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acase@tulane.edu

acase@tulane.edu

CD8 T cells play a critical role in the clearance of pathogenic bacteria, viruses, and protozoan parasites. Upon encountering their cognate antigen through either infection or vaccination, naïve CD8 T cells undergo robust proliferative expansion, which is followed by contraction and the formation of a memory population. Memory CD8 T cells are long-lived, and because they persist in increased numbers and possess enhanced functional abilities compared to naïve CD8 T cells, they are able to provide the host with increased protection following re-infection. Because of these properties, vaccines designed to elicit memory CD8 T cells have the potential to reduce health care burdens related to infection with pathogens including human immuno deficiency virus (HIV), malaria, influenza, and hepatitis virus. However, stimulating protective CD8 T cell responses against these pathogens through vaccination has proven challenging. Therefore, a better understanding of the properties of memory CD8 T cells generated following vaccination, and the characteristics of memory CD8 T cells best suited for providing protection against diverse pathogens is needed. While memory CD8 T cells can be maintained for as long as the life of the host, evidence suggests that their properties change with time after infection. Because CD8 T cell-mediated protection is based upon both the numbers and quality or functional abilities of memory cells present at the time of re-infection, changes in memory CD8 T cell function over time could impact their ability to provide protection upon re-infection. Therefore, a better understanding of how memory CD8 T cells change with time after infection is needed. As part of the studies presented in this thesis, I found that the phenotype and function of memory CD8 T cells including localization, interleukin (IL)-2 cytokine production, responsiveness to homeostatic cytokines, metabolic capabilities, and proliferation and secondary memory generation potential change with time after infection. Interestingly functional changes could not be completely explained by changes in subset composition that occur with time, as changes over time were also seen in defined CD62Lhi subsets. Importantly, functional changes of memory CD8 T cells that occurred with time led to an increased ability to provide protection against a chronic viral infection. These data improve our knowledge of the capabilities of memory CD8 T cells generated following infection, and suggests that the outcome of vaccination strategies designed to elicit protective memory CD8 T cells using single or prime-boost immunizations will depend upon the timing between antigen encounters. Following re-infection, memory CD8 T cells become activated and produce effector cytokines and cytolytic molecules that aid the host in clearing invading microbes. Activation can be triggered not only through cognate antigen recognition, but also by antigen-independent cytokine driven signals. However, our knowledge of how antigen-dependent and –independent signals contribute to CD8 T cell activation and protection following infection is incomplete. In the second part of my thesis, I show that the ability of memory CD8 T cells to become activated in response to inflammation decreases with time after infection, that antigen and inflammation act synergistically to induce activation of memory CD8 T cells, that the presence of cognate antigen enhances activation of memory CD8 T cells that contribute to clearance of infection, and that bystander memory CD8 T cell responses following unrelated bacterial infection do not provide the host with a protective benefit. Together, the data in this thesis further our understanding of memory CD8 T cells generated following infection and/or vaccination, and the properties of memory CD8 T cells important for providing protection upon re-infection with invading pathogens.

Influenza A virus (IAV) is a major cause of serious respiratory illness worldwide, leading to approximately 5 million severe cases and 500,000 deaths per year. Given the disease severity, associated economic costs, and recent appearance of novel IAV strains, there is a renewed interest in developing novel and efficacious “universal” IAV vaccination strategies as well as therapeutic remedies. Previous studies from our laboratory have concentrated on IAV-specific CD8 T cell-mediated protection against IAV infection as IAV-specific CD8 T cells are needed for efficient clearance of virus. Recent studies highlight that immunizations capable of generating local (i.e., nasal mucosa and lung) tissue-resident memory T and B cells in addition to systemic immunity offer the greatest protection against future IAV encounters. Current IAV vaccines are designed to largely stimulate IAV-specific antibodies, but do not generate the lung-resident memory T and B cells induced during IAV infections. In order to effectively generate lung-resident memory populations, it is believed a local antigen depot is needed as tissue-resident memory formation is enhanced by the presence of local antigen. Recently, polyanhydride nanoparticles have been demonstrated to slowly release their contents at the site of inoculation serving as an antigen depot. However, the ability of an intranasal vaccination with polyanhydride nanoparticles to induce IAV-specific lung-resident immune responses and provide protection against subsequent IAV infection has not been determined. Here, I report on the intranasal administration of a biocompatible polyanhydride nanoparticle-based IAV vaccine (IAV-nanovax). IAV-nanovax is capable of providing protection against subsequent homologous and heterologous IAV infections in both inbred and outbred populations. My findings demonstrate that vaccination with IAV-nanovax promotes the induction of germinal center B cells within the lungs that are associated with both systemic IAV-specific IgG as well as local lung IAV-specific IgG and IgA antibodies. Furthermore, intranasal IAV-nanovax vaccination leads to a significant increase in IAV-specific CD4 and CD8 T cells within the lung vasculature as well as in the lung tissue. Most importantly, my studies demonstrate that IAV-nanovax induced lung-resident IAV-specific CD4 and CD8 T cells express canonical tissue-resident memory markers. This dissertation further explores a novel regulation pathway previously identified by our laboratory where plasmacytoid dendritic cells (pDCs) eliminate IAV-specific CD8 T cells early during high-dose and high-pathogenic IAV infections in a FasL:Fas (pDCs:CD8 T cell) dependent manner. However, recent studies suggest that B cells are the predominate lymphocyte to express FasL in mice. Here, I demonstrate that FasLpos B cells greatly outnumber FasLpos pDC within the lung draining lymph nodes (dLNs) during IAV infections. Interestingly, my results demonstrate the presence of two subsets, CD11cpos and CD11cneg, of FasL-expressing B cells that differentially influence the IAV-specific CD8 T cell response during high-dose IAV infections. While CD11cneg B cells kill IAV-specific CD8 T cells, contributing to lethality during high-dose IAV infections, CD11cpos B cells may instead be protective. In addition to the negative impacts of high-dose IAV infections, I also demonstrate that chronic ethanol (EtOH) consumption detrimentally impacts existing IAV-specific CD8 T cell memory responses. Here, my results reveal that chronic EtOH consumption causes a numerical loss in existing IAV-specific CD8 T cell memory responses. This numerical loss in existing IAV-specific CD8 T cell memory is associated with a reduction in cytotoxic activity within the lungs as well as an increase in morbidity and mortality during a secondary IAV challenge. Together, the results presented herein demonstrate the ability of a novel polyanhydride nanovaccine to induce robust pulmonary IAV-specific T and B cell responses and further our understanding of factors that can negatively impact IAV-specific CD8 T cells as well as protection against IAV infection. Overall these findings highlight the importance of IAV-specific CD8 T cells, as well as CD4 T cells and B cells, in providing protection against IAV infections.

O número de jovens infectados por HIV vem aumentando nas últimas décadas, o que salienta a necessidade de estratégias vacinais que sejam imunogênicas em fase precoce de vida capazes de induzir resposta de longa duração. A vacina quimérica LAMP-1/p55Gag, associa o gene que codifica a LAMP-1 (proteína de associação da membrana lisossomal) e o gene da gag do HIV-1, direciona o tráfego da proteína viralpara os compartimentos MIIC, possibilitando a apresentação dos peptídeos virais pela classe II do Complexo Principal de Histocompatibilidade (MHC II). Esta vacina quimérica é imunogênica em camundongos BALB/c adultos e neonatos e crucial para induzir resposta T e B de longa duração, com produção de elevados níveis de anticorpos. Contudo, os mecanismos imunológicos envolvidos na indução da resposta humoral da vacina LAMP/Gag, como a geração de células T auxiliares foliculares (TFH), ainda não são conhecidos no período neonatal. O objetivo do estudo foi avaliar a geração de células TFH, T citotóxicos e B foliculares em camundongos neonatos submetidos à imunização com as vacinas LAMP/Gag (LG) e Gag (G). Inicialmente,avaliamos a imunogenicidade das vacinas gênicas na imunização neonatal aos sete dias de idade em camundongos de linhagem C57BL/6. Os resultados mostram que a imunização neonatal com a vacina LG é capaz de aumentara frequência de células secretoras de IFN-&#978 aos peptídeos imunodominantes da região gag do HIV-1 e de células T CD8&#43IFN-&#978&#43 comparadas a vacina Gag. A imunização neonatal com a vacina LG também levou a produção de títulos elevados de anticorpos IgG1 anti-p24 e aumento da porcentagem de células secretoras de IgG1 Gag-específicas. O priming neonatal com LG é capaz de promover resposta celular e humoral anti-Gag de longa duração. Além disto, a imunização neonatal (ip) com LG foi capaz de induzir células TFH (CD4&#43CXCR5&#43PD-1&#43Bcl-6&#43), linfócitos T CD8&#43 foliculares (TFC) (CD8&#43CXCR5&#43) e formação de centro germinativo (CG) nos linfonodos mesentéricos, contudo, ambas as vacinas induziram células B foliculares (CD19&#43CXCR5&#43). Apesar da menor frequência de TFH dos neonatos em relação a adultos na imunização com LG, houve frequência similar de células TFC. A imunização intradérmica convencional induziu aumento do número de células TFH nos linfonodos inguinais já ao terceiro dia após o reforço vacinal, embora frequência similar de células TFH, TFC e B foliculares. Neste período foi possível observar que a vacina LG também induziu a geração de células B de CG. Outra peculiaridade da vacina LG neonatal foi o aumento da expressão gênica da enzima citidina deaminase (AID). Os resultados mostram que a vacina L/AMP/Gag é imunogênica na fase neonatal de camundongos C57BL/6 quanto à geração de resposta celular e humoral antígeno-específica e resposta de longa duração, similarmente aos camundongos BALB/c. Os dados mostraram que a vacina LG é eficaz na indução de células T foliculares, na maturação de tecidos linfoides com formação de CGs e na indução de transcritos para AID. No conjunto, os achados evidenciam que a estratégia da vacina quimérica L/AMP/Gag é eficaz neste período da vida, e possui importante papel adjuvante na maturação da resposta humoral. / The number of young people infected with HIV has been increasing in recent decades, which highlights the need for vaccine strategies that are immunogenic at early phase of life able of inducing long-term response. The chimeric LAMP-1/p55Gag vaccine, associates the gene encoding LAMP-1 (lysosomal associated membrane protein) and the HIV-1 gag gene, directs the traffic of viral protein to MIIC compartments, leading to presentation of the viral peptides through class II of the Major Histocompatibility Complex (MHC II). This chimeric vaccine is immunogenic in adult and neonatal BALB/c mice and crucial to induce long-term T and B responses, producing high levels of antibodies. However, the immunological mechanisms involved in the induction of the humoral response of the LAMP/Gag vaccine, such as the generation of T follicular helper cells (TFH), are unknown in the neonatal period. The objective of this study was to evaluate the generation of TFH, and follicular cytotoxic T cells and B cells in neonates submitted to immunization with the LAMP/Gag (LG) and Gag (G) vaccines. The results show that neonatal immunization at seven days-old in C57BL/6 mice strain with the LG vaccine is able to increasing the frequency of IFN-&#978-secreting cells to the immunodominant peptides of the HIV-1 gag region and of CD8&#43IFN-&#978&#43 T cells compared to the Gag vaccine. Neonatal immunization with the LG vaccine led to the production of high titers of anti-p24 IgG1 antibodies and the increased percentage of Gag-specific IgG1 secreting cells. Neonatal priming with LG is able to promote long-lasting anti-Gag humoral and cellular response. Moreover, neonatal (ip) immunization with LG was able to induce TFH cells (CD4&#43CXCR5&#43PD-1&#43Bcl-6 &#43), follicular CD8 &#43 T cells (TFC) (CD8&#43CXCR5&#43) and germinal center (GC) formation in the mesenteric lymph nodes, whereas both vaccines induced follicular B cells (CD19&#43CXCR5&#43). Despite the lower frequency of TFH in neonates in relation to adult counterpartin the immunization with LG, a similar percentage of TFC cells was observed. Conventional immunization by intradermal immunization induced an increased number of TFH cells in inguinal lymph nodes on the third day after booster vaccination, despite the similar frequency of follicular TFH, TFC and B cells. In this period the LG vaccine also induced generation of CG B cells. Another peculiarity of the LG neonatal vaccine was the increase in the gene expression of the enzyme activation-induced cytidine deaminase (AID).The results show that the LAMP/Gag vaccine is immunogenic in the neonatal phase of C57BL/6 mice for the generation of antigen-specific humoral and cellular response and long-term response, similar to BALB/c mice. The findings showed effective induction of follicular T cells, maturation of lymphoid tissues with formation of GCs and up-regulation oftranscripts for AID. Taken together, our findings demonstrate that the LAMP/Gag chimeric vaccine strategy is effective at this time in life, and has an important adjuvant role in the maturation of the humoral response.

During hematopoiesis, multilineage progenitor cells and the precursors are committed to individual hematopoietic lineages. In normal myelopoiesis, the immature myeloid cells (IMCs) differentiate into macrophages, neutrophils or dendritic cells. However, under tumor burden, these IMCs differentiate into myeloid derived suppressor cells (MDSCs) result in an up-regulation of immune suppressive factors and pro-tumor effect. The development of normal or malignant is tightly controlled by endogenous signals such as transcription factors and epigenetic regulations. HDAC11 is the newest identified members of the histone deacetylase (HDAC) family. Previous study in our group had identified HDAC11 as a negative regulator of interleukin 10 (IL-10) production in antigen-presenting cells (APCs). However, the mechanisms of HDAC11 in regulating myeloid cells differentiation and function remained unclear. We have uncovered for the first time that in the absence of HDAC11, upon LPS stimulation, neutrophils isolated form mice displays an over-production of pro-inflammatory cytokines such as TNF-alpha and IL-6. Strikingly, these HDAC11KO neutrophils showed a significantly higher migratory and phagocytosis activity, resulting from an overexpression of the migratory receptor and cytokine CXCR/L2. We have performed Chromatin Immunoprecipitation (ChIP) analysis on the neutrophils and discovered that HDAC11 was recruited to the promoter regulatory region of these genes we have identified. This part of data will be discussed mainly in chapter 2. Not only does HDAC11 plays a crucial role in the neutrophil function, our group have also found out that lacking of HDAC11 result in an increased suppressive activity of the Myeloid-derived Suppressor Cells (MDSCs). The previous publication of our group had shown that the tumor bearing mice experienced a much more aggressive growth pattern in the HDAC11 KO mice compare with C57BL/6 wild type control. MDSCs isolated from mice lacking HDAC11 appeared to gain increased capability to suppress the function of antigen-specific CD8+ T cells in vitro. Followed by this initial study, in chapter 3, we observed an up-regulation of both expression and enzymatic activity of arginase 1 and Nos2, two enzymes that are crucial in regulating MDSCs suppressive function. The aberrant enzymatic activity of Arg1 and Nos2 in HDAC11KO MDSCs is possibly result from an over-expression of the lineage-specific transcription factor C/EBPβ, which is previously proved to be essential for the differentiation of functional MDSCs. Furthermore, our ChIP data confirmed that HDAC11 may play as an negative regulator of C/EBPβ. Recently, our lab had demonstrated that T cells lacking HDAC11 gained a hyperactive phenotype and anti-tumor effect, indicating that HDAC11 may play a dual role in the host immune system. We further performed an adoptive transfer therapy to C57BL/6 tumor bearing mice. Our data showed that the additional administration of HDAC11KO MDSCs could eliminate, at least partially, the anti-tumor effect by adoptive transfer of HDAC11KO T cells. Taken together, we have uncovered a previously unknown role for HDAC11 as a transcriptional regulator in the myeloid cells differentiation and function. Based on our data and previous work from our lab, we propose a dual role of HDAC11 played in the host immune system. In the absence of HDAC11, host defenders such as neutrophils and T cells are functionally more aggressive against intruders such as pathogen and cancer. However, the immune suppressors such as MDSCs became more suppressive. The contradictory role HDAC11 played in the immune system may provide some insights for the assessment of the pharmacological value of HDAC11 and contribute to the development of novel immunotherapeutic strategies.

Current immune suppressive strategies fail to induce donor-recipient immune tolerance after allogeneic hematopoietic cell transplantation. Accordingly, patients suffer morbidity and mortality from graft vs. host disease (GVHD) and prolonged immune suppressive therapy. Biologic insight into transplantation tolerance is needed, and translation of such insight to novel clinical strategies may improve clinical outcomes. We report original investigation at seminal phases of this process including initial prophylactic immune suppression, onset of acute graft vs. host disease, and ultimate immune suppression discontinuation: In a controlled randomized clinical trial, we demonstrate that sirolimus-based immune suppression reduces risk for acute GVHD, ameliorates the severity of subsequent chronic GVHD, and supports reconstitution of functional regulatory T cells. Study of tissue-infiltrating CD4+ T cell subsets in acute GVHD target organs supports a pathogenic role for Th17 cells. Finally, we demonstrate that peripheral blood transcriptional biomarkers provide mechanistic insight into human transplantation tolerance. These data signal progress, and suggest rational translational efforts to achieve transplantation tolerance.

Airway hyperresponsiveness (AHR) is one of the primary features of allergic airways disease. Despite continuous allergen exposure atopic asthmatics do not develop progressively worsening AHR. The mechanism(s) that limit AHR are unknown. Two valid candidates are regulatory T cells (Treg) and antigen presenting cells (APC). Dendritic cells (DC) are the main APC within the airways. Presentation of allergens to T cells can result in the differentiation and expansion of different subsets of T cells including effector Treg cells. The precise role of Treg and DC in the attenuation of allergen-induced AHR remains unknown. The general aim of this thesis is to investigate mechanisms to limit AHR in a murine model of atopic asthma. Specific aims are to: 1. develop a murine model of allergen-induced attenuation of AHR, 2. determine the potential role of regulatory T cells (Treg) in allergen-induced AHR attenuation, and 3. determine the potential role of airway dendritic cells (DC) in allergen-induced AHR attenuation. Balb/c mice were sensitised with intraperitoneal Ovalbumin (OVA) in aluminium hydroxide and challenged with a single, 3-weeks or 6-weeks of OVA aerosols. Aerosols were 1% OVA in sterile saline delivered for 30 minutes for three days per week. Animals were sacrificed 24 hours after the final aerosol for measurements of lung function and Methacholine (MCh) responsiveness (low-frequency forced oscillation technique), collection of bronchoalveolar lavage fluid (BALF) and serum. '...' In contrast, 6-weeks of OVA challenges decreased Treg numbers back to control levels. Adoptive transfer of 1x106 Treg taken from DLN of 3-week challenged mice attenuated AHR in single-OVA recipients (p<0.05). Furthermore, in vivo depletion of Treg in 3-week OVA challenged mice restored AHR (p<0.05 compared with control). Similar proportions of CD4+ T cells became activated following both aerosol regimes, however total numbers of airway CD4+ T cells were decreased (p<0.05), and OVA-specific CD4+ T cell proliferation in DLN was reduced (p<0.05) after 3-weeks versus one OVA aerosol. Analysis of antigen handling by airway APC populations showed antigen uptake (OVA-647) and processing (DQ-OVA) by macrophages and airway DC subsets to be down-regulated (p<0.05) after 3-weeks of OVA aerosols. In addition, adoptive transfer of Treg into single-OVA recipients did not affect antigen handling by airway APC populations. These data suggest that Treg are responsible for allergen-induced attenuation of AHR in vivo in established airways disease. AHR attenuation was associated with an altered function of airway DC, resulting in reduced antigen capture and processing, leading to limited clonal expansion of antigen-specific CD4+ T cells with limited production of Th2 cytokines. Furthermore, Treg were not directly responsible for the down-regulation of allergen capture in the airways. In conclusion, knowledge of the role of Treg and DC in attenuation of AHR could potentially result in improved and more directed therapies for the attenuation of AHR in atopic asthmatics.

Abstract not available