Thesis (Ph. D.)--University of Nevada, Reno, 2005. / Includes bibliographical references. Online version available on the World Wide Web.

Thesis (M.S.)--University of Southern California, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Southern California, 1999. / Includes bibliographical references.

Thesis (Ph.D. in Clinical Sciences) -- University of Colorado at Denver and Health Sciences Center, 2005. / Typescript. Includes bibliographical references (leaves 140-156). Free to UCDHSC affiliates. Online version available via ProQuest Digital Dissertations;

<p>Glioblastoma (GBM) is a grade IV astrocytoma in which the median overall survival is approximately 15 months at time of diagnosis. Even with the current multi- modal therapeutic approach of surgery, chemotherapy with the DNA alkylating agent temozolomide, and radiation therapy, GBM remains uniformly lethal. Immunotherapeutic interventions are a burgeoning field in many different cancer treatments. They offer the exquisite specificity endowed by the immune system with minimal toxicities and new methods are being developed to enhance the endogenous immune responses.</p><p>With the recent identification of human cytomegalovirus (CMV) present within glioblastoma tissue but void in the surrounding normal healthy parenchyma there have been significant efforts aimed at understanding the biologic implications of the presence of the virus within GBM tissues with preliminary work demonstrating several capabilities of the virus to enhance the oncogenic process. </p><p>Likewise, a key area of importance in the development and design of effective immunotherapeutic platforms is the identification and targeting of tumor-specific antigens. The success of any immunotherapy platform relies heavily on the ability to selectively target antigens present within tumors but absent on healthy tissue, regardless of its role in tumorigenesis, as well as having robust immunogenic properties.</p><p>CMV offers a plethora of possible targets, as it is the largest known DNA virus that infects humans, yet very little is known about its biological significance in glioblastoma pathogenesis as well as the most efficacious and immunogenic targets for immunotherapeutic development. </p><p>We have been able to elucidate more thoroughly the feasibility and potency of an immunologic platform targeting CMV within glioblastoma utilizing a multi-antigen multi-component peptide based strategy that demonstrated significant immunogenicity and anti-tumor activity in pre-clinical models utilizing various assays. We have also developed several sensitive and specific detection methodologies including: 1) custom gene expression microarrays, 2) multiplex real time quantitative polymerase chain reaction (RT-qPCR) assays, 3) a massively parallel RNA deep sequencing platform, and 4) immunological assays. We have also successfully determined the capacity for endogenous CMV gene expression to be maintained in primary glioblastoma cell lines as well as examining the preponderance of CMV gene expression in a subpopulation of glioma stem cell-like cells, the slow cycling GBM cells established from primary tumor tissues, in an attempt to illuminate some of the biologic underpinnings of CMV with respect to GBM pathogenesis.</p><p>Taken together, these data lay the groundwork for the development of a more efficacious vaccination strategy targeting CMV in GBM. The screening strategies employed throughout this work will allow for an accurate antigenic profile of CMV in GBM which will subsequently permit the design of a more robust peptide vaccine for the next generation of cancer vaccine. We have also begun to describe some of the interesting biologic phenomena associated with CMV in GBM, as our results demonstrate continued viral gene expression in glioma stem cell-like cell populations indicating viral tropism for certain cell types.</p> / Dissertation

Neutrophils provide a rapid first response to invading pathogens and orchestrate the immune response. They are able to employ potent antipathogenic mechanisms such as phagocytosis, reactive oxygen species (ROS) generation, protease release from granules, and formation of neutrophil extracellular traps (NETs). Despite this, certain pathogens have evolved mechanisms to benefit from neutrophil effector functions. Human cytomegalovirus (HCMV) is a clinically important pathogen that infects the majority of the human population. Monocytes are considered the main vehicle of HCMV dissemination throughout the body, but little research has been done on its interaction with neutrophils. The virus encodes a range of immunomodulatory proteins including an IL-8 homologue that acts as a powerful neutrophil chemoattractant. Viral conservation of a protein that recruits neutrophils to the site of HCMV infection suggests that the interaction between neutrophils and HCMV provides an overall advantage to the virus, but little evidence exists so far to suggest this is the case. Here I report that human peripheral blood neutrophils exposed to a clinical strain of HCMV display a profound survival phenotype, as assessed by morphology, phosphatidylserine exposure, cell permeability, and caspase-3/7 activity. This occurs in the absence of viral gene production. Neutrophils also upregulated their release of inflammatory cytokines in response to HCMV, with higher concentrations of IL-6, IL-8, and MIP-1α detected in the secretomes of infected neutrophils. These secretomes induced monocyte chemotaxis and increased monocyte permissivity to HCMV infection, as well as augmented survival in healthy, uninfected neutrophils. These experiments were confirmed with clean HCMV after the discovery of contaminating Mycoplasma spp. in the viral inocula of the initial experiments. Mycoplasma-HCMV coinfection induced an autophagic phenotype in neutrophils, as assessed by Western blotting and qPCR of autophagy-related components. Inhibition of autophagy using 3-MA reversed a profound survival effect. The unintended inclusion of Mycoplasma spp. further led to the serendipitous discovery of yet another pathogenic ability to overcome neutrophil immune functions: contaminating Mycoplasma spp. as well as Mycoplasma pneumoniae profoundly degraded NETs. These extracellular chromatin structures were stimulated using PMA or pyocyanin, and their release was dependent on the generation of ROS: severely ROS-deficient murine bone marrow neutrophils were unable to generate NETs. However, small amounts of ROS were sufficient for NETs generation, as neutrophils from acute respiratory distress syndrome patients, including many that had attenuated ROS-responses, were still capable of NETs generation. The NETs-degradative properties of mycoplasma were confirmed by fluorescence confocal and scanning electron microscopy, as well as spectrophotometry and agarose gel electrophoresis. This study demonstrates that two pervasive pathogens, HCMV and M. pneumoniae, both frequently found in coinfections in clinical contexts, are able to overcome neutrophil antipathogenic mechanisms to potentially enhance pathogen dissemination. These data provide not only a novel example of manipulation of an anti-viral response in a cell not productively infected, but also a novel example of pathogenic NETs degradation. These findings may have implications on our understanding of mycoplasma and HCMV pathogenesis and provide new targets for the generation of therapies.

Orientadores: Ilka de Fatima Santana Ferreira Boin, Raquel Silveira Bello Stucchi / Tese (doutorador) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-24T02:50:29Z (GMT). No. of bitstreams: 1 Silva_AnaCarolinaGuardiada_D.pdf: 4973684 bytes, checksum: b2c754b94b99a119ae7e84ac207a9555 (MD5) Previous issue date: 2013 / Resumo: Introdução: As infecções oportunistas constituem um dos principais problemas para os transplantados de fígado. O Citomegalovírus (CMV) e o Herpesvirus humano 6 (HHV- 6) são patógenos oportunistas freqüentes nesses pacientes, e o HHV-6 tem sido associado a várias desordens tais como a encefalite. A PCR em tempo real (RT-PCR) é o padrão ouro de diagnóstico para os herpesvirus, pois tem melhor precisão, maior rendimento e menos risco de contaminação em comparação com outros testes convencionais. Objetivo: Este estudo teve como objetivo avaliar a cinética viral do HHV-6 e CMV por RT-PCR nos pacientes submetidos ao transplante hepático correlacionando-a com a presença de encefalite e complicações clínicas ocorridas no período pós-transplante. Método: Foram analisadas prospectivamente pela RT- PCR a carga viral do CMV e HHV-6 de 30 pacientes transplantados de fígado. A monitorização dos pacientes foi realizada prospectivamente desde o pré-transplante (imediatamente antes do ato cirúrgico - dia zero) com amostras do doador e receptor, e no pós-transplante: 2ª, 3ª, 4ª, 6ª, 8ª, 10ª e 12ª semanas, somando 270 amostras de soro. O protocolo foi seguido de acordo com os requerimentos para pesquisas e foi aprovado pelo Comitê de Ética em Pesquisada da Faculdade de Ciências Médicas da Universidade Estadual de Campinas (CEP nº 430/2003). Os achados clínicos foram obtidos através dos prontuários. Para a detecção e quantificação do DNA dos vírus CMV e HHV-6 foram usados os Kits comerciais "CMV Real-TM Quant" e "HHV-6 Real-TM Quant". Os testes de Nested-PCR e antigenemia foram realizados rotineiramente para o vírus CMV, pelos laboratórios do HC-Unicamp, e seu resultados obtidos eletronicamente. A análise estatística comparou as variáveis categóricas usando o teste exato de Fisher. Para identificar os fatores associados ao aumento da carga viral foi utilizado o método das Equações de Estimação Generalizadas e medidas de acurácia. Resultados: Treze (43%) dos 30 pacientes apresentaram infecção pelo HHV-6 e 26 (86%) apresentaram infecção pelo CMV. Nove pacientes apresentaram encefalite após o transplante de fígado sendo que sete deles tiveram infecção pelo HHV-6 (p=0,0012), assim com o aumento da carga viral do HHV-6 se constatou a presença de encefalite após o transplante de fígado (p= 0.0226). O RT- PCR (p= 0,0306) para o CMV mostrou aumento significativo na segunda a quarta semana e décima a décima segunda semanas em relação aos outros testes, mostrando-se também mais sensível. Conclusão: concluímos que o aumento da carga viral do HHV-6 foi associado com a presença de encefalite após o transplante de fígado e a técnica de PCR em tempo real se mostrou como o teste mais sensível para detecção e monitorização do CMV nos pacientes transplantados de fígado / Abstract: Introduction: Opportunistic infections are a major problem for liver transplantation patients. Cytomegalovirus (CMV) and human herpesvirus 6 (HHV-6) are opportunistic common pathogens and HHV-6 has been associated with several disorders such as encephalitis. Real-time PCR (RT-PCR) is the gold standard for diagnosis of herpesvirus, as it has better accuracy, higher efficiency and less risk of contamination compared to other conventional tests. Objective: The aim of study was to evaluate the viral kinetics of HHV-6 and CMV by RT-PCR in patients undergoing liver transplantation and correlated with the presence of encephalitis complications occurring in the post-transplant period. Methods: We prospectively analyzed by RT-PCR the viral load of CMV and HHV-6 in 30 liver transplant patients. Monitoring of patients was performed prospectively from pretransplant (immediately before surgery-day zero) with donor and recipient samples and posttransplant: 2nd, 3rd, 4th, 6th, 8th, 10th and 12th weeks with a total of 270 serum samples. The protocol was followed according to the requirements for research and was approved by the Ethics Research Committee of the Faculty of Medical Sciences State University of Campinas (CEP nº 430/2003). The clinical findings were obtained from the medical records. For detection and quantification of DNA of the CMV and HHV-6 virus the commercial kits "Real- CMV Quant TM" and "HHV-6 Real -TM Quant" were used. Nested-PCR and antigenemia tests were performed routinely for CMV virus and their results obtained electronically. Statistical analysis comparing categorical variables was applied using Fisher exact test. To identify associated factors with increased viral load the method of Generalized Estimation Equation (GEE) and the accuracy and precision was used. Results: Thirteen (43 %) of the thirty patients had HHV-6; 26 (86 %) had CMV infection. Nine patients had encephalitis after liver transplantation and seven of them had HHV-6 (p = 0.0012) and with an increasing viral load of HHV-6 the presence of encephalitis after liver transplantation was found (p = 0.0226). RT-PCR (P = 0.0306 ) CMV showed a significant increase at the 2nd to 4th week and 10th to 12th week compared to the other tests, having also more sensibility. Conclusion: We concluded that the increase in viral load of HHV-6 was associated with the presence of encephalitis after liver transplantation and the technique of real-time PCR was shown to be the best sensibility test for the detection and monitoring of CMV in our liver transplant patient / Doutorado / Fisiopatologia Cirúrgica / Doutora em Ciências da Cirurgia

Orientadores: Ilka de Fátima Ferreira Santana Boin, Raquel Silveira Bello Stucchi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-20T01:05:47Z (GMT). No. of bitstreams: 1 Sampaio_AnaMaria_D.pdf: 2807263 bytes, checksum: d6e4e66e4a1625c1079f11fd900f0137 (MD5) Previous issue date: 2012 / Resumo: O herpes vírus humano HHV-6 e HHV-7 pertencem à subfamília herpes virinae, família herpes viridae, são vírus universais e após infecção primária permanecem latentes no organismo, podendo ser reativados por período de imunossupressão. O objetivo da pesquisa visou a padronização e implantação da antigenemia para diagnóstico precoce de HHV-6 e HHV-7 e a realização da sorologia para HHV-6 em pacientes submetidos ao transplante de fígado do Hospital das Clínicas da Unicamp. A partir dos dados obtidos da antigenemia para HHV-6 e HHV-7, avaliou com os achados de antigenemia do HCMV, N-PCR para HCMV, HHV-6, HHV-7 e outros aspectos clinico-laboratoriais. O protocolo foi seguido de acordo com os requerimentos para pesquisas e foi aprovado pelo Comitê de Ética Institucional da Faculdade de Ciências Médicas (FCM) da Universidade Estadual de Campinas (Unicamp). Conseguiu-se para o estudo amostras de 32 pacientes, com idade mediana de 47 (18-66) anos, sendo 20 (62,5%) do sexo masculino e 12 (37,5%) do sexo feminino. A monitorização dos pacientes foi realizada prospectivamente desde o pré-transplante e no pós-transplante, de modo semanal no 1º e 2º, quinzenal no 3º mês e mensal do 4º mês até o final do 6º mês. A partir de linfócitos extraídos de sangue periférico realizou-se a detecção de antígenos de HHV-6 com anticorpos monoclonais C65206M (marca Biodesign International, France) e MAB8535 (marca Biodesign International - USA) e conjugados de soro de coelho anti-IgG de camundongo Z0412-1 (marca Dako - CA, USA) e soro de cabra anti-IgG de coelho marcado com peroxidase 81-6120 (marca Zymed, CA, USA). Para a detecção de antígenos de HHV-7 foi utilizado o anticorpo monoclonal de rato KR4 (marca Advance Biotechnologies, Canada), conjugado soro de coelho anti-imunoglobulina de camundongo P0260 (marca Dako Cytomation, USA) e conjugado soro de cabra anti-IgG de coelho 81-6120 (marca Zymed, CA, USA) diluídos em PBS/BSA e aplicados sobre a fixação celular. Foi realizado a detecção de anticorpos IgM anti HHV-6 pelo teste de Elisa (marca Panbio, USA). Com essas metodologias a detecção de IgM anti HHV-6 foi positiva em 15,6% dos pacientes no pré transplante, 25% na quarta semana, 40,6% na 12 semana e em 46,9% na 24 semana após o enxerto. A antigenemia para HCMV, HHV-6 e HHV-7 foi positiva em 46,9%, 62,5% e 46,8% respectivamente. A N-PCR para HCMV e HHV-6 ocorreu em 81% dos casos, e para HHV-7 foi de 46,8%. Detectou-se que 50% dos pacientes estudados tiveram doença por HCMV. A doença causada pelo HHV-6 foi em 46,8% dos pacientes e em 15,6% para HHV-7. A concomitância de doenças foi observada nos pacientes com HCMV e HHV-6 em 21,9% e em 15,6% dos pacientes com HHV-6 e HHV-7. A doença causada pelos beta herpes vírus foi detectada com maior frequência ao redor da quinta semana. E os episódios de doença para HHV-6 e HHV-7 surgiram antes do aparecimento da doença por HCMV. Este estudo confirma a relevância da infecção pelo HCMV, HHV-6 e HHV-7 e a importância do monitoramento através de técnicas para a detecção precoce desses agentes, possibilitando a utilização de um tratamento preemptivo, com redução do risco de doença / Abstract: Introduction: The human herpes viruses type 6 (HHV-6) and 7 (HHV-7) belong to the herpes virus subfamily, herpes viridae family, are universal viruses and after primary infection remain latent in the organism and may be reactivated during an immunosuppression period. The aims of the research were to standardize, implement and monitor antigenemia for early diagnosis of HHV-6 and HHV-7 and serology for HHV-6 in patients who underwent liver transplantation in the Hospital of the State University of Campinas. The data obtained for HHV-6 and HHV-7 antigenemia were correlated with results for HCMV, N-PCR for HCMV, HHV-6, HHV-7 and other clinical and laboratorial aspects. The protocol was followed according to the research requirements and was approved by the Institutional Ethics Committee of the State University of Campinas. Thirty-two patients were studied, mean age 47 (18-66) years old, in which 20 (62.5%) were male and 12 (37.5%) were female. The monitoring of the patients was carried out prospectively since pre-transplantation and during post-transplantation period; weekly in the first and second month, fortnightly in the third month and monthly up to the sixth month. Detection of HHV-6 antigens was held from lymphocytes extracted from peripheral blood using monoclonal antibodies C65206M (Biodesign International, France) and MAB8535 (Biodesign International-USA); rabbit anti-mouse IgG Z0412-1 (Dako, USA) conjugate serum and goat anti-rabbit marked with peroxidase IgG 81-6120 (Zymed, USA) conjugate serum. For HHV-7 antigens detection, KR4 (Advance Biotechnologies, Canada) mouse monoclonal antibody, conjugate P0260 (Dako Cytomation, USA) rabbit anti-mouse IgG serum and conjugate goat anti-rabbit IgG serum 81-6120 (Zymed, USA) were used, diluted in PBS/BSA and applied over the cell fixation. IgM anti HHV-6 antibody detection was held by ELISA test (Panbio, USA). Using this methodology IgM anti HHV-6 detection was positive for 15.6% of the patients in pre-transplantation, 25% in the fourth week, 40,6% in the twelfth week and 46,9% in the 24th week after the transplantation. HCMV, HHV-6 and HHV-7 antigenemia was positive in 46.9%, 62.5% and 46.8%, respectively. HCMV and HHV-6 PCR occurred in 81% of the cases and for HHV-7, 46.8% of the cases. It was detected that 50% of the patients manifested HCMV disease. Disease manifested in 46.8% and 15.6% of the patients for HHV-6 and HHV-7, respectively. Concomitance of the diseases was observed in patients with HCMV and HHV-6 in 21.9% and 15.6% of the patients with HHV-6 and HHV-7. The disease caused by beta herpes virus was detected with higher frequency around the fifth week. HHV-6 and HHV-7 disease episodes appeared prior to HCMV disease. This study confirms the relevance of HCMV, HHV-6 and HHV-7 infection and the importance of monitoring through techniques for early detection of these agents, allowing the usage of a preemptive treatment, reducing the risk of disease / Doutorado / Fisiopatologia Cirúrgica / Doutor em Ciências

Murine cytomegalovirus (MCMV) encodes a non-coding RNA, m169, that inhibits the cellular miRNA, miR-27. Previous studies have shown that the overexpression of miR-27 in vitro suppresses replication of MCMV and degradation of miR-27 by m169 is important for the viral replication during the lytic stage of infection in vivo. To understand why the virus specifically targets this cellular miRNA for degradation, this thesis focuses on identification of cellular target genes of miR-27 that are involved in viral growth in the lytic infection. Microarray analysis was conducted to globally examine cellular genes differentially expressed following miR-27 overexpression or repression during MCMV infection. Data obtained from the microarray analysis were analysed in order to select potential targets of miR-27 for functional screening. Functional screening involved siRNA knockdown of individual genes followed by infection with a GFP reporter virus (GFP-MCMV) to assess the effects on viral growth. Knockdown of 5 out of 55 genes (Rpl18a, Lyar, Itga5, Mapkapk3 and Pik3r1) led to a significant reduction in GFP expression. Based on luciferase reporter assays, Mapkapk3 was validated as a direct target of miR-27 with a seed site interaction in its 3’UTR. Mutation of this site in the mRNA was shown to eliminate miR-27-mediated repression. Analysis of MAPKAPK3 protein levels upon infection demonstrates that the protein levels are higher in cells infected with wild type MCMV versus the m169 deletion virus (MCMV Δm169). This is in line with the difference in miR-27 levels in the two infections showing a decrease of miR-27 in wild type MCMV and unaltered levels in MCMV Δm169 infection. Mapkapk3 is a direct downstream target of p38 mitogen-activated protein (MAP) kinase within the p38 MAP kinase pathway, which has previously been shown to be an essential pathway for CMV replication. Expression levels of substrates of MAPKAPK3 including HSP27 and ATF1 were examined during infection to evaluate whether they are regulated by miR-27. The level of phosphorylation of HSP27 was shown to correlate with the levels of MAPKAPK3 during infection and was higher in cells infected with wild type MCMV versus MCMV Δm169. This suggests that MAPKAPK3 and its substrate, HSP27, are regulated by miR-27 during MCMV infection. This work provides an important foundation for further functional studies on the role of Mapkapk3 and its substrates in MCMV infection and its capacity to be dynamically regulated by miR-27. Based on the microarray analysis upon miR-27 overexpression, it was shown that miR-27 has an impact on the cell cycle, consistent with previous studies. Functional analysis of miR-27 in the cell cycle using miR-27 mimics and inhibitors demonstrated that the mimics cause an increase of cells in S phase at early time points (12 and 14 h), whereas the inhibition of miR-27 results in a significant reduction in the S phase population and accumulation of cells in G1 phase. Luciferase reporter assays confirmed that two genes known to be associated with the cell cycle are direct targets of miR-27: polycomb ring finger oncogene 1 (Bmi1) and caveolin 1 (Cav1). Knockdown of Bmi1 and Cav1 leads to a significant decrease in the number of cells in S phase and accumulation of cells in the G1 phase; however, this is the opposite result to that observed with the miR-27 mimics. These results suggest that the increase in cells in the S phase induced by miR-27 mimics is unlikely to be associated with targeting of Bmi1 and Cav1. Furthermore, knockdown of Bmi1 and Cav1 does not affect viral replication in vitro. Since miR-27 induces the transition of cells from the G1 to S phase, further studies are required to identify the miR-27 targets involved in this function. To identify direct targets of miR-27 through biochemical methods, one chapter of this thesis was devoted to developing CLASH datasets (cross-linking, ligation and sequencing of hybrid). This technique can directly map miRNA-mRNA interactions within the Argonaute protein (AGO). Initially, a NIH 3T3 stable cell line expressing AGO2 with a double affinity tag at the N terminus was generated. Analysis of the stable cell line revealed no significant alteration of miR-27 regulation or change in permissiveness to MCMV compared to wild type cells, making this amenable to further studies. Using the stable cell line, the CLASH protocol was carried out and preliminary data collected. In summary, this thesis identifies a direct target of miR-27, Mapkapk3, that is an important gene in MCMV replication that requires further investigation. Mapkapk3 is a substrate of p38 in the p38 MAP kinase pathway which is a signal transduction mediating numerous biological processes in response to cellular stresses including CMV infection. Furthermore, miR-27 overexpression was found to stimulate the G1/S transition of the cell cycle, and miR-27 inhibition had the opposite effect. Previous evidence has shown that MCMV and HCMV arrest the cell cycle in the G1 phase and inhibit host DNA synthesis to create an optimal condition for viral gene expression and DNA replication. Given that MCMV arrests host cells in the G1 phase, it is possible that degradation of miR-27 by MCMV contributes to this effect. Since miR-27 regulates both Mapkapk3 and the cell cycle, it seems likely that a number of targets and pathways underlie the antiviral properties of this miRNA.

Les infections par cytomégalovirus sont un problème majeur en transplantation rénale du fait de l’augmentation du risque de perte de greffon et de l’augmentation de la morbi-mortalité des patients. Toutefois la mise en place d’un traitement prophylactique par ganciclovir a significativement fait diminuer l’incidence de ces infections. Cette efficacité est toutefois limitée par une importante hématotoxicité notamment des neutropénies. La survenue de cet évènement indésirable conduit à une réduction des doses voire à un arrêt du traitement, favorisant ainsi l’émergence de résistances virales. Ces résistances sont un problème grandissant chez les personnes transplantées du fait du manque de protocole de prise en charge de celles-ci. Dans ce contexte notre objectif était de mieux comprendre la survenue et le mécanisme de cette toxicité. Dans un premier temps nous avons étudié le métabolisme intracellulaire du ganciclovir chez des patients. Nous avons remarqué qu’il y a une forte corrélation entre l’exposition à la forme active du ganciclovir et la diminution du nombre de neutrophiles au 3ème mois de traitement. Nous avons par la suite étudié l’impact de variations génétiques sur des transporteurs. Nous avons remarqué qu’un polymorphisme était fortement associé à une diminution du nombre de neutrophiles et qu’il entrainait également une augmentation de la concentration intracellulaire de ganciclovir à l’aide d’un modèle in vitro. Cette thèse fournit de nouveaux outils d’exploration du métabolisme et de l’accumulation intracellulaire du ganciclovir qui pourraient être utiles pour la prévention de la survenue de neutropénies sous ganciclovir. / Cytomegalovirus infection is a major issue in transplant patients as it affects the graft survival and contributes to patients’ morbi-mortality. The implementation of ganciclovir prophylaxis has significantly decreased its incidence, however GCV frequently induces neutropenia. This adverse effect leads to a decrease in the ganciclovir dose or to a discontinuation of the therapy, thereby favoring viral resistance. Resistance to ganciclovir is a growing problem in solid organ transplantion because of the lack of proper data to support treatment decisions when it is encountered. In this context we aim at better understanding the factors involved in this toxicity. First we explored the intracellular metabolism of ganciclovir in patients’ white blood cells. We found that the active form of ganciclovir is associated with neutrophil toxicity at month 3 of treatment. Then we explored the effect of targeted polymorphisms among transporter genes in two cohorts of renal transplant patients. We found that a single nucleotide polymorphism is strongly associated with a decrease in the neutrophil count and in ganciclovir intracellular accumulation. This thesis provides relevant tools for a deeper exploration of ganciclovir intracellular metabolism and accumulation which might be useful for the prevention of ganciclovir induced neutropenia.