Stimulation of CD40 on APCs through CD40L expressed on helper CD4+ T cells activates and “licenses” the APCs to prime CD8+ T cell responses. While other stimuli, such as TLR agonists, can also activate APCs, it is unclear to what extent they can replace the signals provided by CD40-CD40L interactions. In this study, we used an adoptive transfer system to re-examine the role of CD40 in the priming of naïve CD8+ T cells. We find an approximately 50% reduction in expansion and cytokine production of TCR-transgenic T cells in the absence of CD40 on all APCs, and on dendritic cells in particular. Moreover, CD40-deficient and CD40L-deficient mice fail to develop endogenous CTL responses after immunization and are not protected from a tumor challenge. Surprisingly, the role for CD40 and CD40L are observed even in the absence of CD4+ T cells; in this situation, the CD8+T cell itself provides CD40L. Furthermore, we show that although TLR stimulation improves T cell responses, it cannot fully substitute for CD40. We also investigated whether CD40-CD40L interactions are involved in the generation, maintenance, and function of memory CD8+ T cells. Using a virus infection system as well as a dendritic cell immunization system, we show that the presence of CD40 on DCs and other host APCs influences the survival of activated effector cells and directly affects the number of memory CD8+ T cells that are formed. In addition, memory CD8+ T cell persistence is slightly impaired in the absence of CD40. However, CD40 is not required for reactivation of memory CD8+ T cells. It seems that CD40 signals during priming also contribute to memory CD8+ T cell programming but this function can be independent of CD4+T cells, similar to what we showed for primary responses. Altogether, these results reveal a direct and unique role for CD40L on CD8+ T cells interacting with CD40 on APCs that affects the magnitude and quality of primary as well as memory CD8+ T cell responses.

Dengue virus (DENV) infects 50-100 million people worldwide every year and is the causative agent of dengue fever (DF) and the more severe dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). There are four genetically and immunologically distinct DENV serotypes (DENV-1, DENV-2, DENV-3, and DENV-4). Evidence suggests that an increased risk for DHF/DSS during secondary infection with a heterologous DENV serotype is due to an immunopathological response mediated by serotype-cross-reactive memory T cells from the primary infection. Furthermore, epidemiological studies have shown that the sequence of infection with different DENV serotypes affects disease severity. Though much has been learned from human studies, there exist uncontrollable variables that are intrinsic in this system such as genetic factors and unknown infection histories. These factors can skew experimental results, making interpretations difficult. Therefore, a murine model to study the immunologic aspects of sequential dengue infections would be an asset to the field of dengue research. To examine the effect of sequential infection with different DENV serotypes on the CD8+ T cell response, we immunized Balb/c mice with a primary DENV infection on day 0 and subsequently challenged with a heterologous secondary DENV infection on day 28. We tested all possible sequences of infection with the four serotypes. We analyzed the T cell response to two previously defined epitopes on the DENV E (Ld-restricted) and NS3 (Kd-restricted) proteins. Using ELISPOT and intracellular cytokine staining, we measured the frequency of T cells secreting IFNγ and TNFα in response to stimulation with these epitopes during three phases: acute primary, acute secondary, and the memory phase after primary infection. We found that the T cell response in heterologous secondary infections was higher in magnitude than the response in acute primary infection or during the memory phase. We also found that the hierarchy of epitope specific responses, as measured by IFNγ secretion, was influenced by the sequence of infections. The adoptive transfer of immune serum or immune splenocytes suggested that memory T cells from the primary infection responded to antigens from the secondary infection. In vitroexperiments with T cell lines generated from mice with primary and secondary DENV infections suggested the preferential expansion of crossreactive memory T cells. In testing all of the different possible sequences of infection, we observed that two different sequences of infection (e.g., DENV-2 followed by DENV-1 versus DENV-2 followed by DENV-3) resulted in differential CD8+ T cell responses to the NS3 peptide even though both secondary infection serotypes contain the identical peptide sequence. To investigate this phenomenon, we examined the role of CD4+ T cell help on the memory CD8+ T cell response. We found that CD4+ T cell cytokine responses differ depending on the sequence of infection. In addition, it was also shown that crossreactivities of the CD4+ T cell response are also sequence-dependent. Moreover, denguespecific memory CD4+ T cells can augment the secondary CD8+ T cell response. Taken together, we demonstrated that this serotype sequence-dependent phenomenon is the result of differential help provided by cross-reactive memory CD4+T cells. The findings in this novel mouse model support the hypothesis that both CD4+ and CD8+ serotype-cross-reactive memory T cells from a primary dengue virus infection alter the immune response during a heterologous secondary dengue virus infection. These data further elucidate potential mechanisms whereby the specific sequence of infection with different dengue virus serotypes influences disease outcomes in humans.

Made available in DSpace on 2015-07-22T20:50:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-04-29. Added 1 bitstream(s) on 2015-08-11T03:25:40Z : No. of bitstreams: 1 Publico-062a.pdf: 992519 bytes, checksum: 41750ff4e6e38ad6517d6c7541049844 (MD5). Added 1 bitstream(s) on 2015-08-11T03:25:40Z : No. of bitstreams: 2 Publico-062a.pdf: 992519 bytes, checksum: 41750ff4e6e38ad6517d6c7541049844 (MD5) Publico-062b.pdf: 1669897 bytes, checksum: 5ca81b8b1f9a75f45902de9ce4bc36f7 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O GB vírus C (GBV-C) está constituído por uma fita única de RNA de polaridade positiva e pertence à família Flaviviridae. Possui uma seqüência e organização genómica parecida ao vírus da hepatite C, (HCV). A infecção pelo GBV-C não foi associada a nenhuma patologia, embora, na co infecção com o HIV, tenha sido associada a uma sobrevida maior e retardo no desenvolvimento da imunodeficiência. O efeito benéfico do GBV-C parece ser mediado por alterações na resposta imune celular; contudo, os possíveis mecanismos para explicar esse efeito ainda não foram esclarecidos. Neste trabalho investigamos a freqüência e características genotípicas assim como o impacto da infecção pelo GBV-C nos indivíduos infectados pelo HIV-1. No primeiro manuscrito examinamos os conhecimentos descritos na literatura referentes à coinfecção e propusemos algumas hipóteses para explicar esses efeitos. Posteriormente, descrevemos a taxa de infecção, a prevalência, incidência e características genotípicas do GBV-C nesta população. Assim, uma considerável freqüência de infecção pelo GBV-C foi observada e a análise filogenética dos isolados de GBV-C mostraram ser do genótipo 1 e 2. Foi observada também uma correlação inversa entre a carga viral do GBV-C e a carga viral do HIV na inclusão e um ano depois, assim como uma correlação positiva, mas não significativa, entre a carga viral do GBV-C e a contagem de linfócitos T CD4+. Finalmente, avaliamos o efeito da viremia pelo GBV-C na ativação celular em recém infectados pelo HIV-1. Os pacientes foram agrupados em GBV-C viremicos e não virémicos e foram avaliados para a contagem de linfócitos T, marcadores de ativação celular e carga viral do GBV-C e HIV-1. Foram realizadas análises de univariada e multivariada para identificar variáveis associadas com ativação celular. Demonstramos que a viremia pelo GBV-C foi correlacionada com uma diminuição da ativação celular nos indivíduos HIV positivos e este efeito mostrou se independente da carga viral do HIV. Assim, esta associação entre a replicação do GBV-C e menor ativação celular pode explicar, pelo menos em parte, a proteção conferida pelo GBV-C na progressão da doença nos indivíduos infectados pelo HIV-1. / GB virus C (GBV-C) is a single stranded positive sense RNA virus, which is a member of the Flaviviridae. It has a close sequence homology and genomic organization to hepatitis C virus (HCV). No disease has been associated with GBV-C infection but coinfection with human immunodeficiency virus (HIV) leads to improved morbidity and mortality for the HIV infected subjects. The mechanism of the beneficial effect of GBV-C appears to be mediated by alterations in the cellular immune response. In this study we investigated the frequency and genotyping characteristics as well as the impact of the GBV-C infection among recently HIV-1 infected individuals. In the first manuscript we examined the current knowledge concerning this co-infection and developed hypotheses to explain its effects. Subsequently, we described the rate of infection, the prevalence, incidence and genotypic GBV-C characteristics in this population. In that regard, a considerable frequency of GBV-C infection was observed and the phylogenetic analysis of the GBVC isolates revealed the predominance of genotypes 1 and 2. Also, it was observed an inverse correlation between GBV-C load and HIV-1 load at the enrollment and after one year of follow-up, and a positive, but not statistically significant, correlation between GBV-C load and CD4+ T lymphocyte counts. Finally, we have investigated the effect of GBV-C viremia on T cell activation in early HIV-1-infection. The volunteers were enrolled into two groups: GBV-C viremic and non viremic, all co-infected with HIV-1. They were evaluated for T cell counts, cellular activation markers, GBV-C RNA detection, and HIV-1 viral load. Non-parametric univariate and multivariate analyses were carried out to identify the variables associated with cellular activation. We demonstrated that the GBV-C viremia is correlated with a lower T cell activation in HIV-1-infected individuals and this effect was independent of HIV-1 viral load. The association between GBV-C replication and lower T-cell activation may explain, at least in part, the protection conferred by this virus against disease progression to immunodeficiency in HIV-1-infected patients. / TEDE / BV UNIFESP: Teses e dissertações

O transplante renal é atualmente o tratamento de escolha para pacientes com doença renal crônica em estágio 5, devido aos seus melhores resultados na morbimortalidade e melhor qualidade de vida dos pacientes, quando comparado com o tratamento dialítico. No entanto, apesar desses resultados positivos, a sobrevida dos enxertos renais em longo prazo não se modificou. As principais causas de falências tardias do transplante renal são as alterações crônicas do enxerto, caracterizadas por componentes de rejeição crônica e efeitos nefrotóxicos relacionados aos inibidores da calcineurina. O desenvolvimento de estratégias visando modular o sistema imunológico, interferindo no balanço entre mecanismos efetores e reguladores, capazes de induzir a aceitação do órgão (tolerância) seria a melhor alternativa para este cenário. No entanto, os mecanismos imunológicos envolvidos no processo da imunorregulação são pouco compreendidos, o que dificulta a identificação de casos tolerantes e a definição de estratégias para a sua modulação. Dentre as possíveis moléculas envolvidas no processo de imunomodulação, destacam-se a Forkhead Box P3 (FOXp3), marcador de células reguladoras e a enzima indoleamina 2,3 dioxigenase (IDO), reconhecida recentemente como tendo função central na tolerância materno-fetal. No presente estudo, foram utilizadas técnicas de imunohistoquímica para identificar linfócitos T efetores (CD3+), FOXp3 e IDO em biópsias de aloenxerto renal e correlacionar sua expressão com a evolução clínica do enxerto 12 meses após a biópsia. A relação entre células reguladoras e efetoras foi avaliada pelas relações FOXp3/CD3 e IDO/CD3. Devido à limitação do reconhecimento e do diagnóstico de casos de tolerância, só foi possível analisar a expressão destes marcadores em 1 único caso de paciente tolerante. Por outro lado, o estudo do perfil da expressão destes marcadores em outras situações clínicas deve contribuir para a melhor compreensão dos mecanismos envolvidos. Neste contexto, no presente estudo foram analisadas 63 biópsias de enxerto renal em diferentes situações clínicas: enxerto Sem Rejeição (SemRA; n=13), Rejeição Aguda (RA; n=21) e lesões crônicas (LC; n=29) além de 1 caso de paciente com diagnóstico clínico de tolerância operacional (Tolerante; n=1). Este paciente evoluiu com disfunção do enxerto, reiniciou terapia dialítica com a descontinuação do tratamento imunossupressor e após 2 anos em programa de hemodiálise, recuperou a função do enxerto, sendo, então, submetido a biópsia do enxerto renal. As biópsias incluídas foram subdivididas de acordo com a Classificação de Banff-09. As rejeições agudas mediadas por linfócitos T foram classificadas em RA-Banff I (n=15) e RA-Banff II (n=6). Os casos com Lesões Crônicas também foram subdivididos de acordo com a Classificação de Banff-09 em Fibrose intersticial/Atrofia tubular (FIAT; n=15) e Rejeição Crônica Ativa (RCA; n=14). RESULTADOS: analisado isoladamente, o caso Tolerante apresentou um número expressivo de células CD3+ (814 cel/mm2) e FOXp3+ (100,9 cel/mm2), assim como elevada relação FOXp3/CD3 (12,4x102).No entanto, apresentou uma baixa expressão de IDO (0,41% área marcada).Nos casos do grupo RA o número de células CD3+. foi significativamente maior que em LC e SemRA (973±127 cel/mm2; 242±43 cel/mm2 e 0,7 ± 0,4 cel/mm2, respectivamente; p<0,001 vs LC e p<0,0001 vs SemRA). Células CD3+ foram detectadas em todos os compartimentos estudados: interstício, túbulos, vasos, e glomérulos no grupo RA e no grupo LC. Comparando os grupos, houve predomínio de células CD3+ no interstício (p<0,0001) do grupo RA. Na subanálise segundo a Classificação de Banff-09, não houve diferença entres os subgrupos de RA na análise de células CD3+ por compartimentos. Por outro lado, na análise do grupo LC, no subgrupo RCA foram detectadas significativamente mais células CD3+ que em FIAT no interstício (322±66 cel/mm2 vs 145±32 cel/mm2; p<0,05) e nos túbulos (30,7±10 cel/mm2 vs 6±2 cel/mm2; p<0,05). O número de células FOXp3+ foi significativamente maior nos casos do grupo RA (43±10 cel/mm2) comparado com LC e SemRA (20±4 cel/mm2 e 0,1±0,1 cel/mm2, respectivamente; p<0,05 vs LC e p<0,0001 vs SemRA). Na distribuição por compartimentos, tanto em RA quanto em LC houve a predominância de células FOXp3+ no interstício, porém não houve diferença estatística entre os 2 grupos. Na análise de células FOXp3+ por compartimentos do grupo LC segundo a Classificação de Banff-09, não houve diferença entres os subgrupos. A relação FOXp3/CD3 foi significativamente maior no grupo LC que no RA (17±5 vs 5±1; p<0,05). Na análise do grupo LC, a relação FOXp3/CD3 foi significativamente maior em FIAT que em RCA (25±8 vs 8±2; p<0,05). A análise da expressão de IDO não revelou diferença na comparação dos grupos SemRA, RA e LC. Não houve diferença também na expressão de IDO, tanto entre os grupos Banff I e Banff II, quanto entre os grupos FIAT e RCA. A relação IDO/CD3, foi significativamente maior no grupo LC do que no grupo RA (18±6 vs 3±1; p<0,05). Apesar da presença de células FOXp3+ ter sido maior nos casos com diagnóstico de rejeição aguda como descrito na literatura, não houve correlação da sua expressão com uma maior função do enxerto na análise de 12 meses após a biópsia, nem com a sobrevida do enxerto em 12 meses. Nos casos com diagnóstico de lesões crônicas, a maior relação FOXp3/CD3 se correlacionou negativamente com a função do enxerto 12 meses após a biópsia. A expressão de IDO também não se correlacionou com uma melhor função, nem com a sobrevida do enxerto na análise em 12 meses após a biópsia. A análise dos resultados apresentados sugere o envolvimento dos marcadores estudados na resposta inflamatória ocasionada pelo aloreconhecimento, uma vez que estão presentes em cenários imunológicos distintos, aparentemente, mediando o dano tecidual no microambiente do aloenxerto. No entanto, não há dados o suficiente para apontar para um papel das células FOXp3+ e da IDO no desenvolvimento de tolerância ao aloenxerto no presente estudo. Concluindo, ainda não está claro o quanto a presença de Tregs e IDO limitam os processos de rejeição/cronificação ou participam desses processos, sendo sua presença ainda controversa / Currently, kidney transplantation is choice therapy for patients with chronic kidney disease in stage 5, due to their good results in morbidity and improved quality of life compared with dialysis treatment. However, despite these positive results, renal grafts survival in the long term has not changed. The major cause of failures in long-term in kidney transplant are chronic graft changes, characterized by chronic rejection and components related to the nephrotoxic effects of calcineurin inhibitors. The development of strategies to modulate the immune system interfering with the balance between regulatory and effector mechanisms, capable of inducing organ acceptance (tolerance), would be the excellent alternative in this scenario. However, the immunological mechanisms involved in the immunoregulation are poorly understood, hindering to identify cases tolerant as well as developing strategies for their modulation. Within the possible molecules involved in immunomodulation, stand out the Forkhead Box P3 (FOXp3), a marker of regulatory cells, and the enzyme indoleamine 2,3 dioxygenase (IDO), recently recognized by their role in maternal-fetal tolerance. In this present study, we used immunohistochemical techniques to identify T lymphocytes (CD3+), FOXp3 and IDO in renal allograft biopsies and to correlate its expression with graft function 12 months after the biopsy procedure. The relationship between regulatory and effector cells was analysed by FOXp3/CD3 and IDO/CD3 ratios. Due to limited recognition and diagnosis of tolerance cases, only was possible to analyze the expression of these markers in one single case of tolerant patient. On the other hand, the study of the expression of these markers in other clinical situations, should contribute to a better understanding of the mechanisms involved. In this context, the present study analyzed 63 renal allograft biopsies in different clinical situations: no graft rejection (NR, n = 13), acute rejection (AR, n = 21) and chronic injury (CI, n = 29). In addition, one patient with clinical operational tolerance diagnosis (tolerant, n = 1) was analyzed. This patient developed graft dysfunction, restarted dialysis discontinuation of immunosuppressive treatment. After 2 years on dialysis therapy, recovered graft function and then was submitted to renal allograft biopsy. The biopsies included in this study were subdivided according to the Banff-09 classification. The acute rejection mediated by T lymphocytes was classified in Banff I (n = 15) and Banff II (n = 6). Cases that showed chronic injury were also subdivided according to the Banff-09 classification in Interstitial Fibrosis/Tubular Atrophy (IFTA, n = 15) and Chronic Rejection (CR, n = 14). Results: Analyzed separately, the tolerant case showed an expressive number of CD3+ cells (814 cells/mm2) and FOXp3+ cells (100.9 cells/mm2). Also, expressive FOXp3/CD3+ ratio (12,4x102) and low IDO expression (0.41% area).In AR group the number of CD3+ cells was significantly higher compared with CI and NR groups (973 ± 127 cells/mm2; 242 ± 43 cells/mm2 and 0.7 ± 0.4, cells/mm2, respectively; p<0.001 vs CI and p <0.0001 vs NR). In AR and CI groups CD3+ cells were detected in all compartments studied: interstitium, tubules, vessels and glomeruli. Comparing the groups, there was a predominance of CD3+ cells in the interstitium (p<0.0001) of AR group. No difference was observed between Banff I and Banff II subgroups analysis of CD3+ in the compartments. On the other hand, in the CR subgroup analysis was detected in significantly higher of CD3+ cells in the interstitium compared with IFTA (322 ± 66 cells/mm2 vs. 145 ± 32 cells/mm2, p<0.05) and in tubules (30,7±10 cells/mm2 vs. 6±2 cells/mm2, respectively; p<0.05). The number of FOXp3+ cells was significantly higher in the AR group (43±10 cells/mm2) compared with CI and NR (20±4 cells/mm2 and 0.1±0.1 cells/mm2, respectively; p<0,05 vs CI and p<0,0001 vs NR). The distribution of compartments, both AR and in CI predominated FOXp3+ cells in the interstitium, but there was no statistical difference between the 2 groups. In the FOXp3+ cells analysis, CI do not showed difference between subgroups in the compartments. The relationship FOXp3/CD3 was significantly higher in AR group compared in the CI group (17 ± 5 vs. 5 ± 1; p<0.05). In the CI group analysis, FOXp3/CD3 ratio was significantly higher in IFTA compared with CR (25±8 vs 8±2; p<0.05). IDO expression analysis shows no difference when compared NR, AR and CI groups. No difference in IDO expression analysis in Banff I compared with Banff II, and IFTA compared with CR was observed. The relationship of IDO/CD3, was significantly higher in the CI group when compared with AR group (18±6 vs 3±1, p<0.05). Despite the presence of FOXp3+ cells was higher in cases with a diagnosis of acute rejection as described in the literature, there was no correlation of its expression with improved graft function in the 12 months analysis after the biopsy procedure, as well as with graft survival in 12 months. In cases with a diagnosis of chronic injuries, FOXp3/CD3 ratio was negatively correlated with graft function 12 months after the biopsy procedure. The analysis of these results led us to speculate about the involvement of these markers in the inflammatory response, mediating the tissue damage in the microenvironment of the graft, once it is immunological distinct scenarios, however, in this study, there is no enough data to point to a role in development of tolerance. In conclusion, it is unclear how the presence of Tregs and IDO limit the allograft rejection/chronicity or participate in this process, and their presence is still controversial

Orientadores: Patrícia Maria Bergamo Favaro, Sara Teresinha Olalla Saad / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-21T08:21:12Z (GMT). No. of bitstreams: 1 Lopes_MatheusRodrigues_M.pdf: 3896765 bytes, checksum: d056b823ef7d5306e932f125ae5b6eaa (MD5) Previous issue date: 2012 / Resumo: As síndromes mielodisplásicas (SMD) são um grupo heterogêneo de doenças caracterizadas por hematopoese ineficaz e risco de progressão para leucemia mieloide aguda (LMA). SMD de baixo de risco é caracterizada por um aumento de apoptose na medula óssea e alterações clínicas com perfil autoimune, enquanto que na SMD de alto risco há uma evasão imune, baixa apoptose e danos secundários ao DNA, contribuindo para a progressão para LMA. Essas evidências, junto com os dados de terapia imunossupressora em pacientes com SMD, sugerem o papel do sistema imune na progressão desta doença. Entretanto, o papel do sistema imune não é claro, e estudos que abordem o perfil das células T são importantes para o melhor entendimento da patogênese da SMD. Formin-like 1 (FMNL1) pertence à família de proteínas formina, indispensáveis para muitos processos fundamentais actina-dependentes. FMNL1 é restritamente expressa em células derivadas de linhagem hematopoética e superexpressa em células neoplásicas hematopoéticas malignas. Recentemente, foi descrito que FMNL1 está envolvida no processo de citotoxicidade de células CD8+. Desse modo, estudar a expressão de FMNL1 tanto nos linfócitos como nas células da MO dos pacientes com SMD, poderia contribuir para o melhor entendimento do papel dessa nova proteína neste modelo de neoplasia hematológica. No presente estudo, foi observada uma diminuição significativa na contagem absoluta de linfócitos periféricos no grupo SMD, após ajuste para idade, quando comparada com o grupo de doadores saudáveis (controle). Entretanto, houve um aumento da frequência de células CD3+, resultante do aumento significativo das subpopulações de células CD3+CD4+ no grupo de alto risco e CD3+CD8+ no grupo de baixo risco, de acordo com as classificações FAB e WHO. A razão CD4:CD8 encontrou-se aumentada no grupo de alto risco comparado com o de baixo risco. Dependência transfusional foi correlacionada positivamente com a porcentagem de CD3+CD4+, enquanto que a idade dos pacientes correlacionou-se de forma negativa com a porcentagem de CD3+ e CD3+CD8+. Os níveis de expressão de FOXP3, nas células CD3+ de sangue periférico, foram significativamente menores no grupo de baixo risco quando comparado com o grupo controle, e esse padrão se repetiu para a expressão de IL10. A quantificação dos transcritos de IL10 correlacionou-se negativamente com a porcentagem de células CD3+CD8+. Em conclusão, evidenciamos que pacientes com SMD apresentaram um menor número de linfócitos, porém com a frequências das células T CD3+, CD3+CD4+ e CD3+CD8+ aumentadas. Os pacientes de baixo risco apresentaram uma diminuição da expressão de FOXP3 e de IL10, quadro característico de um microambiente apoptótico e inflamatório. Já no grupo de alto risco, a expressão de FOXP3 e de IL10 aumenta em relação ao grupo de baixo risco. É interessante ressaltar que nos pacientes com SMD houve uma correlação entre o aumento da expressão de IL10 e a diminuição das células T CD3+CD8+, sugerindo a contribuição das Tregs na progressão da doença através da produção de IL10. A análise da expressão de FMNL1 em células CD3+ de sangue periférico não denotou diferenças significativas entre os pacientes com SMD e o grupo controle. Entretanto observou-se uma correlação positiva entre a expressão de FMNL1 e o número de células CD3+CD4+ e ambos com a dependência transfusional. Quanto à expressão de FMNL1 em amostras de MO, houve uma expressão significativamente menor nos pacientes com SMD quando comparado com as células de doadores normais, além de uma correlação negativa entre FMNL1 e número de citopenias. Usando modelos de linhagens celulares hematopoéticas para a diferenciação, observou-se um aumento significativo na expressão gênica e protéica de FMNL1 durante a diferenciação megacariocítica. Esses resultados sugerem a participação de FMNL1 na ativação de linfócitos CD4+ no sangue periférico e na diferenciação hematopoética na medula óssea / Abstract: Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by ineffective hematopoiesis and risk of progression towards acute myeloid leukemia. Low-risk MDS is characterized by increased apoptosis in the bone marrow (BM), with a clinical autoimmune profile, whereas in high-risk MDS an immune evasion, low apoptosis and secondary DNA damage occurs, contributing to the progression of AML. This evidence, together with the data of immunosuppressive therapy in patients with MDS, suggests a role of the immune system in the progression of this disease. However, this role of the immune system is remains unclear, and studies that address the profile of T cells are important for a better understanding of the pathogenesis of MDS. Formin-like 1 (FMNL1) belongs to the family of proteins formina indispensable for many fundamental processes in actin-dependent. FMNL1 is strictly expressed in hematopoietic lineage derived cells, and overexpressed in malignant hematopoietic neoplastic cells. FMNL1 has recently been reported to be involved in the cytotoxicity of CD8+ cells. Thus, studies on the expression of FMNL1, both in lymphocytes and BM cells of MDS patients, could contribute to a better understanding of the role of this protein in this new model of hematologic malignancy. In the present study, we observed a significant decrease in absolute peripheral lymphocyte counts in the MDS group, after adjusting for age, compared with the healthy donor group (control). However, there was an increased frequency of CD3+, resulting in a significant increase of the CD3+CD4+ subpopulation in high risk and CD3+CD8+ in MDS low risk, according to FAB and WHO classifications. CD4:CD8 ratio was increased in the high risk when compared to the low risk group. Transfusion dependence was positively correlated with the percentage of CD3+CD4+, whereas the age of patients correlated negatively with the percentage of CD3+ and CD3+CD8+. The expression levels of FOXP3, in peripheral blood CD3+ cells, was significantly lower in the low risk group compared to controls and this pattern was repeated for the expression of IL10. Interestingly, IL10 transcripts correlated negatively with the percentage of CD3+CD8+. In conclusion, we found that patients with MDS had a lower lymphocyte number, however presented an increased frequency of CD3+ and CD3+CD8+ T cells. Our low risk patients showed a decreased expression of FOXP3 and IL10, characteristic of apoptotic and inflammatory microenvironment. In the high risk group, the expression of FOXP3 and IL10 was normal. Interestingly, there was a correlation between increasing expression of IL10 and reduction of CD3+CD8+ T cells in patients, suggesting the contribution of Treg in disease progression due to IL10 production. Analysis of FMNL1expression in CD3+ cells of peripheral blood showed no significant differences between patients with MDS and the control group. However, there was a positive correlation between FMNL1 expression and the number of CD3+CD4+, and both were transfusion dependence. FMNL1 expression in BM samples was significantly lower in MDS patients when compared with cells from normal donors, and there was a negative correlation between FMNL1 and number of cytopenias. Using models of hematopoietic cell lineages for differentiation, we observed an increase in gene and protein expression of FMNL1 during megakaryocytic and granulocytic differentiation. These results suggest the participation of FMNL1 in the activation of CD4+ lymphocytes in peripheral blood and bone marrow hematopoietic differentiation / Mestrado / Fisiopatologia Médica / Mestre em Ciências

Taquizoítos de T. gondii esterilizados por radiação ionizante é uma vacina interessante para induzir uma imunidade semelhante à infecção, mas sem a formação de cistos. Neste estudo avaliamos as populações celulares do sangue e do baço induzidas pela imunização, a resposta imune humoral, celular e a proteção após desafio com parasitas viáveis. Camundongos foram imunizados com taquizoítos de T. gondii irradiados por v.o. ou i.p.. Os animais foram desafiados com 10 cistos da cepa ME-49 ou VEG por via oral e apresentaram altos níveis de proteção com baixa carga parasitária. Camundongos imunizados por i.p. e v.o. apresentaram anticorpos específicos no soro e o aumento das populações de células B, plasmócitos, células TCD4+ e TCD8+ tanto no sangue como no baço. As células esplênicas de camundongos imunizados por i.p. mostraram a produção de IL-10, IFN-&#947; e IL-4. Células TCD4+ e células B do baço de camundongos imunizados por i.p. proliferaram após a estimulação com antígeno. A imunização com esse modelo vacinal induziu uma resposta imune mediada com células B, TCD4+ e TCD8+, com aumento da resposta imune humoral e celular que são necessárias para proteção do hospedeiro após uma infecção. Essa resposta imune induzida é uma resposta semelhante a uma infecção natural, sendo assim o desenvolvimento de vacinas utilizando a radiação ionizante como uma ferramenta, pode ser um modelo atrativo e eficiente para testar novos imunógenos no futuro. / Tachyzoites of T. gondii sterilized by ionizing radiation is an interesting vaccine for inducing immunity to infection similarly but without the formation of cysts. In this study we evaluated the cell populations from blood and spleen induced by immunization, the humoral immune response, cellular and protection after challenge with viable parasites. Mice were immunized with irradiated tachyzoites of T. gondii by v.o. or i.p.. The animals were challenged with 10 cysts of the ME-49 or VEG strain orally and showed high levels of protection with low worm burden. Immunized mice by i.p. and v.o. present specific antibodies in the serum and increased populations of B cells, plasma cells, CD4+ and CD8+ T cells in blood and spleen. The spleen cells of immunized mice by i.p. showed the production of IL-10, IFN-&#947; and IL-4. CD4+ T cells and B cells in the spleen of immunized mice i.p. proliferated upon stimulation with antigen. The immunization with this vaccine model induced an immune response mediated by B cells, CD4+ and CD8+ with increased humoral and cellular immune response are necessary for host protection after infection. This induced immune response is a response similar to natural infection, therefore the development of vaccines using ionizing radiation as a tool, can be an attractive and efficient model for testing new immunogens in the future.

Itk and Rlk are members of the Tec kinase family of non-receptor protein tyrosine kinases that are preferentially expressed in T cells. Numerous previous studies have demonstrated that these proteins play an important a role in the regulation of signalling processes downstream of TCR activation in CD4+ T cells, particularly in the phosphorylation of PLCγl. In addition, Itk and Rlk have both been shown to be important for CD4+ T cell development, differentiation, function and homeostasis following TCR activation. In the absence of Itk and Rlk, CD8+ SP thymocytes and T cells develop a memory/previously activated phenotypic profile, however, very little is known about the influence of Itk and Rlk on CD8+ T cell development and function. This study illustrates a previously unappreciated role for Itk and Rlk in the regulation of cytokine signals during CD8+ SP thymocyte maturation, and in the development of the memory CD44hi profile of Itk -/- and Itk -/- Rlk -/- CD8+ SP thymocytes and CD8+ T cells. This study also provides the first detailed study of the role of loss of Itk and particularly both Itk and Rlk in CD8+ signalling and function and shows that these Tec kinase family members play an important role in the maintenance of CD8+ T cell fitness and function, particularly in the ability of CD8+ T cells to accumulate in response to infection. Collectively, my studies demonstrate a critical role for Itk and Rlk in the generation of optimal CD8+ T cell responses. They also raise the novel observation that these proteins may be involved on the regulation of cytokine signals in T cells.

T lymphocytes are essential components of the immune system and as such are continually regulated by a variety of factors. Every step of their development, survival and function is tightly monitored to ensure their ability to recognize most foreign agents and mount adaptive immune responses during pathogenic infections, while remaining tolerant to self-antigens. Among the many factors that participate in the regulation of T cell development and function are the cytokines. Cytokines that signal through the common gamma (γс) chain and the Janus kinase 3 (Jak3) include IL-2, -4, -7, -9, -15, and -21 and have been implicated in the regulation of every stage in the life of a T cell. Therefore, it is not surprising that mutations in the γс chain or Jak3 lead to a SCID condition in humans and mice. Specifically, Jak3-deficient mice are characterized by a reduction in thymic cellularity and dysregulated T cell homeostasis. They have an expansion of memory-like CD4+ mature T cells and an almost complete absence of mature CD8+ T cells. By investigating the TCR repertoire of CD4+ T cells in the thymus and spleen of Jak3-/- mice, I deduced that the CD4+ T cell activation and expansion is TCR-specific and takes place in the periphery of the mice. After crossing Jak3-deficient mice to Bcl-2 transgenic mice I showed that the developmental block observed in Jak3-/- mice could not be rescued by the anti-apoptotic factor, despite the fact that its expression did increase, slightly, the total numbers of developing thymocytes. The enforced expression of Bcl-2 was also not sufficient to revert the dysregulation of T cell homeostasis in Jak3-/- mice. Finally, in order to further understand the role played by γс cytokines during T cell function, I investigated the ability of mature Jak3-/- CD8+ T cells to become activated and differentiate into effector cells in response to a viral infection. My results indicate that CD8+ T cells are activated and proliferate in response to a viral infection, but their survival, as well as their ability to proliferate and differentiate into effector cells are greatly impaired, resulting in the inability of Jak3-deficient mice to mount a protective response.

The focus of this dissertation is the role of specific CD8+ T cells in the pathogenesis of a highly lethal human viral disease, hantavirus pulmonary syndrome (HPS). HPS is a zoonotic disease caused by transmission of Sin Nombre virus (SNV) from chronically infected deer mice. In humans, this fulminant infection is characterized by lung capillary leakage, respiratory failure and cardiogenic shock. Individuals with HLA-B*3501 have an increased risk of developing severe HPS, and the majority of defined CD8+ T cell epitopes in SNV are presented by this HLA allele, suggesting that CD8+ T cell responses to SNV contribute to pathogenesis. We speculate that CD8+ T cell mediated immune responses to SNV antigens in pulmonary endothelial cells contribute to the pathology of HPS. Specifically, we hypothesize that there are quantitative and/or qualitative differences in SNV-specific CD8+ T cell responses in HPS patients with moderate vs. severe disease. In this dissertation I measured the frequencies of SNV-specific CD8+ T cells during acute HPS. Using HLA/peptide tetramers, I quantitated circulating SNV-specific CD8+ T cells of all the available HLA-B35+ patients with HPS caused by SNV. This is the first time hantavirus-specific T cells have been quantitated during acute infection. I report that between 2.9% and 44.2% of the CD8+ T cells were specific for the three SNV epitopes in combination during acute disease in the patients analyzed in this study. These levels are very high in comparison to the frequencies reported in the literature for other acute human viral infections. Furthermore, I report significantly higher frequencies of SNV-specific T cells in patients with severe HPS requiring mechanical ventilation (up to 44.2% of CD8+ T cells) than in moderately ill HPS patients hospitalized but not requiring mechanical ventilation (up to 9.8% of CD8+ T cells). These results imply that virus-specific CD8+ T cells contribute to HPS disease outcome. In this dissertation I also provide preliminary data on qualitative aspects of SNV-specific T cells. Analysis of the TCR repertoire of SNV-specific T cell lines isolated from the PBMC of acute HPS patients raises the possibility that SNV-specific T cells express a limited number of TCR Vβ alleles; however, this is quite speculative because it is based on the analysis of only seven CTL lines. Analysis of cytokine expression by the CTL lines in response to in vitro antigen-specific stimulation indicate that SNV-specific T cells are capable of secreting IFN-γ, TNF-α, and IL-13 upon stimulation. The data presented in this dissertation extend previous studies, which suggested a role for virus-specific T cells in HPS pathogenesis and support our hypothesis that virus-specific CD8+ T cells contribute to HPS disease outcome. The results of this study will be useful in the design of future therapeutic strategies for this emerging human pathogen. The conclusions of this study may also benefit the study of other human viral hemorrhagic fevers. Improved understanding of the mechanism of pathogenesis of severe viral zoonoses will result in better treatment and prevention strategies.

T cell vaccines against Mycobacterium tuberculosis (Mtb) and other pathogens are based on the principle that memory T cells rapidly generate effector responses upon challenge, leading to pathogen clearance. Despite eliciting a robust memory CD8+ T cell response to the immunodominant Mtb antigen TB10.4 (EsxH), we find the increased frequency of TB10.4-specific CD8+ T cells conferred by vaccination to be short-lived after Mtb challenge. To compare memory and naïve CD8+ T cell function during their response to Mtb, we track their expansions using TB10.4-specific retrogenic CD8+ T cells. We find that the primary (naïve) response outnumbers the secondary (memory) response during Mtb challenge, an effect moderated by increased TCR affinity. To determine whether the expansion of polyclonal memory T cells is restrained following Mtb challenge, we used TCRb deep sequencing to track TB10.4-specific CD8+ T cells after vaccination and subsequent challenge in intact mice. Successful memory T cells, defined by their clonal expansion after Mtb challenge, express similar CDR3b sequences suggesting TCR selection by antigen. Thus, both TCR-dependent and independent factors affect the fitness of memory CD8+ responses. The impaired expansion of the majority of memory T cell clonotypes may explain why some TB vaccines have not provided better protection.