Enhanced cytotoxicity and decreased CD8 dependence of human cancer-specific cytotoxic T lymphocytes after vaccination with low peptide dose.

In mice, vaccination with high peptide doses generates higher frequencies of specific CD8+ T cells, but with lower avidity compared to vaccination with lower peptide doses. To investigate the impact of peptide dose on CD8+ T cell responses in humans, melanoma patients were vaccinated with 0.1 or 0.5 mg Melan-A/MART-1 peptide, mixed with CpG 7909 and Incomplete Freund's adjuvant. Neither the kinetics nor the amplitude of the Melan-A-specific CD8+ T cell responses differed between the two vaccination groups. Also, CD8+ T cell differentiation and cytokine production ex vivo were similar in the two groups. Interestingly, after low peptide dose vaccination, Melan-A-specific CD8+ T cells showed enhanced degranulation upon peptide stimulation, as assessed by CD107a upregulation and perforin release ex vivo. In accordance, CD8+ T cell clones derived from low peptide dose-vaccinated patients showed significantly increased degranulation and stronger cytotoxicity. In parallel, Melan-A-specific CD8+ T cells and clones from low peptide dose-vaccinated patients expressed lower CD8 levels, despite similar or even stronger binding to tetramers. Furthermore, CD8+ T cell clones from low peptide dose-vaccinated patients bound CD8 binding-deficient tetramers more efficiently, suggesting that they may express higher affinity TCRs. We conclude that low peptide dose vaccination generated CD8+ T cell responses with stronger cytotoxicity and lower CD8 dependence.

Functions of the human papillomavirus type 16 E4 protein

1. Abstract Cervical cancer is thought to be the consequence of infection by human papillomaviruses (HPV). In the majority of cases, DNA from HPV type 16 (HPV16) is found in malignant cervical lesions. The initial steps leading to transformation of an infected cell are not clearly understood but in most cases, disruption and integration of the episomal viral DNA must take place. As a consequence, the E2 and E4 genes are usually not expressed whereas the E6 and E7 oncogenes are highly expressed. However, in a normal infection in which the viral DNA is maintained as an episome, all viral genes are expressed. The pattern according to which the viral proteins are made, and therefore the life cycle of the virus, is tightly linked to the differentiation process of the host keratinocyte. The study of the viral oncogenes E6 and E7 has revealed crucial functions in the process of malignant transformation such as degradation of the p53 tumor suppressor protein, deregulation of the Retinoblastoma protein pathway and activation of the telomerase ribonucleoprotein. All these steps are necessary for cancerous lesions to develop. However, the loss of the E2 gene product seems to be necessary for sufficient expression of E6 and E7 in order to achieve such effects. In normal infections, the E4 protein is made abundantly in the later stages of the viral life cycle. Though extensive amounts of work have been carried out to define the function of E4, it still remains unclear. In this study, several approaches have been used to try and determine the functions of E4. First, a cell-penetrating fusion protein was designed and produced in order to circumvent the chronic difficulties of expressing E4 in mammalian cells. Unfortunately, this approach was not successful due to precipitation of the purified fusion protein. Second, the observation that E4 accumulates in cells having modified their adhesion properties led to the hypothesis that E4 might be involved in the differentiation process of keratinocytes. Preliminary results suggest that E4 triggers differentiation. Last, as E4 has been reported to collapse the cytokeratin network of keratinocytes, a direct approach using atomic force microscopy has allowed us to test the potential modification of mechanical properties of cells harboring reorganized cytokeratin networks. If so, a potential role for E4 in viral particle release could be hypothesized. 2. Résumé Il a été établi que le cancer du col de l'utérus se développe essentiellement à la suite d'une infection par le virus du papillome humain (HPV). Dans la majorité des cas analysés, de l'ADN du HPV de type 16 (HPV16) est détecté. Les étapes initiales de la transformation d'une cellule infectée sont mal connues mais il semble qu'une rupture du génome viral, normalement épisomal, suivi d'une intégration dans le génome de la cellule hôte soient des étapes nécessaires dans la plupart des cas. Or il semble qu'il y ait une sélection pour les cas où l'expression des oncogènes viraux E6 et E7 soit favorisée alors que l'expression des gènes E2 et E4 est en général impossible. Par contre, dans une infection dite normale où le génome viral n'est pas rompu, il n'y pas développement de cancer et tous les gènes viraux sont exprimés. L'ordre dans lequel les protéines virales sont produites, et donc le cycle de réplication du virus, est intimement lié au processus de différentiation de la cellule hôte. L'étude des protéines oncogènes E6 et E7 a révélé des fonctions clés dans le processus de transformation des cellules infectées telles que la dégradation du suppresseur de tumeur p53, la dérégulation de la voie de signalisation Rb ainsi que l'activation de la télomérase. Toutes ces activités sont nécessaires au développement de lésions cancéreuses. Toutefois, il semble que l'expression du gène E2 doit être empêchée afin que suffisamment des protéines E6 et E7 soient produites. Lorsque le gène E2 est exprimé, et donc lorsque le génome viral n'est pas rompu, les protéines E6 et E7 n'entraînent pas de telles conséquences. Le gène E4, qui se trouve dans la séquence codante de E2, a aussi besoin d'un génome viral intact pour être exprimé. Dans une infection normale, le gène E4 est exprimé abondamment dans les dernières étapes de la réplication du virus. Bien que de nombreuses études aient été menées afin de déterminer la fonction virale à E4, aucun résultat n'apparaît évident. Dans ce travail, plusieurs approches ont été utilisées afin d'adresser cette question. Premièrement, une protéine de fusion TAT-E4 a été produite et purifiée. Cette protéine, pouvant entrer dans les cellules vivantes par diffusion au travers de la membrane plasmique, aurait permis d'éviter ainsi les problèmes chroniques rencontrés lors de l'expression de E4 dans les cellules mammifères. Malheureusement, cette stratégie n'a pas pu être utilisée à cause de la précipitation de la protéine purifiée. Ensuite, l'observation que E4 s'accumule dans les cellules ayant modifié leurs propriétés d'adhésion a suggéré que E4 pourrait être impliqué dans le procédé de différentiation des kératinocytes. Des résultats préliminaires supportent cette possibilité. Enfin, il a été montré que E4 pouvait induire une réorganisation du réseau des cytokératines. Une approche directe utilisant le microscope à force atomique nous a ainsi permis de tester une potentielle modification des propriétés mécaniques de cellules ayant modifié leur réseau de cytokératines en présence de E4. Si tel est le cas, un rôle dans la libération de particules virales peut être proposé pour E4.

CD103 marks a subset of human CD34(+)-derived langerin(+) dendritic cells that induce T-regulatory cells via indoleamine 2,3-dioxygenase-1.

Indoleamine 2,3-dioxygenase 1 (IDO1) is an immunosuppressive molecule expressed in some subsets of normal and neoplastic cells. Mature human dendritic cells (DCs) have been shown to express IDO1, but little is known about its expression and function during DC differentiation from bone marrow hematopoietic stem/progenitor cells (HSPCs). Here, we show that during in vitro differentiation along the myeloid DC lineage, CD34(+) HSPCs acquire IDO1 expression, which acts in a tolerogenic manner by inducing a population of fully functional CD4(+)CD25(+) FOXP3(+) T-regulatory cells. Phenotypically, CD1a(+)CD14(-) HPSC-derived DCs expressed IDO1, langerin, CD11b, and CD1c. Cell-sorting experiments demonstrated that IDO1 expression is found in a subset of CD1a(+)CD14(-)langerin(+) cells, expressing CD103, which is capable of inducing T-regulatory cells in an IDO1-dependent manner. In conclusion, DC differentiation from CD34(+) HSPCs results in the expression of a functionally active IDO1 protein in CD1a(+)langerin(+), CD103-expressing DCs. These data point toward IDO1 expression as part of a tolerogenic signature during DC development.

The Human Mesenchymal Stromal Cell-Derived Osteocyte Capacity to Modulate Dendritic Cell Functions Is Strictly Dependent on the Culture System.

In vitro differentiation of mesenchymal stromal cells (MSC) into osteocytes (human differentiated osteogenic cells, hDOC) before implantation has been proposed to optimize bone regeneration. However, a deep characterization of the immunological properties of DOC, including their effect on dendritic cell (DC) function, is not available. DOC can be used either as cellular suspension (detached, Det-DOC) or as adherent cells implanted on scaffolds (adherent, Adh-DOC). By mimicking in vitro these two different routes of administration, we show that both Det-DOC and Adh-DOC can modulate DC functions. Specifically, the weak downregulation of CD80 and CD86 caused by Det-DOC on DC surface results in a weak modulation of DC functions, which indeed retain a high capacity to induce T-cell proliferation and to generate CD4(+)CD25(+)Foxp3(+) T cells. Moreover, Det-DOC enhance the DC capacity to differentiate CD4(+)CD161(+)CD196(+) Th17-cells by upregulating IL-6 secretion. Conversely, Adh-DOC strongly suppress DC functions by a profound downregulation of CD80 and CD86 on DC as well as by the inhibition of TGF-β production. In conclusion, we demonstrate that different types of DOC cell preparation may have a different impact on the modulation of the host immune system. This finding may have relevant implications for the design of cell-based tissue-engineering strategies.

Connexin43 Inhibition Prevents Human Vein Grafts Intimal Hyperplasia.

Venous bypass grafts often fail following arterial implantation due to excessive smooth muscle cells (VSMC) proliferation and consequent intimal hyperplasia (IH). Intercellular communication mediated by Connexins (Cx) regulates differentiation, growth and proliferation in various cell types. Microarray analysis of vein grafts in a model of bilateral rabbit jugular vein graft revealed Cx43 as an early upregulated gene. Additional experiments conducted using an ex-vivo human saphenous veins perfusion system (EVPS) confirmed that Cx43 was rapidly increased in human veins subjected ex-vivo to arterial hemodynamics. Cx43 knock-down by RNA interference, or adenoviral-mediated overexpression, respectively inhibited or stimulated the proliferation of primary human VSMC in vitro. Furthermore, Cx blockade with carbenoxolone or the specific Cx43 inhibitory peptide 43gap26 prevented the burst in myointimal proliferation and IH formation in human saphenous veins. Our data demonstrated that Cx43 controls proliferation and the formation of IH after arterial engraftment.

Structural and functional properties of two human FXYD3 (Mat-8) isoforms.

Six of 7 FXYD proteins have been shown to be tissue-specific modulators of Na,K-ATPase. In this study, we have identified two splice variants of human FXYD3, or Mat-8, in CaCo-2 cells. Short human FXYD3 has 72% sequence identity with mouse FXYD3, whereas long human FXYD3 is identical to short human FXYD3 but has a 26-amino acid insertion after the transmembrane domain. Short and long human FXYD3 RNAs and proteins are differentially expressed during differentiation of CaCo-2 cells. Long human FXYD3 is mainly expressed in nondifferentiated cells and short human FXYD3 in differentiated cells and both FXYD3 variants can be co-immunoprecipitated with a Na,K-ATPase antibody. In contrast to mouse FXYD3, which has two transmembrane domains for lack of cleavage of the signal peptide, human FXYD3 has a cleavable signal peptide and adopts a type I topology. After co-expression in Xenopus oocytes, both human FXYD3 variants associate stably only with Na,K-ATPase isozymes but not with H,K-ATPase or Ca-ATPase. Similar to mouse FXYD3, short human FXYD3 decreases the apparent K(+) and Na(+) affinity of Na,K-ATPase over a large range of membrane potentials. On the other hand, long human FXYD3 decreases the apparent K(+) affinity only at slightly negative and positive membrane potentials and increases the apparent Na(+) affinity of Na,K-ATPase. Finally, both short and long human FXYD3 induce a hyperpolarization activated current, similar to that induced by mouse FXYD3. Thus, we have characterized two human FXYD3 isoforms that are differentially expressed in differentiated and non-differentiated cells and show different functional properties.

Finding and characterizing Partially Methylated Domains in human haematopoietic cells

DNA cytosine methylation has been demonstrated to be a central epigenetic modification that has essential roles in a myriad of cellular processes. Some examples of these include gene regulation, DNA-protein interactions, cellular differentiation, X-inactivation, maintenance of genome integrity by suppressing transposable elements and viruses, embryogenesis, genomic imprinting and tumourigenesis. This list is increasingly growing thanks to recent advances in genome-wide technologies, like Whole Genome Bisulfite Sequencing (WGBS-Seq). The development of this technology in research has allowed the identification of new features of the DNA methylation landscape that was not possible using previous technologies, like Partially Methylated Domains (PMDs). PMDs have been found in several cell lines, as well as in both healthy and cancer primary samples. They have been described as regions with high variability in methylation levels across individual CpG sites and intermediate methylation levels on average with respect to the genome. Here, we performed an extensive search of PMDs in a big dataset of different haematopoietic primary cells from both myeloid and lymphoid lineages. We found and characterized significant PMDs in plasma B cells, confirming that PMDs are a phenomenon that is restricted to certain differentiated cells. Additionally, we found loci aberrantly hypomethylated in a myeloma sample which overlapped with plasma B cell PMDs. Genome-wide comparison of the myeloma and plasma B cell sample revealed that this is probably also the case for other loci.

Nitric oxide sustains IL-1β expression in human dendritic cells enhancing their capacity to induce IL-17-producing T-cells.

The role played by lung dendritic cells (DCs) which are influenced by external antigens and by their redox state in controlling inflammation is unclear. We studied the role played by nitric oxide (NO) in DC maturation and function. Human DCs were stimulated with a long-acting NO donor, DPTA NONOate, prior to exposure to lipopolysaccharide (LPS). Dose-and time-dependent experiments were performed with DCs with the aim of measuring the release and gene expression of inflammatory cytokines capable of modifying T-cell differentiation, towardsTh1, Th2 and Th17 cells. NO changed the pattern of cytokine release by LPS-matured DCs, dependent on the concentration of NO, as well as on the timing of its addition to the cells during maturation. Addition of NO before LPS-induced maturation strongly inhibited the release of IL-12, while increasing the expression and release of IL-23, IL-1β and IL-6, which are all involved in Th17 polarization. Indeed, DCs treated with NO efficiently induced the release of IL-17 by T-cells through IL-1β. Our work highlights the important role that NO may play in sustaining inflammation during an infection through the preferential differentiation of the Th17 lineage.

Ancient DNA of the extinct Lava shearwater (Puffinus olsoni) from the Canary Islands reveals incipient differentiation within the P. puffinus complex

The loss of species during the Holocene was, dramatically more important on islands than on continents. Seabirds from islands are very vulnerable to human-induced alterations such as habitat destruction, hunting and exotic predators. For example, in the genus Puffinus (family Procellariidae) the extinction of at least five species has been recorded during the Holocene, two of them coming from the Canary Islands.

Enhancement of human adipose-derived stem cell expansion and stability for clinical use

Co-culture techniques associating both dermal fibroblasts and epidermal keratinocytes have shown to have better clinical outcome than keratinocyte culture alone for the treatment of severe burns. Since fat grafting has been shown to improve scar remodelling, new techniques such as cell-therapy-assisted surgical reconstruction with isolated and expanded autologous adipose-derived stem cells (ASCs) would be of benefit to increase graft acceptation. Therefore, integrating ASCs into standardized procedures for cultured skin grafting could be of benefit for the patient if cell quality and quantity could be maintained. The purpose of this study was to evaluate ASC processing from adult tissue with simple isolation (without enzymatic steps), expansion (low density of 325-3,000 cells/cm2) and storage conditions to assure methods to enhance the cellular resistance when transferred back to the patient. Co-culture with cell-banked skin progenitor cells (FE002-SK2) showed an increase of 40-50% ASCs yield at high passages alongside with a better preservation of morphology, proper adipogenic and osteogenic differentiation and efficient biocompatibility with 3D collagen scaffolds. ASCs can be considered as a valuable additional cell source to be delivered in biological bandages to the patient in a need of tissue reconstruction such as burn patients.

Regulating Mechanisms of Gonadal and Pituitary Tumorigenesis in Mice Producing Human Chorionic Gonadotropin

Human chorionic gonadotropin (hCG) and luteinizing hormone (LH) are structurally and functionally similar glycoprotein hormones acting through the same luteinizing hormone chorionic gonadotropin receptor (LHCGR). The functions of LH in reproduction and hCG in pregnancy are well known. Recently, the expression of LHCGR has been found in many nongonadal tissues and cancers, and this has raised the question of whether LH/hCG could affect the function or tumorigenesis of these nongonadal tissues. We have also previously generated an hCG expressing mouse model presenting nongonadal phenotypes. Using this model it is possible to improve our understanding of nongonadal action of highly elevated LH/hCG. In the current study, we analyzed the effect of moderately and highly elevated hCG levels on male reproductive development and function. The main finding was the appearance of fetal Leydig cell (FLC) adenomas in prepubertal males. However, the development and differentiation of FLCs were not significantly affected. We also show that the function of hCG is different in FLCs and in adult Leydig cells (ALC), because in the latter cells hCG was not able to induce tumorigenesis. In FLCs, LHCGR is not desensitized or downregulated upon ligand binding. In this study, we found that the testicular expression of two G protein-coupled receptor kinases responsible for receptor desensitization or downregulation is increased in adult testis. Results suggest that the lack of LHCGR desensitization or downregulation in FLCs protect testosterone (Te) synthesis, but also predispose FLCs for LH/hCG induced adenomas. However, all the hCG induced nongonadal changes observed in male mice were possible to explain by the elevated Te level found in these males. Our findings indicate that the direct nongonadal effects of elevated LH/hCG in males are not pathophysiologically significant. In female mice, we showed that an elevated hCG level was able to induce gonadal tumorigenesis. hCG also induced the formation of pituitary adenomas (PA), but the mechanism was indirect. Furthermore, we found two new potential risk factors and a novel hormonally induced mechanism for PAs. Increased progesterone (P) levels in the presence of physiological estradiol (E2) levels induced the formation of PAs in female mice. E2 and P induced the expression and nuclear localization of a known cell-cycle regulator, cyclin D1. A calorie restricted diet was also able to prevent the formation of PAs, suggesting that obesity is able to promote the formation of PAs. Hormone replacement therapy after gonadectomy and hormone antagonist therapy showed that the nongonadal phenotypes observed in hCG expressing female mice were due to ovarian hyperstimulation. A slight adrenal phenotype was evident even after gonadectomy in hCG expressing females, but E2 and P replacement was able to induce a similar phenotype in WT females without elevated LH/hCG action. In conclusion, we showed that the direct effects of elevated hCG/LH action are limited only to the gonads of both sexes. The nongonadal phenotypes observed in hCG expressing mice were due to the indirect, gonadal hormone mediated effects of elevated hCG. Therefore, the gonads are the only physiologically significant direct targets of LHCGR signalling.

Interleukin-4 induced leukocyte differentiation

Monocytes, macrophages and dendritic cells (DCs) are important mediators of innate immune system, whereas T lymphocytes are the effector cells of adaptive immune responses. DCs play a crucial role in bridging innate and adaptive immunity. Naïve CD4+ Th progenitors (Thp) differentiate to functionally distinct effector T cell subsets including Th1, Th2 and Th17 cells, which while being responsible for specific immune functions have also been implicated in pathological responses, such as autoimmunity, asthma and allergy. The main objective of this thesis is to dissect the signalling networks involved in the IL-4 induced differentiation of two important leukocyte subtypes, Th2 cells and DCs. Gene expression profiling lead to identification of over 200 genes which are differentially expressed during cytokine induced differentiation of human monocytes to DCs or macrophages and which are likely to be essential for the proper biological functions of these cell types. Transcriptome analysis demonstrated the dynamic regulation of gene expression by IL-12 and IL-4 during the initiation of Th cell differentiation, which was partly counteracted by an immunosuppressive cytokine, TGFβ, present in the culture media. Results from RNAi mediated gene knockdown experiments and global gene expression analysis elucidated that SATB1 regulates multiple genes important for Th cell polarization or function as well as may compete with GATA3 for the reciprocal regulation of IL-5 transcription. In conclusion, the results obtained have extended our system-level understanding of the immune cell differentiation processes and provide an excellent basis for the further functional studies which could lead to development of improved therapeutic approaches for a range of immunological conditions.

Pluripotency and genetic stability of human pluripotent stem cells

Pluripotent cells have the potential to differentiate into all somatic cell types. As the adult human body is unable to regenerate various tissues, pluripotent cells provide an attractive source for regenerative medicine. Human embryonic stem cells (hESCs) can be isolated from blastocyst stage embryos and cultured in the laboratory environment. However, their use in regenerative medicine is restricted due to problems with immunosuppression by the host and ethical legislation. Recently, a new source of pluripotent cells was established via the direct reprogramming of somatic cells. These human induced pluripotent stem cells (hiPSCs) enable the production of patient specific cell types. However, numerous challenges, such as efficient reprogramming, optimal culture, directed differentiation, genetic stability and tumor risk need to be solved before the launch of therapeutic applications. The main objective of this thesis was to understand the unique properties of human pluripotent stem cells. The specific aims were to identify novel factors involved in maintaining pluripotency, characterize the effects of low oxygen culture on hESCs, and determine the high resolution changes in hESCs and hiPSCs during culture and reprogramming. As a result, the previously uncharacterized protein L1TD1 was determined to be specific for pluripotent cells and essential for the maintenance of pluripotency. The low oxygen culture supported undifferentiated growth and affected expression of stem cell associated transcripts. High resolution screening of hESCs identified a number of culture induced copy number variations and loss of heterozygosity changes. Further, screening of hiPSCs revealed that reprogramming induces high resolution alterations. The results obtained in this thesis have important implications for stem cell and cancer biology and the therapeutic potential of pluripotent cells.

Cycle modulation of insulin-like growth factor-binding protein 1 in human endometrium

Endometrium is one of the fastest growing human tissues. Sex hormones, estrogen and progesterone, in interaction with several growth factors, control its growth and differentiation. Insulin-like growth factor 1 (IGF-1) interacts with cell surface receptors and also with specific soluble binding proteins. IGF-binding proteins (IGF-BP) have been shown to modulate IGF-1 action. Of six known isoforms, IGF-BP-1 has been characterized as a marker produced by endometrial stromal cells in the late secretory phase and in the decidua. In the current study, IGF-1-BP concentration and affinity in the proliferative and secretory phase of the menstrual cycle were measured. Endometrial samples were from patients of reproductive age with regular menstrual cycles and taking no steroid hormones. Cytosolic fractions were prepared and binding of 125I-labeled IGF-1 performed. Cross-linking reaction products were analyzed by SDS-polyacrylamide gel electrophoresis (7.5%) followed by autoradiography. 125I-IGF-1 affinity to cytosolic proteins was not statistically different between the proliferative and secretory endometrium. An approximately 35-kDa binding protein was identified when 125I-IGF-1 was cross-linked to cytosol proteins. Secretory endometrium had significantly more IGF-1-BP when compared to proliferative endometrium. The specificity of the cross-linking process was evaluated by the addition of 100 nM unlabeled IGF-1 or insulin. Unlabeled IGF-1 totally abolished the radioactivity from the band, indicating specific binding. Insulin had no apparent effect on the intensity of the labeled band. These results suggest that IGF-BP could modulate the action of IGF-1 throughout the menstrual cycle. It would be interesting to study this binding protein in other pathologic conditions of the endometrium such as adenocarcinomas and hyperplasia.

Establishment of new murine embryonic stem cell lines for the generation of mouse models of human genetic diseases

Embryonic stem cells are totipotent cells derived from the inner cell mass of blastocysts. Recently, the development of appropriate culture conditions for the differentiation of these cells into specific cell types has permitted their use as potential therapeutic agents for several diseases. In addition, manipulation of their genome in vitro allows the creation of animal models of human genetic diseases and for the study of gene function in vivo. We report the establishment of new lines of murine embryonic stem cells from preimplantation stage embryos of 129/Sv mice. Most of these cells had a normal karyotype and an XY sex chromosome composition. The pluripotent properties of the cell lines obtained were analyzed on the basis of their alkaline phosphatase activity and their capacity to form complex embryoid bodies with rhythmically contracting cardiomyocytes. Two lines, USP-1 and USP-3, with the best in vitro characteristics of pluripotency were used in chimera-generating experiments. The capacity to contribute to the germ line was demonstrated by the USP-1 cell line. This cell line is currently being used to generate mouse models of human diseases.