The involvement of regulatory T cells (Tregs) in immune homeostasis is now recognized as one of the fundamental mechanisms of immune tolerance. While several different types of Tregs cooperate to establish and maintain immune homeostasis, much current research is focused on defining the characteristics of the CD4⁺CD25⁺ Treg subset, as these cells can mediate dominant, long-lasting and transferable tolerance in many experimental models. The aim of this research was to characterize the biological role of a protein known as forkhead box P3 (FOXP3) that was initially identified as an essential transcription factor for the development of mouse CD4⁺CD25⁺ Tregs, in human CD4⁺ T cells. Following confirmation that, like mouse Tregs, human Tregs also expressed high levels of FOXP3, several approaches were used to investigate the role of this protein in human CD4⁺ T cells. 1) Characterization of endogenous FOXP3 expression in CD4⁺ T cell subsets revealed that this protein is not a Treg-specific marker as was previously thought. Instead, low-level and transient expression was found to be typical of highly activated non-regulatory effector T cells. 2) To generate large numbers of Tregs suitable for cellular therapy, the capacity of ectopic FOXP3 expression to drive Treg generation in vitro was explored. It was found that high and constitutive expression mediated by a lentiviral vector, but not fluctuating expression driven by a retroviral vector, was sufficient to generate suppressive cells. Over-expression strategies were also used to characterize a novel splice isoform unique to human cells, FOXP3Δ2 (FOXP3b). 3) To further probe the requirements of FOXP3 to induce suppressor function, a system for conditionally-active FOXP3 ectopic expression was developed. These studies established that FOXP3 acts a quantitative regulator rather than a “master switch” for Tregs, and that there is a temporal component to its capacity to direct Treg phenotype and function. In summary, this research has significantly expanded the understanding of the biological function of FOXP3 in human CD4⁺ T cells. Based on the potential of these cells to be manipulated for therapy, this work contributes to the field of immunology on both academic and clinical research fronts.

The involvement of regulatory T cells (Tregs) in immune homeostasis is now recognized as one of the fundamental mechanisms of immune tolerance. While several different types of Tregs cooperate to establish and maintain immune homeostasis, much current research is focused on defining the characteristics of the CD4⁺CD25⁺ Treg subset, as these cells can mediate dominant, long-lasting and transferable tolerance in many experimental models. The aim of this research was to characterize the biological role of a protein known as forkhead box P3 (FOXP3) that was initially identified as an essential transcription factor for the development of mouse CD4⁺CD25⁺ Tregs, in human CD4⁺ T cells. Following confirmation that, like mouse Tregs, human Tregs also expressed high levels of FOXP3, several approaches were used to investigate the role of this protein in human CD4⁺ T cells. 1) Characterization of endogenous FOXP3 expression in CD4⁺ T cell subsets revealed that this protein is not a Treg-specific marker as was previously thought. Instead, low-level and transient expression was found to be typical of highly activated non-regulatory effector T cells. 2) To generate large numbers of Tregs suitable for cellular therapy, the capacity of ectopic FOXP3 expression to drive Treg generation in vitro was explored. It was found that high and constitutive expression mediated by a lentiviral vector, but not fluctuating expression driven by a retroviral vector, was sufficient to generate suppressive cells. Over-expression strategies were also used to characterize a novel splice isoform unique to human cells, FOXP3Δ2 (FOXP3b). 3) To further probe the requirements of FOXP3 to induce suppressor function, a system for conditionally-active FOXP3 ectopic expression was developed. These studies established that FOXP3 acts a quantitative regulator rather than a “master switch” for Tregs, and that there is a temporal component to its capacity to direct Treg phenotype and function. In summary, this research has significantly expanded the understanding of the biological function of FOXP3 in human CD4⁺ T cells. Based on the potential of these cells to be manipulated for therapy, this work contributes to the field of immunology on both academic and clinical research fronts.

Investigamos o agonista de Guanilato Ciclase solúvel, BAY 41-2272, como alternativa para compensar falhas nas funções de monócitos. Avaliamos in vitro o efeito do fármaco em células humanas de linhagem e de sangue periférico. O BAY, em células THP-1 e monócitos, aumentou a expressão de CD11b, CD18, CD14, TLR4, TLR2 e CD163 e induziu a produção de TNF-<font face=\"Symbol\">a, IL-1<font face=\"Symbol\">b, IL-6 e IL-12p70. Além disso, o fármaco aumentou a expressão gênica (CYBB, CYBA e NCF2) e protéica (p67PHOX e gp91PHOX) da NADPH oxidase. Ainda, o BAY ativa a via do NF-kB (p65) (dependente de PKG). Mais importante, o fármaco aumentou a atividade microbicida de monócitos de pacientes com DGC e deficiência de MPO a S. aureus e C. albicans. Em animais, o BAY 41-2272 induziu intenso influxo de macrófagos para o peritônio e inflamação. Ainda, potencializou o espraiamento, atividade fagocítica, atividade microbicida, produção espontânea de óxido nítrico e de peróxido de hidrogênio induzida por PMA, em macrófagos peritoneais, aumentando a proteção dos animais desafiados com C. albicans. Em conjunto, nossos resultados confirmam o potencial do BAY 41-2272, ou sua via (GCs/PKG), como alternativa para o desenvolvimento de terapias contra infecções. / We investigated the soluble guanylate cyclase agonist, BAY 41-2272, as an alternative to compensate for failures in of monocytes function. We evaluated the in vitro effect of the drug on human cells lines and peripheral blood cells. The BAY increased expression of CD11b, CD18, CD14, TLR4, TLR2 and CD163 and induce the production of TNF-<font face=\"Symbol\">a, IL-1<font face=\"Symbol\">b, IL-6 and IL-12p70 in THP-1 cells and monocytes. Furthermore, the drug increased NADPH oxidase gene (CYBB, CYBA and NCF2) and protein (gp91phox and p67phox) expression. Also, BAY activates the PKG-dependent NF-kB pathway (p65). More importantly, the drug increased microbicidal activity against S. aureus and C. albicans of monocytes from patients with CGD and MPO deficiency. In animals, BAY 41-2272 induced intense influx of macrophages to the peritoneum and inflammation. BAY potentiated the spreading, phagocytic activity, microbicidal activity, spontaneous production of nitric oxide and PMA-induced hydrogen peroxide release by peritoneal macrophages, increasing host protection against C. albicans. Taken together, our results confirm the potential of BAY 41-2272, or its pathway (sGC / PKG), as an alternative for the development of therapies against infections.

Mesmo com o constante avanço no estudo da sibilância e asma, existem inúmeras controvérsias sobre a participação da exposição à endotoxina, background genético e ativação celular. Investigamos a participação da exposição à endotoxina ambiental e o papel do LPS no desenvolvimento dos fenótipos de sibilância e asma. Para tanto selecionamos crianças sibilantes e não sibilantes, e crianças asmáticas e não asmáticas, sendo seu sangue coletado e as PBMC cultivadas com LPS. O sobrenadante foi colhido para análise de citocinas por ELISA, e analisamos os polimorfismos nos genes de CD14 e TLR4 por PCR-RFLP. Não encontramos relação entre a exposição à endotoxina ambiental e o quadro de sibilância. Observamos que PBMC estimuladas ou não com LPS de crianças sibilantes e asmáticas produzem baixos níveis de IL-12 e IFN-<font face=\"Symbol\">&#947 quando comparado com crianças não sibilantes e não asmáticas. Os polimorfismos de TLR4 e CD14 não tiveram associação com sibilância ou asma. Nossos dados sugerem que não somente a polarização Th2 é importante para desenvolver essas patogenias, mas também uma diminuição na resposta Th1. / Although the great advance in the study of asthma and wheezing, there are numerous controversies about the involvement of endotoxin exposure, genetic background and cellular activation. We investigated the involvement of environmental endotoxin exposure and the role of LPS in the development of phenotypes wheezing and asthma. For experiments we selected wheezing and non-wheezing, and asthmatic and non-asthmatic children, and their blood collected and the PBMC cultured with LPS. The supernatant was collected for analysis cytokines by ELISA, and analyzed CD14 and TLR4 polymorphisms by PCR-RFLP. There was no relationship between environmental endotoxin exposure and the framework of wheezing. We observed that LPS-stimulated PBMC of wheezing and asthmatic children produce lower levels of IL-12 and IFN-<font face=\"Symbol\">&#947 when compared with non-wheezing and non-asthmatic children. The polymorphisms TLR4 and CD14 were not associated with wheezing or asthma. Our data suggest that not only Th2 polarization is important to develop these diseases, but also a decrease in Th1 response.

A cromoblastomicose é uma micose crônica que causa lesões granulomatosas e supurativas que atingem a pele e o tecido subcutâneo. Micose cosmopolita e freqüentemente observada no Brasil. As lesões aumentam progressivamente e posteriormente podem desenvolver um processo crônico e que geralmente não respondem a uma terapia convencional. Entretanto o mecanismo de defesa da resposta imune adaptativa, principalmente das células T na cromoblastomicose ainda não está definido. Em nosso estudo avaliamos a produção de citocinas e a resposta linfoproliferativa de diferentes amostras de sangue de pacientes com cromoblastomicose e indivíduos saudáveis in vitro após estimulação com antígenos do fungo. Além disso, nos acompanhamos esses pacientes sob terapia antifúngica em diferentes períodos de tratamento. Este estudo mostrou que a forma grave da cromoblastomicose é caracterizada pelo aumento na produção de IL-10 e deficiência na proliferação das células T após estimulação com antígenos do fungo. Ao contrario, pacientes com a forma leve da doença foram capazes de secretar predominantemente IFN-&#947;, que é uma citocina importante para defesa do hospedeiro. Em adição eles secretaram menores quantidades de IL-10 e suas células T proliferaram eficientemente in vitro após estimulação do fungo. Os pacientes avaliados após 6 meses de terapia antifúngica as células T proliferaram e secretaram altos níveis de IFN-&#947; eficientemente após estimulação. Ao contrário, pacientes com 12 meses de tratamento ocorreu um aumento na produção de IL-10 uma diminuição nos níveis de linfoproliferação. Interessantemente, os monócitos obtidos desses pacientes durante a doença foram capazes expressar moléculas co-estimulatorias (CD80 e CD86) e também aumento nos níveis de HLA-DR após estimulação com LPS. Além disso, monócitos desses pacientes secretam altos níveis de IL-12 e TNF-&#945;, sugerindo que a suscetibilidade desses pacientes não apresentam uma deficiência na apresentação de antígeno por monócitos. Em suma, em nossos resultados mostraram que alta secreção de IFN-&#947; e eficiente proliferação de células T de pacientes com cromoblastomicose está diretamente relacionada com a forma leve da doença, enquanto que a produção de IL-10 e diminuição na proliferação de células T caracterizam a forma grave da doença. / Chromoblastomycosis is a chronic granulomatous and suppurative disease that causes lesions mainly in skin and subcutaneous tissues. Although found worldwide, this mycosis is frequently observed in tropical countries such as Brazil. The skin lesions increase slowly and progressively in a chronic process that usually relapse even after canonical treatment. However, the mechanism of the host adaptive immune response, specially the role of T cells, in chromoblastomycosis is still unclear. In studies here, we evaluated the cytokine production and T cell response of peripheral blood mononuclear cells (PBMC) from different patients and healthy controls upon in vitro stimulation with fungal antigens. Moreover, we performed a follow-up study in patients undergoing long-term antifungal treatment. We collected PBMC samples from patients with an active form (either severe or mild skin lesions) of chromoblastomycosis and PBMC samples from healthy individuais. In PBMC from patients with a severe form of the disease we found a predominant production of IL-10 over IFN-gamma and a deficiency in T cell proliferation upon fungal antigen stimulation. In contrast, PBMC from patients in a mild form of the disease were able to secrete predominantly IFN-gamma, a cytokine important for host defense. In addition, they secreted low amounts of IL-10 and their T cells efficiently proliferated under in vitro stimulation with the fungal antigens. Surprisingly, the patients undergoing 6 months antifungal therapy PBMC from patients secreted higher amounts of IFN-gamma and their T cells proliferated efficiently upon stimulation. On the contrary, PBMC from patients after 12m of treatment showed an increase in IL-10 secretion followed by an inefficient T cell proliferation. Interestingly, monocytes obtained from patients during chronic phase of the disease were able to up-regulate their co-stimulatory molecules (CD80 and CD86) as well as their HLA-DR upon in vitro fungal stimulation. Moreover, monocytes from these patients secreted high amounts of pro-inflammatory cytokines IL-12 and TNF-alfa, suggesting that susceptibility of patients must be due to a immune deficiency other than a monocyte deactivation. Altogether, our data clearly show that a higher secretion of IFN-gamma and an efficient T cell proliferation of PBMC from infected individuals can distinguish the mild from the severe form of the chromoblastomycosis

The involvement of regulatory T cells (Tregs) in immune homeostasis is now recognized as one of the fundamental mechanisms of immune tolerance. While several different types of Tregs cooperate to establish and maintain immune homeostasis, much current research is focused on defining the characteristics of the CD4⁺CD25⁺ Treg subset, as these cells can mediate dominant, long-lasting and transferable tolerance in many experimental models. The aim of this research was to characterize the biological role of a protein known as forkhead box P3 (FOXP3) that was initially identified as an essential transcription factor for the development of mouse CD4⁺CD25⁺ Tregs, in human CD4⁺ T cells. Following confirmation that, like mouse Tregs, human Tregs also expressed high levels of FOXP3, several approaches were used to investigate the role of this protein in human CD4⁺ T cells. 1) Characterization of endogenous FOXP3 expression in CD4⁺ T cell subsets revealed that this protein is not a Treg-specific marker as was previously thought. Instead, low-level and transient expression was found to be typical of highly activated non-regulatory effector T cells. 2) To generate large numbers of Tregs suitable for cellular therapy, the capacity of ectopic FOXP3 expression to drive Treg generation in vitro was explored. It was found that high and constitutive expression mediated by a lentiviral vector, but not fluctuating expression driven by a retroviral vector, was sufficient to generate suppressive cells. Over-expression strategies were also used to characterize a novel splice isoform unique to human cells, FOXP3Δ2 (FOXP3b). 3) To further probe the requirements of FOXP3 to induce suppressor function, a system for conditionally-active FOXP3 ectopic expression was developed. These studies established that FOXP3 acts a quantitative regulator rather than a “master switch” for Tregs, and that there is a temporal component to its capacity to direct Treg phenotype and function. In summary, this research has significantly expanded the understanding of the biological function of FOXP3 in human CD4⁺ T cells. Based on the potential of these cells to be manipulated for therapy, this work contributes to the field of immunology on both academic and clinical research fronts. / Medicine, Faculty of / Medicine, Department of / Experimental Medicine, Division of / Graduate

Despite the chronic debate in the etiology of crohn's disease (cd), a debilitating inflammatory bowel disease (ibd) closely related to ulcerative colitis (uc), an emerging interest in a possible mycobacterial role has been marked. Granuloma and pathologic manifestations in cd resemble aspects found in tuberculosis, leprosy and paratuberculosis. The latter, a chronic enteritis in cattle, goat, sheep and primates, which is similar to human enteritis, also known as cd, is caused by a fastidious, slow growing mycobacterium avium subspecies paratuberculosis (map). Due to the similarities between cd and paratuberculosis, a mycobacterial cause in cd has been proposed. Recent discovery of a possible association between nod2/card15 mutations and risk of cd added support to microorganism-host interactions. In this study, a possible mycobacterial role in cd etiology has been evaluated by investigating the presence of map dna, the state of the cellular immune response and microarray gene expression profiling in peripheral blood and surgical tissue from cd, uc and healthy control subjects. Nested pcr detected map dna in tissue from 10/12(83%) cd patients compared to 1/6(17%) non-ibd subjects. Fluorescence in situ hybridization (fish) with the aid of confocal scanning laser microscopy (cslm) detected map dna in 8/12(67%) cd subjects compared to 0/6(0%) in non-ibd subjects. The detection of map dna by either technique in tissue from cd subjects is significant compared to non-ibd subjects (p < 0.05). Map dna was also detected in both inflamed and non-inflamed tissue from patients with cd suggesting map infiltration in human tissue. Correlation of possible map presence and the function of polymorphonuclear leukocytes (pmn) and peripheral blood mononuclear cells (pbmc) in 19 cd patients and 12 controls have been evaluated. Pmn phagocytosis of viable fitc-map was suppressed in 13/19(68%) cd patients compared to 0/12(0%) in healthy controls (p<0.05). Pbmc phagocytosis of viable fitc-map was suppressed in 5/19(26%) of cd patients compared to 0/12(0%) of healthy controls (p<0.05). The proliferative response of pbmc with t-cell majority from cd and controls subjects was evaluated against pha, candida albicans, pwm and map ppd. Dysfunctional proliferative response against pha was found in 8/19(42%) cd patients compared to 1/12(8.3%) in controls suggesting possible t-cell anergy. Pbmc from 11 cd subjects reacted normally to pha, 7/11(64%) reacted strongly to map ppd suggesting previous exposure to mycobacteria, and 3/11(27%) did not react with map ppd suggesting lack of pre-exposure to mycobacteria. From the seven mycobacterial pre-exposed samples, 6/7(86%) showed a normal ability to recall antigens by activated macrophages when exposed to c. Albicans, and all 7 samples had a normal pwm response. Finally, microarray-chip technology was employed to identify the expression profile of genes that have a role in the immune response of cd patients. Rna was isolated from fresh buffy coats from 8 healthy controls, 2 cd, and 1 uc patients. Chips with an estimated of 30,000 human genes were hybridized to cdna from these samples. We found that 17% of the total number of genes was differentially expressed. Over 200 genes were involved in the immune response, 7 genes where common to both forms of ibd (uc and cd), and 8 genes were found to be either downregulated in cd and upregulated in uc or viceversa. The ifngr1 gene, which encodes the ligand-binding chain of the ifn-gamma receptor, was found to be downregulated in 2/2(100%) of cd patients, but not in uc patients. It is known that defects in ifngr1 are a cause of atypical mycobacterial infection and bcg infection. Patients suffering from this deficiency have an immunologic defect predisposing them to infection with mycobacteria. This correlates with the proposed theory as map being the causative agent of cd. Furthermore, the results indicate a host susceptibility requirement for the establishment of mycobacterial infection in cd patients. Further characterization of ifngr1 using real-time pcr is underway. Collectively, detection of map dna in the majority of cd tissue and the alteration in pmn and pbmc to respond efficiently to map may be related to the fact that mycobacterial pathogens infect phagocytic cells of susceptible hosts and consequently the immune response is dysregulated. Furthermore, the fact that a gene linked to mycobacterial susceptibility was found to be downregulated in cd patients only, strengthens the mycobacterial etiology of cd. In general, the data suggest a possible role for a bacterial pathogen in cd pathogenesis.

<p>Cytomegalovirus (CMV) is a widespread infection affecting 50-90% of the human population. A typical silent primary infection is followed by life-long persistence in the host under control by virus-specific CD8 (“killer”) and CD4 (“helper”) T cells. Although harmless in most people, CMV may cause disease and sequelae in patients with deficient cellular immunity, such as AIDS patients, recipients of organ transplants and children who have acquired the virus before birth. In this thesis we have characterized the cellular immunity to CMV in immunocompetent subjects, in patients receiving transplants and in infants.</p><p>In healthy individuals with latent CMV, the frequencies of CMV-specific CD8 T cells varied considerably between the donors. Within the same individual, the changes over time were usually small. In patients with primary, symptomatic CMV infection, the frequencies of CMV-specific CD8 T cells peaked within the first month after the appearance of symptoms. The frequencies then declined to levels similar to those in latently infected CMV carriers. The CD4 T-cell function followed the same pattern, but with lower peak values.</p><p>Immunosuppressed renal transplant patients with latent CMV had CMV-specific CD4 cell function similar to healthy controls. The frequencies of CMV-specific CD8 T cells were also comparable, but their function was impaired. When renal transplant recipients were investigated longitudinally, we found that their CMV-specific T cells decreased rapidly after transplantation. Whereas the frequencies and function of CD8 T cells rebounded within 3 months, CD4 T-cell recovery was impaired during the entire first year after transplantation.</p><p>Finally, the frequencies and function of CMV-specific T-cells were investigated in children with congenital and postnatal CMV. CMV-specific CD8 T cells could be detected in even the youngest children, suggesting that these cells can develop early in life. In contrast, CMV specific CD4 T cells were low or absent in the youngest children but increased slowly with age.</p>

Células dendríticas (DCs) são células do sistema imunológico muito importantes no processo de indução de imunidade, capazes de conectar respostas imunes inata e adquirida e levar à ativação de células T e B. Recentemente demonstrou-se que é possível direcionar antígenos diretamente para as DCs in vivo através da administração de baixas doses de uma proteína recombinante híbrida fusionada a um anticorpo monoclonal específico para receptores presentes na superfície destas células. Dois dos anticorpos monoclonais utilizados tem a capacidade de ligar-se aos receptores endocíticos DEC205 e DCIR2 presentes na superfície de duas sub-populações distintas de DCs.Construiu-se anticorpos híbridos em fusão com os genes que codificam a proteína MSP-119 presente na superfície das formas merozoítas de P.yoelii e P.vivax. Ensaios de imunização mostraram que o anticorpo anti-DEC fusionado a qualquer das duas proteínas foi capaz de induzir principalmente uma resposta imune celular quando administrado na presença de diferentes adjuvantes. Já a resposta imune humoral foi modulada dependendo de várias combinações. / Dendritic cells (DCs) are cells of the immune system very important in the process of induction of immunity. They are able to connect innate and acquired immune responses and lead to activation of T and B cells. Recently it was shown that it is possible to target antigens directly to DCs in vivo by the administration of low doses of a recombinant hybrid protein consisting of a monoclonal antibody specific for receptors present on the surface of these cells fused with the antigen of interest. When these hybrid antibodies were injected in animals in the presence of a DC maturation stimulus, strong immune response against different antigens was obtained. Two of the monoclonal antibodies used have the ability to bind to either the DEC205 or the DCIR2 endocytic receptors present on the surface of two distinct DC sub-populations. In this work, we constructed hybrid antibodies fused with the sequence encoding the MSP-119 protein present on the surface P. yoelii and P. vivax merozoites. Most antibodies were successfully produced and maintained their ability to bind to their respective receptors. Immunization trials showed that the anti-DEC antibody fused to any of the two proteins was able to induce mainly a cellular immune response when administered in the presence of adjuvants. On the other hand, the humoral immune response depends of some combinations.

Linfócitos T CD4+ tem a capacidade de diferenciação em várias subpopulações, como Th1, com habilidades distintas para o combate das infecções. Uma vez que estas células exerceram suas funções efetoras, é necessária a retração das populações para restauração da homeostase do sistema imunológico, o que pode acorrer por morte celular induzida por ativação (AICD). Baseado em dados obtidos anteriormente por nosso grupo de pesquisa, o presente estudo buscou investigar se a PGE2 protegeria linfócitos T CD4+ diferenciados in vitro, da mesma forma que protegeu hibridomas DO11.10 da AICD. Para isso, utilizamos linfócitos T CD4+ de baço total ou purificados de camundongo C57Bl/6 selvagem e polarizados para Th1, na presença de anti-CD3, anti-CD28 e citocina IL-12 por 4 dias. Observamos que, tanto em células CD4+ purificadas quanto CD4+ de baço total, as células Th1 não foram protegidas do processo de AICD pela PGE2, sugerindo que uma proteção não seja vantajosa quando a célula já se encontra em estágios avançados de seu ciclo, evitando o desenvolvimento de autoimunidades. / CD4+ T cells have the ability to differentiate into several subsets, such as Th1, with distinct abilities to fight infections. Once these cells exerted their effector functions, their elimination is necessary to restore the immune system homeostasis, which may occur by activation-induced cell death (AICD). Based on data previously obtained by our research group, this study aimed to investigate whether PGE2 protects in vitro differentiated CD4+ T cells, the same way that it protected DO11.10 hybridomas from AICD. To assess this, we used CD4+ T cells from total splenocytes or purified CD4+ T lymphocytes from C57Bl/ 6 wildtype mice, polarized to Th1 in the presence of anti-CD3, anti-CD28 and IL-12 for 4 days. We observed that the generated Th1 cells, in both conditions of purified CD4+ T cells or the ones from total splenocytes, were not protected from the process of AICD by PGE2, suggesting that this protection is not advantageous when these cells are already in advanced stages of their life cycle, thus avoiding the development of autoimmune diseases.