Aims: To explore the clinical significance of EBV infection in adult renal transplant recipients when detected in the late post-transplant period. Methods: (1) A prospective observational study recruiting 499 stable adult kidney transplant recipients with serial blood sampling for EBV DNAemia and assessment of clinical outcomes and associated factors. (2) A retrospective analysis of PTLD incidence, timing and outcomes in relation to EBV infection. Results: EBV DNAemia in stable kidney transplant recipients is common, found in 46% of recruited individuals screened over 1 year, with persistent DNAemia seen in 10%. DNAemia prevalence increased significantly with time from transplant (p<0.0001) from 16% within 1 year of transplant to 66% in those transplanted for 20-24 years. High baseline DNA levels predicted persistence of DNAemia. Time adjusted analyses showed significant association of DNAemia with EBV seronegative status and previous PTLD and low DNAemia rates with Mycophenolate Mofetil (MMF) use and lymphopenia. The mechanism did not appear to be directly linked to MMF induced B cell depletion. Chronic high viral load detection was significantly associated with time from transplant, EBV seronegative status at transplant, ciclosporin use and plasma detection of DNA. No significant differences in overall patient survival at 3 years, clinical symptoms or clinical findings such as anaemia, thrombocytopenia or rate of decline in renal function were seen between stable transplant recipients with and without EBV DNAemia. PTLD incidence also increases with time from transplant and was greatest during the 10th-14th post-transplant years. Disease was EBV positive in 68% cases. No statistically significant differences in overall patient survival, or overall disease complete response rates were seen in relation to recipient EBV serostatus or EBV status of PTLD histology. Conclusions: EBV DNAemia prevalence increases with time from transplant but was not associated with worse patient or graft survival or specific symptoms. PTLD incidence including EBV negative disease also increases with time from transplant but response rates and survival were not influenced by EBV serostatus or histological status.

S-metolachlor is an effective herbicide used to control/suppress annual grasses, nutsedges and several broadleaf weeds in sweetpotato. However, a decline in storage root quality and yield has been reported under certain environmental conditions. Information is limited on the effect of S-metolachlor application followed immediately by rainfall on sweetpotato growth and development under different temperatures, as well as the optimum application time. Therefore, the objectives of this study were to evaluate sweetpotato responses to interactive effects of S-metolachlor, temperature and rainfall, and to determine S-metolachlor optimum application time. A sunlit, controlled environment experiment was conducted to investigate sweetpotato response to S-metolachlor and rainfall immediately after application under different temperatures. Sweetpotato slips were transplanted into sandy soil filled pots. Treatment combinations included five levels of S-metolachlor, 0.00, 0.86, 1.72, 2.58 and 3.44 kg ha-1, two levels of rainfall, 0 and 38 mm and three temperatures, 25/17, 30/22 and 35/27 °C, day/night. After POST application of S-metolachlor and rainfall, all plants were transferred to sunlit growth chambers that were maintained at their respective temperatures and ambient CO2 concentration for 60 days. In another experiment, S-metolachlor application time was varied to investigate sweetpotato growth and development. Two levels of S-metolachlor 0.0 and 1.0 kg ha-1 and three application times 0, 5 and 10 days after transplanting (DAT) were used and plants were harvested five times, 5, 10, 15, 20 and 80 DAT to estimate plant growth and development. Shoot, root and total plant biomass yields declined with increasing concentration of S-metolachlor across temperatures. In addition, storage root yield and quality decline was S-metolachlor rate dependent and aggravated by rainfall immediately after herbicide treatment across temperatures. S-metolachlor was more injurious on most plant component parameters in the optimum and high temperatures where plant growth was vigorous than in the low temperatures. S-metolachlor application at 0 and 5 days affected sweetpotato growth, including storage roots, but delaying until 10 days minimized the injury. These results can be used to weigh the risk of crop injury against the weed control benefits of S-metolachlor when making management decisions, and to determine application time based on weather information.

BACKGROUND: The incidence and mortality of renal cell carcinoma (RCC) after kidney transplantation (KTx) remain unclear. This study's aims were (1) to investigate the pooled incidence/incidence trends, and (2) to assess the mortality/mortality trends in KTx patients with RCC. METHODS: A literature search was conducted using the MEDLINE, EMBASE and Cochrane databases from inception through October 2018. Studies that reported the incidence or mortality of RCC among kidney transplant recipients were included. The pooled incidence and 95% CI were calculated using a random-effect model. The protocol for this meta-analysis is registered with PROSPERO; no. CRD42018108994. RESULTS: A total of 22 observational studies with a total of 320,190 KTx patients were enrolled. Overall, the pooled estimated incidence of RCC after KTx was 0.7% (95% CI: 0.5-0.8%, = 93%). While the pooled estimated incidence of de novo RCC in the native kidney was 0.7% (95% CI: 0.6-0.9%, = 88%), the pooled estimated incidence of RCC in the allograft kidney was 0.2% (95% CI: 0.1-0.4%, = 64%). The pooled estimated mortality rate in KTx recipients with RCC was 15.0% (95% CI: 7.4-28.1%, = 80%) at a mean follow-up time of 42 months after RCC diagnosis. While meta-regression analysis showed a significant negative correlation between year of study and incidence of de novo RCC post-KTx (slopes = -0.05, = 0.01), there were no significant correlations between the year of study and mortality of patients with RCC ( = 0.50). Egger's regression asymmetry test was performed and showed no publication bias in all analyses. CONCLUSIONS: The overall estimated incidence of RCC after KTX was 0.7%. Although there has been a potential decrease in the incidence of RCC post-KTx, mortality in KTx patients with RCC has not decreased over time.

A cardiomiopatia dilatada (CMD) é caracterizada pela dilatação progressiva com redução da função contráctil do ventrículo esquerdo ou de ambos os ventrículos, podendo ser de origem viral e/ou imune, genética ou idiopática. Devido às inúmeras variáveis envolvidas na patogênese da CMD, atualmente não existe uma opção terapêutica definitiva para seu tratamento, sendo o transplante cardíaco o tratamento de escolha para a insuficiência cardíaca refratária. Trabalho anterior aventou a hipótese de simbiose entre microrganismos interferindo na resposta imune no tecido miocárdico. Assim, o presente estudo teve como objetivo verificar se a presença de antígenos ou DNA de agentes infecciosos associados à inflamação em corações explantados de pacientes com CMD Idiopática está relacionada com o desenvolvimento de rejeição moderada/grave no coração do doador após o transplante cardíaco. Foram estudadas amostras de miocárdio de pacientes transplantados por CMD Idiopática, agrupadas em: RMP (N = 6), rejeição moderada persistente, RM (n = 7) rejeição resolvida após pulsoterapia e SR (n = 5) sem rejeição. A inflamação foi quantificada por imunohistoquímica e os agentes infecciosos por imunohistoquímica, biologia molecular, hibridação in situ e microscopia eletrônica de transmissão. Houve maior número de macrófagos no grupo RMP, e mais células B e maior expressão de HLA classe II no grupo SR. A imunohistoquímica mostrou maior quantidade de M. pneumoniae e de HBC nos grupos RMP e RM. O grupo SR mostrou correlação positiva entre quantidade de gene Bb e antígeno de enterovírus. A biologia molecular demonstrou a presença dos genes M. pneumoniae, Borrelia burgdorferi, HHV6 e PVB19 em todos os grupos de estudo. A microscopia eletrônica revelou a presença de estruturas compatíveis com microrganismos que apresentam características de micoplasma, borrelia, enterovírus, HHV6 e parvovírus. Agentes infecciosos podem ser o fator causal e/ou perpetuador da lesão miocárdica em pacientes com CMD idiopática, uma vez que esses achados iniciais sugerem que a presença de microrganismos em simbiose no miocárdio está associada com pior prognóstico pós-transplante / Dilated cardiomyopathy (DCM) is characterized by progressive dilation with reduction of contractile function of the left ventricle or both ventricles, which may be viral and/or immune, genetic or idiopathic. Because of countless variables involved in the DCM, currently there is no definitive therapeutic option for its treatment, being heart transplant the treatment for choice of refractory heart failure. A previous study hypothesized that symbiosis between microorganisms may interfere in immune system in myocardial tissue. Thus, the present study had the objective to determine if presence of antigens or DNA of infectious agents associated with inflammation in explanted hearts of patients with idiopathic DCM is related to the development of moderated/severe rejection in donor\'s heart after cardiac transplantation. Myocardial samples from patients transplanted by Idiopathic DCM were studied, grouped in: PMR (n=6) persistent moderate rejection, MR (n=7) rejection resolved after pulse therapy and NR (n=5) no rejection, without moderate rejection, in which inflammation was quantified by immunohistochemistry and infectious agents by immunohistochemistry, molecular biology, in situ hybridization technique and transmission electron microscopy. There was higher amount of macrophages in PMR group, and more B cells (p=0.0001) and higher HLA class II expression (p= < 0.0001) in NR group. Immunohistochemistry showed M. pneumoniae (p=0.003) and HBc (p=0.0009) antigens in PMR and MR groups. NR showed positive correlation between amount of Bb genes and enterovirus antigens. Molecular biology demonstrated the presence of M. pneumoniae, Borrelia burgdorferi, HHV6 and PVB19 genes in all studied groups. Electron microscopy revealed the presence of structures compatible with mycoplasma, borrelia, enterovirus, herpesvirus 6 and parvovirus. Infectious agents may be the causal and/or perpetuating factor of myocardial injury in patients with Idiopathic DCM, since these initial findings suggest that the microorganisms in symbiosis in the myocardium of these patients is associated with worst prognosis after transplantation

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23421号 / 医博第4766号 / 新制||医||1053(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 小濱 和貴, 教授 妹尾 浩, 教授 川口 義弥 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Le virus Epstein-Barr (VEB) est fortement associé au développement de syndromes lymphoprolifératifs (SLP) en greffe pédiatrique. Ce virus a la capacité d’immortaliser les lymphocytes B et de provoquer leur prolifération incontrôlée chez l’hôte immunodéprimé. Plusieurs études démontrent que le cycle lytique du virus jouerait un rôle primordial dans la genèse des SLP en produisant des particules virales pouvant infecter les cellules B adjacentes. Chez un individu immunodéprimé, ces cellules B nouvellement infectées peuvent donner naissance à une expansion lymphocytaire. Le projet présenté dans ce mémoire fait partie d’un programme de recherche visant à élucider le rôle de l’infection productive par le VEB dans le développement des SLP. L’objectif précis de ce projet est de développer un anticorps monoclonal chimère contre la glycoprotéine gp350 du VEB dans le but de neutraliser le virus et d’ainsi prévenir son entrée dans les cellules B. Notre laboratoire a construit une version chimère de l’anticorps monoclonal murin 72A1, lequel se lie à la gp350 et bloque l’infection. Les premiers essais ont révélé la présence de chaînes non fonctionnelles (aberrantes) dans l’hybridome produisant l’anticorps 72A1. La construction de la chaîne légère authentique est maintenant complète alors que celle de la chaîne lourde est toujours en cours. Le processus de caractérisation de l’anticorps chimère inclura des essais de cytotoxicité à médiation cellulaire dépendante des anticorps (ADCC). Dans cette optique, une lignée cellulaire exprimant de façon stable la gp350 a été établie. Notre anticorps chimère anti-gp350 pourrait éventuellement être utilisé comme thérapie préventive chez les greffés présentant un risque élevé de SLP en empêchant l’infection des cellules B adjacentes. / The Epstein-Barr virus (EBV) is associated with B-cell post-transplant lymphoproliferative disease (PTLD). EBV has the unique property of immortalizing B lymphocytes, thereby causing their uncontrolled proliferation in an immunocompromised host. Certain evidence suggests that EBV productive infection may play a primary role in the genesis of PTLD by generating virus particles which can infect bystander B cells. In an immunocompromised individual, these infected B cells may then give rise to expanding B-cell clones. The project presented in this thesis is part of a research program seeking to elucidate the role of EBV productive infection in the genesis of PTLD. The specific aim of this work was to design a chimeric monoclonal antibody against the EBV envelope glycoprotein gp350 in order to neutralize the virus, thereby preventing entry into B cells. Our laboratory constructed a chimeric version of the murine monoclonal antibody, 72A1, which binds to gp350 and blocks infection. The initial cloning attempts revealed the presence of nonfunctional (aberrant) transcripts in the hybridoma line producing the 72A1 antibody. The chimeric version of the authentic light chain is now completed while the chimeric heavy chain construction is ongoing. As part of the characterisation process for the chimeric antibody, a cell line stably expressing surface gp350 was generated. This gp350-expressing cell line will be used for antibody dependent cellular cytotoxicity assays (ADCC). This anti-gp350 chimeric antibody could be useful as a preventive therapy in transplant patients at high risk for PTLD by blocking the infection of bystander B cells.

Le virus Epstein-Barr (VEB) est un pathogène opportuniste qui a la capacité d’immortaliser les lymphocytes B et de provoquer une prolifération maligne, appelée syndrome lymphoprolifératif post-transplantation (SLP), chez les individus immunodéprimés. A l’intérieur de ce groupe, les personnes à plus haut risque sont les enfants, puisqu’ils sont à risque de développer une infection primaire par le VEB pendant leur régime d’immunosuppression post-greffe. Dans le but de développer un anticorps préventif, notre laboratoire s’est attardé au rôle du cycle lytique du VEB dans le développement du SLP. À cette fin, le premier objectif du présent projet vise à fournir la preuve expérimentale de l’existence ou non d’une phase réplicative productive pendant l’infection aiguë des lymphocytes B sanguins. Un examen des événements qui se déroulent au tout début de l’infection par le VEB tant au niveau de la réplication virale qu’au niveau de l’expression des gènes lytiques précoces et tardifs a révélé l’existence d’une phase réplicative productive pendant l’infection aiguë. Ceci a permis de justifier l’élaboration, dans notre laboratoire, d’un anticorps chimère (murin-humain) neutralisant, dirigé contre la protéine gp350 située sur l’enveloppe virale. Le deuxième objectif, quant à lui, vise à fournir la preuve expérimentale de la capacité neutralisante de cet anticorps chimère. Des essais de caractérisation in vitro ont démontré une capacité de reconnaissance de la protéine cible, notamment la gp350, et une capacité de neutralisation du virus par l’anticorps chimère. L’anticorps chimère anti-gp350 pourra faire l’objet d’essais précliniques in vivo en vue d’évaluer sa capacité à reconnaître le virus et à prévenir l’apparition de tumeurs de type SLP chez les souris SCID. Il pourrait être éventuellement utilisé, par la suite, comme traitement préemptif contre les tumeurs dans l’espoir de mieux gérer les patients à risque de développer un SLP. / Epstein-Barr virus (EBV) is an opportunistic pathogen in immunocompromised transplant patients. In these patients EBV infection can lead to malignant B-cell lymphoproliferation, called post-transplant lymphoproliferative disease (PTLD). This thesis project aimed to investigate the role of lytic EBV infection in the genesis of PTLD. The first experimental objective was to provide in vitro proof that EBV could induce productive replication upon acute in vitro infection of B cells. Data obtained through study of viral DNA replication and transcription during the first 96 hours post-infection indicate that lytic infection does occur. These results provided justification for proceeding to the second experimental objective which involved the characterization of an anti-gp350 human-mouse chimeric antibody for its capacity to recognize and neutralize EBV. Results showed that this antibody did possess neutralization activity. Further study of this anti-gp350 chimeric antibody in SCID mice is necessary in order to evaluate its in vivo efficacy against PTLD.

Résumé en français : Notre équipe étudie les mécanismes de l’apoptose induite par la nutline-3, une molécule capable de se fixer sur MDM2 et d’activer la p53, dans différents types de lymphomes associés au virus d’Epstein-Barr (EBV) comme le lymphome de Burkitt (LB) ou syndromes lymphoprolifératifs post-transplantation (PTLD). Nos résultats montrent que la nutline-3 induit l’apoptose des cellules de LB EBV (-) alors que les cellules EBV (+) en latence de type III sont résistantes. Mon travail de thèse a consisté à étudier les mécanismes impliqués dans ce phénomène de résistance afin de mettre en place des stratégies pour les contourner. Une première étude initiée par les résultats d’une analyse transcriptomique, effectuée après traitement avec la nutline-3 de deux lignées qui ne diffèrent que par leur statut EBV, nous a permis de montrer que : 1) l’autophagie est induite en réponse au traitement dans les cellules EBV (+) en latence de type III ; 2) ces cellules expriment fortement Bécline-1 et présentent une activation constitutive de l’autophagie ; 3) l’autophagie contribue à la résistance de ces cellules à l’apoptose. Par ailleurs, nos résultats indiquent que la protéine anti-apoptotique Bcl-2 est également impliquée dans la résistance de ces cellules et que l’utilisation d’ABT-737, un inhibiteur de Bcl-2, restaure leur sensibilité à la nutline-3. L’efficacité de ce composé a donc été évaluée in vivo, seul ou en combinaison avec des traitements conventionnels (Cyclophosphamide pour le LB et Rituximab pour les PTLD). Les résultats obtenus lors de ces études pré-cliniques montrent que : 1) ABT-737 réduit considérablement la croissance tumorale et augmente la survie de souris xénogreffées avec des cellules d’une lignée lymphoblastoïde (LCL, utilisées comme modèle pour les PTLD) alors qu’il n’a pas d’effets chez les souris xénogreffées avec une lignée de LB ; 2) la combinaison BT-737/Cyclophosphamide permet de limiter la croissance tumorale durant le traitement mais n’améliore pas la survie des souris xénogreffées avec une lignée de LB ; 3) l’association ABT-737/Rituximab est très efficace et induit une rémission complète chez 70% des souris xénogreffées avec la lignée de LCL / - Résumé en anglais : Our team is working on the mechanisms of apoptosis induced by nutlin-3, a small molecule which binds to MDM2 and activates p53, in different lymphomas associated with Epstein-Barr virus such as Burkitt lymphoma (BL) or Post-transplant lymphoproliferative disorder (PTLD). Our results show that nutlin-3 strongly induce apoptosis in EBV (-) cells whereas EBV (+) latency III cells are much more resistant. The aim of my PhD project was to study the mechanisms involved in the resistance of EBV (+) latency III cells to apoptosis and to develop new therapeutic strategies to bypass these mechanisms. A transcriptomic analysis was realized after treatment with nutlin-3 of two cell lines which only differs by their EBV status. Based on the results obtained, a study was performed which allow us to show that: 1) autophagy is induced after nutlin-3 treatment in EBV (+) latency III cells; 2) these cells strongly expressed beclin-1 and present a constitutively high level of autophagy; 3) autophagy is involved in the resistance of apoptosis observed in these cells. Furthermore, our results demonstrate that Bcl-2 also contributes to the resistance of EBV (+) latency III cells and that treatment with ABT-737, a Bcl-2 inhibitor, restores their susceptibility to nutlin-3 treatment. We thus assessed the efficiency of this compound in vivo, in monotherapy or associated with conventional treatments (Cyclophosphamide for BL and Rituximab for PTLD). Results obtained during these pre-clinical studies show that: 1) ABT-737 reduces tumor growth and increase the overall survival of mice xenografted with a lymphoblastoïd cell line (LCL, used as a model for PTLD studies) but has no effects on mice xenografed with BL cell lines; 2) the association ABT-737/Cyclophosphamide reduces tumor growth during treatment but doesn’t improve the overall survival of mice xenografed with BL cell lines; 3) the association ABT-737/Rituximab is very efficient and induces 70% of complete remission in mice xenografted with LCL.

A doença linfoproliferativa pós transplante (DLPT) é a proliferação tecidual secundária mais comum em crianças submetidas a transplante de órgãos sólidos, e representa um espectro de proliferação linfoide clínica e morfologicamente heterogêneo que vai desde uma hiperplasia policlonal indolente até linfomas agressivos. Aproximadamente 80% das DLPT estão associadas ao vírus Epstein Barr (EBV) e é originaria de células B, entre 10 a 15% tem origem em células T e aproximadamente 1% em células natural killer. O status sorológico negativo para EBV pré transplante e o grau de imunossupressão são os fatores de risco de maior relevância para o desenvolvimento desta enfermidade. A apresentação clínica é diversa e sintomas constitucionais podem estar presentes simulando infecção e ou rejeição ao órgão transplantado. A confirmação do diagnóstico por exame histopatológico é, habitualmente, necessária e a hibridização in situ geralmente detecta as partículas de EBV nos tecidos examinados. A melhor opção terapêutica ainda não está definida e atualmente o tratamento consiste na redução da imunossupressão associada ao uso do anticorpo Anti CD20 e ou quimioterapia citotóxica além da terapia celular disponível em alguns centros. Este estudo teve por objetivos avaliar a resposta tumoral ao uso do anticorpo Anti CD20 na DLPT de células B EBV positivas pós transplante de órgãos sólidos, além de associar a neoplasia à eventual inclusão genômica de DNA/EBV na célula neoplásica. Foram analisados retrospectivamente os prontuários de vinte e três pacientes com até 18 anos incompletos admitidos na Unidade de Internação do Serviço de Onco- Hematologia do Instituto da Criança (ICR) e Instituto do Tratamento do Câncer Infantil (ITACI) que desenvolveram DLPT CD20 positiva pós transplante de órgãos sólidos comprovada histologicamente entre 8 de março de 1995 e 13 de agosto de 2011. Todos foram submetidos à redução da imunossupressão, treze receberam Anti CD20 isolado, três Anti CD20 associado à quimioterapia citotóxica e sete pacientes não fizeram uso desta droga. A sobrevida global em dois anos dos pacientes que receberam Anti CD20 foi de 81,45% e quando comparada à sobrevida global de 37,5% dos que não receberam a droga revelou diferença estatística significativa (p=0,02). Todos os pacientes tiveram a detecção da proteína de latência viral de EBV Latent Membrane Protein1 (LMP1) na célula tumoral através da técnica de hibridização in situ realizada em blocos de parafina devidamente armazenados ao diagnóstico. A curta duração do tratamento com o Anti CD20, a toxicidade aceitável em relação às demais alternativas terapêuticas, a possibilidade de seu uso exclusivo, sua eficácia inclusive na doença de histologia agressiva e associação às demais alternativas de tratamento na doença refratária sugerem a inclusão desta droga no arsenal terapêutico atualmente disponível / Post-transplant lymphoproliferative disease (PTLD) is the most common secondary tissue proliferation that occurs in children after solid organ transplantation and represents a spectrum of clinical lymphoid proliferation and morphologic heterogeneity that goes from an indolent polyclonal hyperplasia to aggressive lymphomas. Approximately 80% of PTLD is associated with Epstein Barr virus (EBV) and is of B-cell origin, 10 to 15% of T-cells and approximately 1% of natural killer cells. EBV pretransplant seronegativity and the degree of immunosuppression are the most relevant risk factors for developing the disease. Clinical presentation is diverse and constitutional symptoms may simulate infection and/or organ transplanted rejection. Histopathologic examination is usually necessary to confirm diagnosis and, generally, in situ hybridization detects the EBV particles in examined tissues. The best treatment option is yet to be determined and the current treatment consists of immunosuppression reduction associated with the use of anti CD20 antibody and/or cytotoxic chemotherapy besides cell therapy only available in some centers. This study aimed to evaluate tumor response to the use of anti CD20 antibody in positive B-cell EBV PTLD after solid organ transplantation and the association of the neoplasia to the eventual inclusion of genomic EBV/DNA in the tumor cell. We retrospectively analyzed medical records of twenty-three patients under 18 years of age who were admitted to the inpatient unit of Serviço de Onco- Hematologia do Instituto da Criança (ICR) e Instituto do Tratamento do Câncer Infantil (ITACI) who developed histologically proven CD20 positive pediatric PTLD after solid organ transplantation between 8 March 1995 and 13 August 2011. All patients were submitted to immunosuppression reduction, thirteen received isolated Anti CD20, three Anti CD20 associated with cytotoxic chemotherapy and seven patients did not use this drug. The estimated 2-year overall survival rates of patients who received anti CD20 was 81.45% and when compared to the overall survival rates of those who did not receive the drug it was 37, 5%, showing a statistically significant difference (p = 0.02). All patients had the Epstein-Barr virus latency protein (latent membrane protein1 - LMP1) detected in tumor paraffin embedded stored at diagnosis by the in situ hybridization technic. The short duration of the Anti CD20 treatment, its acceptable toxicity compared to other therapeutic alternatives, the possibility of its exclusive use, its effectiveness in aggressive histology disease and the association with other treatment alternatives in refractory disease, suggest this drug inclusion to the currently available therapeutic arsenal

A doença linfoproliferativa pós transplante (DLPT) é a proliferação tecidual secundária mais comum em crianças submetidas a transplante de órgãos sólidos, e representa um espectro de proliferação linfoide clínica e morfologicamente heterogêneo que vai desde uma hiperplasia policlonal indolente até linfomas agressivos. Aproximadamente 80% das DLPT estão associadas ao vírus Epstein Barr (EBV) e é originaria de células B, entre 10 a 15% tem origem em células T e aproximadamente 1% em células natural killer. O status sorológico negativo para EBV pré transplante e o grau de imunossupressão são os fatores de risco de maior relevância para o desenvolvimento desta enfermidade. A apresentação clínica é diversa e sintomas constitucionais podem estar presentes simulando infecção e ou rejeição ao órgão transplantado. A confirmação do diagnóstico por exame histopatológico é, habitualmente, necessária e a hibridização in situ geralmente detecta as partículas de EBV nos tecidos examinados. A melhor opção terapêutica ainda não está definida e atualmente o tratamento consiste na redução da imunossupressão associada ao uso do anticorpo Anti CD20 e ou quimioterapia citotóxica além da terapia celular disponível em alguns centros. Este estudo teve por objetivos avaliar a resposta tumoral ao uso do anticorpo Anti CD20 na DLPT de células B EBV positivas pós transplante de órgãos sólidos, além de associar a neoplasia à eventual inclusão genômica de DNA/EBV na célula neoplásica. Foram analisados retrospectivamente os prontuários de vinte e três pacientes com até 18 anos incompletos admitidos na Unidade de Internação do Serviço de Onco- Hematologia do Instituto da Criança (ICR) e Instituto do Tratamento do Câncer Infantil (ITACI) que desenvolveram DLPT CD20 positiva pós transplante de órgãos sólidos comprovada histologicamente entre 8 de março de 1995 e 13 de agosto de 2011. Todos foram submetidos à redução da imunossupressão, treze receberam Anti CD20 isolado, três Anti CD20 associado à quimioterapia citotóxica e sete pacientes não fizeram uso desta droga. A sobrevida global em dois anos dos pacientes que receberam Anti CD20 foi de 81,45% e quando comparada à sobrevida global de 37,5% dos que não receberam a droga revelou diferença estatística significativa (p=0,02). Todos os pacientes tiveram a detecção da proteína de latência viral de EBV Latent Membrane Protein1 (LMP1) na célula tumoral através da técnica de hibridização in situ realizada em blocos de parafina devidamente armazenados ao diagnóstico. A curta duração do tratamento com o Anti CD20, a toxicidade aceitável em relação às demais alternativas terapêuticas, a possibilidade de seu uso exclusivo, sua eficácia inclusive na doença de histologia agressiva e associação às demais alternativas de tratamento na doença refratária sugerem a inclusão desta droga no arsenal terapêutico atualmente disponível / Post-transplant lymphoproliferative disease (PTLD) is the most common secondary tissue proliferation that occurs in children after solid organ transplantation and represents a spectrum of clinical lymphoid proliferation and morphologic heterogeneity that goes from an indolent polyclonal hyperplasia to aggressive lymphomas. Approximately 80% of PTLD is associated with Epstein Barr virus (EBV) and is of B-cell origin, 10 to 15% of T-cells and approximately 1% of natural killer cells. EBV pretransplant seronegativity and the degree of immunosuppression are the most relevant risk factors for developing the disease. Clinical presentation is diverse and constitutional symptoms may simulate infection and/or organ transplanted rejection. Histopathologic examination is usually necessary to confirm diagnosis and, generally, in situ hybridization detects the EBV particles in examined tissues. The best treatment option is yet to be determined and the current treatment consists of immunosuppression reduction associated with the use of anti CD20 antibody and/or cytotoxic chemotherapy besides cell therapy only available in some centers. This study aimed to evaluate tumor response to the use of anti CD20 antibody in positive B-cell EBV PTLD after solid organ transplantation and the association of the neoplasia to the eventual inclusion of genomic EBV/DNA in the tumor cell. We retrospectively analyzed medical records of twenty-three patients under 18 years of age who were admitted to the inpatient unit of Serviço de Onco- Hematologia do Instituto da Criança (ICR) e Instituto do Tratamento do Câncer Infantil (ITACI) who developed histologically proven CD20 positive pediatric PTLD after solid organ transplantation between 8 March 1995 and 13 August 2011. All patients were submitted to immunosuppression reduction, thirteen received isolated Anti CD20, three Anti CD20 associated with cytotoxic chemotherapy and seven patients did not use this drug. The estimated 2-year overall survival rates of patients who received anti CD20 was 81.45% and when compared to the overall survival rates of those who did not receive the drug it was 37, 5%, showing a statistically significant difference (p = 0.02). All patients had the Epstein-Barr virus latency protein (latent membrane protein1 - LMP1) detected in tumor paraffin embedded stored at diagnosis by the in situ hybridization technic. The short duration of the Anti CD20 treatment, its acceptable toxicity compared to other therapeutic alternatives, the possibility of its exclusive use, its effectiveness in aggressive histology disease and the association with other treatment alternatives in refractory disease, suggest this drug inclusion to the currently available therapeutic arsenal