Acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) are blood cancers that are often treated with stem cell transplantation (SCT). Since SCT treatments have variable success, especially in adults with AML whose disease frequently relapses, novel and more effective solutions must be considered. In this thesis, I will explore one type of immunotherapy in murine models for ALL (L1210) and AML (C1498) using in vitro and in vivo techniques such as flow cytometry and transcriptomics. In my approach, I am attempting to enhance the immunogenicity of whole cell vaccines by pre-infecting the leukemia cells with oncolytic virus (OV) and thus producing leukemia infected cell vaccines (ICVs). While it has been previously shown that L1210-ICV pre-treatment works well in protecting mice from ALL challenge, I have found that pre-immunization with C1498-ICV has a limited efficacy in protecting animals from AML progression. By investigating the downstream effects of ICV, I was able to show that unlike C1498 cells, L1210 cells produce previously unknown immunogenic factors following OV infection.

Currently, in most situations, the autologous immune system is unable to eradicate the residual leukemic burden persisting after chemo-radiotherapy, but a balance can be established between leukemic and immune cells leading to a clinical remission for several months or years. If this balance is broken, a clinical relapse can occur. The high incidence of relapses in human cancers demonstrates the frequent inefficacy of the immune system to control these residual cells. In this context, allogeneic hematopoietic stem cell transplantation (HSCT) has been proven to be the most effective way to reinforce the immune reaction against leukemia, graft-versus-leukemia (GVL) effect and, so, achieve a definitive eradication of the residual disease in a significant proportion of patients. Indeed, the whole concept of HSCT evolved from an organ transplant concept (to replace a defective ill organ with a new healthy one) to the concept of creating an extraordinary immunotherapeutic platform in which the donor immune system contributes to the eradication of the residual leukemic cells. Thus, the past and present issues remain those of finding the best immunomodulatory modalities to achieve a full engraftment, a powerful GVL effect and no or moderate graft-versus-host disease (GVHD). Different ways to reach this goal, such as post transplant cytokine modulation, specific or global cellular depletion of the graft and post transplant global or specific donor immune cell add-backs, are still extensively studied. Nevertheless, the persistent high relapse rate (RR) observed in leukemia patients after HSCT remains the most important cause of death before transplant-related toxicities. Moreover, since only about 40 to 70% (depending on the ethnic context) of patients with high-risk hematological malignancies, eligible for allogeneic HSCT, have a fully HLA-matched sibling or matched unrelated donor (MUD), a great deal of effort has been invested to make the use of an alternative haploidentical sibling donor feasible. The advantage of this procedure is the immediate availability of a donor for almost all patients. The aim of the work described in this thesis has been to implement a strategy to transplant a patient using a HLA haploidentical donor. The strategy is to try to improve DFS that could be applied both in the autologous or allogeneic context: first, by using nonspecific immune manipulation post transplant and then, by developing specific strategies directed against leukemia antigens. Particularly in the allogeneic situation, the aim was to increase the GVL effect without inducing or aggravating the deleterious GVHD. The first part of this thesis described our own clinical results, consisting of three consecutive phase I/II studies, in which we tried to determine the feasibility of giving prophylactic donor lymphocyte infusions (DLI) post transplant and the effect of replacing granulocyte colony-stimulating factor (G-CSF), typically used to speed up neutrophil recovery, with granulocyte macrophage colony-stimulating factor (GM-CSF), which is known for its immunomodulatory properties. The slow immune reconstitution in haploidentical transplant is chiefly responsible for the high incidence of early lethal viral and fungal infections, and most probably for early relapses; therefore, we sought to accelerate and strengthen the post transplant immune reconstitution without increasing the GVHD rate. Thus, we have studied the impact of post transplant growth factor administration and of unselected DLI in haploidentical transplant. We have also implemented, in our center, anti-cytomegalovirus (CMV) specific T cell generation and infusion to improve anti-CMV immune reconstitution. Since then, our results have been pooled in a multi-center analysis performed by the European Bone Marrow Transplantation group (EBMT) allowing us to compare our results with those of the entire group. We have also participated in the design of an ongoing study aimed at selectively depleting the graft from alloreactive T cells, and improving post transplant T cell add-backs. In our attempts to generate and expand ex vivo lymphocytes (directed against pathogens (CMV) and leukemia-associated antigens, Wilms' tumor gene 1 (WT1) and to use them in vivo, we found inconsistent results (in the case of WT1) using classical clinical grade dendritic cells (DC) generated and matured in bags, as was the case for the majority of the teams worldwide. This led us to question the full functionality of these DC and we undertook a thorough comparative analysis of DC generated and differentiated in bags and in plates (typical for most pre-clinical studies). This analysis showed us that one cannot transpose pre-clinical studies (using culture plates) directly to clinical protocols (generally using clinical grade culture bags) and that DC generated in bags are functionally deficient. We learned that, if we want to use a DC vaccine to improve the GVL effect in haploidentical transplant, we will have to be careful about the technique by which they are generated. To improve immunotherapeutic approaches, the understanding of the mechanisms underlying tumor tolerance and how to manipulate them is critical in the development of new effective immunotherapeutic clinical trials. This is why we currently focus on how to obtain effective in vivo anti-leukemia immune reactions using an ex-vivo manipulated product to trigger the immunotherapeutic response. More specifically, we are analyzing the impact of regulatory T cell (Tregs) depletion and function for an adequate anti-leukemic immune response. This pre-clinical work aims at improving the outcome of leukemia patients who have relapsed and been put back into second remission and at decreasing the RR after HSCT, especially in the field of haploidentical transplantation. In conclusion, haploidentical transplantation has become a valuable tool. The results are at least similar to those obtained using MUD when performed in the same group of patients. Specific immunomodulation post transplant can affect events such as GVHD and GVL, but clinically we are still at the level of nonspecific manipulations. It is our hope that ongoing pre-clinical work will enable us to perform specific anti-pathogen and anti-leukemia immune manipulation that will favorably influence the patient outcome. / Dans la majorité des situations, le système immunitaire autologue est incapable d’éradiquer les cellules leucémiques résiduelles qui échappent à la radiothérapie et à la chimiothérapie, cependant un équilibre peut s’établir entre les cellules leucémiques et immunitaires aboutissant à une rémission pouvant durer plusieurs mois ou années. Si cet équilibre se rompt, une rechute clinique peut se déclarer. Dans ce contexte, il est prouvé que la greffe allogénique de cellules souches hématopoïétiques est le moyen le plus efficace de renforcer les réactions immunitaires contre la leucémie par la réaction du greffon contre la leucémie et ainsi d’obtenir une éradication définitive de la maladie résiduelle chez un nombre significatif de patients. En effet, le concept global de l’allogreffe de cellules souches hématopoïétiques a évolué du concept de transplantation d’organe (remplacement d’un organe malade par un nouvel organe sain) vers celui de créer une extraordinaire plateforme d’immunothérapie à travers laquelle le système immunitaire du donneur contribue à l’éradication des cellules leucémiques persistantes. Donc, la problématique reste celle de trouver les meilleures modalités d’immunomodulation pour achever une prise du greffon, un effet anti-leucémique puissant du greffon, et l’absence ou un minimum d’effet du greffon contre l’hôte. Différentes stratégies existent pour atteindre cet objectif, comme l’utilisation de cytokines pour moduler la reconstitution immunitaire, des déplétions cellulaires globales ou spécifiques du greffon et l’infusion de cellules immunes «globales» ou spécifiques du donneur après greffe. Ces stratégies sont encore largement à l’étude. Néanmoins, la persistance d’un taux de rechute élevé observé chez les patients leucémiques, après allogreffe reste la cause principale de décès, avant celle liée à la toxicité de la greffe. De plus, étant donné que seulement environ 40 à 70% (dépendant de l’origine ethnique) des patients avec une hémopathie à haut risque, éligibles pour une greffe allogénique, ont un donneur familial ou non familial complètement HLA compatible, des efforts importants ont été développés pour rendre faisable l’utilisation de donneurs familiaux alternatifs, haploidentiques. L’avantage de cette approche est l’accès immédiat à un donneur pour quasiment tous les patients. Le but du travail décrit dans cette thèse a été l’implémentation d’une stratégie d’allogreffe utilisant un donneur haploidentique. Le travail vise également à développer de façon plus large des stratégies qui peuvent améliorer le taux de survie sans rechute, non seulement dans le contexte des greffes haploidentiques, mais également dans le cadre des greffes allogéniques en général, ainsi que dans les situations autologues : premièrement, par la manipulation immunitaire non spécifique après greffe et ensuite par le développement de stratégies spécifiques dirigées contre des antigènes leucémiques. En particulier dans la situation allogénique, le but a été d’augmenter l’effet du greffon contre la leucémie sans induire ou aggraver l’effet délétère du greffon contre l’hôte. La première partie de la thèse décrit les résultats cliniques de notre propre protocole de greffe haploidentique, qui a consisté en trois études consécutives de phase I/II. Dans ces études, nous avons voulu déterminer la faisabilité de réaliser des infusions prophylactiques de lymphocytes du donneur après transplantation, et l’impact du remplacement du « granulocyte colony-stimulating factor » (G-CSF), largement utilisé pour permettre une récupération en polynucléaires neutrophiles plus rapide, par du « granulocyte-macrophage colony-stimulating factor » (GM-CSF), lequel est connu pour ses propriétés immunomodulatrices différentes. La reconstitution immunitaire très lente après greffe haploidentique est majoritairement responsable de l’incidence élevée de décès par infections virales et fungiques précoces, et très probablement des rechutes précoces. C’est pourquoi nous avons cherché à accélérer et à renforcer la reconstitution immunitaire post-greffe sans augmenter la fréquence de réaction du greffon contre l’hôte. Nous avons donc étudié l’impact de l’administration de facteurs de croissance et l’infusion de lymphocytes non sélectionnés du donneur en post greffe haploidentique. Nous avons également implémenté dans notre centre, la génération et l’infusion de lymphocytes T spécifiques anti-cytomégalovirus (CMV) afin d’améliorer la reconstitution immunitaire anti-CMV. D’autre part, nos résultats ont été regroupés dans une étude multicentrique menée par le groupe européen de transplantation de moelle osseuse (EBMT), ce qui nous a permis de comparer nos résultats avec ceux de l’entièreté du groupe. Nous avons parallèlement participé à la conception d’une étude actuellement en cours ayant pour but d’améliorer la reconstitution immunitaire après greffe par la déplétion sélective du greffon en lymphocytes T alloréactifs et par l’infusion après greffe de lymphocytes T du donneur également sélectivement déplétés en lymphocytes T alloréactifs. Afin d’optimaliser l’effet anti-leucémique du système immunitaire, nous avons débuté un protocole de vaccination par cellules dendritiques (DCs). Ces cellules dendritiques étaient chargées en lysat de blastes leucémiques dans le cas de patients présentant au diagnostic une leucémie aigue surexprimant l’oncogène 1 de la tumeur de Wilms (WT1). Néanmoins dans nos travaux de génération et d’expansion ex-vivo de lymphocytes T spécifiques de l’antigène WT1, utilisant les DCs de grade clinique, générées et maturées en poches, nous avons rencontré des résultats inconsistants, comme c’était le cas dans la majorité des protocoles cliniques internationaux de vaccination. Nous nous sommes alors posé la question de la fonctionnalité globale de ces cellules et nous avons entrepris une analyse comparative poussée des DCs générées et différenciées en poches ou en plaques. Les DCs générées en plaques sont celles utilisées dans la plupart des travaux précliniques. Cette analyse nous a montré que l’on ne pouvait pas directement transposer les résultats précliniques basés sur des DCs générées en plaques dans des protocoles cliniques basés sur des DCs générées en poches, car ces dernières présentent des déficits fonctionnels importants. Nous avons appris que si l’on voulait utiliser un vaccin à base de cellules dendritiques pour améliorer l’effet du greffon contre la leucémie dans les greffes allogéniques, nous devions être très attentifs quant au protocole utilisé pour la génération de ces vaccins cellulaires. Pour améliorer les approches immunothérapeutiques, la connaissance des mécanismes qui établissent la tolérance tumorale et des façons de manipuler ceux-ci, est critique dans le développement de nouveaux protocoles efficaces. C’est pourquoi nous nous concentrons actuellement sur les conditions nécessaires à l’obtention in vivo d’une réaction immune anti-leucémique efficace lors de l’utilisation d’un produit cellulaire manipulé ex vivo. Plus spécifiquement, nous analysons l’impact de la déplétion en lymphocytes T régulateurs (Tregs) sur la réponse anti-leucémique. Ce travail préclinique a pour but d’améliorer le devenir de patients leucémiques qui ont rechutés et ont été mis en seconde rémission, ainsi que de diminuer le taux de rechute après allogreffe, spécifiquement après greffe haploidentique. En conclusion, la transplantation haploidentique est actuellement un outil précieux pour de nombreux patients. Les résultats sont au minimum similaires à ceux qui sont obtenus par les greffes non-familiales HLA identiques lorsqu’elles sont pratiquées dans les mêmes groupes de patients. L’immunomodulation spécifique après greffe peut affecter des événements comme la réaction du greffon contre l’hôte et la réaction du greffon contre la leucémie, mais en pratique clinique nous en sommes encore au niveau de la manipulation aspécifique. Nous espérons que les travaux précliniques actuels vont nous permettre d’appliquer des stratégies spécifiques et d’obtenir une manipulation immune anti-leucémique qui aura une influence favorable significative sur le devenir des patients.

Oncolytic viruses can be genetically modified to limit their replication in normal cells rendering them a cancer specific treatment. In addition, they can induce a 'danger signal' in the form of pathogen- and damage-associated molecular patterns leading to anti-tumour immunity. Furthermore, they can be armed with various immunomodulatory molecules to further enhance anti-tumour immunity. In this project I aim to exploit these qualities to develop a translatable cancer vaccine. Virus-infected cancer cells were injected subcutaneously in a prime/boost regimen. Dying cancer cells will release the required danger signal leading to dendritic cell activation and cross-presentation of tumour associated antigens to T cells to elicit an anti-tumour immune response. Our results in the murine pancreatic cancer model showed that vaccination with virusinfected DT6606 cells induced tumour specific immunity capable of protecting vaccinated animals against re-challenge with tumour cells. The highest level of interferon gamma production, a surrogate marker of anti-tumour immunity, was achieved when animals were primed with adenovirus-infected cells. There was no significant difference between various boost groups. To enhance the safety of the proposed protocol a secondary treatment was introduced to arrest the proliferation of tumour cells prior to injection. Our results confirmed that secondary treatment with mitomycin does not affect the induction of tumour specific immunity and it does not affect the release of pathogen-associated molecular patterns in the form of viral proteins and DNA. To test our vaccination regimen in head and neck squamous cell carcinoma (HNSCC) we develop a clinically relevant mouse model using SCC7, B4B8 and LY2 cells to replicate various clinical scenarios including locally advancing disease and post excision locoregional recurrence. Vaccinating mice with HNSCC cells pre-infected with our recently developed tumour-targeted triple-deleted adenovirus (AdTD) resulted in a cell-specific antitumour immune response. In addition, it resulted in an increase in effector memory T-cells of both CD4+ and CD8+ phenotypes. Efficacy studies showed our vaccination can significantly slow down the growth rate of tumours in locally advancing disease. This led to increase survival of the vaccinated mice although it did not reach statistical significance. To further enhance the efficacy of our vaccination regimen, we aimed to increase T cell trafficking to the tumour site. CCL25 is a gut homing chemokine. Priming T cells in the presence of CCL25 will lead to upregulation of the surface expression of α4β7 integrin. The latter is a ligand of MAdCAM-1, a cell adhesion molecule highly expressed in the gut and pancreatic tumours. The α4β7/MAdCAM-1 interaction results in preferential homing of activated T cells to these organs. We hypothesised that vaccinating mice with pancreatic tumour cells pre-infected with a CCL25-armed adenovirus will lead to increased T cell trafficking to pancreatic tumours leading to enhanced efficacy. Although we achieved encouraging results in our pilot experiment, we did not detect any significant increase in α4β7 expression once we added a secondary treatment to the vaccination protocol. Similarly, efficacy experiments in the pancreatic cancer transgenic KPC mice did not show any difference in survival between AdTD-CCL25 and the control virus although both groups showed a trend towards increased survival compared to naïve mice. In conclusion, Virus-infected cancer cell vaccine is a potentially promising immunotherapeutic strategy that can be combined with traditional cancer therapies to increase survival of HNSCC and pancreatic cancer patients.

Human immunodeficiency virus type 1 (HIV-1) is the cause of acquired immune deficiency syndrome (AIDS). HIV-1 is a worldwide epidemic that currently affects over 35 million people worldwide, and continues to spread at an appalling rate. A universal HIV-1 preventive vaccine is considered to be the optimal solution in achieving the ultimate goal of AIDS eradication. Regretfully, most endeavors thus far of developing a prophylactic vaccine have been largely disappointing. Highly Active Anti-Retroviral Therapy (HAART) has been shown to reduce the plasma HIV-1 RNA level to below the detection limit of clinical assays (50 copies/ml); it combines three or more antiretroviral drugs which belong to at least two different classes – targeting distinct steps in the viral life cycle, and inhibiting viral replication. However, unless the infection is eradicated, strict adherence to a lifelong treatment regimen is required. HAART is limited by its high cost, drug availability, complicated administration schedules, serious side effects, and the potential that the virus will ultimately develop drug resistance. A more plausible approach lies in therapeutic vaccines that provide immunity to partially control viral replication postinfection – delaying or minimizing ART, and offering “drug holidays”. The primary goal of a therapeutic vaccine is to effectively induce HIV-1 specific cytotoxic T lymphocyte (CTL) responses, which plays a critical role in control of viral proliferation. Dendritic cells (DCs)-based therapeutic vaccines have been showing the most promising results. However, the therapeutic efficacy of DCs based vaccines is limited. This is partially due to the fact that DCs induced CD8+ T cell responses are largely CD4+ T cell dependent, while HIV-1 infection usually renders the immune system very “helpless” from CD4+ T cells. In addition, infection, impaired function, and physical depletion of DCs are often reported during the early stage. Furthermore, DCs are often found to be inflammatory and immunosuppressive, which is mainly mediated by the interaction between HIV-1 Env gp120 and DC receptors. Thus, the search for a novel therapeutic vaccine strategy is warranted. Using T-APC (T cells-antigen-presenting cells) as a novel T cell-based vaccine has emerged as a potential candidate for a HIV-1 therapeutic vaccine, which aims at boosting HIV-specific CTL responses. Our previous work demonstrated that CD4+ and CD8+ T cells derived from ovalbumin (OVA)-specific T cell receptor (TCR) transgenic OT II and OT I mice via co-culture with OVA-pulsed DCs (DCOVA) can be activated, acquiring pMHC I, pMHC II, and costimulatory molecules, thus act as CD4+ T helper-antigen-presenting cells (Th-APCs) and CD8+ cytotoxic T-antigen-presenting cells (Tc-APCs). We also elucidated that DC-derived exosomes (EXO), which are 50- to 90-nm diameter vesicles containing antigen-presenting, tetraspan, adhesion, and costimulatory molecules, can transfer the antigen-presenting activity of DCs to activated CD4+T cells through EXO uptake. EXOOVA-targeted activated CD4+T (aTexo) cells can (1) stimulate more efficient central memory CD8+ CTL responses and T cell memory than EXOOVA or DCOVA, (2) activate CD8+ CTL responses independent of CD4+Th cells, and (3) counteract CD4+25+regulatory T (Tr) cell-mediated immune suppression. These results formed the new concept of novel EXO-targeted CD4+ T cell vaccines. In this study, we tailored EXO-targeted T cells vaccine by using polyclonal activated CD8+ T cells instead of CD4+ T cells, as CD4+ T cells served as the primary target for HIV-1 infection. We showed that (1) OVA-specific exosome-targeted CD8+ T cell-based vaccine (OVA-Texo) can stimulate efficient OVA-specific CD8+ CTL and memory responses, inducing sufficient antitumor immunity against OVA-expressing tumor cells in mouse models. (2) This exosome-targeted CD8+ T cell-based vaccine strategy could be applied to HIV-1-Gag protein, provoking effective Gag-specific CD8+ CTL, T cell memory, and antitumor immunity against Gag-expressing tumor cells. (3) Engineering Gag-Texo with up-regulated 4-1BBL (APC derived costimulatory molecule) expression could improve the performance of Gag-Texo vaccine. (4) OVA-Texo is able to evoke a successful immune response in bystander chronic infection, converting CD8+ T cell exhaustion, restoring effector functions of exhausted CD8+ T cells. Moreover, combination of OVA-Texo vaccine with PD-L1 blockage in a dual treatment could result in a synergistic effect in rescuing CTLs exhaustion in chronic infection. Those desired features make EXO-targeted CD8+ T cells vaccine an appealing novel strategy in HIV-1 infection. The EXO-targeted CD8+ T cells vaccine may be applicable to therapeutic HIV treatment through the use of autologous T cells with uptake of EXOs derived from engineered DCs.

The ultimate goal of antitumor vaccines is to develop memory CD8+ cytotoxic T lymphocytes (CTLs), which are critical mediators of antitumor immunity. Previous work in our lab demonstrated that the ovalbumin (OVA)-specific CD4+ T cell-based (OVA-TEXO) vaccine generated using OVA-pulsed dendritic cell (DCOVA)-released exosomes (EXOOVA) stimulates CTL responses via interleukin (IL)-2 and costimulatory CD80 signaling. To assess the potential involvement of other costimulatory pathways and to define the key constituent of costimulation for memory CTL development, we first immunized wild-type (WT) C57BL/6 and gene-knockout mice with WT CD4+ OVA-TEXO cells or OVA-TEXO cells with various molecular deficiencies. We then assessed OVA-specific primary and recall CTL responses using PE-H-2Kb/OVA257–264 tetramer and FITC-anti-CD8 antibody staining by flow cytometry. We also examined antitumor immunity against the OVA-expressing B16 melanoma cell line BL6-10OVA. We demonstrate that CD4+ OVA-TEXO cells form immunological synapses with cognate CD8+ T cells in vitro. By assessment of the pattern of ex vivo interactions between OTI CD8+ T cells and OVA-TEXO or (Kb-/-)TEXO cells lacking peptide/major histocompatibitity complex (pMHC)-I expression, we provide the first visible evidence on the critical role of exosomal pMHC-I in targeting OVA-TEXO to cognate CD8+ T cells using two-photon microscopy. By assessing primary and recall CTL responses in mice immunized with OVA-TEXO cells or with OVA-TEXO cells lacking the costimulatory molecules CD40L, 4-1BBL or OX40L, we demonstrated that these costimulatory signals are dispensable for CTL priming by OVA-TEXO cells. Interestingly, CD40L, but not 4-1BBL or OX40L, plays a crucial role in the development of functional memory CTLs against BL6-10OVA tumors. Overall, this work suggests that a novel CD4+ T cell-based vaccine that is capable of stimulating long-term functional CTL memory via CD40L signaling may represent a novel, efficient approach to antitumor vaccination. Breast cancer is the most common cancer among women in the western world. Approximately 20-30% of invasive breast carcinomas are proto-oncogene human epidermal growth factor receptor (HER)-2 positive and associated with increased metastatic potential and poor prognosis. The survival benefit of anti-HER2 driven therapies demonstrated in clinical trials indicates that HER2 is one of the most promising molecules for targeted therapy to date. Above results prompt us to assess whether CD4+ T-cell-based vaccine can stimulate efficient HER2-specific CD8+ CTL responses and antitumor immunity in transgenic mice with HER2-specific self-immune tolerance. We prepared HER2-specific HER2-TEXO using ConA-stimulated CD4+ T cells with uptake of exosomes released from HER2-expressing AdVHER2-transfected DCs. We found that HER2-TEXO vaccine is capable of inducing HER2-specific CTL responses and protective immunity against transgene HLA-A2/HER2-expressing B16 melanoma BL6-10HLA-A2/HER2 in 2/8 double transgenic HLA-A2/HER2 mice with HER2-specific self-immune tolerance. The remaining 6/8 mice had significantly prolonged survival. Therefore, the novel T cell-based HER2-TEXO vaccine may provide a new therapeutic alternative for women with HER2+ breast cancer. In contrast to CD4+CD25+ regulatory T cells (Tregs), mechanisms of CD8+CD25+ Treg-mediated immunosuppression are not well understood. In this study, we purified polyclonal CD8+CD25+ Tregs from C57BL/6 mouse splenocytes and expanded them in culture medium containing CD3/CD28 microbeads. By using these amplified CD8+CD25+ Tregs, we demonstrated that CD8+CD25+ Tregs inhibit naive CD4+ T-cell proliferation and induce naive T-cell anergy by up-regulating T-cell anergy-associated early growth response 2 (EGR2), and by decreasing T-cell proliferation and IL-2-secretion upon stimulation. They also impact the expression of perforin on effector CTLs and directly induce perforin-mediated CTL apoptosis. CD8+CD25+ Tregs, when pulsed with OVA323-339 peptide, exert an enhanced inhibition. Interestingly, CD8+CD25+ Tregs, when pulsed with myelin oligodendrocyte glycoprotein (MOG)35-55 peptide, become capable of inhibiting MOG35-55-induced experimental autoimmune encephalomyelitis (EAE). Two-photon microscopic observations suggest that OVA323-339-pulsed (armed) CD8+CD25+ Tregs reduce the interactions between DCs and cognate CD4+ T cells ex vivo by increasing velocities of T cells in mouse lymph nodes. Therefore, redirecting antigen-specificity to nonspecific CD8+CD25+ Tregs can be achieved for enhanced immunosuppression through their arming with the antigen-specific pMHC-II complexes. This approach may have great impact on improvement of endogenous polyclonal Treg-mediated immunotherapy for autoimmune diseases. Taken together, our studies demonstrate that nonspecific polyclonal CD4+ T cells and CD8+CD25+ Tregs, when armed with HER2 and MOG antigen-specific pMHC-I and -II complexes, become capable of stimulating enhanced HER2-specific CTL responses and antitumor immunity in double transgenic HLA-A2/HER2 mice and inducing enhanced MOG-specific immunosuppression in MOG-induced EAE mice, respectively. Therefore, redirecting antigen specificity to nonspecific CD4+ T and CD8+CD25+ Tregs by pMHC complex arming may have great impact in development of novel T cell-based vaccines for treatment of cancer and autoimmune diseases.

abstract: Combination therapy has shown to improve success for cancer treatment. Oncolytic virotherapy is cancer treatment that uses engineered viruses to specifically infect and kill cancer cells, without harming healthy cells. Immunotherapy boosts the body's natural defenses towards cancer. The combination of oncolytic virotherapy and immunotherapy is explored through deterministic systems of nonlinear differential equations, constructed to match experimental data for murine melanoma. Mathematical analysis was done in order to gain insight on the relationship between cancer, viruses and immune response. One extension of the model focuses on clinical needs, with the underlying goal to seek optimal treatment regimens; for both frequency and dose quantity. The models in this work were first used to estimate parameters from preclinical experimental data, to identify biologically realistic parameter values. Insight gained from the mathematical analysis in the first model, allowed for numerical analysis to explore optimal treatment regimens of combination oncolytic virotherapy and dendritic vaccinations. Permutations accounting for treatment scheduled were done to find regimens that reduce tumor size. Observations from the produced data lead to in silico exploration of immune-viral interactions. Results suggest under optimal settings, combination treatment works better than monotherapy of either type. The most optimal result suggests treatment over a longer period of time, with fractioned doses, while reducing the total dendritic vaccination quantity, and maintaining the maximum virotherapy used in the experimental work. / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics for the Life and Social Sciences 2016

No description available.

The past 10 years has seen mother to child transmission (MTCT) of HIV-1 shift from being one of the predominant forces in the global epidemic to a phenomenon that is largely preventable and envisioned as being on the path to elimination. This thesis is based on two cohorts of Kenyan infants recruited before and after the development of effective antiretroviral interventions to prevent MTCT. Two main lines of enquiry are pursued with the aim to contribute to improved health outcomes of infants affected by HIV-1. The first seeks to further our understanding of the capacity of the infant cytotoxic T lymphocyte (CTL) response to influence viral evolutionary dynamics in early infection. Chapter 3 presents a modern phylogenetic analysis of longitudinal viral sequences derived from infants following in utero or peripartum infection. The results indicate that despite high levels of viral replication, infant CTL selection pressure plays a significant role in shaping early viral evolution. The second stems from an accumulating body of evidence that suggests that infants born to HIV-1 infected mothers who themselves are free from infection, termed HIV-1 exposed uninfected (HEU) infants, nevertheless face significantly higher rates of infectious disease- associated morbidity and mortality than HIV-1 unexposed infants. This study therefore sought to characterise the immunological status of HEU infants with particular emphasis on the phenotypic and functional properties of the T cell compartment. Chapter 4 presents the immunological characterisation of a cohort of healthy Kenyan infants recruited as a control population at two time points in early life. Chapter 5 present a cross-sectional comparison of HEU and control infant cohorts. The results suggest a level of altered immunological reactivity with respect to the T helper type 1 (Th1) response to polyclonal stimulation. In addition a compromised memory Th1 response was observed following polyclonal stimulation and following stimulation with Bacillus Calmette-Guerin and tetanus toxoid vaccine antigens.

Neisseria meningitidis causes 500,000 cases of meningitis and septicaemia annually worldwide, with a mortality rate of approximately 10%. Most disease in developed countries is caused by serogroup B infection, against which there is no universal vaccine. Opa proteins are major meningococcal outer membrane proteins, and a limited number of Opa variants have been associated with hyperinvasive serogroup B meningococci, suggesting their use as a potential novel vaccine. Immunisation of mice with recombinant Opa elicited high levels of meningococcal-specific serum bactericidal antibody (SBA), demonstrating proof in principle of this approach. Opa proteins mediate bacterial adherence to host cells and modulate human cellular immunity, and there are conflicting data regarding their effects on CD4⁺ T cells. opa genes from N. meningitidis strain H44/76 were cloned into the plasmid vector pBluescript, disrupted using antibiotic resistance cassettes and transformed into H44/76 to sequentially disrupt the four opa genes. This produced a unique panel of 15 isogenic Opa-deficient strains, including an Opa-negative strain, which enabled investigation of the immunomodulatory role of surface-expressed Opa proteins. There was no consistent effect of Opa expressed on the surface of OMVs and inactivated bacteria on CD4⁺ T cells, with significant heterogeneity of responses between individuals. The rate of Opa phase variation was between 10^-3 and 10^-4, and increased 180-fold following transformation of bacteria with unrelated DNA. These data support further investigation of Opa as a potential meningococcal vaccine component, and highlight the importance of host and bacterial factors in the development of OMV vaccines.

S. pneumoniae é um patógeno de grande impacto em saúde pública e vacinas comerciais têm cobertura limitada e alto custo. Como alternativa, desenvolveu-se uma vacina celular de baixo custo, cuja produção envolve apenas a separação das bactérias do caldo e sua inativação. Neste trabalho, foram avaliados processos descontínuo, descontínuo alimentado e contínuo com reciclo de células, cuja produção de biomassa foi 3 vezes maior que a do descontínuo. Vacinas obtidas nos 3 processos foram utilizadas em ensaios de imunização de camundongos e induziram níveis similares de IgG e IL-17A. Anticorpos ligaram-se e induziram a deposição de moléculas do sistema complemento sobre a superfície do pneumococo. Ademais, induziram fagocitose de diferentes cepas encapsuladas da bactéria. Camundongos imunizados foram protegidos contra sepse após aspiração da cepa virulenta WU2. Portanto, o processo contínuo com reciclo permitiu a obtenção de maior número de doses sem alterar a qualidade da vacina e o ensaio opsonofagocítico poderia ser utilizado como potencial correlato de proteção. / S. pneumoniae is a pathogen of great impact on public health and commercially available vaccines have limited coverage and high cost. As alternative, a low-cost whole cell vaccine was developed, whose production involves only the cell separation and inactivation. In this work, we evaluated batch, fed-batch and continuous cultivation with cell recycle. The biomass production was 3-fold higher in continuous process than batch. Vaccines obtained from these 3 processes were used to immunize mice and all vaccines induced comparable levels of IgG and IL-17A. Antibodies were able to bind and induce deposition of complement onto pneumococcal surface, besides to induce phagocytosis of several encapsulated pneumococcal strains in opsonophagocytic assays. Immunized mice were protected from fatal aspiration-sepsis using the virulent pneumococcal strain WU2. Therefore, the continuous process with cell recycle yielded a higher number of doses without altering the quality of the vaccine and opsonophagocytic assay could be used as a potential correlate of protection.