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Natalizumab-induced progressive multifocal leukoencephalopathy appears to be unleashed by complex interactions between viral and immunological host factors leading the latent form of JC virus to become pathogenic. Positive anti-JC virus antibody status, prior use of immunosuppressants, and increasing duration of natalizumab treatment have been proposed as risk factors for progressive multifocal leukoencephalopathy in multiple sclerosis patients, but while they may help to identify the most appropriate patients for natalizumab, their use have some limitations. Therefore, a large body of studies is ongoing to identify alternative, reliable immunological markers capable to improve the safety and efficacy of therapy, and to guide tailored clinical decisions.

Vaccination, designed to trigger a protective immune response against infection, is a trigger for mild inflammatory responses. Vaccination studies can address the question of inflammation initiation, levels, and resolution as well as its regulation for respective studied pathogens. Such studies largely based on analyzing the blood components including specific antibodies and cytokines were usually constrained by number of participants and volume of collected blood sample. Hence, blood-based studies may not be able to cover the full dynamic range of inflammation responses induced by vaccination. In this review, the potential of using saliva in addition to blood for studying the kinetics of inflammatory response studies was assessed. Saliva sampling is noninvasive and has a great potential to be used for studies aimed at analysing the magnitude, time course, and variance in immune responses, including inflammation after vaccination. Based on a literature survey of inflammatory biomarkers that can be determined in saliva and an analysis of how these biomarkers could help to understand the mechanisms and dynamics of immune reactivity and inflammation, we propose that the saliva-based approach might have potential to add substantial value to clinical studies, particularly in vulnerable populations such as infants, toddlers, and ill individuals.

Summary Activation of cellular immunity, mainly cytotoxic T cells, plays an important role in the · mechanisms of cyclic acute exacerbation of hepatocellular damage (AE) in hepatitis B virus (HBV) carriers. Monitoring of the dynamics of immunoreactivity is clinically important to manage the patients and recognize the mechanism of liver damage. Serum neopterin has been widely- recognized as a marker of actiyation of cell-mediated immunity. We observed the clinical course of five hepatitis Be antigen I HBeAg ) positive HBV carriers with recurrent AE for mean eighteen months by monitoring of serum neopterin using a RIA kit. Alanine amino transferase (ALT) and HBeAg were also measured serially as markers for hepatocne necrosis and viral replication, respectively During follow-up period. each patient had several episodes of AE alternating with normal or nearly normal liver function. The levels of serum neopterin changed dynamically related to those of HBeAg and ALT Temporal analysis of these makers before, during and after the episodes of AE showed a close involvement of the viral replication prior to the hepatocellular injury as well as the activation of cellular immunity following the viral replication. Immunological monitoring of serum neopterin could provide useful information about the dynamic interaction between virus replication, cellular immunoreactivity and hepatocellular damage. It was thought that serum neopterin can be used as a complementary marker to follow and manage chronic hepatitis B patients.

Over the last half century, kidney and liver transplantation have been recognized as the treatment of choice for children with end-stage renal or liver failure. Greater understanding of the molecular mechanism of rejection and tolerance, as well as development of reliable assays that can measure accurately the status of the immune response, not only would help clinicians customize the prescription of immunosuppressive drugs in individual recipients, but also might contribute to optimization of outcome in pediatric organ transplantation. In addition, despite improved immunosuppression (IS) protocols, infants still face a variety of chronic complications such as drug toxicity, infection, and malignancies. Thus, a major goal in organ transplantation is to define the optimal immunosuppressive load, according to the individual immunological profile of the transplant patient. Ideally, from a clinical perspective, the de novo donor-recipient encounter should be monitored in pre-transplantation and the immediate post-transplantation period, allowing the early diagnosis of ongoing rejection processes. In this thesis, we review the specificities of the immune system in infants; we then discuss the mechanisms of rejection and the terminology underlying the generic concept of “transplant tolerance”. This review focuses on the several immunological assays studied or under development in pediatric organ transplantation. We subsequently attempted to find predictive tests in order to evaluate the patient’s immunological risk of early rejection after organ transplantation. Forty pediatric patients (median age: 2.1 years, range: 4 months - 13 years) who received an orthotopic liver transplantation between 1994 and 2004 in the Pediatric Liver Transplant Program at Saint-Luc University Clinics in Brussels, Belgium, were included in this study. First, using antigen non-specific assays, we investigated the evolution of pre-transplant and post-transplant serum soluble CD30 (sCD30), interferon- gamma (IFN-γ) and interleukin-10 (IL-10) circulating levels in the recipients who developed acute rejection as compared to patients with early graft acceptance. The frozen serum of the patients was analyzed to measure sCD30, IL-10 and IFN-γ serum levels at pre-transplantation baseline (day 0) and post-transplantation at day 7. The delta value of serum sCD30 between day 0 and 7 was compared with the delta value of IFN-γ and of IL-10 circulating levels on the same day. This study showed that increased serum sCD30 could be correlated with increased IL-10 circulating levels, but not with IFN-γ levels in the post-transplantation period. Neither pre-transplantation sCD30, nor sCD30 at day 7 post-transplantation could be correlated with acute rejection in liver graft recipient. The monitoring of sCD30 might constitute a tool to assess the risk of acute rejection in renal transplant but, at least in our limited series, did not appear to constitute a useful marker for early immunological monitoring in liver allograft recipients. Next, we used the enzyme-linked immunosorbent (ELISPOT) as an antigen-specific assay to analyze the detailed kinetics of granzyme-B (GrB) producing cells before and during the early post-transplantation period. We also investigated the pre- and post-transplantation secretion of GrB in pediatric liver recipients who developed acute rejection compared to patients with graft acceptance. Peripheral blood mononuclear cells (PBMC) from pediatric recipients were serially tested for GrB-producing donor-reactive cells at baseline and at days 7, 14, 28 post-transplantation. This study demonstrated that single GrB ELISPOT pre-transplantation could not predict the occurrence of early post-transplant acute rejection; similarly, GrB frequencies at days 7, 14 and 28 could not be correlated with acute rejection in pediatric liver recipients. However, a kinetic analysis of these data demonstrated that GrB increased significantly at day 7 from baseline in the rejection group. Thus, a kinetic monitoring of GrB ELISPOT variation was found helpful to predict or confirm early rejection in the liver allograft recipients. In the future, further research should therefore be encouraged, to identify the role of sCD30 and GrB ELISPOT kinetic assays in combination with a number of techniques, e.g. regulatory T cell, proteomics transcriptional profiling, and DNA microarray assays. Accordingly, a multidisciplinary approach should be established through multicenter studies including assessment of dynamic profiles, so that ideal strategies can be identified for implemention in the immunological monitoring of kidney and liver transplant in pediatric recipients. Au cours du dernier demi-siècle, la transplantation du rein et du foie a été identifiée comme traitement de choix pour les enfants atteints d’insuffisances rénales ou hépatiques terminales. L’étude du mécanisme moléculaire du rejet et de la tolérance, ainsi que le développement des tests fiables qui reflètent fidèlement les réponses immunitaires, aideraient non seulement les cliniciens à adapter les immunosuppresseurs pour chaque individu, mais pourraient également contribuer à optimiser de la survie des enfants transplantés. En outre, malgré l'amélioration des protocoles d’IS, les enfants doivent prendre des médicaments à vie avec un risque important de complications chroniques telles que la toxicité, l'infection et les cancers. Dès lors, en transplantation d'organe, il convient de définir la dose optimale des immunosuppresseurs, selon le profil immunologique de chaque patient. Idéalement, dans une perspective clinique, la réponse immunitaire du receveur vis-à-vis de son donneur devrait être suivie dans le décours de la transplantation afin de détecter immédiatement un rejet précoce post-transplantation ou un état de tolérance au décours de la greffe. Dans cette thèse, nous avons réalisé une revue de la littérature sur les spécificités du système immunitaire chez l’enfant ; par la suite nous avons abordé les mécanismes du rejet et les terminologies du concept général de «tolérance au greffon». Cette revue se concentre sur plusieurs tests immunologiques étudiés ou développés en transplantation d'organe pédiatrique. Ensuite, nous avons essayé de trouver des tests prédictifs dans le but d'évaluer le risque du rejet précoce après transplantation d'organe. 40 enfants (âge médian : 2.1 ans, range : 4 mois - 13 ans) du programme de transplantation hépatique des Cliniques universitaires de Saint-Luc à Bruxelles, ayant été transplantés entre 1994 et 2004, ont été inclus dans cette étude. Tout d'abord, en utilisant un test « antigène non spécifique », nous avons étudié l'évolution des concentrations sériques de CD30 soluble, IFN-γ et IL-10 en pré- et post-transplantations dans deux groupes, l’un ayant présenté un épisode du rejet aigu, l’autre ayant une évolution sans épisode de rejet. Les sérums congelés des patients ont été utilisés pour mesurer les taux de sCD30, IL-10 et IFN-γ pré-transplant (jour 0) et post-transplant au jour 7. La valeur du delta de sCD30 sérique entre le jour 0 et 7 a été comparée à la valeur du delta d'IFN-γ et d’IL-10 circulant au même jour. Cette étude a démontré que l’augmentation du sCD30 pouvait être corrélée avec l’augmentation d’IL-10 circulant, mais pas avec l’IFN-γ dans la période post-transplantation. Ni le sCD30 pré-transplantion, ni le sCD30 post-transplantion au jour 7 n'ont pu être corrélés avec le rejet aigu chez les receveurs de greffe de foie. Le monitoring du sCD30 pourrait bien constituer un marqueur utile pour évaluer le risque de rejet aigu chez les patients transplantés du rein mais, dans notre série limitée, ce marqueur n’a pas semblé valable pour la surveillance immunologique précoce des patients greffés du foie. Ensuite, nous avons utilisé « the enzyme-linked immunosorbent assay » (ELISPOT) comme test « antigène spécifique », pour analyser la cinétique du GrB, produit par les cellules du receveur stimulées avec les cellules du donneur avant et au cours de la période précoce post-transplantation. Nous avons également comparé les valeurs dans deux groupes ayant présenté ou non un épisode de rejet aigu. La production de GrB par les cellules mononucléées du sang périphérique des receveurs pédiatriques qui ont été stimulées avec les cellules du donneur, a été analysée au jour 0 avant transplantation ainsi qu’aux jours 7, 14 et 28 après transplantation. Cette étude a démontré que le GrB ELISPOT pré-transplantation ne permet pas de prévoir le rejet précoce, de même que la production du GrB aux jours 7, 14 et 28 ne peut être corrélée avec le développement d’un rejet aigu. Par contre, l’étude cinétique du GrB ELISPOT a démontré une augmentation significative du jour 0 au jour 7 dans le groupe de rejet. Le monitoring cinétique du GrB pourrait donc être un moyen utile afin de prévoir ou confirmer la survenue d’un rejet précoce chez les patients greffés du foie. De futures recherches sont à encourager afin d’identifier le rôle du sCD30 et du GrB ELISPOT en association avec la détection des lymphocytes T régulateurs, du profil de transcription protéomique, des microarrays, etc. Par conséquent, une approche multidisciplinaire et multicentrique, y compris l'évaluation des profils dynamique, devrait permettre de dégager, en vue de leur mise en oeuvre, des stratégies idéales dans le suivi immunitaire en greffe rénale et hépatique pédiatriques. (MED 3) -- UCL, 2009

DiGeorge syndrome (DGS) is a congenital disorder characterized by typical facial features, hypoparatyroidism, conotruncal cardiac defects and thymic hypoplasia. Although there are some reports addressing lymphocytes counts and function in DGS children over time, few data have been reported on the T-cell receptor V beta (TCRBV) repertoire in relation to disease progression. The aim of this study was to evaluate the degree and nature of immunodeficiency and to investigate a possible correlation to clinical findings. We used third complementary region (CDR3) size spectratyping as a tool for monitoring T-cell repertoire diversity in 7 DGS's children. The rate of thymic output, the phenotype and function of peripheral T-cells and the humoral immunity were also investigated. At baseline a profound alteration of the TCR repertoire was noted, mainly in the CD8+ T-cells, in DGS patients when compared to a control group. Furthermore, analysis of thymic output showed a significant decrease in TCR rearrangement excision circles (TRECs) levels in the patient group. Immunoglobulin abnormalities were also detected. The observed TCR repertoire alterations, although not statistically significant, may suggest an increased susceptibility to infections. A parallel increase in the TCR repertoire diversity and clinical improvement occurred during the follow-up. Our results confirm that the extent of immunodeficiency is highly variable and could improve through childhood, and indicate that TCR repertoire may be a useful marker to clinically monitor thymic function in this primary immunodeficiency.