use of different mouse strains revealed that HVR5 substitution also led to dramatically less adenovirus liver transduction and associated toxicity, whereas HVR5-modified Ad were still able to transduce different cell lines efficiently, including primary hepatocytes. We showed that HVR5 modification did not significantly change Ad blood clearance or liver uptake at early times. However, we were able to link the lower liver transduction to enhanced HVR5-modified Ad liver clearance and impaired use of blood factors. Most importantly, HVR5-modified vectors continued to transduce tumors in vivo as efficiently as their wild-type counterparts. Taken together, our data provide a rationale for future design of retargeted vectors with a safer profile.

DYRK1A interacts with the REST/NRSF-SWI/SNF chromatin remodelling complex to deregulate gene clusters involved in the neuronal phenotypic traits of Down syndrome

The molecular mechanisms that lead to the cognitive defects characteristic of Down syndrome (DS), the most frequent cause of mental retardation, have remained elusive. Here we use a transgenic DS mouse model (152F7 line) to show that DYRK1A gene dosage imbalance deregulates chromosomal clusters of genes located near neuron-restrictive silencer factor (REST/NRSF) binding sites. We found that Dyrk1a binds the SWI/SNF complex known to interact with REST/NRSF. The mutation of a REST/NRSF binding site in the promoter of the REST/NRSF target gene L1cam modifies the transcriptional effect of Dyrk1a-dosage imbalance on L1cam. Dyrk1a dosage imbalance perturbs Rest/Nrsf levels with decreased Rest/Nrsf expression in embryonic neurons and increased expression in adult neurons. Using transcriptome analysis of embryonic brain subregions of transgenic 152F7 mouse line, we identified a coordinated deregulation of multiple genes that are responsible for dendritic growth impairment present in DS. Similarly, Dyrk1a overexpression in primary mouse cortical neurons induced severe reduction of the dendritic growth and dendritic complexity. We propose that DYRK1A overexpression-related neuronal gene deregulation via disturbance of REST/NRSF levels, and the REST/NRSF-SWI/SNF chromatin remodelling complex, significantly contributes to the neural phenotypic changes that characterize DS.

Palmitoylation of the P2X7 receptor, an ATP-gated channel, controls its expression and association with lipid rafts

The P2X7 receptor (P2X7R) is an ATP‐gated cationic channel expressed by hematopoietic, epithelial, and neuronal cells. Prolonged ATP exposure leads to the formation of a nonselective pore, which can result in cell death. We show that P2X7R is associated with detergent‐resistant membranes (DRMs) in both transfected human embryonic kidney (HEK) cells and primary macrophages independently from ATP binding. The DRM association requires the posttranslational modification of P2X7R by palmitic acid. Treatment of cells with the palmitic acid analog 2‐bromopalmitate as well as mutations of cysteine to alanine residues abolished P2X7R palmitoylation. Substitution of the 17 intracellular cysteines of P2X7R revealed that 4 regions of the carboxyl terminus domain are involved in palmitoylation. Palmitoylation‐defective P2X7R mutants showed a dramatic decrease in cell surface expression because of their retention in the endoplasmic reticulum and proteolytic degradation. Taken together, our data demonstrate that P2X7R palmitoylation plays a critical role in its association with the lipid microdomains of the plasma membrane and in the regulation of its half‐life.— Gonnord, P., Delarasse, C., Auger, R., Benihoud, K., Prigent, M., Cuif, M. H., Lamaze, C., Kanellopoulos, J. M. Palmitoylation of the P2X7 receptor, an ATP‐gated channel, controls its expression and association with lipid rafts. FASEB J. 23, 795–805 (2009)

Intratumoral induction of CD103 triggers tumor-specific CTL function and CCR5-dependent T-cell retention.

We have reported previously that the interaction of alpha(E)(CD103)beta(7) integrin, expressed on a CD8(+) tumor-infiltrating lymphocyte (TIL) clone but not on a peripheral blood lymphocyte (PBL) counterpart, with the epithelial marker E-cadherin on human lung tumor cells plays a crucial role in T-cell receptor-mediated cytotoxicity. We show here that both TIL and PBL clones are able to migrate toward autologous tumor cells and that chemokine receptor CCR5 is involved in this process. Adoptive transfer of the PBL clone in the cognate tumor engrafted in nonobese diabetic/severe combined immunodeficient mice and subsequent coengagement of T-cell receptor and transforming growth factor-beta1 receptor triggers CD103 expression on T-cell surface resulting in strong potentiation of antitumor lytic function. Moreover, interaction of alpha(E)beta(7) integrin with E-cadherin, but not lymphocyte function-associated antigen-1 with intercellular adhesion molecule-1, promotes CCR5 recruitment at the immunologic synapse formed between TIL and tumor cells, leading to inhibition of T-cell sensitivity to CCL5 chemotactic gradient. These results provide evidence for a role of tumor microenvironment, namely MHC class I-restricted antigen presentation and transforming growth factor-beta1 secretion, in regulating the effector phase of tumor-specific CTL response. They also suggest a unique role of CD103 in T-cell retention at the tumor site by a CCR5-dependent mechanism.

Two Key Challenges for Effective Adenovirus-Mediated Liver Gene Therapy: Innate Immune Responses and Hepatocyte-Specific Transduction

Adenovirus (Ad) are valuable vectors for liver gene therapy because of their intrinsic ability to transduce hepatocytes following intravenous administration. However, the effective application of these vectors, including helper-dependent Ad unable to trigger viral gene expression, for liver gene therapy in humans has been limited due to several obstacles. First, their high immunogenicity triggers a complex immune response, both innate and adaptive, that leads to hepatocyte destruction, reducing the duration of transgene expression. This high immunogenicity also induces a long lasting cellular and humoral immunity that impairs subsequent re-administration. Second, Ad vectors transduce not only hepatocytes but also other cell types from the liver or other organs. This Ad vector dissemination contributes to their toxicity and immunogenicity, further reducing the effective period of transgene expression. A better understanding of the interactions between Ad vectors and their host underlying the acute liver toxicity and hepatocyte transduction is required to improve the efficacy and duration of gene delivery in vivo. The aim of this review is to discuss insights into the cellular and molecular mechanisms involved in Ad vector-mediated innate immune responses. Current advances in the knowledge of Ad liver tropism and the influence of blood components on Ad vector uptake by the liver will be discussed. Finally, different approaches developed to minimize Ad vector toxicity, optimize delivery and increase transgene expression will be summarized. The full potential of Ad vectors will only be reached when their immunogenicity is abolished and hepatocyte-specific transduction achieved.

Gene therapy of rat medullary thyroid cancer by naked nitric oxide synthase II DNA injection

Nitric oxide (NO), produced by NO synthase II (NOS II), is the main mediator of the tumoricidal action of activated macrophages. In the present study we examined the potential of the NOS II gene as a suicide gene for medullary thyroid cancer (MTC) therapy.

Development of human single-chain antibodies to the transferrin receptor that effectively antagonize the growth of leukemias and lymphomas.

The major route of iron uptake by cells occurs through transferrin receptor (TfR)-mediated endocytosis of diferric-charged plasma transferrin (holo-Tf). In this work, we pursued TfR antibodies as potential cancer therapeutics, characterizing human single-chain variable antibody fragments (scFv) specific for the human TfR isolated from a phage display library. We hypothesized that many of these antibodies would function as ligand mimetics because scFvs from the library were selected for binding and internalization into living cells. In support of this hypothesis, the anti-TfR scFvs identified were antagonists of TfR binding to holo-Tf, particularly two of the most potent antibodies, 3TF12 and 3GH7, which blocked the in vitro proliferation of a number of hematopoietic cancer cell lines. We optimized this activity of 3TF12 and 3GH7 by engineering 55-kDa bivalent antibody formats, namely, F12CH and H7CH, which could block cell proliferation with an IC(50) of 0.1 microg/mL. We found that the mechanism of the scFv antibody cytotoxicity was unique compared with cytotoxic anti-TfR monoclonal antibodies that have been described, causing cell surface upregulation of TfR along with the inhibition of holo-Tf cell uptake and induction of cell death. In a nude mouse model of erythroleukemia, administration of F12CH reduced tumor growth. Together, our findings define a new class of fully human anti-TfR antibodies suitable for immunotherapy against tumors whose proliferation relies on high levels of TfR and iron uptake, such as acute lymphoid and myeloid leukemias.

The role of IL-6 in the inflammatory and humoral response to adenoviral vectors.

The major concern for the use of adenoviral vectors for gene therapy is the viral‐induced immune response that has been shown to be responsible for short‐term transgene expression and inefficient viral readministration. In vivo studies and clinical trials with recombinant adenovirus have suggested a role for interleukin 6 (IL‐6) in the inflammatory reaction that follows Ad‐infection. IL‐6 plays an important role in the acute‐phase innate response, in the differentiation of B‐cells and in the activation of the Th2 cell subsets.

B lymphocytes mediate Fas‐dependent cytotoxicity in MRL/lpr mice

The Fas/Fas ligand (FasL) pathway is one of the two major effector mechanisms of T cell‐mediated cytotoxicity. To prevent nonspecific killing by lymphoid cells, FasL expression on the cell surface of immune effector cells is strictly regulated. However, MRL/lpr autoimmune‐prone mice massively overexpress FasL on their T lymphocytes, which render them able to kill Fas+ targets in vitro and in vivo. It is surprising that we show in the present work that B lymphocytes purified from MRL/lpr spleen cells express FasL to the same extent as T cells at the mRNA and protein level. These B cells are potent cytotoxic effectors against Fas+ but not Fas− targets. The B lymphocyte effectors were used ex vivo without any in vitro activation by B cell stimuli. Furthermore, we found that MRL/lpr B lymphocytes have the same cytotoxic potential as natural killer cells, which have been characterized as potent, Fas‐mediated, cytotoxic effectors. The level of membrane‐anchored FasL increases with the size of the B cell and cell‐surface activation marker CD69 expression, indicating that the expression of FasL is up‐regulated in parallel with the activation state of the B cell. The activated B cell population contained the major cytotoxic activity, and a minor part was associated with CD138/Syndecan‐1+ plasma cells.