Auch unter physiologischen Bedingungen finden sich T-Zellen und andere Leukozyten nicht nur in den Sinusoiden, sondern auch im Parenchym der Leber. Da die Leber u. a. verschiedene Aufgaben für das Immunsystem übernimmt (z. B. Deletion aktivierter T Zellen, Induktion peripherer Toleranz), könnte die Akkumulation der T-Zellen in der Leber - neben der immunologischen Überwachung der Leber - Voraussetzung für ihre Modulation sein. In der vorliegenden Arbeit wurde der Einfluss von Leber-sinusoidalen Endothelzellen (LSEC), der Barriere zwischen Blut und Leber-Parenchym, auf CD4+ T-Zellen untersucht. Zum einen zeigte sich, dass die LSEC sowohl die spontane Transmigration der T-Zellen, als auch ihre Chemotaxis zu CXCL9 und CXCL12 effizienter unterstützen als andere Endothelien. Eine endotheliale Aktivierung durch die Chemokine wurde als Mechanismus ausgeschlossen. Dagegen schien eine effiziente Präsentation der Chemokine auf der luminalen LSEC-Oberfläche nach Aufnahme von abluminal für die gesteigerte Transmigration der T Zellen verantwortlich zu sein. Die LSEC könnten somit in vivo an der Rekrutierung von T-Zellen in die Leber beteiligt sein, indem sie eine rasche Wanderung der T-Zellen aus dem Blut ins Parenchym und möglicherweise auch zurück in die Zirkulation zulassen. Des Weiteren konnte gezeigt werden, dass die LSEC fähig sind, naive CD4+ T-Zellen in vitro Antigen-spezifisch zu aktivieren. Im Vergleich zu professionellen APZ war hierfür eine höhere Antigen-Dosis notwendig, die Expansion schwächer und es waren kaum Effektorzytokin-Produzenten detektierbar. Diese konnten jedoch durch Restimulierung mit professionellen APZ induziert werden (reversibler Phänotyp), was auf einen unreifen Differenzierungsstatus der T-Zellen schließen ließ. Es bleibt zu prüfen, in welchem Maße die Aktivierung naiver CD4+ T-Zellen durch LSEC in vivo stattfindet und diese durch LSEC aktivierten CD4+ T-Zellen funktionelle Bedeutung, z. B. regulatorische Kapazität, für das Immunsystem besitzen. / The liver plays a major role for the metabolism, but it is also of general importance for the immune system, e.g. for the deletion of activated T cells or the induction of peripheral tolerance. Under physiological conditions T cells and other leukocytes can be found in the liver, in the sinusoids as well as in the parenchyma. This hepatic accumulation of T cells might be due to immunosurveillance, but it would also be a prerequisite for modulation of T cells by hepatic cells. The present study investigated two different aspects of the interaction of liver sinusoidal endothelial cells (LSEC), the barrier between the sinusoidal lumen and the hepatic parenchyma, and CD4+ T cells. In the first part of the study it could be demonstrated that LSEC support the spontaneous transmigration of CD4+ T cells as well as their chemotaxis to CXCL12 and CXCL9 more efficiently than other endothelial cells. Whereas a direct endothelial activation by chemokines could be excluded the efficient chemokine presentation at the luminal LSEC surface (after abluminal uptake) might be responsible for the enhanced T cell transmigration. The findings suggest that LSEC might be involved in the recruitment of T cells by supporting a rapid transendothelial migration. The second part of the study focused on the characteristics of LSEC in the context of antigen presentation. LSEC were able to prime and expand naïve CD4+ T cells in vitro but less effective than professional APC as proven by weaker expansion of cells, a requirement for higher antigen concentration and the lack of cytokine producing T cells. The “immature effector” phenotype of the CD4+ T cells primed on LSEC was reversible since it could be overcome by restimulation on professional APC. In conclusion these data suggest that antigen presentation by LSEC results in activation but incomplete differentiation of CD4+ T cells.

Das Ziel dieser Arbeit war, die funktionellen Charkteristika von humanen antigenerfahrenen CD4-T-Zellen in Relation zur Expression von IL-7Ra und CCR7 zu untersuchen. Im Rahmen dessen wurden zwei verschiedene experimentelle Ansätze wurden gewählt: Zur Analyse von Populationen, die während einer Primärantwort auftreten, wurden antigenerfahrene CD4-T-Zellen in vitro mit TSST-beladenen dendritischen Zellen stimuliert. Der zweite Ansatz bestand darin, zirkulierende antigenerfahrene CD4-T-Zellen entsprechend ihrer CCR7- und IL7R-Expression zu isolieren, um die heterogenen zirkulierenden T-Zellen zu untersuchen. Die Experimente zeigen, daß IL7RhiCCR7+ T-Zellen Charakteristika zentraler Gedächtniszellen besitzen. IL7RlowCCR7–identifiziert hingegen Zellen mit Effektor-T-Zellmerkmalen. Dementsprechend wiesen IL7RlowCCR7– T-Zellen ein stark verringertes Zellüberleben auf, waren stark beeinträchtigt in darin in Anwesenheit von homöostatischen Zytokinen zu proliferieren und exprimierten nur wenig IL-2. Im Gegenzug überlebten IL7RhiCCR7+ T-Zellen gut, reagierten auf homöostatische Zytokine, sekretierten IL-2 und expandierten nach antigenspezifischer Stimulation. Interessanterweise erkannten ex vivo isolierte IL7Rlow T-Zellen vornehmlich persistierende Antigene. Dies weist darauf hin, daß diese Zellen chronisch aktiviert sind. In vitro konnte demonstriert werden, daß die funktionelle Ausprägung der den zentralen Gedächtniszellen ähnlichen IL7RhiCCR7+ T-Zellen deutlich von der Stärke der Stimulation während der Generierung der IL7RhiCCR7+ T-Zellen abhängt. Dieser Umstand stützt die Hypothese, daß die Quantität der Signale während der primären Stimulation die Richtung der Zelldifferenzierung bestimmt und ein solcher Mechanismus zur Heterogenität der zentralen Gedächtnis-T-Zellen in vivo beiträgt. Zusammenfassend kann man feststellen, daß, sich die Marker CCR7 und IL7R in Kombination als ein wertvoll zur Identifizierung von CD4-Gedächtnis- und –Effektor-T-Zellen erweisen / The aim of this work was to elucidate the functional characteristics of human antigen-experienced CD4 T cells according to the expression of IL7RAlpha and CCR7. Two different approaches were used: in order to analyze the subsets occurring during a primary response, antigen-experienced CD4 cells were analyzed in vitro after priming with the superantigen TSST. The signal strength of TCR-stimulation during the priming was modulated in order to understand how the levels of stimulation might influence the generation of memory-like T cells. The second approach was to isolate circulating CD4 T cells expressing different combinations of CCR7 and IL7R in order to analyze the heterogeneous pool of antigen-experienced cells found under steady state conditions ex vivo. The results revealed that both in vitro and ex vivo the IL7RhiCCR7+ T cell subset corresponds to cells with TCM characteristics whereas IL7RlowCCR7– identifies cells with effector characteristics. Correspondingly, IL7RlowCCR7–CD4 T cells showed low survival rates, impaired proliferation in the presence of homeostatic cytokines and a low IL-2 production, IL7RhiCCR7+ CD4 T cells survived well, responded to homeostatic cytokines, secreted IL-2 and expanded upon antigenic stimulation. Notably, ex vivo isolated IL7Rlow T cells preferentially recognized under steady state conditions persistent antigens, suggesting that these cells are chronically activated. Finally, it was demonstrated that IL7RhiCCR7+ TCM-like cells generated in vitro acquired different functional properties depending on the strength of stimulation during the priming. This fact supports the concept that the amount of signal received during the priming influences the cell fate decision contributing to the heterogeneity of the TCM pool in vivo. In summary, despite some differences observed between in vitro and ex vivo CD4 T cell subsets, the combination of the markers CCR7 and IL7R is useful to distinguish memory- from effector-like CD4 T cells.

Submitted by PPG Pediatria e Sa?de da Crian?a (pediatria-pg@pucrs.br) on 2018-02-16T19:08:17Z No. of bitstreams: 1 Tese Vers?o Final Tiago Fazolo 18_01_2018.pdf: 3827531 bytes, checksum: b081e8333d16cb49ba00d0df25dff485 (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2018-02-22T17:20:04Z (GMT) No. of bitstreams: 1 Tese Vers?o Final Tiago Fazolo 18_01_2018.pdf: 3827531 bytes, checksum: b081e8333d16cb49ba00d0df25dff485 (MD5) / Made available in DSpace on 2018-02-22T17:35:15Z (GMT). No. of bitstreams: 1 Tese Vers?o Final Tiago Fazolo 18_01_2018.pdf: 3827531 bytes, checksum: b081e8333d16cb49ba00d0df25dff485 (MD5) Previous issue date: 2017-03-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Respiratory syncytial virus (RSV) is the most common etiologic agent in severe lower respiratory tract infections (LRTI) in children. RSV-associated LRTI is the main cause of bronchiolitis, pneumonia and exacerbation of asthma. This infection is responsible for the high rates of hospitalizations related to respiratory diseases worldwide, especially in children younger than 2 years. Currently, annual mortality rate due to RSV infections is worrying worldwide and is estimated at approximately two hundred thousand cases. The treatment strategies to RSV infections are limited. Ribavirin is an approved drug for use in RSV infections, but its use is limited due to adverse side-effects and risks posed to health professionals who handle it. Palivizumab is a monoclonal antibody which targets RSV F glycoprotein and its use is only indicated as a prophylactic measure. This treatment is already accepted in several countries for groups of high risk children (premature children, with chronic lung disease and with congenital heart disease). However, palivizumab has a high cost for public health and is not available in all countries. The development of an effective RSV vaccine to generate a long-lasting immunological memory response that prevents infection may be the best alternative because it will reduce high public health expenditures with antiviral drugs and monoclonal antibodies. The first attempt in the search for a vaccine against RSV was in the 1960s. This vaccine produced high levels of serum antibodies but could not protect against infection. Children who were vaccinated developed a more serious disease when later infected with the same virus. To date, there is no licensed vaccine for RSV, so the search for effective vaccines is an important focus of research. Natural RSV infections do not induce lasting protective memory, and multiple reinfections can occur lifetime. Nasal secretions from infected infants presented a small number of regulatory CD4 T cells (Treg) in peripheral blood, an increase in interleukin 4 (IL-4) production and T helper type 2 (Th2) response. Treg cells are important for controlling an exacerbated increase in immune responses. A reduction of the Tregs caused by the RSV infection generates an exacerbation of the pulmonary disease due to a Th2 response. The M209-223 RSV peptide was identified to increase IFN-? production by peptide-specific CD4 T cells after challenge with the virus. The treatment with this peptide also induced an increase in pulmonary Treg frequency in infected mice. Recently, it has also been shown that Tregs aid in the development of a T CD8+ effector response, which is crucial for the control of RSV viral load. Our hypothesis is that the RSV M209-223 peptide impacts in the differentiation of CD4 T cells, increasing the population of specific Treg, reducing lung inflammation and modulating the anti-RSV immune response. This peptide in animal model induces the differentiation of specific Treg. Our findings suggest that vaccination with M209-223 peptide results in the differentiation of specific CD4 T cells into conventional effectors and Treg cells. Vaccination with this peptide decreased the expansion of a Th2 response in animals infected with RSV, protecting both the infection site and systemically. We believe that this approach could be an important component in vaccination strategies against this virus. / O v?rus sincicial respirat?rio (VSR) ? o agente etiol?gico mais comum nas infec??es graves do trato respirat?rio inferior (TRI) em crian?as. As infec??es do TRI associada com o VSR s?o a principal causa de bronquiolite, pneumonia e exacerba??o da asma. As TRI causadas pelo VSR s?o respons?veis pelas altas taxas das hospitaliza??es relacionadas ?s doen?as respirat?rias em todo o mundo, principalmente em crian?as menores de dois anos. Atualmente a taxa de mortalidade anual mundial devido ?s infec??es pelo VSR ? preocupante e ? estimada em aproximadamente duzentas mil crian?as. As estrat?gias de tratamento contra o VSR utilizadas s?o limitadas. A ribavirina ? um f?rmaco aprovado no uso para infec??es pelo VSR, por?m sua utiliza??o ? limitada devido aos efeitos secund?rios adversos e aos riscos que representam para os profissionais da sa?de que o manipulam. O palivizumabe ? um anticorpo monoclonal dirigido contra a glicoprote?na F do v?rus e sua utiliza??o ? apenas como medida profil?tica. Este tratamento j? ? aceito em v?rios pa?ses nos grupos de crian?as de alto risco (crian?as prematuras, com doen?a pulmonar cr?nica e com cardiopatia cong?nita). Entretanto o palivizumabe tem um alto custo para sa?de p?blica, n?o sendo disponibilizado em todos os pa?ses. O desenvolvimento de uma vacina eficaz contra o VSR pode ser a melhor alternativa, pois ao gerar resposta de mem?ria duradoura que previne a infec??o e reduz, desta forma, os altos gastos com a sa?de p?blica, com os f?rmacos antivirais e com os anticorpos monoclonais. A primeira tentativa na busca de uma vacina contra o VSR foi na d?cada de 60. A vacina produzida estimulou n?veis moderadamente elevados de anticorpos no soro, mas n?o conseguiu proteger contra ? infec??o. As crian?as que foram vacinadas desenvolveram uma doen?a mais grave quando mais tarde infectados com o v?rus. At? o presente momento n?o existe nenhuma vacina licenciada para o VSR. Desta forma, a busca de vacinas eficazes constitui um importante foco de pesquisa em todo mundo. As infec??es naturais pelo VSR n?o induzem mem?ria protetora duradoura, ocorrendo m?ltiplas reinfec??es ao longo da vida. Em crian?as infectadas, observou-se um n?mero reduzido de c?lulas T CD4+ regulat?rias (Treg) no sangue perif?rico, um aumento na produ??o de interleucina 4 (IL-4) e uma resposta T helper do tipo 2 (Th2) nas secre??es nasais. As c?lulas Treg s?o importantes para controlar um aumento exagerado da resposta imunol?gica. Por este fato acredita-se que quando h? uma redu??o das Tregs causada pela infec??o do VSR ocorre uma exacerba??o da doen?a pulmonar devido uma resposta Th2. Foi identificado que o pept?deo M209-223 do VSR aumenta a produ??o de IFN-? nas c?lulas T CD4+ ap?s o desafio com VSR. O tratamento com este mesmo pept?deo tamb?m apresentou um aumento na frequencia de c?lulas Treg ap?s infec??o prim?ria pelo VSR. Recentemente tamb?m foi demonstrado que as Tregs auxiliam no desenvolvimento de uma resposta efetora T CD8+, que ? crucial para o controle da carga viral do VSR. Nossa hip?tese ? que o pept?deo M209-223 do VSR influencia na diferencia??o das c?lulas T CD4+, aumentando a popula??o de c?lulas T efetoras e regulat?rias espec?ficas, reduzindo a inflama??o pulmonar e modulando a resposta imune. Os nossos resultados sugerem que a vacina??o com pept?deo M209-223 resulta na diferencia??o de c?lulas T CD4+ espec?ficas em efetoras convencionais, que produzem mais IFN-? e em c?lulas Treg. A vacina??o com este pept?deo diminuiu a expans?o de uma resposta Th2 nos animais infectados com o VSR, protegendo da inflama??o exacerbada tanto no local da infec??o como sistemicamente. Acreditamos que esta abordagem pode constituir um componente importante nas estrat?gias de vacina??o contra este v?rus.

Le syndrome de Sjögren primitif (SSp) est une maladie auto-immune (MAI) systémique ayant des caractéristiques communes avec le lupus érythémateux. Ces caractéristiques incluent des mécanismes physiopathologiques et des facteurs de predispositions génétiques. Notre équipe et d’autres groupes ont pu mettre en evidence une signature interféron (IFN) dans les glandes salivaires et les PBMCs de patients ayant un SSp. Cette découverte a permis de mettre en évidence de nouvelles voies à explorer dans la pathogénie du SLE et SSp en permettant la focalisation des recherches sur le rôle de l’immunité innée et de la voie IFN.Nous avons confirmé le rôle de 2 gènes importants dans le SSp, impliqués dans les voies des IFN. Le premier est IRF5 sur la voie IFN de type I et STAT4 sur la voie IFN de type II. Nous avons pu mettre en évidence une fonctionnalité de l’allèle à risque d’IRF5 (Polymorphisme Indel situé dans le promoteur). Concernant STAT4, son expression n’était pas altérée par le SNP associé à la maladie. Toutefois, l’ARNm de STAT4 était corrélé à l’expression des gènes IFN de type I. Les dérégulations épigénétique pourraient jouer un rôle important dans la pathogénie de nombreuses MAI, en particulier la méthylation de l’ADN qui est hautement liée à l’extinction de l’expression des gènes. Nous avons étudié la méthylation du promoteur d’IRF5 et nous n’avons pas trouvé de régulation de ce promoteur par le méthylation. Une analyse de la méthylation avec une approche globale du méthylome est en cours dans notre équipe et permettra d’identifier de gènes cibles d’une dérégulation épigénétique pouvant être impliqués dans les MAI.Nous avons essayé de comprendre la relation entre STAT4 et gènes IFN de type I. Ainsi, nous rapportons que l’IL-12 induit spécifiquement l’IFN de type I par intéraction entre deux partenaires cellulaires, les lymphocytes T CD4+ et les cellules dendritiques plasmacytoïdes. Ces résultats pourraient expliquer l’implication des polymorphismes de STAT4 dans les MAI dépendantes de l’IFN de type I. Ces résultats suggèrent également que les MAI dépendantes des IFN de type I et II ne s’opposent pas. Elles seraient seulement le Yin et le Yang d’un facteur d’activation commun, STAT4, capable d’induire les IFNs de type I et II. / Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease (AID) that presents similar characteristics to systemic lupus erythematosus. These characteristics include pathophysiology and genetic factors. Our team and other groups have highlighted an interferon (IFN) signature in salivary glands and PBMCs from patients with Sjögren syndrome. This signature demonstrates new pathways in pSS and lupus, focusing research on innate immunity and in the IFN pathway.We have confirmed the implication of 2 genes in the pSS, and these genes are involved in the IFN pathway. The first gene is IRF5 which is in the type I IFN pathway and the second is STAT4 which is in the type II IFN pathway. We have shown a functional consequence of IRF5 at-risk allele. Regarding STAT4, the associated SNP did not altered STAT4 mRNA expression but was highly correlated with type I IFN genes expression.The epigenetic deregulation could play a triggering role in autoimmune diseases, particularly through DNA methylation which is highly implicated in the suppression of gene expression. We studied the methylation of IRF5 promoter and found no methylation. Our team is currently undertaking a global approach with methylome analysis. This methylome study will assess specific gene methylation patterns and will allow a better understanding of the role of these genes in autoimmune diseases.We further demonstrated that IL-12 specifically induces a type I IFN signature through a CD4+ T cells and pDCs crosstalk. These results could explain the implication of STAT4 polymorphism not only in type II IFN-dependent AIDs but also in type I IFN-dependent AIDs. Our data confirm that type I IFN- and type II IFN-mediated AIDs do not have to be opposed. They are only the yin and the yang of a common STAT4 activation which may induce secretion of both cytokines.

A proporção de idosos portadores da síndrome da imunodeficiência adquirida (aids) tem aumentado de maneira importante nos últimos anos e, até a presente data, existem poucos estudos que abordam a infecção nessa população especial. As particularidades imunológicas decorrentes do fenômeno da imunossenescência podem acarretar mudanças significativas na evolução da infecção pelo HIV, bem como na resposta ao tratamento. O objetivo maior desta Tese foi avaliar o impacto da idade na recuperação funcional do sistema imune de pacientes com aids acima de 55 anos, quando tratados adequadamente com terapia anti-retroviral, caracterizando a resultante imunológica da idade avançada e da infecção pelo HIV. Para tanto, foram estudados quatro grupos experimentais: indivíduos jovens saudáveis ou com aids, e indivíduos acima de 55 anos saudáveis ou com aids. Todos os pacientes com aids estavam recebendo terapia anti-retroviral, em sucesso terapêutico. No primeiro artigo apresentado, avaliamos resposta linfoproliferativa e produção de citocinas in vitro e resposta humoral in vivo mediante desafio antigênico com toxóide tetânico (TT) em indivíduos previamente vacinados contra o tétano. Os resultados mostraram deficiências imunológicas significativas relacionadas à idade avançada no que diz respeito a produção de IgG anti-TT, resposta linfoproliferativa e produção de IFN-. Em contrapartida, a produção de IL-10 foi significativamente maior nos indivíduos acima de 55 anos, infectados ou não pelo HIV. No segundo artigo, foram caracterizadas as subpopulações de células T mediante estímulo policlonal ou específico com antígenos do envelope do HIV (Env). Em culturas não-estimuladas de PBMC do grupo com aids e idade avançada, observamos frequência reduzida de células T naive e de memória central, associada a aumento de células T efetoras. Quando estimuladas policlonalmente, essas culturas apresentaram deficiência na produção de IFN- e hiperprodução de IL-10, como na resposta ao TT. Mediante estímulo específico com Env, a citometria de fluxo revelou frequência elevada de células T CD4+FoxP3-CD152+ com forte marcação intracelular para IL-10, indicando predomínio do fenótipo Tr-1, e não das células Treg clássicas. Interessantemente, em ambos os artigos, a replicação viral in vitro foi significativamente menor nos pacientes com aids acima de 55 anos, condizendo com a excelente resposta virológica desses pacientes ao tratamento antirretroviral. A neutralização da IL-10 com anticorpo anti-IL-10 nas culturas ativadas pelos peptídeos Env aumentou de forma significativa a replicação viral no sobrenadante. Tanto na resposta ao TT quanto aos peptídeos Env, o bloqueio da IL-10 aumentou os níveis de citocinas pró-inflamatórias, mas não melhorou a produção de IFN- dos pacientes acima de 55 anos com aids. Coletivamente, os achados dessa Tese revelam distúrbios em vários segmentos da resposta imune, particularmente no compartimento Th1, de pacientes acima 55 anos com aids e adequadamente tratados, sugerindo que, para esses pacientes, a reconstituição imune pós-tratamento não ocorre com a mesma eficácia que no jovem. Apesar do aumento da produção de IL-10 provavelmente contribuir, ao menos em parte, para o controle virológico, pode comprometer a resposta tanto ao próprio HIV, quanto a outros desafios antigênicos, a exemplo do toxóide tetânico. Sugere-se, portanto, a necessidade de recomendações específicas de manejo clínico para esse grupo de pacientes / The proportion of aged persons living with the acquired immunodeficiency syndrome (aids) has importantly increased in recent years and, up to the present moment, there are few studies that address the infection in this particular population. The immunological nuances resulting from the immunosenescence phenomenon may promote significant alterations in the clinical course of HIV infection, as well as in treatment response. The major purpose of this Thesis was to evaluate the impact of age on the functional immune recovery in aids patients aged more than 55 years, when adequately treated with anti-retroviral therapy, characterizing the immunological result of advanced age and HIV infection. Thus, four experimental groups were enrolled: healthy or HIV-infected young adults, and healthy or HIV-infected adults over 55 years old. All the HIV-infected patients had diagnosis of aids and were under anti-retroviral treatment with therapeutic success. In the first presented article, we evaluated the lymphoproliferative response and cytokine production in vitro and humoral response in vivo, after antigenic challenge with tetanus toxoid (TT) in previously immunized individuals against tetanus. The results revealed significant age-related immunological impairments concerning anti-TT IgG production, lymphoproliferative response and production of IFN-. On the other hand, the production of IL-10 significantly higher in individuals aged more the 55 years, HIV-infected or not. In the second article, T cell subsets were characterized after polyclonal activation or specific stimulus with antigens derived from the HIV envelope (Env). In fresh unstimulated PBMC cultures obtained from the aged aids patients, there was a reduced frequency of naïve and central memory T cells, associated with increased frequency of effector T cells. When polyclonally stimulated, these cultures showed deficient production of IFN- and hyperproduction of IL-10, like in response to TT. In Env-stimulated cultures, flow cytometry revealed high frequency of T CD4+FoxP3-CD152+ T cells with strong intracellular staining for IL-10, indicating a dominant Tr-1 phenotype, and not the classical Treg cells. Interestingly, in both articles, the viral replication in vitro was significantly lower aids patients over 55 years old, which is in consonance with their excellent virological response to anti-retroviral treatment. IL-10 neutralization with anti-IL-10 antibody in Env-activated cultures enhanced the viral replication in culture supernantants. Both in TT and in Env-peptides-stimulated cultures, the IL-10 blockade enhanced the levels of pro-inflammatory cytokines, but it did not improve IFN- production from aged aids patients. Altogether, the results reported in this Thesis reveal disturbances in several segments of the immune response, particularly in the Th1 compartment, of anti-retroviral-treated aids patients older than 55 years, suggesting that, for these patients, immune reconstitution after treatment does not occur with the same efficacy as in young patients. And although the enhanced IL-10 production probably contributes, at least in part, to the virological control, it can compromise the immune response both to HIV and to other antigenic challenges, such as tetanus toxoid. It is suggested, therefore, the need for specific recommendations regarding the clinical management of these patients

Die Einwanderung von T-Zellen in ein Gewebe wird durch selektive Wechselwirkungen mit vaskulären Endothelzellen kontrolliert. In der vorliegenden Arbeit wurde der Frage nachgegangen, ob Interaktionen zwischen Lebersinusendothelzellen (LSEC) und CD4+ T-Zellen die gewebespezifische Migration von CD4+ T-Zellen beeinflussen und damit Relevanz für den Verlauf spezifischer Immunantworten haben. Die Präsentation von Antigenen durch zytokinaktivierte LSEC erhöhte die Adhäsion und Transmigration antigenspezifischer CD4+ T-Zellen. Die Daten deuten auf eine Rolle des Lebersinusendothels bei der entzündungsinduzierten, antigenabhängigen Rekrutierung von CD4+ T-Zellen in das Lebergewebe hin. Eine antigenabhängige Aktivierung naiver CD4+ T-Zellen durch LSEC sowie deren Bereitstellung von Retinolsäure induzierte die Expression von darmspezifischen Homingrezeptoren auf CD4+ T-Zellen. LSEC-aktivierte CD4+ T-Zellen migrierten in das Darmgewebe von C57BL/6-Mäusen. Die Ergebnisse legen den Schluss nahe, dass LSEC einen darmspezifischen Homingphänotyp und damit die Migration von in der Leber aktivierten CD4+ T-Zellen in den Darm induzieren. Die Bereitstellung von Chemokinen durch LSEC mittels Transzytose und Immobilisierung verstärkte die Transmigration von CD4+ T-Zellen durch das Endothel. Die Gabe eines Inhibitors der endothelialen Chemokintranszytose während einer Concanavalin A-induzierten Autoimmunhepatitis supprimierte den Verlauf der Hepatitis und führte zu einer verminderten Migration von aktivierten CD4+ T-Zellen in das Lebergewebe. Diese Daten weisen dem Lebersinusendothel eine aktive Beteiligung in der chemokinabhängigen Rekrutierung von CD4+ T-Zellen in die Leber zu. In der vorliegenden Arbeit wurde die Modulation der gewebespezifischen Migration von CD4+ T-Zellen über Antigenpräsentation und Chemokinbereitstellung durch das Lebersinusendothel gezeigt und damit weitere spezifische Aspekte in der Funktion der Leber als immunologisches Organ beschrieben. / T-cell immigration into a tissue is controlled by selective interactions with vascular endothelial cells. The present study addressed the question if interactions between liver sinusoidal endothelial cells (LSEC) and CD4+ T cells influence the tissue-specific migration of CD4+ T cells and thus have relevance for the course of specific immune responses. Antigen presentation by cytokine-activated LSEC increased adhesion and transmigration of antigen-specific CD4+ T cells. These results indicate an involvement of LSEC in the inflammation-induced, antigen-specific migration of CD4+ T cells into the liver tissue. Antigen-specific activation of naive CD4+ T cells by LSEC and their supply of retinoic acid induced expression of gut-specific homing receptors on CD4+ T cells. LSEC-activated CD4+ T cells migrated into the intestine of C57BL/6 mice. The findings presented here imply that LSEC induce a gut-specific homing phenotype resulting in migration of liver-activated CD4+ T cells into the intestine. The active supply of chemokines by LSEC via transcytosis and immobilization enhanced transmigration of CD4+ T cells. Administration of an inhibitor of the endothelial chemokine transcytosis during Concanavalin A-induced autoimmune hepatitis suppressed hepatitis and resulted in reduced migration of activated CD4+ T cells into the liver tissue. The data show the impact of LSEC on the chemokine-dependent recruitment of CD4+ T cells into the liver. In the present study the modulation of the tissue-specific migration of CD4+ T cells by LSEC via antigen presentation and supply of chemokines was demonstrated. Thus, additional functional aspects concerning the immunologic functions of the liver were described.

L’infection par le VIH-1 est caractérisée par une activation chronique du système immunitaire et par une réduction graduelle du nombre de lymphocytes TCD4+, qui contribuent à une détérioration lente du système immunitaire menant à la phase SIDA. Paradoxalement, ce sont majoritairement des lymphocytes T CD4+ non infectés qui sont détruits et la cause de ce phénomène reste encore inconnue. Certaines protéines virales, dont la protéine accessoire Vpr, sont soupçonnées de jouer un rôle dans ce processus. Synthétisée tardivement, Vpr est incorporée à l’intérieur des virions, en plus d’être relâchée sous forme soluble dans le milieu extracellulaire. La principale fonction biologique de Vpr est l’induction d’un arrêt de cycle en phase G2/M, via le recrutement du complexe d’ubiquitine E3 ligase CUL4A-DDB1VprBP et l’activation de la voie de dommage à l’ADN contrôlée par la kinase ATR. Une étude démontre que l’activation des voies de dommages à l’ADN conduit à l’expression de ligands du récepteur activateur NKG2D, exprimés par les cellules NK, déclenchant leurs fonctions cytolytiques. Chose intéressante, plusieurs études suggèrent que le VIH-1 régule positivement l’expression des ligands de NKG2D à la surface des lymphocytes T CD4+ infectés. Cependant, le facteur viral impliqué dans ce processus reste encore indéfini. Le but de cette thèse était d’évaluer le rôle de Vpr dans la modulation des fonctions cytolytiques des cellules NK et son implication potentielle dans la destruction des lymphocytes T CD4+. Nos travaux ont permis de démontrer que l’expression de Vpr, seule ou dans le contexte de l’infection, est suffisante afin d’augmenter spécifiquement l’expression du ligand de NKG2D, ULBP2, au niveau de lymphocytes T CD4+ primaires. Conséquemment, Vpr augmente ainsi la susceptibilité de ces cellules à une lyse par des cellules NK autologues. Nous démontrons que cette régulation positive d’ULBP2 repose sur la capacité de Vpr de recruter le complexe d’ubiquitine E3 ligase DDB1-CUL4AVprBP et l’activation de la voie de dommage à l’ADN ATR. Plus important encore, nous apportons des preuves que Vpr augmente également l’expression d’ULBP2 au niveau des cellules non infectées lors d’une infection de lymphocytes TCD4+ par le VIH-1. À cet effet, nous montrons que l’acheminement de Vpr au niveau de lymphocytes T CD4+ non infectés via des particules virales défectives est suffisant afin de réguler positivement ULBP2 et d’augmenter leur lyse par des cellules NK autologues. De plus, nous décrivons pour la première fois que Vpr, sous forme soluble, a la capacité d’induire des dommages à l’ADN et de réguler positivement ULBP2 suite à la transduction de différents types cellulaires, incluant des cellules T. Globalement, nos résultats démontrent que Vpr est un facteur viral clé impliqué dans la régulation positive des ligands de NKG2D induite par le VIH-1. Cette régulation positive d’ULBP2 pourrait alors contribuer à la destruction des lymphocytes T CD4+ infectés et non infectés via l’activation des fonctions cytolytiques des cellules NK. Une meilleure compréhension de la contribution de cette activité de Vpr dans la pathogenèse du VIH-1 a le potentiel de permettre le développement de nouvelles cibles ou stratégies thérapeutiques contre le VIH-1. / Chronic immune activation and gradual depletion of CD4+ T cells are hallmarks of HIV-1 infection, which are thought to contribute to the progressive deterioration of the host’s immune response that ultimately leads to AIDS. Paradoxically, the majority of CD4+ T cells that are destroyed are uninfected and causes for this bystander effect of infection on CD4+ T cells remains unclear. Some HIV-1 proteins, including the accessory protein Vpr, are suspected to play a role in this process. Vpr, expressed late during HIV-1 infection, is shown to be incorporated within the budding virions as well as secreted as soluble protein in the extracellular medium from the infected cells. The main biological function of Vpr is the induction of a G2/M cell-cycle arrest through the recruitment of the E3 ubiquitin ligase complex DDB1-CUL4AVprBP and activation of the ATR-mediated DNA damage pathway. One study showed that activation of DNA damage pathways leads to the expression of specific ligands for the activating receptor NKG2D expressed on NK cells, thus triggering NK cell cytolytic function. Interestingly, several evidences suggest that HIV-1 upregulates expression of specific NKG2D ligands on infected CD4+ T cells. However, the viral factor involved in this process remains undefined. The aim of this thesis was to evaluate the role of Vpr in modulating NK cell cytolytic function and its potential involvement in CD4+ T cells depletion. Our work demonstrated that the expression of Vpr, alone or in the context of HIV-1 infection, is sufficient to specifically increase expression of the NKG2D ligand, ULBP2, on primary CD4+ T cells. Consequently, these CD4 T cells become more susceptible to autologuous NK cell-mediated lysis. Our studies have shown that this Vpr-mediated ULBP2 upregulation requires the recruitment of the E3 ubiquitin ligase complex DDB1-CUL4AVprBP and the activation of the ATR-mediated DNA damage pathway. More importantly, we provide evidence that Vpr augments ULBP2 expression on both infected and uninfected bystander cells during HIV-1 infection of primary CD4+ T lymphocytes. In that context, we show that delivery of Vpr into uninfected cells via defective viral particles is sufficient to upregulate ULBP2 and increase their susceptibility to autologuous NK cell-mediated killing. In addition, we describe for the first time that soluble Vpr has the ability to induce DNA damages and upregulate ULBP2 upon transducing target cells, including T cells. Overall, our results show that Vpr is a key HIV-1 factor involved in the upregulation of NKG2D ligands induced by HIV-1. This upregulation of UBP2 might contribute to depletion of infected and uninfected CD4 + T cells through activation of NK cell cytolytic functions. A better understanding of the contribution of this new activity of Vpr in HIV-1 pathogenesis has the potential to enable the development of new therapeutic targets or therapeutic strategies against HIV-1.

Le Streptocoque de groupe B (GBS) est un important agent d’infection invasive pouvant mener à la mort et demeure la cause principale de septicémie néonatale à ce jour. Neuf sérotypes ont été officiellement décrits basés sur la composition de la capsule polysaccharidique (CPS). Parmi ces sérotypes, le type III est considéré le plus virulent et fréquemment associé aux maladies invasives graves, telle que la méningite. Malgré que plusieurs recherches aient été effectuées au niveau des interactions entre GBS type III et les cellules du système immunitaire innées, aucune information n’est disponible sur la régulation de la réponse immunitaire adaptative dirigée contre ce dernier. Notamment, le rôle de cellules T CD4+ dans l’immuno-pathogenèse de l’infection causée par GBS n’a jamais été étudié. Dans cet étude, trois différents modèles murins d’infection ont été développé pour évaluer l’activation et la modulation des cellules T CD4+ répondantes au GBS de type III : ex vivo, in vivo, et in vitro. Les résultats d’infections ex vivo démontrent que les splénocytes totaux répondent à l’infection en produisant des cytokines de type-1 pro-inflammatoires. Une forte production d’IL-10 accompagne cette cascade inflammatoire, probablement dans l’effort de l’hôte de maintenir l’homéostasie. Les résultats démontrent aussi que les cellules T sont activement recrutées par les cellules répondantes du système inné en produisant des facteurs chimiotactiques, tels que CXCL9, CXCL10, et CCL3. Plus spécifiquement, les résultats obtenus à partir des cellules isolées T CD4+ provenant des infections ex vivo ou in vivo démontrent que ces cellules participent à la production d’IFN-γ et de TNF-α ainsi que d’IL-2, suggérant un profil d’activation Th1. Les cellules isolées T CD4+ n’étaient pas des contributeurs majeurs d’IL-10. Ceci indique que cette cytokine immuno-régulatrice est principalement produite par les cellules de l’immunité innée de la rate de souris infectées. Le profil Th1 des cellules T CD4+ a été confirmé en utilisant un modèle in vitro. Nos résultats démontrent aussi que la CPS de GBS a une role immuno-modulateur dans le développement de la réponse Th1. En résumé, cette étude adresse pour la première fois, la contribution des cellules T CD4+ dans la production d’IFN-γ lors d’une infection à GBS et donc, dans le développement d’une réponse de type Th1. Ces résultats renforcent d’avantage le rôle central de cette cytokine pour un control efficace des infections causées par ce pathogène. / Group B Streptococcus (GBS) is an important agent of life-threatening invasive infections and remains the leading cause of neonatal sepsis to this day. Nine serotypes have been officially described based on capsular polysaccharide (CPS) composition. Among them, capsular type III is considered one of the most virulent and frequently associated with severe invasive diseases, such as meningitis. Although extensive research has been done on the interactions between GBS type III and various cells of the innate immune system, no information is available on the regulation of the adaptive immune response against this pathogen. In particular, the role of CD4+ T cells in the immuno-pathogenesis of the infection caused by GBS has never been assessed. In this study, three different models of murine infection were developed to evaluate activation and modulation of responding CD4+ T cells against GBS type III: ex vivo, in vivo, and in vitro. Ex vivo analysis of total splenocytes showed that GBS induces the release of type-1 pro-inflammatory cytokines. A strong IL-10 production follows this inflammatory cascade, indicating the host effort to maintain homeostasis. Results also indicate that T cells were actively recruited by responding innate immune cells via the release of chemotactic factors such as CXCL9, CXCL10, and CCL3. More specifically, results obtained from isolated CD4+ T cells from ex vivo or in vivo infections showed that they actively participate in the production of IFN-γ and TNF-α, as well as IL-2, suggesting a Th1 profile of activation. On the other hand, isolated CD4+ T cells were not main sources of IL-10. This observation suggests that this immuno-regulatory cytokine is produced mainly by cells of the spleen innate immune system of infected animals. The CD4+ Th1 cell profile was confirmed using an in vitro model of infection. Our results also suggest that the GBS CPS plays an immuno-modulatory role in the development of a Th1 response. In summary, this study addresses for this first time the contribution of CD4+ T cells in IFN-γ production during GBS infection, and thus, in the development of a Th1 response. Our data further highlight the central role of this cytokine for effective control of GBS infections.

Les vaccins à base de cellules dendritiques (DCs) constituent une avenue très populaire en immunothérapie du cancer. Alors que ces cellules peuvent présenter des peptides exogènes ajoutés au milieu, l’efficacité de chargement de ces peptides au le complexe majeur d'histocompatibilité (CMH) de classe II est limitée. En effet, la majorité des molécules du CMH II à la surface des DCs sont très stable et l’échange de peptide spontané est minime. Confinée aux vésicules endosomales, HLA-DM (DM) retire les peptides des molécules du CMH II en plus de leur accorder une conformation réceptive au chargement de peptides. Il est possible, cependant, de muter le signal de rétention de DM de façon à ce que la protéine s’accumule en surface. Nous avons émis l’hypothèse que ce mutant de DM (DMY) sera aussi fonctionnel à la surface que dans la voie endosomale et qu’il favorisera le chargement de peptides exogènes aux DCs. Nous avons utilisé un vecteur adénoviral pour exprimer DMY dans des DCs et avons montrer que la molécule augmente le chargement de peptides. L’augmentation du chargement peptidique par DMY est autant qualitatif que quantitatif. DMY améliore la réponse T auxiliaire (Th) du coté Th1, ce qui favorise l’immunité anti-cancer. Du côté qualitatif, le chargement de peptides résulte en des complexes peptide-CMHII (pCMH) d’une conformation supérieure (conformère). Ce conformère (Type A) est le préféré pour la vaccination et DMY édite avec succès les complexes pCMH à la surface en éliminant ceux de type B, lesquels sont indésirables. La fonction de DM est régulée par HLA-DO (DO). Ce dernier inhibe l’habilité de DM à échanger le peptide CLIP (peptide dérivée de la chaîne invariante) en fonction du pH, donc dans les endosomes tardifs. Mes résultats indiquent que la surexpression de DO influence la présentation des superantigènes (SAgs) dépendants de la nature du peptide. Il est probable que DO améliore indirectement la liaison de ces SAgs au pCMH dû à l’accumulation de complexe CLIP-CMH, d’autant plus qu’il neutralise la polarisation Th2 normalement observée par CLIP. Ensemble, ces résultats indiquent que DMY est un outil intéressant pour renforcer le chargement de peptides exogènes sur les DCs et ainsi générer des vaccins efficaces. Un effet inattendu de DO sur la présentation de certains SAgs a aussi été observé. Davantage de recherche est nécessaire afin de résoudre comment DMY et DO influence la polarisation des lymphocytes T auxiliaires. Cela conduira à une meilleure compréhension de la présentation antigénique et de son étroite collaboration avec le système immunitaire. / Dendritic cell peptide-based vaccines are the most common immunotherapy approach in cancer therapy. While, in principle, dendritic cells (DCs) could be loaded efficiently by exogenously added tumor peptides, their loading efficacy is severely reduced due to low number of peptide-receptive MHC II on cell surface. Most surface MHC II molecules are either occupied by endogenous peptides or are inactive due to a conformation that is not receptive for free peptides. In MHC II antigen presentation pathway, HLA-DM (DM) in acidic endosomal vesicles removes the self-peptides and grants a peptide receptive conformation to MHC II. Mutating of an intracellular sorting motif in DM, renders its accumulation on cell surface. We hypothesized that the mutant DM (DMY) is functional on cell surface and can generate peptide receptive MHC II on surface of DCs for exogenous peptide loading. By using an adenoviral vector that expresses DMY, we found that DMY is functional on surface of DCs. DMY supplied peptide receptive MHC II on surface of DCs and improved exogenous peptide loading. The improvement of peptide loading by DMY is both quantitative and qualitative. DMY improves helper T cell (Th) response in Th1 direction that favors anti-cancer immunity. The qualitative improvement of peptide loading extends to loading of superior conformational isomer (conformer) of peptide-MHC complexes. This superior conformer (type A) is the favourite type for vaccination approaches and DMY successfully edits peptide-MHC conformers on cell surface level by eliminating undesirable one (type B). Function of DM is regulated by HLA-DO (DO) and it is well accepted that in acidic pH of late endosomes, DO inhibits function of DM by preventing removal of class II associated invariant chain peptide (CLIP) from peptide binding groove of MHC II. My results indicate that DO overexpression, changes binding of peptide-dependent superantigens to MHC II molecules. Superantigens (SAgs) are small microbial proteins that bind out side peptide binding groove of MHC II. DO probably enhances binding of peptide-dependent SAgs by forcing the accumulation of CLIP on the cell surface of antigen presenting cells. DO also neutralizes Th2 polarization by CLIP. Collectively, these results indicate that DMY is a valuable tool for improvement of exogenous peptide loading in DCs vaccines. An unnoticed effect of DO on SAgs binding was also recognized. Further investigations are needed to clarify the mechanisms by which, DMY and DO influence Th polarization. This would provide a better understanding of antigen presentation pathway and its interaction with immune system.

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