Anti-tumour effect of monoclonal antibodies against selected antigens expressed by B-cells in Chronic Lymphocytic Leukaemia : strategies to enhance the efficacy of immunotherapy

Résumé : Les anticorps monoclonaux ont une place de plus en plus prépondérante dans le traitement des lymphomes et leucémies. Dans cette étude, trois anticorps monoclonaux murins, dirigés contre les antigènes CDS, CD71 et HLA-DR exprimés à la surface des cellules de leucémies lymphoïdes chroniques (LLC), ont été évalués. In vitro, les anticorps radiomarqués ont montrés des bonnes liaisons spécifiques sur les différentes cellules cibles. L'anti-CD71 inhibait la prolifération de la plupart des lignées cellulaires testées avec une accumulation des cellules en phase S précoce du cycle cellulaire. L'anti-HLA-DR inhibait aussi la prolifération des lignées leucémique JOK1-5.3 et lymphoïde Daudi. Cette inhibition était associée à une agrégation des cellules. Aucune induction d'apoptose n'a pu être clairement observée avec ces anticorps. L'anti-CD5 n'a montré aucun effet d'inhibition de croissance in vitro. In vivo, l'injection des anticorps individuellement augmentait significativement la survie médiane de souris SCID greffées avec des cellules JOK1-5.3 en i.p. De plus, l'anticorps antiCD5 combiné à l'anti-HLA-DR ou l'anti-CD71, sous certaines conditions, inhibait complètement le développement tumoral dans la quasi totalité des souris traitées avec une augmentation significative de l'efficacité comparée aux anticorps seuls. L'augmentation de l'efficacité thérapeutique des anticorps monoclonaux par les cytokines, dont l'IL-2, a déjà été montrée dans la littérature. Au regard du meilleur comportement de l'IL-2 sous la forme complexée à un anticorps anti-IL-2, nous avons évalué l'efficacité de l'IL-2/anti-IL-2 seul ou combinés au rituximab chez différents modèles tumoraux s.c. (BL60.2, Daudi, Ramos) ou i.p. (JOK15.3) de souris SCID. Le complexe IL-2/anti-IL-2 a montré un effet anti-tumoral dans les souris greffées avec BL60.2 et Daudi. Le traitement IL-2/anti-IL-2 combiné au rituximab a montré une efficacité accrue chez des souris avec BL60.2 par rapport au rituximab seul. En revanche, nous n'avons pas observé de différence avec IL-2/anti-IL-2 seul.Aussi, nous avons évalué l'utilisation de l'agent couplant tri-fonctionnel TMEA pour produire des anticorps bispecifiques. Les expériences préliminaires avec les anticorps rituximab et herceptine, ont mis en évidence sur gel SDS-Page la formation de dimers (~100kDa) et de trimers (~150kDa). Les anticorps bispecifiques sont composés d'un fragment Fab' d'une spécificité et de un ou deux fragments Fab' de l'autre spécificité permettant de moduler la capacité de liaison. Nous avons enfin montré qu'une construction anti-CD5/anti-CD20 était capable de se lier indépendamment ou simultanément à ses antigènes cibles. En conclusion, ce travail a montré l'efficacité thérapeutique des trois anticorps monoclonaux étudiés dans un model de LLC in vivo, et plus particulièrement l'intérêt de certaines combinaisons. D'autre part, nous avons montré l'efficacité anti-tumorale du complexe IL-2/anti-IL-2 in vivo. Des études futures devront permettre de définir un régime favorable pour augmenter l'efficacité de la thérapie avec les anticorps monoclonaux. Enfin, nous avons montré la faisabilité d'utiliser l'agent couplant TMEA pour produire des anticorps bispécifiques fonctionnels.Abstract : Monoclonal antibody (mAb) therapy has become an integral part in different treatments of lymphomas and leukaemias. In this study, we describe three murine mAbs directed against the CD5, CD71 and HLA-DR antigens expressed on chronic lymphocytic leukaemia cells (CLL). In vitro, radiolabeled purified mAbs showed good specific binding on live target cells. Anti-CD71 mAb inhibited proliferation of most cell lines with an accumulation of responding cells in early S-phase of the cell cycle, but without induction of apoptosis. Anti-HLA-DR mAb showed proliferation inhibition of leukaemia JOK1-5.3 and lymphoid Daudi cells, associated with cell aggregation, but again no specific sign of apoptosis was observed. Anti-CD5 mAb did not show any growth inhibitory effect in vitro. In vivo, in a model of SCID mice grafted i.p. with JOK1-5.3 cells, injection of individual mAbs induced significant prolongation of median survival, up to complete inhibition of tumour growth in some mice. Antibody combination of anti-CD5 with anti-HLA-DR or anti-CD71, evaluated in an early treatment, completely inhibited tumour growth in most mice, with a significant efficacy enhancement as compared to mAb used as single agents. Previous reports described the improved efficacy of mAb therapy when combined with cytokines such as IL-2. Relying further on the improved efficacy of IL-2 when administered as an immune complex with anti-IL-2 mAb, we evaluated the anti-tumour effect of the IL-2/anti-IL-2 complex alone or combined with rituximab in subcutaneous (BL60.2, Daudi, Ramos) or i.p. (JOK1-5.3) tumour models in SCID mice. The IL-2/anti-IL-2 complex demonstrated an anti-tumour effect in BL60.2 and Daudi grafted SCID mice. Combination of IL-2/anti-IL-2 treatment with rituximab showed increased efficacy as compared to rituximab alone in BL60.2 grafted mice. However, no difference was observed with IL-2/anti-IL-2 complex alone in these experiments. Finally, we evaluated the feasibility of producing bispecific antibodies (bsAbs) using a trifunctional coupling agent, called TMEA. In preliminary experiments coupling rituximab with herceptine Fab' fragments we obtained the formation of dimers (~100kDa) and trimers (~150kDa) as observed on SDS-Page gel. This method allowed us to produce bsAb with one Fab' fragments of one specificity and one or two Fab' fragments of the second specificity. An anti-CD5/anti-CD20 bsAb was shown to bind targeted antigen either independently or simultaneously. In conclusion, these data show that the three mAbs were all able to induce significant growth inhibition of the JOK1-5.3 cell line in vivo, and efficacy was enhanced when used in combination. IL2/anti-IL-2 complex displayed anti-tumour efficacy in vivo. Further evaluation is necessary to define the most favourable combination to improve mAb therapy. BsAb were produced using the tri-functional agent allowing antibody fragments with relatively good binding. The poor yield obtained with such chemical couplings limited the use of these constructs in preclinical experiments.

Predicting global change impacts on plant species' distributions: Future challenges

Given the rate of projected environmental change for the 21st century, urgent adaptation and mitigation measures are required to slow down the on-going erosion of biodiversity. Even though increasing evidence shows that recent human-induced environmental changes have already triggered species' range shifts, changes in phenology and species' extinctions, accurate projections of species' responses to future environmental changes are more difficult to ascertain. This is problematic, since there is a growing awareness of the need to adopt proactive conservation planning measures using forecasts of species' responses to future environmental changes. There is a substantial body of literature describing and assessing the impacts of various scenarios of climate and land-use change on species' distributions. Model predictions include a wide range of assumptions and limitations that are widely acknowledged but compromise their use for developing reliable adaptation and mitigation strategies for biodiversity. Indeed, amongst the most used models, few, if any, explicitly deal with migration processes, the dynamics of population at the "trailing edge" of shifting populations, species' interactions and the interaction between the effects of climate and land-use. In this review, we propose two main avenues to progress the understanding and prediction of the different processes A occurring on the leading and trailing edge of the species' distribution in response to any global change phenomena. Deliberately focusing on plant species, we first explore the different ways to incorporate species' migration in the existing modelling approaches, given data and knowledge limitations and the dual effects of climate and land-use factors. Secondly, we explore the mechanisms and processes happening at the trailing edge of a shifting species' distribution and how to implement them into a modelling approach. We finally conclude this review with clear guidelines on how such modelling improvements will benefit conservation strategies in a changing world. (c) 2007 Rubel Foundation, ETH Zurich. Published by Elsevier GrnbH. All rights reserved.

Les groupes de parole de prévention de la récidive au sein des SPIP: une évolution centrée sur la gestion du risque, entre théorie et adaptation pratique

En France, les différentes réorientations pénales et les missions confiées au Service Pénitentiaire d'Insertion et de Probation (SPIP) placent l'évaluation des risques de récidive et leur prévention au centre de la pratique professionnelle des Conseillers Pénitentiaires d'Insertion et de Probation (CPIP). Les récentes évolutions législatives des missions des SPIP, les mutations identitaires et des pratiques qu'elles impliquent -en particulier les Groupes de Paroles de Prévention de la Récidive (GPPR)-, caractérisent une évolution centrée sur la gestion du risque. Partant de critiques dans la littérature sur la notion de gestion du risque de récidive dans les pratiques pénales et de ce qu'elle induit dans les modes d'appréhension des sujets et dans les interventions professionnelles, l'article met en relation les réorientations vers une gestion du risque telles qu'elles peuvent apparaître dans les textes, missions et référentiel du SPIP, avec une évaluation des pratiques professionnelles centrées sur les GPPR intégrés au sein des SPIP. Y a-t-il infiltration et remodelage des pratiques ? Si c'est bien le cas, on examine où se situe le niveau pertinent de cette influence et du réaménagement des pratiques.

An analysis of visual adaptation and contrast perception for tone mapping

Tone Mapping is the problem of compressing the range of a High-Dynamic Range image so that it can be displayed in a Low-Dynamic Range screen, without losing or introducing novel details: The final image should produce in the observer a sensation as close as possible to the perception produced by the real-world scene. We propose a tone mapping operator with two stages. The first stage is a global method that implements visual adaptation, based on experiments on human perception, in particular we point out the importance of cone saturation. The second stage performs local contrast enhancement, based on a variational model inspired by color vision phenomenology. We evaluate this method with a metric validated by psychophysical experiments and, in terms of this metric, our method compares very well with the state of the art.

Neuronal adaptation effects in decision making

Recently, there has been an increased interest on the neural mechanisms underlying perceptual decision making. However, the effect of neuronal adaptation in this context has not yet been studied. We begin our study by investigating how adaptation can bias perceptual decisions. We considered behavioral data from an experiment on high-level adaptation-related aftereffects in a perceptual decision task with ambiguous stimuli on humans. To understand the driving force behind the perceptual decision process, a biologically inspired cortical network model was used. Two theoretical scenarios arose for explaining the perceptual switch from the category of the adaptor stimulus to the opposite, nonadapted one. One is noise-driven transition due to the probabilistic spike times of neurons and the other is adaptation-driven transition due to afterhyperpolarization currents. With increasing levels of neural adaptation, the system shifts from a noise-driven to an adaptation-driven modus. The behavioral results show that the underlying model is not just a bistable model, as usual in the decision-making modeling literature, but that neuronal adaptation is high and therefore the working point of the model is in the oscillatory regime. Using the same model parameters, we studied the effect of neural adaptation in a perceptual decision-making task where the same ambiguous stimulus was presented with and without a preceding adaptor stimulus. We find that for different levels of sensory evidence favoring one of the two interpretations of the ambiguous stimulus, higher levels of neural adaptation lead to quicker decisions contributing to a speed–accuracy trade off.

Free-and open source software for a course on network management: authoring and enactment of scripts based on collaborative learning strategies

This paper describes a Computer-Supported Collaborative Learning (CSCL) case study in engineering education carried out within the context of a network management course. The case study shows that the use of two computing tools developed by the authors and based on Free- and Open-Source Software (FOSS) provide significant educational benefits over traditional engineering pedagogical approaches in terms of both concepts and engineering competencies acquisition. First, the Collage authoring tool guides and supports the course teacher in the process of authoring computer-interpretable representations (using the IMS Learning Design standard notation) of effective collaborative pedagogical designs. Besides, the Gridcole system supports the enactment of that design by guiding the students throughout the prescribed sequence of learning activities. The paper introduces the goals and context of the case study, elaborates onhow Collage and Gridcole were employed, describes the applied evaluation methodology, anddiscusses the most significant findings derived from the case study.

Learning design twofold strategies for teacher-led inquiry andstudent active learning

This workshop paper states that fostering active student participation both in face-to-face lectures / seminars and outside the classroom (personal and group study at home, the library, etc.) requires a certain level of teacher-led inquiry. The paper presents a set of strategies drawn from real practice in higher education with teacher-led inquiry ingredients that promote active learning. Thesepractices highlight the role of the syllabus, the importance of iterative learning designs, explicit teacher-led inquiry, and the implications of the context, sustainability and practitioners’ creativity. The strategies discussed in this paper can serve as input to the workshop as real cases that need to be represented in design and supported in enactment (with and without technologies).

Vertical Product Differentiation, Entry-Deterrence Strategies, and Entry Qualities, September 2005

We analyze the entry of a new product into a vertically differentiated market in which an entrant and an incumbent compete in prices. Here the entry-deterrence strategies of the incumbent firm rely on “limit qualities.” With a sequential choice of quality, a quality-dependent marginal production cost, and a fixed entry cost, we relate the entry-quality decision and the entry-deterrence strategies to the level of entry cost and the degree of consumer heterogeneity. Quality-dependent marginal production costs in the model entail the possibility of inferior-quality entry as well as an incumbent’s aggressive entry-deterrence strategies of increasing its quality level toward potential entry. Welfare evaluation confirms that social welfare is not necessarily improved when entry is encouraged rather than deterred.

Testing for local adaptation in brown trout using reciprocal transplants.

ABSTRACT: BACKGROUND: Local adaptation can drive the divergence of populations but identification of the traits under selection remains a major challenge in evolutionary biology. Reciprocal transplant experiments are ideal tests of local adaptation, yet rarely used for higher vertebrates because of the mobility and potential invasiveness of non-native organisms. Here, we reciprocally transplanted 2500 brown trout (Salmo trutta) embryos from five populations to investigate local adaptation in early life history traits. Embryos were bred in a full-factorial design and raised in natural riverbeds until emergence. Customized egg capsules were used to simulate the natural redd environment and allowed tracking the fate of every individual until retrieval. We predicted that 1) within sites, native populations would outperform non-natives, and 2) across sites, populations would show higher performance at 'home' compared to 'away' sites. RESULTS: There was no evidence for local adaptation but we found large differences in survival and hatching rates between sites, indicative of considerable variation in habitat quality. Survival was generally high across all populations (55% +/- 3%), but ranged from 4% to 89% between sites. Average hatching rate was 25% +/- 3% across populations ranging from 0% to 62% between sites. CONCLUSION: This study provides rare empirical data on variation in early life history traits in a population network of a salmonid, and large-scale breeding and transplantation experiments like ours provide powerful tests for local adaptation. Despite the recently reported genetic and morphological differences between the populations in our study area, local adaptation at the embryo level is small, non-existent, or confined to ecological conditions that our experiment could not capture.

Current drug discovery strategies against arenavirus infections.

Arenaviruses are a large group of emerging viruses including several causative agents of severe hemorrhagic fevers with high mortality in man. Considering the number of people affected and the currently limited therapeutic options, novel efficacious therapeutics against arenaviruses are urgently needed. Over the past decade, significant advances in knowledge about the basic virology of arenaviruses have been accompanied by the development of novel therapeutics targeting different steps of the arenaviral life cycle. High-throughput, small-molecule screens identified potent and broadly active inhibitors of arenavirus entry that were instrumental for the dissection of unique features of arenavirus fusion. Novel inhibitors of arenavirus replication have been successfully tested in animal models and hold promise for application in humans. Late in the arenavirus life cycle, the proteolytic processing of the arenavirus envelope glycoprotein precursor and cellular factors critically involved virion assembly and budding provide further promising 'druggable' targets for novel therapeutics to combat human arenavirus infection.

Cross National Contact Strategies

Using paradata gathered from the 11-nation Survey of Health, Ageing and Retirement in Europe (SHARE), this paper examines the impact of the first contact attempt and the first contact properties, respectively, on contact and response efficiency using logistic multilevel models. We find that despite the different sample frames and interviewer compensation structure between countries, there are no considerable country effects with respect to making contact, once interviewer effects are controlled. Moreover, results point to an increased efficiency associated with evenings especially on Sundays, at least on the very first contact attempt. For attempts that result in initial contact, Saturday afternoons are most likely to eventually lead to completed interviews, followed by initial contact on weekdays during the daytime. We hypothesize that this may be due to the SHARE sample being composed of people aged 50 and over.

Vaccination Strategies against Highly Pathogenic Arenaviruses: The Next Steps toward Clinical Trials.

Vaccination is one of the most valuable weapons against infectious diseases and has led to a significant reduction in mortality and morbidity. However, for most viral hemorrhagic fevers caused by arenaviruses, no prophylactic vaccine is available. This is particularly problematic as these diseases are notoriously difficult to diagnose and treat. Lassa fever is globally the most important of the fevers caused by arenaviruses, potentially affecting millions of people living in endemic areas, particularly in Nigeria. Annually, an estimated 300,000 humans are infected and several thousands succumb to the disease. The successful development of the vaccine "Candid#1" against Junin virus, the causative agent of Argentine hemorrhagic fever, proved that an effective arenavirus vaccine can be developed. Although several promising studies toward the development of a Lassa fever vaccine have been published, no vaccine candidate has been tested in human volunteers or patients. This review summarizes the immunology and other aspects of existing experimental arenavirus vaccine studies, discusses the reasons for the lack of a vaccine, and proposes a plan for overcoming the final hurdles toward clinical trials.

Nine-month-olds' triangular interactive strategies with their parents' couple in low-coordination families: A descriptive study

Observing infants in triadic situations has revealed their triangular competence; namely, their ability to interact with both parents by simultaneously sharing their attention and affects with them. Infants' triangular interaction is linked with the coparenting unit's degree of coordination; in high-coordination (HC) families, parents act as a team in relation to the child, thus drawing clear and flexible boundaries with them; in low-coordination (LC) families, parents either avoid direct interaction with each other and include the child in their unit or join together against the child and exclude him or her, thus drawing inconsistent boundaries with the child. We explored the interactive strategies of LC 9-month-olds (n = 15) with those of their parents, comparing them with HC parents (n = 23) in two conditions: playing with both parents at the same time and witnessing their parents' dialogue. LC infants' affects were less positive; they addressed fewer positive triangular bids to their parents and tended to use a less triangular interactive mode. Thus, LC infants had fewer opportunities than did HC infants to acquire skills necessary for coping with triangular interaction. L'observation de nourrissons dans des situations triadiques a révélé leur compétence triangulaire, c'est-à-dire la capacité à interagir avec les deux parents en partageant simultanément leur attention et leurs affects avec eux. L'interaction triangulaire des nourrissons est liée au degré de coordination de l'unité de coparentage. Dans les familles à coordination élevée (abrégé HC en anglais, CE en français), les parents agissent en relation à l'enfant en tant qu'équipe, et établissent donc des limites claires et flexibles avec les enfants. Dans les familles à coordination faible (abrégé LC en anglais, CF en français), les parents évitent soit l'interaction directe l'un avec l'autre et incluent l'enfant dans leur unité, ou bien ils se liguent contre l'enfant et l'excluent, établissant donc des limites contradictoires avec l'enfant. Nous explorons les stratégies interactives de bébés de 9 mois CF avec celle de leurs parents, en les comparant avec des parents CE (N = 23) dans deux conditions: le jeu avec les deux parents au même moment et l'observation du dialogue des parents. Les affects des bébés CF étaient moins positifs. Les bébés se tournaient moins triangulairement vers leurs parents et avaient tendance à utiliser un mode interactif moins triangulaire. Les bébés CF avaient donc moins de chances que les bébés CE d'acquérir les compétences nécessaires pour faire face avec une interaction triangulaire.