Microbiology and Immunology Department Theses and Dissertations

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A Human Pluripotent Stem Cell-Derived In Vitro Model of the Blood-Brain Barrier in Cerebral Malaria
(2024-01) Gopinadhan, Adnan; John, Chandy C.; Nelson, David E.; Bauer, Margaret E.; Absalon, Sabrina; Tran, Tuan M.
Blood-brain barrier (BBB) disruption is a central feature of cerebral malaria (CM), a severe complication of Plasmodium falciparum (Pf) infections. In CM, sequestration of Pf-infected red blood cells (Pf-iRBCs) to brain endothelial cells combined with inflammation, hemolysis, microvasculature obstruction and endothelial dysfunction mediates BBB disruption, resulting in severe neurologic symptoms including coma and seizures, potentially leading to death or long-term sequelae. In vitro models have advanced our knowledge of CM-mediated BBB disruption, but the physiological relevance remains uncertain. I aimed to develop a novel in vitro model of the BBB in CM using human induced pluripotent stem cell-derived brain microvascular endothelial cells (hiPSC-BMECs) that mimic a near in vivo barrier phenotype. hiPSC-BMECs were co-cultured with HB3var03 strain Pf-iRBCs up to 9 hours. Barrier integrity was measured using transendothelial electrical resistance (TEER). Localization and expression of tight junction (TJ) proteins, occludin and zona occludin-1 (ZO-1), and endothelial marker, intercellular adhesion molecule 1 (ICAM-1) was determined using immunofluorescence imaging (IF) and western blotting (WB). Expression of angiogenic and cell stress markers were also measured. hiPSC-BMECs showed improved barrier integrity and localization of TJ proteins compared to immortalized BMECs. After 6-hours of co-culture with Pf-iRBCs, hiPSC-BMECs showed reduced TEER and disruption of TJ protein localization compared to co-culture with uninfected RBCs (RBCs), but no change in TJ protein expression was observed by WB in the Pf-iRBCs co-cultures. Expression of ICAM-1 on hiPSC-BMECs co-cultured with Pf-iRBCs was higher compared to co-culture with RBCs. In addition, there was an increase in expression of the angiogenin, platelet factor 4, and phospho-heat shock protein-27 in the Pf-iRBCs co-cultures compared to co-cultures with RBCs. These findings demonstrate the physiological relevance of our hiPSC-BMEC-based in vitro model of the BBB, as determined by elevated TEER and appropriate TJ protein localization. In co-culture with Pf-iRBCs, breakdown in the barrier integrity, changes in TJ protein localization, increase in expression of ICAM-1, and of markers of angiogenesis and cellular stress, all point towards a more relevant in vitro model, suitable for investigating pathogenic mechanisms underlying BBB disruption in CM.
ANTI-TUMOR AND RADIO-SENSITIZING PROPERTIES OF AD-IU2, A PROSTATE-SPECIFIC REPLICATION-COMPETENT ADENOVIRUS ARMED WITH TRAIL
(2009-03-18T18:58:00Z) Jimenez, Juan Antonio; Gardner, Thomas A.; Kao, Chinghai; Crabb, David W.; Harrington, Maureen A.; Roman, Ann
In this thesis, I investigated the preclinical utility and antitumor efficacy of TRAIL delivered by Ad-IU2, a prostate-specific replication-competent adenovirus (PSRCA), against androgen-independent prostate cancer. Through transcriptional control of adenoviral early genes E1a, E1b and E4, as well as TRAIL by two bidirectional prostate-specific enhancing sequences (PSES), expression of TRAIL as well as adenoviral replication was limited to prostate-specific antigen and prostate-specific membrane antigen (PSA/PSMA)-expressing cells. Ad-IU2 replicated efficiently in and was restricted to PSA/PSMA-positive prostate cancer cells and induced 5-fold greater apoptosis in androgen-independent CWR22rv and C4-2 prostate cancer cells than the PSRCA control not expressing TRAIL. Ad-IU2 exhibited superior killing efficiency in PSA/PSMA-positive prostate cancer cells at doses 5 to 8-fold lower than that required by a non-TRAIL expressing PSRCA to produce a similar effect. This enhanced cytotoxic effect was not observed in non-prostatic cells, however. As an enhancement of its therapeutic efficacy, Ad-IU2 exerted a bystander effect through either direct cell-to-cell contact or soluble factors present in conditioned media from Ad-IU2-infected cells. In vivo, Ad-IU2, as compared to a control PSRCA, markedly suppressed the growth of subcutaneous CWR22rv xenografts at six weeks post-treatment (3.1 vs. 17.1-fold growth of tumor). The treatment of androgen-independent prostate cancer with Ad-IU2 prior to external beam radiation therapy (EBRT) significantly reduced clonogenic survival with dose reduction factors of 4.91 and 2.43 for CWR22rv and C4-2 cells, respectively. Radio-sensitization by Ad-IU2 was restricted to PSA/PSMA-positive cells. Combinatorial radio-gene therapy resulted in accumulation of cells in G1 phase and a perturbation of the radiation-induced G2 phase arrest. This multi-modal approach combining viral lysis, apoptosis-inducing gene therapy, and radiation therapy could have great impact in achieving complete local tumor control while reducing radiation dose and associated treatment morbidities. This would result in improvement of the clinical outcome of patients with high risk prostate cancer.
Biological Functions of Intracellular Hepatitis B e Antigen
(2019-09) Mitra, Bidisha; Guo, Haitao; Androphy, Elliot J.; Kaplan, Mark; Yu, Andy; Lu, Tao
The function(s) of the intracellular form of HBeAg, previously reported as the preCore protein intermediate (p22) without the N-terminal signal peptide, remains elusive. Here, we propose to elucidate the translocation of p22 during its formation from endoplasmic reticulum (ER) to cytosol, how it differs from core in its inability to form a capsid and the biological functions of cytoplasmic and nuclear p22. Firstly, we have identified that a portion of p22, after the cleavage of its signal peptide in ER, is released back into the cytosol through an ERAD-independent mechanism, as neither wildtype nor dominant-negative p97 affected the ER-to-cytosol translocation of p22 or ER-Golgi secretion of HBeAg. Secondly, despite sharing the same sequence with core protein except for the extended 10 amino acid precore region at the N-terminus, we observed that p22 wildtype and C-7Q mutant are unable to form a capsid. Thirdly, we report that p22 but not the secreted HBeAg significantly reduced interferon stimulated response element (ISRE) activity and expression of interferon stimulated genes (ISGs) upon interferon-alpha (IFN- α) stimulation. Furthermore, in line with this, RNA-seq analysis of ISG induction profile from IFN-α treated patients showed that HBeAg(+) patients exhibited reduced and weak antiviral ISG upregulations compared to HBeAg(-) patients. Further, mechanistic study indicated that while p22 did not alter the total STAT1 or p-STAT1 levels in IFN-α treated cells, it blocked the nuclear translocation of p-STAT1 by interacting with karyopherin α1, indicating that the cytoplasmic p22 may impede JAK-STAT signaling to help the virus evade host innate immune response and cause resistance to IFN therapy in patients. Additionally, nuclear p22 and nuclear core were found to interact with the promoter regions (ISRE – containing) of ISGs, suggesting a new mechanism of inhibition of ISG expression upon stimulation. Finally, we found that the nuclear p22 can bind to cccDNA minichromosome and affects cccDNA maintenance and/or transcription. Thus, our results indicate that there is a novel ER sorting mechanism for the distribution of the intracellular and secretory HBeAg, and the intracellular HBeAg may contribute to HBV persistence by interfering with IFN-α elicited JAK-STAT signaling and regulating cccDNA metabolism.
CD166 modulates disease progression and osteolytic disease in multiple myeloma
(2016-03-16) Xu, Linlin; Xu, Linlin
Multiple myeloma (MM) is an incurable malignancy characterized by the proliferation of neoplastic plasma cells in the bone marrow (BM) and by multiple osteolytic lesions throughout the skeleton. We previously reported that CD166 is a functional molecule on normal hematopoietic stem cells (HSC) that plays a critical role in HSC homing and engraftment, suggesting that CD166 is involved in HSC trafficking and lodgment. CD166, a member of the immunoglobulin superfamily capable of mediating homophilic interactions, has been shown to enhance metastasis and invasion in several tumors. However, whether CD166 is involved in MM and plays a role in MM progression has not been addressed. We demonstrated that a fraction of all human MM cell lines tested and MM patients’ BM CD138+ cells express CD166. Additionally, CD166+ cells preferentially home to the BM of NSG mice. Knocking-down (KD) CD166 expression on MM cells with shRNA reduced their homing to the BM. Furthermore, in a long-term xenograft model, NSG mice inoculated with CD166KD cells showed delayed disease progression and prolonged survival compared to mice receiving mock transduced cells. To examine the potential role of CD166 in osteolytic lesions, we first used a novel Ex Vivo Organ Culture Assay (EVOCA) which creates an in vitro 3D system for the interaction of MM cells with the bone microenvironment. EVOCA data from MM cells lines as well as from primary MM patients’ CD138+ BM cells demonstrated that bone osteolytic resorption was significantly reduced when CD166 was absent on MM cells or calvarial cells. We then confirmed our ex vivo findings with intra-tibial inoculation of MM cells in vivo. Mice inoculated with CD166KD cells had significantly less osteolytic lesions. Further analysis demonstrated that CD166 expression on MM cells alters bone remodeling by inhibiting RUNX2 gene expression in osteoblast precursors and increasing RANKL to OPG ratio in osteoclast precursors. We also identified that CD166 is indispensable for osteoclastogenesis via the activation of TRAF6-dependent signaling pathways. These results suggest that CD166 directs MM cell homing to the BM and promotes MM disease progression and osteolytic disease. CD166 may serve as a therapeutic target in the treatment of MM.
CD4+ T cell mediated tumor immunity following transplantation of TRP-1 TCR gene modified hematopoietic stem cells
(2013-12-10) Ha, Sung Pil; Touloukian, Christopher E.; Broxmeyer, Hal E.; Gardner, Thomas A.; Harrington, Maureen A.; He, Johnny J.
Immunotherapy for cancer has held much promise as a potent modality of cancer treatment. The ability to selectively destroy diseased cells and leave healthy cells unharmed has been the goal of cancer immunotherapy for the past thirty years. However, the full capabilities of cancer immunotherapies have been elusive. Cancer immunotherapies have been consistently hampered by limited immune reactivity, a diminishing immune response over time, and a failure to overcome self-tolerance. Many of these deficiencies have been borne-out by immunotherapies that have focused on the adoptive transfer of activated or genetically modified mature CD8+ T cells. The limitations inherent in therapies involving terminally differentiated mature lymphocytes include limited duration, lack of involvement of other components of the immune system, and limited clinical efficacy. We sought to overcome these limitations by altering and enhancing long-term host immunity by genetically modifying then transplanting HSCs. To study these questions and test the efficiency of gene transfer, we cloned a tumor reactive HLA-DR4-restricted CD4+ TCR specific for the melanocyte differentiation antigen TRP-1, then constructed both a high expression lentiviral delivery system and a TCR Tg expressing the same TCR genes. We demonstrate with both mouse and human HSCs durable, high-efficiency TCR gene transfer, following long-term transplantation. We demonstrate the induction of spontaneous autoimmune vitiligo and a TCR-specific TH1 polarized memory effector CD4+ T cell population. Most importantly, we demonstrate the destruction of subcutaneous melanoma without the aid of vaccination, immune modulation, or cytokine administration. Overall, these results demonstrate the creation of a novel translational model of durable lentiviral gene transfer, the induction of spontaneous CD4+ T cell immunity, the breaking of self-tolerance, and the induction of anti-tumor immunity.
Characterization of a Novel Fis1 Interactor Required for Peripheral Distribution of the Mitochondrion of Toxoplasma Gondii
(2021-02) Jacobs, Kylie; Arrizabalaga, Gustavo; Gilk, Stacey; Graham, Brett; John, Chandy; Yang, Frank
Toxoplasma’s singular mitochondrion is extremely dynamic and undergoes morphological changes throughout the parasite’s life cycle. While intracellular‚ the mitochondrion is maintained in a lasso shape that stretches around the parasite periphery and is in close proximity to the pellicle‚ suggesting the presence of membrane contact sites. Upon egress‚ these contact sites disappear‚ and the mitochondrion retracts and collapses towards the apical end of the parasite. Once reinvaded‚ the lasso shape is quickly reformed‚ indicating that dynamic membrane contact sites regulate the positioning of the mitochondrion. We discovered a novel protein (TgGT1_265180) that associates with the mitochondrion via interactions with the fission related protein Fis1. Knockout of TgGT1_265180‚ which we have dubbed LMF1 for Lasso Maintenance Factor 1‚ results in a complete disruption of the normal mitochondrial morphology. In intracellular LMF1 knockout parasites, the mitochondrial lasso shape is disrupted‚ and instead it is collapsed as normally only seen in extracellular parasites. Additionally, proper mitochondrial segregation is disrupted‚ resulting in parasites with no mitochondrion and extra mitochondrial material outside of the parasites. These gross morphological changes are associated with a significant reduction of parasite propagation and can be rescued by reintroduction of a wildtype copy of LMF1. Co-immunoprecipitations and Yeast Two-Hybrid predict interactions with the parasite pellicle. Therefore, we hypothesize that LMF1 mediates contact between the mitochondrion and the pellicle in a regulatable fashion‚ and that the LMF1-dependent morphodynamics are critical for parasite propagation. Current studies are focused on characterizing the consequences of mitochondrial collapse and identifying proteins that interact with LMF1 to position the mitochondrion to the periphery of the parasite.
Characterization of Allergen-Specific Immunoglubulin E Development in a Food Allergy Model and Its Regulation by T Follicular Helper and T Follicular Regulatory Cells
(2023-05) Chen, Qiang; Dent, Alexander; Kaplan, Mark; Brutkiewicz, Randy; Zhou, Baohua
Food allergy is a highly prevalent and serious disease regulated by immunoglobin E (IgE) antibodies specific for food allergens.The development of IgE is regulated by T follicular helper cells (TFH) and T follicular regulatorycells (TFR) in the germinal center (GC). We aimed to understandthe regulation of IgEin the GC by TFH and TFR cellsusinga mouse food allergy model. We found that the dosage and timingof allergen delivery into thegut is criticalfor allergen-specific IgE development, in part because the timing of allergen delivery affected the expression of regulatory factors by TFH and TFR cells. We studied FGL2, an inhibitory factor, and found that down-regulation of FGL2 in TFH cells was important for the allergic IgEresponse. Apart from inhibitory factors, TFH cell-derived IL-4 is required for IgE responses. We unexpectedlyfound that TFR cells in food allergy produce comparable amountsof IL-4 to TFH cellsand IL-4–expressing TFR cells promoteallergen-specific IgEin food allergy. The IgE response is highly sensitive to IL-4 levels, suggesting the need for extra IL-4 from TFR cells. However,TFR cells have distinct functionsdepending on the immune environment, since TFR cells repress IgEinanairway inflammation model. We found that TFR cells in airway inflammation have a different gene expression profile from TFR cells in food allergy, whichmay explain their distinct functions. Lastly, previous studies showed that high-affinity IgE driving anaphylactic reactions is produced via IgG1-switchedintermediate B cells. We challenged this paradigm by showing that high-affinity IgE develops in the absence ofIgG1-switchedB cellsin our food allergy model.Overall, our studies reveal that IgE is regulated by novel pathways in food allergy. We hope to exploit these new pathways to develop new specific therapies for food allergy.
Characterization of Hepatitis C Virus Infection of Hepatocytes and Astrocytes
(2014) Liu, Ziqing; Yu, Andy; He, Johnny J.; Brutkiewicz, Randy R.; Kao, Cheng C.; Sullivan Jr., William J.
Approximately 2.8% of the world population is currently infected with hepatitis C virus (HCV). Neutralizing antibodies (nAbs) are often generated in chronic hepatitis C patients yet fail to control the infection. In the first two chapters of this study, we focused on two alternative routes of HCV transmission, which may contribute to HCV’s immune evasion and establishment of chronic infection. HCV was transmitted via a cell-cell contact-mediated (CCCM) route and in the form of exosomes. Formation of HCV infection foci resulted from CCCM HCV transfer and was cell density-dependent. Moreover, CCCM HCV transfer occurred rapidly, involved all four known HCV receptors and intact actin cytoskeleton, and led to productive HCV infection. Furthermore, live cell imaging revealed the temporal and spatial details of the transfer process. Lastly, HCV from HCV-infected hepatocytes and patient plasma occurred in both exosome-free and exosome-associated forms and the exosome-associated HCV remained infectious, even though HCV infection did not significantly alter exosome secretion. In the third chapter, we characterized HCV interaction with astrocytes, one of the putative HCV target cells in the brain. HCV infection causes the central nervous system (CNS) abnormalities in more than 50% of chronically infected subjects but the underlying mechanisms are largely unknown. We showed that primary human astrocytes (PHA) were very inefficiently infected by HCV, either in the free virus form or through cell-cell contact. PHA expressed all known HCV receptors but failed to support HCV entry. HCV IRES-mediated translation was functional in PHA and further enhanced by miR122 expression. Nevertheless, PHA did not support HCV replication regardless of miR122 expression. To our great surprise, HCV exposure induced robust IL-18 expression in PHA and exhibited direct neurotoxicity. In summary, we showed that CCCM HCV transfer and exosome-mediated HCV infection constituted important routes for HCV infection and dissemination and that astrocytes did not support productive HCV infection and replication, but HCV interactions with astrocytes and neurons alone might be sufficient to cause CNS dysfunction. These findings provide new insights into HCV infection of hepatocytes and astrocytes and shall aid in the development of new and effective strategies for preventing and treating HCV infection.
Characterization of Normal and Preleukemic Hematopoietic Stem Cell Responses to Physiologic and Extra-Physiologic Oxygen Tension
(2022-08) Aljoufi, Arafat; Kaplan, Mark H.; Zhang, Chi; Srour, Edward F.; Kapur, Reuben
Hematopoietic stem and progenitor cells (HSCs/HPCs) transplantation is a curative treatment for a variety of hematologic and non-hematologic diseases. Successful HSC transplantation requires infusing patients with a sufficient number of long-term engrafting HSCs. As a result, research efforts have focused on optimizing the collection process. Previous work established that harvesting mouse bone marrow HSCs under low oxygen tension similar to that reported for the bone marrow niche in situ (physioxia), results in enhanced HSC recovery and function. However, collecting bone marrow cells under physioxia is not a clinically viable approach. Here, I demonstrated that the collection and processing of peripheral blood mobilized with G-CSF alone or G-CSF and Plerixafor under physioxia resulted in a greater number of phenotypically defined long-term engrafting HSCs. Using high-resolution single cell sequencing to explore the molecular programs governing HSCs under physioxia, I identified increased expression of genes involved in HSC self-renewal and maintenance. In contrast, HSCs under ambient air upregulated genes implicated in HSC differentiation, apoptosis, and inflammatory pathways. Furthermore, wild-type HSCs under physioxia revealed a significant reduction in gene expression and activity of the epigenetic modifier Tet2. Consequently, I evaluated the phenotyping, engraftment potential and gene expression of preleukemic Tet2-/- bone marrow cells under physioxia and ambient air. Unlike wild-type HSCs, Tet2-/- HSCs/HPCs were unresponsive to changes in oxygen tension. Notably, we observed similar phenotypes, functions, and self-renewal and quiescence gene expression in wild-type HSCs under physioxia and Tet2- /- HSCs under physioxia or ambient air. These findings imply that the preserved stemness and enhanced engraftment of HSCs under physioxia may in part be a result of Tet2 downregulation. Understanding the mechanisms regulating wild-type and preleukemic HSCs under physioxia will have therapeutic implications for optimizing HSC transplantation and mitigating the growth advantage of preleukemic stem cells.
Control of inflammation, helper T cell responses and regulatory T cell function by Bcl6
(2014-01-13) Sawant, Deepali Vijay; Dent, Alexander L.; Kaplan, Mark H.; Blum, Janice Sherry, 1957-; Touloukian, Christopher E.
Regulatory T (Treg) cells represent an important layer of immune-regulation indispensible for curtailing exuberant inflammatory responses and maintaining self-tolerance. Treg cells have translational potential for autoimmunity, inflammation, transplantation and cancer. Therefore, delineating the molecular underpinnings underlying the development, suppressor function and stability of Tregs is particularly warranted. The transcriptional repressor Bcl6 is a critical arbiter of helper T cell fate, promoting the follicular helper (Tfh) lineage while repressing Th1, Th2 and Th17 differentiation. Bcl6-deficient mice develop a spontaneous and severe Th2-type inflammatory disease including myocarditis and pulmonary vasculitis, suggesting a potential role for Bcl6 in Treg cell function. Bcl6-deficient Treg cells are competent in controlling Th1 responses, but fail to control Th2 inflammation in an airway allergen model. Importantly, mice with Bcl6 deleted specifically in the Treg lineage develop severe myocarditis, thus highlighting a critical role for Bcl6 in Treg-mediated control of Th2 inflammation. Bcl6-deficient Tregs display an intrinsic increase in Th2 genes and microRNA-21 (miR-21) expression. MiR-21 is a novel Bcl6 gene target in T cells and ectopic expression of miR-21 directs Th2 differentiation in non-polarized T cells. MiR-21 is up-regulated in mouse models of airway inflammation and also in human patients with eosinophilic esophagitis and asthma. Thus, miR-21 is a clinically relevant biomarker for Th2-type pathologies. Our results define a key function for Bcl6 in repressing Gata3 function and miR-21 expression in Tregs, and provide greater understanding of the control of Th2 inflammatory responses by Treg cells.

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