Dengue virus infection affects the heart structurally and functionally. Clinical manifestations of cardiac complications secondary to dengue virus infection vary from self-limiting arrhythmias to severe myocardial infarction, leading to hypotension, pulmonary edema, and cardiogenic shock. However, we report a case of dengue hemorrhagic fever (DHF) complicated by a complete heart block. A female with DHF due to dengue virus serotype 2, presented to the emergency department with fever, headache, rash, and fatigue followed by an episode of syncope. She was found to have a third-degree atrioventricular block, with pulseless polymorphic ventricular tachycardia. Patient was resuscitated and a temporary trans-venous pacemaker was placed. She reverted back to normal sinus rhythm after 4 days of syncope and was subsequently discharged from the hospital after complete resolution of symptoms, without the need for a permanent pacemaker. Physicians are warranted to have high index of suspicion for dengue virus infection as an etiology in patients with acute cardiovascular compromise, especially in tropical areas.

Incidence of dengue fever (DF) has been estimated a 30 fold increase in the past 50 years. Clinical manifestations of DF range from a simple febrile illness with physical soreness to life-threatening dengue hemorrhagic fever (DHF). The need for a better classification of the severity in DEN infections has been proposed to clarify the immunopathogenesis for the prevention and management of serious DEN infections. We attempted to investigate whether different mechanisms involved in the varied manifestations of bleeding tendency and vascular leakage in DF. In a hospital-based study, we first compared clinical features as well as laboratory data including virus load, T helper (Th1/Th2) cytokines, and vascular leakage-related mediators between patients with DHF and DF. Moreover, we defined another class of patients associated with bleeding tendency but not fulfilled with DHF criteria, called DF w/B, for a further comparison. The virus load in blood was not significantly different among DF, DHF and DF w/B. DF patients had a higher Th1 cytokine, IFNr, expression (70.0 ¡Ó 10.7 vs. 33.1 ¡Ó 8.0 vs. 33.0 ¡Ó 7.1 pg/ml; DF vs. DF w/B, p = 0.009; DF vs. DHF, p = 0.002), and both DHF and DF w/B patients had a significantly higher IL-10 levels (14.3 ¡Ó 4.1 vs. 26.2 ¡Ó 3.3 vs. 26.0 ¡Ó 3.5 pg/ml; DF vs. DF w/B, p = 0.023; DF vs. DHF, p = 0.016) than DF patients. Both DHF and DF w/B patients also had a higher rate of secondary dengue infection (DF w/B vs. DHF vs. DF: 50.0%, 74.4% and 14.3%¡A p < 0.001). By contrast, DHF but not DF w/B patients had significantly higher vascular leakage-related mediators: sVCAM-1, PGE2 and TNF£\ levels than DF patients. Patients with DF w/B had a higher platelet counts (DF w/B vs. DHF: 66.0 ¡Ó 8.3 vs. 20.7 ¡Ó 2.1 x109/L, p < 0.001) but lower ALT levels than those with DHF (DF w/B vs. DHF: 56.3 ¡Ó 7.7 and 144.7 ¡Ó 20.5 IU/L). This study provides new insight to different immune mechanisms involved in patients with DF, DF w/B, and DHF. DF involves augmented Th1 reaction, and DF w/B involves altered Th2 reaction, but DHF involves both altered Th2 reaction and augmented vascular insult. Clarification of the immune mechanisms among DF, DFw/B and DHF will facilitate certain specific treatment and prevention of DF patients from varied bleeding tendency and vascular leakage manifestations.

Thesis (M.P.H.M. (Primary Health Care Management))--Mahidol University, 2005.

Thesis (M.P.H.M. (Primary Health Care Management))--Mahidol University, 2007. / LICL has E-Thesis 0024 ; please contact computer services.

Thesis (M.P.H.M.(Primary Health Care Management))--Mahidol University, 2006.

Orientador: Wilson Castro Ferreira Junior / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-16T08:15:58Z (GMT). No. of bitstreams: 1 Vilamiu_RaphaelGustavod'Almeida_D.pdf: 17502226 bytes, checksum: af859cc18d3a4c5a74c324d3e6c0865a (MD5) Previous issue date: 2010 / Resumo: Nesta tese, desenvolvemos uma técnica para gerar grafos à partir de conjuntos de séries temporais considerando a correlação entre estas e uma extensão do Método de Decomposição Empírica (EMD) para grafos (GEMD). Tal trabalho se justifica pelo fato de que uma grande gama de sinais formados por conjuntos de séries temporais não possuem uma localização bem definida em nenhum espaço n-dimensional. Desta forma, as relações entre as séries temporais só são satisfatoriamente representadas com o uso de grafos. Contudo, o desenvolvimento do GEMD é dependente do uso de algum método de interpolação em grafos. Tais métodos são escassos e não produzem propriedades satisfatórias para o uso no GEMD. Para esta finalidade, estendemos a interpolação por Funções de Base Radial (RBF) em Grafos (GRBF), onde a norma euclidiana no cálculo da matriz de interpolação por RBF é substituída pela norma induzida pelo grafo. Testes numéricos sugerem que a extensão possui boas propriedades de convergência e uma técnica é desenvolvida para garantir a existência e unicidade da solução. Finalmente, aplicamos o GEMD em um conjunto de dados de incidência de Dengue Hemorrágica na Tailândia. Os modos intrínsecos encontrados desta forma não apresentam nenhuma onda viajante emanando de nenhuma das províncias, contrastando com o resultado utilizando o EMD original [5]. Além disso, os períodos médios dos modos intrínsecos de [5] são claramente distintos dos encontrados pela decomposição por GEMD / Abstract: In this thesis, we developed a technique to generate a graph from a set of temporal series, which are then decomposed trough an extension of the Empirical Mode Decomposition (EMD) on Graphs (GEMD) created by us. This procedure is justified by the fact that a huge amount of signals cannot be properly localized on an n-dimensional space which can only be properly represented by a graph. The development of the GEMD is dependent on some graph interpolation method. Such methods are scarce in the literature and do not have the necessary properties to accomplish the GEMD decomposition. For this goal, we extend the Radial Basis Functions (RBF) interpolation to graphs (GRBF), where the euclidean norm used in the calculation of the RBF interpolation matrix is substituted by a graph induced norm. Numerical tests suggests that GRBF have good convergence properties and we present a technique which guarantees the existence and uniqueness of the solution. We finally apply the GEMD decomposition to a data set of Dengue Hemorrhagic Fever incidence in Thailand. The intrinsic modes found in this way do not show any traveling wave emanating from any of the provinces, contrasting with the results found using the original EMD [5]. Moreover, the mean period for the intrinsic modes in [5] are clearly diverse of those found by GEMD decomposition / Doutorado / Doutor em Matemática Aplicada

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-11-20T11:26:09Z No. of bitstreams: 2 Tese - Solomar Martins Marques - 2013.pdf: 2691124 bytes, checksum: 04ee7837e335b7d3d617e5d8fe652956 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2014-11-20T11:26:37Z (GMT) No. of bitstreams: 2 Tese - Solomar Martins Marques - 2013.pdf: 2691124 bytes, checksum: 04ee7837e335b7d3d617e5d8fe652956 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-11-20T11:26:37Z (GMT). No. of bitstreams: 2 Tese - Solomar Martins Marques - 2013.pdf: 2691124 bytes, checksum: 04ee7837e335b7d3d617e5d8fe652956 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-04-26 / Introduction: In the 21st century, Brazil has become the country with the highest number of cases of dengue in the world, with a wide distribution of Aedes aegypti in all regions and simultaneous circulation of the four serotypes. The identification of the four serotypes is confirmed in Goiânia, which is among the municipalities and cities with the highest concentration of reported cases. Objective: To identify clinical and laboratory markers associated with complications and severe forms of dengue in Goiania, from 2001 to 2011. Methods: A case-control study in which the cases are severe forms (DHF and CCD) and the controls are patients with CD. Secondary data from the Information System for Notifiable Diseases (Sinan) was used, Brazilian Ministry of Health. Verification of consistency, checking and data analysis was performed by the SPSS 20.0 program. Results: 3359 patients aged under 15 years were laboratory confirmed as dengue, with 349 cases and 3010 controls. It did not differ by gender. It is noted an increased tendency to severity, over the years (X2 for trend = 19.03, p <0.0001). Regarding age, the greatest risk of severe forms strata was 5-9 years old (OR 2.32, 95% CI 1.28 to 4.03) and 10 to 14 years old (OR 2.08, 95% CI 1.50 to 2.89). Discussion: Abdominal pain, hypotension and hemorrhagic phenomena such as petechiae, epistaxis and gastrointestinal bleeding were significantly associated with severity after logistic regression. Regarding the laboratory tests available, hemoconcentration, thrombocytopenia and tourniquet test had statistically significant association with CCD and HDF. We identified 10 patients with neurological complications, including 2 deaths. Conclusions: detailed clinical assessment and collection of blood counts are strongly suggested for all patients in the pediatric age group. This study contributed to consolidate the classical signs and ordinary laboratories as important instruments in both the diagnosis, the prognosis of children and adolescents with dengue disease. / Introdução: No século 21, o Brasil se tornou o país com maior número de casos relatados de dengue no mundo, com ampla distribuição do Aedes aegypti em todas as regiões e circulação simultânea dos quatro sorotipos. Goiânia tem confirmada a identificação dos quatro sorotipos e se encontra entre os municípios e localidades com maior concentração de casos notificados. Objetivo: Identificar marcadores clínicos e laboratoriais associados a formas graves de dengue em menores de quinze anos de idade, na cidade de Goiânia, de 2001 a 2011. Métodos: estudo caso-controle, onde Casos são definidos como formas graves (DCC e FHD) e os Controles, pacientes com DC. Utilizados dados secundários do Sistema de Informação de Agravos de Notificação (Sinan). Feita verificação da consistência, checagem e análise de dados, pelo programa SPSS 20. Resultados: 3.359 menores de 15 anos foram confirmados laboratorialmente como dengue, sendo 349 casos e 3.010 controles. Não apresentaram diferenças quanto ao sexo. Nota-se incremento da tendência de gravidade, ao longo dos anos (X2 p/tendência= 19,03; p<0,0001). Quanto à idade, o maior risco de formas graves foi nos estratos de 5 a 9 anos (OR 2,32; IC95% 1,28 - 4,03) e 10 a 14 anos (OR 2,08; IC95%1,50 - 2,89). Discussão: Dor abdominal, hipotensão e fenômenos hemorrágicos como petéquias, epistaxe e sangramento gastrointestinal tiveram associação estatisticamente significante com gravidade após regressão logística. Respectivo aos exames laboratoriais disponíveis, hemoconcentração, plaquetopenia e prova do laço tiveram associação estatisticamente significante com FHD e DCC. Foram identificados 10 pacientes com complicação neurológica, sendo dois óbitos. Conclusões: avaliação clínica minuciosa e a coleta de hemograma são fortemente sugeridas em todos os pacientes na faixa etária pediátrica. Este trabalho contribuiu para consolidar os sinais clínicos clássicos e os laboratoriais básicos como importantes ferramentas auxiliares, tanto no diagnóstico, quanto no prognóstico de crianças e adolescentes com dengue.

A dengue à transmitida por mosquitos hematÃfagos do gÃnero Aedes das espÃcies aegypti e albopictus. O vÃrus dengue (DENV) pertence à famÃlia Flaviviridae do gÃnero FlavivÃrus e possui quatro sorotipos que foram designados como: DENV-1, DENV-2, DENV-3 e DENV-4. A doenÃa pode manifestar-se como uma enfermidade infecciosa aguda, caracterizada por um amplo espectro clÃnico que varia desde formas de infecÃÃo assintomÃtica ou febre indiferenciada atà as formas graves, com hemorragia e/ou choque. Este estudo apresentou como objetivo descrever os aspectos epidemiolÃgicos, clÃnicos e laboratoriais de pacientes com suspeita de dengue atendidos no Hospital SÃo Josà de DoenÃas Infecciosas (HSJ) e no Hospital Nossa Senhora da ConceiÃÃo (HDNSC) no perÃodo de fevereiro a dezembro de 2010. Dessa forma, foram recrutados 93 pacientes, sendo que, 86 preencheram os critÃrios de inclusÃo. Os pacientes foram recrutados por busca ativa nas emergÃncias e nas enfermarias dos referidos hospitais e submetidos a um protocolo de acompanhamento por meio de uma ficha de avaliaÃÃo clÃnica inicial (1 ao 5Âdia de doenÃa) e de uma ficha de avaliaÃÃo subsequente (6 ao 7 dia de doenÃa). Foram realizadas pelo menos duas mensuraÃÃes de hematÃcrito, plaquetas, alÃm de exames bioquÃmicos e exames especÃficos para dengue. Os sinais e os sintomas mais prevalentes nos pacientes com suspeita de dengue foram: febre, cefaleia e mialgia. Vinte e cinco pacientes (29%) apresentavam manifestaÃÃes hemorrÃgicas espontÃneas, sendo que, as hemorragias cutÃneas (petÃquias e equimoses) foram as mais encontradas (15%). Quando avaliada a populaÃÃo feminina em idade reprodutiva, 6% apresentaram metrorragia. A prova do laÃo foi realizada em 80 pacientes, sendo positiva em 20 pacientes (25%). Dos 86 pacientes, 48 (55,8%) foram positivos para dengue por pelo menos uma das tÃcnicas: imunocromatografia NS1 (16%), RT-PCR (19%), ELISA IgM (44%), imunocromatografia IgM (42%) e ELISA NS1 (27%). O vÃrus dengue foi detectado em 16 pacientes, sendo, DENV-1 em 1 paciente (6,2%), DENV-2 em 14 pacientes (87,5%) e DENV-3 em 1 paciente (6,2%). Vinte e seis pacientes (54,1%) preencheram os critÃrios do MinistÃrio da SaÃde (MS) de Dengue ClÃssica (DC), 10 (20,8%) de Febre HemorrÃgica de Dengue (FHD) e 12 (25%) de Dengue com ComplicaÃÃo (DCC). A relaÃÃo entre sexo feminino e masculino foi de aproximadamente 1,1/1, com predomÃnio maior de adultos jovens. Quanto ao critÃrio de gravidade do MS, 60% dos casos suspeitos de dengue foram classificados como grau II e nenhum caso como grau IV. Dos critÃrios de extravasamento plasmÃtico preconizado pelo MS, a hipoalbuminemia esteve presente em 5 pacientes (10,4%). A queda do hematÃcrito acima de 20% apÃs hidrataÃÃo foi observada em apenas 4 pacientes (8,3%). No perÃodo do estudo, foram diagnosticados dois pacientes com dengue e leptospirose, sendo que um paciente complicou com pÃrpura trombocitopÃnica idiopÃtica, esses pacientes tiveram evoluÃÃo benigna. Portanto salientamos a necessidade de um diagnÃstico precoce, antes do desenvolvimento das manifestaÃÃes graves, de polÃticas de erradicaÃÃo do Aedes e da estruturaÃÃo de um serviÃo de referÃncia. / Dengue is transmitted by blood-sucking mosquitoes of the species of the genus Aedes aegypti and albopictus. Dengue virus (DENV) belongs to the genus Flavivirus of the Flaviviridae family and has four serotypes that were designated as: DENV-1, DENV-2, DENV-3 and DENV-4. The disease can manifest as an acute infectious disease characterized by a wide clinical spectrum ranging from asymptomatic forms of infection or undifferentiated fever to severe forms, with bleeding and / or shock. This study had as objective to describe the epidemiological, clinical and laboratory features of patients with suspected dengue fever treated at the St Joseph Hospital of Infectious Diseases (HSJ) and the Hospital Nossa Senhora da ConceiÃÃo (HDNSC) in the period from February to December 2010. Thus, we recruited 93 patients, 86 met the inclusion criteria. Patients were recruited by an active search in emergencies and in the ward of these hospitals and underwent a follow-up protocol through an initial clinical evaluation form (from day 1 to day 5 of illness) and an evaluation form following (from the 6 to 7 day of illness). Were performed at least two measurements of hematocrit, platelets, and biochemical tests and specific tests for dengue. The signs and symptoms more prevalent in patients with suspected dengue were fever, headache and myalgia. Twenty-five patients (29%) had spontaneous bleeding manifestations and the cutaneous bleeding (petechiae and ecchymosis) were the most frequent (15%). When evaluating the female population of reproductive age, 6% had metrorrhagia. The tourniquet test was performed in 80 patients and was positive in 20 patients. Of 86 patients, 48 (55,8%) were positive for dengue at least one of the techniques: immunochromatography NS1 (16%), RT-PCR (19%), IgM ELISA (44%), IgM immunochromatography (42%) and NS1 ELISA (27%). The dengue virus was detected in 16 patient and, DENV-1 in 1 patient (6.2%), DENV-2 in 14 patients (87.5%) and DENV-3 in 1 patient (6.2%). Twenty- six patients (54,1%) met the criteria of the Ministry of Health (MOH) Classic Dengue (DC), 10 (20,8%) of Dengue Hemorrhagic Fever (DHF) and 12 (25%) of Dengue with complication (DCC). The relationship bet ween females and males were approximately 1.1/1, with higher prevalence in young adults The criterion for severity of MOH, 60% of suspected dengue cases were classified as grade II and none as grade IV. Plasma extravasation of criteria recommended by MOH, hypoalbuminemia was present in 5 patients (10,4%). The drop in hematocrit higher than 20% after hydration was observed in only 4 patients (8,3%). During the study period, two patients were diagnosed with dengue and leptospirosis, and one patient complicated with idiopathic thrombocytopenic purpura, these patients had a benign outcome. Therefore we stress the need for early diagnosis, before the development of severe manifestations, of policies to eradicate Aedes and structure a reference service.

Submitted by Priscila Nascimento (pnascimento@icict.fiocruz.br) on 2013-03-20T19:12:45Z No. of bitstreams: 1 Tiago_Póvoa.pdf: 6904413 bytes, checksum: 89b7d7a97e24eb2dfd28a1d63fbce130 (MD5) / Made available in DSpace on 2013-03-20T19:12:45Z (GMT). No. of bitstreams: 1 Tiago_Póvoa.pdf: 6904413 bytes, checksum: 89b7d7a97e24eb2dfd28a1d63fbce130 (MD5) Previous issue date: 2012 / Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Rio de Janeiro, RJ, Brasil. / A dengue representa um sério problema de saúde pública mundial entre as doenças causadas por arbovírus. Seu agente etiológico, o vírus da dengue, compreende 4 sorotipos antigenicamente distintos (DENV1-4). Os sintomas da dengue variam desde a febre da dengue (FD) até a febre hemorrágica da dengue (FHD) e a síndrome do choque da dengue (SCD). No presente trabalho, iniciamos um estudo com o material obtido de diferentes órgãos (fígado, baço, pulmão, coração e rim) de quatro casos fatais de dengue. Análises histopatológicas revelaram, em todos os casos, áreas com edema e hemorragia; presença de esteatose (micro e macrovesicular) e necrose no fígado; degeneração de fibras cardíacas; necrose tubular aguda dos túbulos contorcidos proximais renais; destruição dos centros germinativos e atrofia de folículos linfóides do baço; espessamento dos septos alveolares e hipertrofia de macrófagos alveolares nos pulmões dos quatro pacientes e também a formação de membrana hialina nos casos 1 e 2. Detectamos antígenos virais em todos os órgãos e também um aumento de infiltrado inflamatório mononuclear, com aumento da população de macrófagos ativados e linfócitos B no rim; predomínio somente de linfócitos B no coração; aumento do número de macrófagos ativados e linfócitos T CD4+ no fígado e pulmão, e de linfócitos T CD8+ no pulmão. No baço, observamos uma diminuição das populações de linfócitos T CD4+, T CD8+ e B. A quantificação de células expressando citocinas mostrou: aumento da expressão de RANTES em todos os órgãos; um equilíbrio entre a produção das citocinas pró-inflamatórias (TNF-α e IFN-γ) e anti-inflamatórias (IL-10 e TGF-β) no fígado, rim e pulmão; aumento das citocinas pró-inflamatórias e diminuição das anti-inflamatórias no baço e o perfil oposto no tecido cardíaco, com predomínio da detecção de TGF-β. Além disso, avaliamos o efeito da infecção com DENV-2 em camundongos BALB/c inoculados pelas vias intraperitoneal (i.p.) e intravenosa (i.v.). A análise histopatológica do fígado e baço destes animais revelou alterações semelhantes às observadas nos casos de dengue (áreas de edema e hemorragia, esteatose, necrose e tumefação no fígado, e desorganização da arquitetura dos folículos no baço). De um modo geral, a inoculação pela via i.p. induziu danos em áreas focais, enquanto a via i.v. provocou lesões mais difusas em ambos os tecidos. Entretanto, essas diferenças entre as vias de inoculação não se refletiram em diferenças nas subpopulações de linfócitos. Verificamos que, em ambos os casos, as alterações das subpopulações linfocitárias ocorreram já no segundo dia de infecção. A quantificação dessas subpopulações revelou uma diminuição de linfócitos B totais e um aumento de linfócitos T CD4+ totais no fígado dos camundongos infectados, enquanto que no sangue, observamos um comportamento inverso dessas subpopulações. Já no baço, verificamos uma diminuição da subpopulação de linfócitos T CD8+ totais e um aumento de linfócitos T CD8+ ativados nos animais com 2 dias de infecção. De um modo geral, tais resultados poderão contribuir para um melhor entendimento da doença e para a validação do modelo experimental murino em novas abordagens vacinais ou terapêuticas. / Dengue is a serious worldwide public health problem among the diseases caused by arboviruses. Its etiologic agent, the dengue virus, comprises four antigenically distinct serotypes (DENV1-4). Dengue symptoms range from the dengue fever (DF) to the dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). In the present work, we initiated a study with materials obtained from different organs (liver, spleen, lung, heart and kidney) of four dengue fatal cases. Histopathological analysis revealed, in all cases, areas with edema and hemorrhage; the presence of steatosis (micro and macrovesicular) and necrosis in the liver; degeneration of cardiac fibers; acute tubular necrosis of renal proximal convoluted tubules; destruction of the germinal centers and atrophy of lymphoid follicles in the spleen; thickened alveolar septa and hypertrophy of alveolar macrophages in the lungs of the four patients and also the presence of hyaline membrane in cases 1 and 2. Virus antigens were detected in all organs as well as an increase of mononuclear cell infiltration, with the increase of activated macrophages population and B lymphocytes in the kidney; predominance of only B lymphocytes in the heart; increased number of activated macrophages and CD4+ T cells in the liver and the lung, and of CD8+ T cells in the lung. In the spleen, we observed a decrease of CD4+ T, CD8+ T and B populations. The quantification of cells expressing cytokines showed: increase of RANTES expression in all organs, a balance between production of proinflammatory (TNF-α e IFN-γ) and anti-inflammatory (IL-10 and TGF-β) cytokines in the liver, kidney and lung; increase of proinflammatory and decrease of anti-inflammatory cytokines in the spleen, while the opposite profile was observed in the cardiac tissue, with the predominance of TGF-β. In addition, we evaluated the effect of DENV-2 infection in BALB/c mice inoculated by the intraperitoneal (i.p.) and intravenous (i.v.) routes. Histopathological analysis in the liver and the spleen of these animals showed alterations similar to those observed in the dengue cases (areas of edema and hemorrhage, steatosis, necrosis and swelling hepatocytes in the liver, as well as disorganization of splenic follicle architectures). In general, results indicated that the i.p. inoculation induced damages in focal areas, whereas the lesions caused by the i.v. route were more diffused in both tissues. However, these differences between the two inoculation routes were not reflected in differences in the lymphocyte subsets. We observed that changes in lymphocyte subpopulations occurred by the second day after infection in both cases. The quantification of these subpopulations revealed a decrease of total B lymphocytes and an increase of total CD4+ T cells in the liver of infected mice, whereas in the blood we were observed an inverse behavior of such subpopulations. In the spleen, we verified a decrease of the total CD8+ T lymphocyte subpopulation and an increased of activated CD8+ T cells, two days after infection. Overall, these results may contribute to a better understanding of the disease and to the validation of this murine experimental model for novel vaccine or therapeutic approaches.

The four serotypes of dengue virus (DENV 1-4) have a significant and growing impact on global health. Dengue disease encompasses a wide range of clinical symptoms, usually presenting as an uncomplicated febrile illness lasting 5-7 days; however, a small percentage of infections are associated with plasma leakage and bleeding tendency (called dengue hemorrhagic fever, DHF), which can result in shock. Epidemiological studies indicate that severe dengue disease most often occurs during secondary heterotypic DENV infection. Additionally, plasma leakage (the hallmark of DHF) coincides with defervescence and viral clearance, suggesting that severe disease arises from the immune response to infection rather than a direct effect of the virus. A number of studies have found increased levels of markers of immune cell activation in patients with DHF compared to patients with the less severe form of disease (DF). These markers include IFNγ, TNFα, soluble CD8, soluble IL-2 receptor, soluble TNF receptor, and CD69, which support a role for T cells in mediating immunopathology. Because of the high homology of DENV 1-4, some degree of serotype-cross-reactivity is seen for most T cell epitopes. A high percentage of DENV-specific T cells recognize multiple DENV serotypes, as demonstrated by peptide-MHC (pMHC) tetramer binding and in vitro functional assays performed on PBMC from subjects vaccinated with an experimental DENV vaccine or naturally-infected subjects with secondary (>1) DENV infection. This thesis sought to address several gaps in the literature, specifically whether T cell responses differ in primary versus secondary (natural) infection. We studied the frequency, phenotype, and function of DENV-specific T cells. We demonstrated substantial serotype-cross-reactivity of antigen-specific T cells generated in response to naturally-acquired primary as well as secondary DENV infection. The frequency of A11-NS3133 epitope-specific T cells during acute infection did not correlate with disease severity. However, the peak frequency occurred earlier in primary infection while the frequency of CD45RA+ T cells declined quicker in secondary infection, suggesting the expansion of DENV-specific memory T cells. DENV-immune T cells exhibited different functional capabilities that were dependent on the particular serotype of infection. Specifically, DENV-1 or -3 stimulation of A11-NS3133 epitope-specific T cell lines resulted in robust function that included IFNγ production, whereas DENV-2 stimulation resulted in limited function that often included MIP-1β but not IFNγ production. These data support a role for T cells in DENV infection and offer new insights into their potential contribution to dengue pathology.