Thesis (Ph. D.)--University of Oklahoma. / Bibliography: leaves 115-153.

Thesis (Ph.D.)--Uniformed Services University of the Health Sciences, 2006 / Typescript (photocopy)

Thesis (Ph.D.)--Uniformed Services University of the Health Sciences, 2006 / Typescript (photocopy)

CD4+ T cells play a central role in immunity. During virus infections, CD4+ T cells provide the necessary help for B cells to secrete anti-viral antibody and may act as effector cells themselves through the secretion of anti-viral cytokines such as IFN-γ and TNF-α. Recent studies in the lymphocytic choriomeningitis virus (LCMV) system have shown that CD4+ T cells are required to maintain the clearance of persistent viral infections as well as maintain virus-specific memory CD8+ cytotoxic T lymphocytes (CTL). Despite these important functions, surprisingly little information exists concerning the longevity, magnitude, and stability of the CD4+ T cell response following a virus infection. This thesis takes advantage of the well-studied LCMV system to address the above issues as well as to examine the role CD4+ T cells play during heterologous virus infections and to determine the fate of CD4+T cells following a high-dose LCMV infection. The cell surface phenotype of the CD4+ T cells was first examined in C57BL/6 mice acutely infected with LCMV. FACS analysis revealed the modulation of several activation markers on CD4+ T cells during an acute infection with LCMV, consistent with an activated cell phenotype. In addition, 25% of the CD4+ T cells were blast-sized by day 7 post-infection (p.i.) even though the total number of CD4+ T cells did not increase in the spleen during the acute infection. Additional studies were performed using CZ-1, a novel monoclonal antibody (mAb) previously generated in our laboratory that defines a sialic acid-dependent CD45RB-associated epitope. Examination of the expression of the CZ-1 antigen on CD4+ T cells following LCMV infection revealed that the blast-sized CD4+ T cells at day 6 p.i. were CZ-1 +. Further cell surface phenotyping showed that those blast cells activated at day 6 p.i. were CD45RB1oCD44hiCD62L-. This contrasts with the CZ-1-CD45RBhiCD441oCD62L+ resting cell population prior to infection. To determine if memory CD4+ T cells continued to express the CZ-1 epitope long after resolution of the LCMV infection, CD4+CZ-1+ and CD4+CZ-1- populations were purified by cell sorting and placed into an in vitro proliferation assay with LCMV-infected antigen-presenting cells (APC). It was found that the CD4+CZ-1+ population contained virtually all of the virus-specific memory. Thus, these studies indicate that the CZ-1 epitope defines a novel activation and memory marker for murine CD4+T cells. Examination of virus-specific cytokine production using ELISPOT assays showed a significant increase in the number of IFN-γ-secreting cells in the spleen during an acute LCMV-infection. CD8+ T cells made up the majority of the IFN-γ-producing cells, but analysis of the cell culture supernatants by ELISA revealed that the CD4+T cells produced more IFN-γ on a per cell basis. No significant increase in IL-4 levels was detected under these experimental conditions. These data suggest that LCMV infection induces primarily a virus-specific Th1 response that is characterized by increased IFN-γ production. No quantitative information was known about the frequency and longevity of the LCMV-specific CD4+ T cell response. Using limiting dilution assays (LDA), I examined the CD4+ T cell precursor (Thp) frequency in C57BL/6 mice infected with LCMV. The virus-specific CD4+ Thp frequency increased from <1/100,000 in uninfected mice to a peak of approximately 1/600 in FACS-purified splenic CD4+ T cell populations by 10 days p.i. with LCMV. After the peak of the response, the CD4+ Thp frequency decreased only about 2-fold per CD4+ T cell to approximately 1/1200 and remained stable into long-term memory. The CD4+ Thp frequency to each of the two known LCMV major histocompatibility complex (MHC) class II-restricted peptides dropped only 2- to 7-fold from the peak of the acute LCMV response into long-term memory. Thus, the CD4+T cell frequencies remain elevated after the acute infection subsides and remain extremely stable throughout long-term immunity. The above results show that LDA can account for +T cells as being virus-specific following LCMV infection. However, using newer, more sensitive assays based on intracellular cytokine production, >20% of the CD4+ T cells secreted IFN-γ after stimulation with phorbol myristic acid and ionomycin during the peak of the acute CD4+ T cell response. In addition, >10% of the CD4+ T cells secreted IFN-γ after stimulation with the LCMV MHC class II-restricted CD4 peptides. Thus, these new sensitive assays reveal a heretofore unappreciated, yet profound antigen-specific CD4+T cell response during LCMV infection. Infection of mice with a series of unrelated viruses, termed heterologous viruses, causes the reduction of memory CD8+ T cells specific to earlier infections. In order to examine the fate of CD4+ T cells under these conditions, I examined cytokine production and followed the CD4+ Thp frequency following heterologous virus infections. Challenge of LCMV-immune mice with vaccinia virus (VV) resulted in a significant increase in both the amount of IFN-γ protein and the frequency of IFN-γ-producing cells in the peritoneal cavity 3 days after infection as compared to control non-immune mice acutely infected with VV or to LCMV-immune mice alone. Intracellular IFN-γ staining revealed that both CD4+ and CD8+ T cells contributed to this increased IFN-γ production. LDA analysis of the LCMV-specific CD4+ Thp frequency following multiple heterologous virus infections or protein antigen immunizations, revealed that the CD4+ Thp frequency remains stable even under conditions that reduce the LCMV-specific CD8+ CTLp frequency. Additional studies using high-dose LCMV Clone 13 demonstrated that, like CD8+ T cells, there is a decline in detectable LCMV-specific CD4+Thp during overwhelming virus infections. The data presented in this thesis help provide a better understanding of the CD4+ T cell response during virus infections. I make several novel observations, including the demonstration that mAb CZ-1 defines a novel activation and memory marker for CD4+ T cells, that the LCMV-specific memory CD4+ Thp frequency remains extremely stable into long-term immunity, and that heterologous virus infections do not disturb the stable memory CD4+ T cell pool following a virus infection. I also provide data using new sensitive assays based on intracellular cytokine production that there is a much more profound antigen-specific CD4+ T cell response during viral infections than has previously been realized. Finally, I provide evidence that the virus-specific CD4+ T cells become unresponsive following a high-dose LCMV Clone 13 infection. Thus, the data presented in this thesis highlight some important similarities and differences between the CD4+ and CD8+ T cell responses during acute viral infections.

The Tec family tyrosine kinases Itk, Tec and Rlk are expressed in T cells. Previous studies have established that these kinases are critical for TCR signaling, leading to the activation of PLCγ1. To further understand the functions of Tec kinases in T cell activation, we took three different approaches. First, we performed a thorough analysis of CD28-mediated signaling events and functional responses with purified naïve T cells from Itk-/- mice and a highly controlled stimulation system. Data from this set of studies definitively demonstrate that CD28 costimulation functions efficiently in naïve CD4+ T cells in the absence of Itk. Second, in order to further study the functions of Tec kinases in vivo, we generated transgenic mouse lines expressing a kinase-dead (KD) mutant of Tec on the Itk-/-Rlk-/- background, hoping to study mice that are functionally deficient for all three Tec kinases. The results hint the importance of the Tec kinases in T cell development and/or survival. Finally, in order to identify potential transcriptional targets of Itk, we used microarray technology to compare global gene expression profiles of naïve and stimulated Itk-/- versus Itk+/- CD4+ T cells. This analysis provided a short list of differentially expressed genes in Itk-/- versus Itk+/- CD4 T cells, providing a starting point for further studies of Itk in T cell activation. Collectively, these studies clarified the role of Itk in CD28 signaling, revealed some unexpected aspects of Tec family kinases in T cells, and indicated potential targets of Itk-dependent signaling pathways in T cells.

A person is exposed to many pathogens throughout their lifetime, and with the resolution of each infection, there remains a pool of pathogen-specific immune cells that protect that person from re-infection with the same pathogen. However, there is a great deal of evidence to suggest that the pool of pathogen-specific memory cells can also participate in the immune response to future infections with unrelated pathogens. Many believe T cells to be cross-reactive in nature because of their interaction with self antigens during development in the thymus and their interaction with foreign antigens once in the periphery. There are many features of the interaction between a T cell and its ligand that facilitate this cross-reactive nature. Based on solved crystal structures, relatively few contacts are required for a stable interaction, and that interaction is often mediated by the flexible CDR3 loops of the T cell receptor that accommodate ligands of various structure. There is also evidence in the murine and human systems that subsets of virus-specific memory CD8 T cells take on an activated phenotype upon infection with an unrelated virus. In murine models, these memory T cell subsets could kill target cells, secrete several cytokines, and proliferate in response to a cross-reactive stimulation, suggesting that a cross-reactive T cell response could impact the outcome of a viral infection. In fact, upon heterologous infection, mice immune to a previous virus were often protected, having lower titers of the second unrelated virus, their epitope-specific and T cell receptor repertoires were often skewed, and they were more prone to immune-mediated pathologies. All of these observations coincided with the presence of cross-reactive T cell responses. Thus, we define heterologous immunity as changes in viral replication and the disease pathology associated with that viral infection as a result of the host's history of infection, and this can be mediated, in part, by cross-reactive CD8 T cell responses. Since many human viral infections are associated with a wide range of disease states, we questioned whether cross-reactive CD8 T cell responses occurred as commonly as they appeared to occur in the murine models and whether they influenced the outcome of such infections. Epstein-Barr virus (EBV) infects over 90% of the U. S. population and has a large genome with the capacity to encode a multitude of T cell epitopes. The first part of this thesis research focuses on the identification of cross-reactive CD8 T cell responses with specificity for known epitopes derived from EBV, a common human virus. We directed our study to HLA-A2-restricted responses because of the common expression of this MHC Class I allele in the U. S. population. This study resulted in the detection of cross-reactive responses with five different specificities that involved either the immunodominant lytic EBV-BMLF1280 epitope or the latent EBNA 3A596epitope. Three of the cross-reactive responses had specificity for epitopes derived from another unrelated, but common, human virus, influenza A virus (IV). Each of these cross- reactive responses had the potential to participate in the collective immune response to acute EBV infection. EBV is also well-suited as a model system to study heterologous immunity in humans, as infection at an early age is frequently asymptomatic, while the same infection during adolescence often results in an immune-mediated syndrome, infectious mononucleosis (IM). Since older individuals have presumably been exposed to more pathogens in their lifetime and, therefore, would have memory CD8 T cell pools with more extensive specificities, we hypothesized that acute EBV infection activated cross-reactive memory CD8 T cell responses that promoted the development of IM. In order to determine if the cross-reactive responses we identified above contributed to the immune response to acute EBV infection, we first screened the blood of IM patients for cross-reactive T cells with specificity for EBV-BMLFl280 and IV-M158. The total number of M1-specific T cells of 5 of 8 patients was increased at presentation with IM, which was suggestive of their specific activation during the EBV infection since a bystander mechanism would have resulted in 8 out of 8 patients having increased numbers of M1-specific T cells. Our hypothesis was further supported by the fact that we clearly detected cross-reactive T cells capable of recognizing both BMLF1 and M1 epitopes in the blood of 2 of the 5 IM patients with an augmented M1-specific T cell frequency. Furthermore, the M1-specific TCR repertoires of those two patients were dramatically skewed, which was an indication of cross-reactive M1-specific T cell expansions and, therefore, participation in the lymphoproliferation characteristic of IM. In addition, T cell lines derived from 3 out of 8 healthy donors with previous exposure to both viruses contained a subset of T cells that responded to both BMLF1 and M1 epitopes, suggesting that these cross-reactive cells are often maintained in memory. These cross-reactive T cells were cytotoxic and produced MIP-1β, IFNγ, and TNFα, functions which could potentially promote the symptoms of IM and, indeed, may have been contributed to the severe case of IM noted in one patient. The final part of this thesis research focused on defining the structure of the cross-reactive TCR that recognized both BMLF1 and M1 epitopes, which have only 33% sequence similarity. In addition, we examined the cross-reactive TCR repertoire organization of multiple individuals to determine the breath and, therefore, the likelihood that this cross-reactive T cell response will occur. These studies revealed that a wide range of Vα and Vβ families can mediate interaction with both epitopes and that the cross-reactive TCR repertoire was unique to each individual, relying heavily on the T cell clones present in that individual's private BMLF1- and M1-specific repertoires. We also observed an increased frequency of TCRs with longer CDR3 regions within the cross-reactive repertoire, which were often extended by non-bulky amino acid residues that could provide these TCRs with more flexibility in order. to accommodate the two different epitope structures. Given that we detected a cross-reactive T cell response with specificity for two immunodominant epitopes derived from two of the most common human viruses among people that share one of the most common MHC Class I alleles in the U. S. population, we predict that cross-reactive T cells are common components of human immune responses. The variability in the magnitude and specificity of each cross-reactive T cell response is dependent on each individual's unique history of infection and th,eir unique TCR repertoire, and such responses likely represent one of many factors that could explain the individual variability in disease severity associated with EBV and many other human viral infections.

Cell cultivation in bioreactors would benefit from developed monitoring systems with online real-time imaging to evaluate cell culture conditions and processes. This opportunity can be provided with the newly developed in situ Microscope also called ISM. The ISM probe is mounted into the wall of a bioreactor and consists of a measurement zone with an illuminating light source to obtain real-time images of moving cells in suspension. The instrument is linked to advanced imaging analysis software which can be specifically adapted for the objects in study. The aim of this project is to analyze the T lymphocyte cell line Jurkat T cells using the ISM equipment and identify specific features of the cells that can be obtained. The results show that the equipment and linked software are suitable for monitoring cell density, cell size distribution and cell surface analysis of the Jurkat cells during cultivation. The ISM could also detect induced changes in cell size caused by osmotic shifts and the course of an infection occurring in the cell suspension using a developed software for online real-time monitoring.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2015-12-30T14:45:37Z No. of bitstreams: 1 Regina Santos Nascimento Avaliação de celulas...2015.pdf: 3386534 bytes, checksum: 28a4bcbab904a339ca7717124724aa89 (MD5) / Approved for entry into archive by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2015-12-30T14:45:53Z (GMT) No. of bitstreams: 1 Regina Santos Nascimento Avaliação de celulas...2015.pdf: 3386534 bytes, checksum: 28a4bcbab904a339ca7717124724aa89 (MD5) / Made available in DSpace on 2015-12-30T14:45:53Z (GMT). No. of bitstreams: 1 Regina Santos Nascimento Avaliação de celulas...2015.pdf: 3386534 bytes, checksum: 28a4bcbab904a339ca7717124724aa89 (MD5) Previous issue date: 2015 / Fundação Oswaldo Cruz, Centro de Pesquisas Gonçalo Moniz. Salvador, BA, Brasil / O HTLV-1 é o agente etiológico da leucemia /linfoma de células T do adulto (ATLL), da paraparesia espástica tropical/ mielopatia associada ao HTLV-1 (HAM/TSP) e da uveíte. Além destas, a ceratoconjutivite seca (CCS), doença multifatorial da lágrima e da superfície ocular, tem sido descrita com maior frequência em indivíduos infectados pelo HTLV-1. Assim como em outras doenças associadas, a CCS tem sido relacionada a uma elevada carga proviral. As células T regulatórias (Treg) são importantes na manutenção da homeostase do sistema imunológico e um comprometimento da imunorregulação exercido por elas pode contribuir para o ambiente inflamatório observado na CCS. Este estudo objetivou avaliar os linfócitos Treg de pacientes com CCS associada à infecção pelo HTLV-1. Foram realizados ensaios de imunofenotipagem por citometria de fluxo para avaliar a frequência de linfócitos T ativados (HLA-DR+) e de células T CD4+ e CD8+ regulatórios (FOXP3+), bem como a produção de IL-10 e TGF-β por estas células. Foram avaliados 37 pacientes infectados pelo HTLV-1 e assintomáticos para HAM/TSP, sendo 27 com diagnóstico positivo para a manifestação ocular (CCS), 10 com diagnóstico negativo (ASS), além de 17 voluntários não infectados pelo vírus (NI). As frequências de linfócitos T CD4+FOXP3+, CD8+FOXP3+, CD4+HLA-DR+ e CD8+HLA-DR+ foram significativamente maiores nos grupos CCS e ASS, quando comparados aos indivíduos não infectados. Quanto à produção das citocinas imunossupressoras, foi observada uma maior frequência de linfócitos T CD4+FOXP3+ duplo produtores de IL-10 e TGF-β no grupo CCS quando comparado ao grupo ASS. Com relação aos linfócitos CD8+FOXP3+, o grupo CCS apresentou uma maior frequência de células mono produtoras de IL-10 quando comparado ao ASS. Nossos resultados sugerem que a menor frequência de células Treg CD8+ produtoras de TGF-β em indivíduos infectados pelo HTLV-1 com CCS, pode contribuir para a intensificação da ativação celular e fisiopatologia da doença. / HTLV-1 is the causative agent of leukemia/lymphoma adult T-cell (ATLL), tropical spastic paraparesis / myelopathy associated with HTLV-1 (HAM / TSP) and uveitis. In addition, keratoconjunctivitis sicca (KCS), a multifactorial disease of the tear and of the ocular surface, has been more frequently reported in patients infected with HTLV-1. As for other HTLV-1-associated diseases, KCS has been related to a high proviral load. Regulatory T (Treg) cells are important in maintaining the homeostasis of the immune system. An impairment in the immunoregulation function of Treg may contribute to the inflammatory environment observed in the KCS. This study aimed to evaluate the Treg cells of patients with KCS associated with HTLV-1. Frequency of activated T cells (HLA-DR+) and CD4+ and CD8+ Treg cells (FOXP3+), as well as IL-10 and TGF-β production by Treg were quantified using flow cytometry. Thirty-seven HTLV-1 individuals were included (27 asymptomatic for HAM/TSP with positive diagnosis of ocular manifestation (KCS), 10 with negative diagnosis (ASS - asymptomatic). Seventeen non-infected individuals were included as controls (NI). The frequencies of CD4+ FOXP3+ T cells, CD8+FOXP3+, CD4+HLA-DR+ and CD8+HLA-DR+ were significantly higher in KCS and ASS groups when compared to non-infected individuals. As the production of immunosuppressive cytokines, a higher frequency of CD4+ FOXP3+ double producers of IL-10 and TGF-β in the KCS group was observed when compared to group ASS. Regarding the CD8+FOXP3+ lymphocytes, the KCS group had a higher frequency of mono cells producing IL-10 when compared to the ASS. Our results suggest that the lower frequency of Treg cells CD8+ TGF-β-producing in individuals infected with HTLV-1 with KCS, may contribute to the intensification of cellular activation and pathophysiology of the disease.

Introdução: Desde a década de 1970, quando se observou que a transfusão pré-transplante renal diminuía a rejeição ao enxerto, o efeito transfusion-related immunomodulation (TRIM) vem sendo estudado, não havendo, ainda, um entendimento completo de seu mecanismo. Recentemente, a descrição das células T reguladoras (TREG) trouxe novas possibilidades de compreensão desse fenômeno, com grande implicação terapêutica. Objetivos: Avaliar a proporção de células TREG antes e após a transfusão de concentrado de hemácias em uma amostra de pacientes clínicos não imunossuprimidos e correlacionar os resultados com o volume transfundido e o tempo de estocagem do sangue. Métodos: Pacientes com diversas patologias clínicas e com indicação de transfusão de concentrado de hemácias foram recrutados consecutivamente. Após assinatura do consentimento informado, o número de células TREG pré e pós-transfusão foi avaliado, bem como sua correlação com o número de unidades transfundidas e o tempo de estocagem. Resultados: Observou-se um aumento estatisticamente significativo na proporção de células TREG (CD4+, CD25+, FOXP3+) 72 horas após a transfusão (p=0,003). Tal aumento mostrou correlação com o número de unidades transfundidas, mas não com o tempo de estocagem (p=0,017 e 0,49, respectivamente). Conclusão: O aumento do numero de células TREG parece estar presente após transfusão de hemácias não leucodepletadas mesmo em uma amostra heterogênea, o que reforça sua importância clínica. A influência do número de unidades mas não do tempo de estocagem corrobora estudos anteriores. O mecanismo molecular do efeito TRIM, bem como seu impacto clínico em um cenário real, ainda precisam ser melhor avaliados. / Background: Transfusion-related immunomodulation (TRIM) has been the subject of research since the 1970s, when transfusion before kidney transplantation was found to decrease the rates of allograft rejection, but the mechanisms underlying this effect have yet to be fully elucidated. The recent description of regulatory T cells (TREG) has paved the way for a new understanding of this phenomenon, with major therapeutic implications. Objectives: To assess the levels of TREG cells before and after transfusion of packed red blood cells in a clinical sample of non-immunosuppressed patients and to correlate findings with the volume of blood transfused and length of storage. Methods: Patients with a variety of clinical conditions and with an indication for transfusion of packed red blood cells were recruited consecutively. After providing informed consent, pre- and post-transfusion TREG levels were measured, and their correlation with number of units transfused and length of storage was assessed. Results: There was a significant increase in the levels of TREG cells (CD4+/CD25+/FOXP3+) within 72 hours of transfusion (p=0.003). This increase correlated with the number of units transfused, but not with length of storage (p=0.017 and 0.49, respectively). Conclusion: An increase in TREG cell levels appears to follow transfusion of non-leukoreduced packed red blood cells even in a heterogeneous sample, which highlights the clinical relevance of this phenomenon. The influence of number of transfused units, but not of length of storage, on the results corroborates the findings of previous non-clinical studies. Further research is warranted to better investigate the molecular mechanism of the TRIM effect, as well as its clinical impact in real-world settings.

Made available in DSpace on 2015-10-06T13:03:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-14. Added 1 bitstream(s) on 2015-10-06T13:18:24Z : No. of bitstreams: 1 000819084.pdf: 1209964 bytes, checksum: 04874bbac5638856dedf456279299e45 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A leishmaniose visceral é uma doença imunomediada que pode causar alterações na população de linfócitos T em diferentes órgãos e tecidos, e também aumento de células inflamatórias no encéfalo de cães infectados. O objetivo deste estudo foi avaliar e caracterizar as lesões encefálicas por meio de análise de cortes histológicos do encéfalo e as subpopulações de linfócitos T CD4+, CD8+, duplo-positivos (DP), duplo-negativos (DN), TCRs αβ e δγ e células dendríticas (cd11c+/MHC-II+) provenientes de linfonodos regionais da cabeça e do linfonodo poplíteo de cães com leishmaniose visceral utilizando citometria de fluxo. Os resultados mostram que encéfalos de cães com LV podem apresentar infiltrados inflamatórios em região de leptomeninges, plexo coroide e região subependimária. Entre os linfonodos, não houve diferença entre as subpopulações de linfócitos T, porém, observamos redução dos linfócitos T CD8+ e aumento dos T DN e TCR δγ enquanto que os CD4+ e DP e TCR αβ mantiveram-se próximos a valores de cães saudáveis, sugerindo assim que os linfócitos DN e TCR δγ podem estar relacionados com a resposta imunológica de cães sintomáticos com LV. Todos esses achados descartam a hipótese de que os linfonodos regionais da cabeça poderiam apresentar um padrão de resposta imune específica relacionada com as lesões encefálicas dos cães / Visceral leishmaniasis (VL) is an immune-mediated disease which may cause changes in T lymphocytes population in different organs and tissues, and also an increase in the inflammatory cells population in the brain of infected dogs. The aim of this study was to evaluate the encephalic lesions in brain sections, and to characterize the T lymphocytes subsets CD4+, CD8+, double-positive (DP), double-negative (DN), the TCRs αβ and δγ, and the dendritic cells (CD11c+/MHC-II+) from the regional lymph nodes of the head and the popliteal lymph node using flow cytometry. The results evidenced that the brain of dogs with VL may present inflammatory infiltrates in leptomeninges, choroid plexus and subependymal area. Between the lymph nodes, there was no difference among the T cell subsets, nevertheless, there was noticed a reduction in the CD8+ lymphocytes and an increase in the DN subset as well as the TCR δγ, while CD4+, DP and TCR αβ were detected in amounts closely related to described reference ranges, which suggests that the DN and TCR δγ lymphocytes may be related to the immune response in symptomatic dogs. Altogether, these findings discard the hypothesis that the regional lymph nodes of the head may present a specific pattern of immune response related to the brain lesions in dogs with VL.