Browsing by Author "Dent, Alexander"
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Item Antibodies and Risk of Clinical Malaria in an Area of Low Malaria Transmission in Western Kenya(2024-12) Odhiambo, Eliud Isaac Onyango; John, Chandy; Dent, Alexander; Cook-Mills, Joan; Schmidt, Nathan; Jerde, TravisChildren and adults are at risk for clinical malaria in areas of low malaria transmission. Antibody or antibody effector mechanism correlates of immunity in these areas, and their differences by age, are poorly characterized. To address this research gap, we evaluated the relationship of Plasmodium falciparum-specific antibody levels and merozoite opsonic phagocytosis to the risk of clinical malaria in a case-control study nested within a cohort of 5,753 individuals in a Kenyan highland area with low malaria transmission. Plasma samples were collected in 2007, and individuals evaluated over 10-year follow-up for risk of clinical malaria. Individuals who developed clinical malaria (cases) were matched by village and age to those who did not (controls). We evaluated total IgG, IgG1, IgG3, IgA, and IgM antibodies to Plasmodium falciparum antigens by cytometric bead assay, and opsonic phagocytosis (OP) by flow cytometry. Antibody and OP levels were compared to risk of clinical malaria in three age groups (< 5 years, 5-14 years and 15 years), adjusting for multiple markers of malaria exposure. Antibody and OP levels increased with age. In children < 5 years old, higher levels of total IgG and IgG1 to the P. falciparum antigen GLURP-R2 and total IgG and IgG3 to the P. falciparum antigen MSP-2 were associated with reduced risk of clinical malaria, but OP levels were not associated with risk of clinical malaria. Conversely, in children 5-14 years old and individuals ≥ 15 years old, higher antibody levels to multiple antigens as well as higher OP levels were associated with increased risk of clinical malaria. In this low transmission area, antibody and OP levels in individuals ≥ 5 years old may serve as markers of malaria risk that add to known risk markers in this area such as insecticide-treated net use, elevation and proximity to forest.Item Bcl6 is a subset-defining transcription factor of lymphoid tissue inducer-like ILC3(Cell Press, 2023) Tachó-Piñot, Roser; Stamper, Christopher T.; King, James I.; Matei-Rascu, Veronika; Richardson, Erin; Li, Zhi; Roberts, Luke B.; Bassett, John W.; Melo-Gonzalez, Felipe; Fiancette, Rémi; Lin, I-Hsuan; Dent, Alexander; Harada, Yohsuke; Finlay, Conor; Mjösberg, Jenny; Withers, David R.; Hepworth, Matthew R.; Microbiology and Immunology, School of MedicineInnate lymphoid cells (ILCs) are tissue-resident effector cells with roles in tissue homeostasis, protective immunity, and inflammatory disease. Group 3 ILCs (ILC3s) are classically defined by the master transcription factor RORγt. However, ILC3 can be further subdivided into subsets that share type 3 effector modules that exhibit significant ontological, transcriptional, phenotypic, and functional heterogeneity. Notably lymphoid tissue inducer (LTi)-like ILC3s mediate effector functions not typically associated with other RORγt-expressing lymphocytes, suggesting that additional transcription factors contribute to dictate ILC3 subset phenotypes. Here, we identify Bcl6 as a subset-defining transcription factor of LTi-like ILC3s in mice and humans. Deletion of Bcl6 results in dysregulation of the LTi-like ILC3 transcriptional program and markedly enhances expression of interleukin-17A (IL-17A) and IL-17F in LTi-like ILC3s in a manner in part dependent upon the commensal microbiota-and associated with worsened inflammation in a model of colitis. Together, these findings redefine our understanding of ILC3 subset biology.Item 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, BaohuaFood 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.Item DEK Protein as a Potential Radio-protective Agent for Hematopoietic Stem Cells (HSCs) and Hematopoietic Progenitor Cells (HPCs) in Mice(2018-07-26) Sharma, Itee; Broxmeyer, Hal E.; Edward, Srour F.; Dent, Alexander; Orschell, ChristieStudies performed by our lab have investigated the potential radioprotective effect of rDEK protein. Although roles played by DEK in cell differentiation, DNA repair, DNA binding, chromatin regulating and different malignancies have been investigated previously in different cell types, the prospect of DEK being used as a potential radioprotective agent for HSCs has not yet been explored. In this study, using primary cells isolated from bone marrow of C57BL/6 mice in vitro, our data indicated that rDEK has the ability to act as potential radioprotector of HSC. Moreover, a significant decrease in percentages of caspase-3 and caspase-9 protease enzymes was observed after irradiation in presence of rDEK. Taken, together the data suggests that DEK imparts its effect as a potential radioprotective agent, via inhibiting the caspase-dependent intrinsic apoptosis pathway. We found no evidence that DEK could act as a radiomitigator but this was not tested in primary cells as well as in animals.Item Distinct Cell Survival and Metabolic Programming Determines Germinal Center Tfh Survival of HIV-1 Infection(2023-07) Syed, Fahim; Yu, Qigui; Dent, Alexander; Yang, Kai; Wan, JunHIV-1 is the causative agent of AIDS in people living with HIV-1 (PLHIV). HIV-1 predominantly targets and kills immune cells that are needed for defense against infections and illnesses. Although therapy can control the spread of HIV-1 in PLHIV and decrease the amount of virus present in the body, some subsets of infected immune cells are able to survive HIV-1 and escape treatment. Any pause in therapy leads to a return to high levels of viral loads due to these surviving infected cells. These subsets of infected immune cells escaping treatment represent a major obstacle to the eradication of HIV-1. One such subset of immune cells, the Germinal Center T follicular helper (GC Tfh) cells, can both survive infection and expand in PLHIV. Using human tonsil tissues, the major site of GC Tfh cells, our lab was able to find two critical factors that influence the GC Tfh cells’ ability to survive and thrive while infected by HIV-1. First, we found that GC Tfh cells have a distinct metabolic profile compared to other types of CD4 T cells found in human tonsils. This was characterized by a preference towards non-glycolytic metabolism even when infected with HIV-1. We found that inhibiting non-glycolytic metabolism resulted in a significant decrease in HIV-1 infected GC Tfh cells. Second, we found that GC Tfh cells sharply upregulate proteins responsible for stopping controlled cell death. We found one of these proteins, BIRC5, was integral to GC Tfh survival of HIV-1 infection. Inhibition of BIRC5 led to overall decreases in surviving infected cells, as well as significant decreases in infected GC Tfh survival. In contrast, inhibition of BIRC5 had no effect on uninfected cells. Our results signify an important advancement in the study of HIV-1 reservoir and will help in developing novel therapeutics to eradicate rather than suppress HIV-1 in PLHIV.Item Follicular regulatory T cells produce neuritin to regulate B cells(Elsevier, 2021) Gonzalez-Figueroa, Paula; Roco, Jonathan A.; Papa, Ilenia; Núñez Villacís, Lorena; Stanley, Maurice; Linterman, Michelle A.; Dent, Alexander; Canete, Pablo F.; Vinuesa, Carola G.; Microbiology and Immunology, School of MedicineRegulatory T cells prevent the emergence of autoantibodies and excessive IgE, but the precise mechanisms are unclear. Here, we show that BCL6-expressing Tregs, known as follicular regulatory T (Tfr) cells, produce abundant neuritin protein that targets B cells. Mice lacking Tfr cells or neuritin in Foxp3-expressing cells accumulated early plasma cells in germinal centers (GCs) and developed autoantibodies against histones and tissue-specific self-antigens. Upon immunization, these mice also produced increased plasma IgE and IgG1. We show that neuritin is taken up by B cells, causes phosphorylation of numerous proteins, and dampens IgE class switching. Neuritin reduced differentiation of mouse and human GC B cells into plasma cells, downregulated BLIMP-1, and upregulated BCL6. Administration of neuritin to Tfr-deficient mice prevented the accumulation of early plasma cells in GCs. Production of neuritin by Tfr cells emerges as a central mechanism to suppress B cell-driven autoimmunity and IgE-mediated allergies.Item IL-21 restricts T follicular regulatory T cell proliferation through Bcl-6 mediated inhibition of responsiveness to IL-2(Springer Nature, 2017-03-17) Jandl, Christoph; Liu, Sue M.; Cañete, Pablo F.; Warren, Joanna; Hughes, William E.; Vogelzang, Alexis; Webster, Kylie; Craig, Maria E.; Uzel, Gulbu; Dent, Alexander; Stepensky, Polina; Keller, Bärbel; Warnatz, Klaus; Sprent, Jonathan; King, Cecile; Microbiology and Immunology, School of MedicineT follicular regulatory (Tfr) cells control the magnitude and specificity of the germinal centre reaction, but how regulation is contained to ensure generation of high-affinity antibody is unknown. Here we show that this balance is maintained by the reciprocal influence of interleukin (IL)-2 and IL-21. The number of IL-2-dependent FoxP3+ regulatory T cells is increased in the peripheral blood of human patients with loss-of-function mutations in the IL-21 receptor (IL-21R). In mice, IL-21:IL-21R interactions influence the phenotype of T follicular cells, reducing the expression of CXCR4 and inhibiting the expansion of Tfr cells after T-cell-dependent immunization. The negative effect of IL-21 on Tfr cells in mice is cell intrinsic and associated with decreased expression of the high affinity IL-2 receptor (CD25). Bcl-6, expressed in abundance in Tfr cells, inhibits CD25 expression and IL-21-mediated inhibition of CD25 is Bcl-6 dependent. These findings identify a mechanism by which IL-21 reinforces humoral immunity by restricting Tfr cell proliferation.Item IL-33 Mediated Th2 Effector Functions are Suppressed in Tregs by Bcl6 and Regulated by Sex(2024-08) Lee, Kyu Been; Dent, Alexander; Richer, Martin; Robinson, Christopher; Yang, KaiAllergic airway inflammation (asthma) is a prevalent and uncurable disease worldwide, affecting many individuals’ quality of life. Although asthma does not form from a singular cause, one primary mediator comes from the exposure to environmental allergens and the improper activation of the T cell subset: T helper 2 (Th2) cells. Th2 cells produce pro-inflammatory cytokines and promote the activation and recruitment of various pro-inflammatory cells into the lung, causing greater damage and inflammatory responses in the organ. Th2 cell’s activation is regulated by another T cell subset, Regulatory T (Treg) cells, by expressing anti-inflammatory cytokines and downregulating the inflammatory response. On the contrary, the release of interleukin-33 (IL-33) from damaged lung epithelial cells transitions Tregs into Th2-like Tregs (ST2+ Tregs) which release both pro-and anti-inflammatory cytokines and cannot suppress the inflammatory disease. However, transcriptional repressor protein B cell lymphoma 6 (Bcl6) provides Tregs a stable follicular phenotype and suppresses the ST2+ Treg transition. Preliminary data revealed that Bcl6 repressive function is dependent on mouse sex, in which Tregs of male mice are more resistant to the ST2+ Treg phenotype than those of female mice. However, the removal of Bcl6 also removed the sex-dependent suppression against the ST2+ Treg transition. The project therefore sought to further confirm and answer whether Bcl6 suppressed the ST2+ Treg phenotype in a sex-dependent manner, ultimately leading to a sex-biased asthma prevalence and severity. We utilized quantitative polymerase chain reaction (qPCR) and next-generation sequencing techniques to uncover which genes Bcl6 regulates, how IL-33 affects chromatin accessibility/gene expression, and what relation sex hormones have with Bcl6 in the expression of Th2 cytokines from Tregs. Currently, we have discovered that estrogen-like chemicals in common cell culturing media may be acting on the estrogen receptor of Tregs and causing differential gene expressions based on media conditions. We also determined that Bcl6 is acting independently of mouse sex to suppress Th2 genes in Tregs, contrary to preliminary findings. Overall, we have obtained insight on the role of the estrogen receptor and Bcl6’s mechanism of suppression in relation to sex.Item MicroRNA 21 is a homeostatic regulator of macrophage polarization and prevents prostaglandin E2-mediated M2 generation(PLoS, 2015-02-23) Wang, Zhuo; Brandt, Stephanie; Medeiros, Alexandra; Wang, Soujuan; Wu, Hao; Dent, Alexander; Serezani, C. Henrique; Department of Microbiology and Immunology, IU School of MedicineMacrophages dictate both initiation and resolution of inflammation. During acute inflammation classically activated macrophages (M1) predominate, and during the resolution phase alternative macrophages (M2) are dominant. The molecular mechanisms involved in macrophage polarization are understudied. MicroRNAs are differentially expressed in M1 and M2 macrophages that influence macrophage polarization. We identified a role of miR-21 in macrophage polarization, and found that cross-talk between miR-21 and the lipid mediator prostaglandin E2 (PGE2) is a determining factor in macrophage polarization. miR-21 inhibition impairs expression of M2 signature genes but not M1 genes. PGE2 and its downstream effectors PKA and Epac inhibit miR-21 expression and enhance expression of M2 genes, and this effect is more pronounced in miR-21-/- cells. Among potential targets involved in macrophage polarization, we found that STAT3 and SOCS1 were enhanced in miR-21-/- cells and further enhanced by PGE2. We found that STAT3 was a direct target of miR-21 in macrophages. Silencing the STAT3 gene abolished PGE2-mediated expression of M2 genes in miR-21-/- macrophages. These data shed light on the molecular brakes involved in homeostatic macrophage polarization and suggest new therapeutic strategies to prevent inflammatory responses.Item The role of follicular helper T cells and the germinal center in HIV-1 gp120 DNA prime and gp120 protein boost vaccination(Taylor & Francis, 2014-07) Hollister, Kristin; Chen, Yuxin; Wang, Shixia; Wu, Hao; Mondal, Arpita; Clegg, Ninah; Lu, Shan; Dent, Alexander; Department of Microbiology and Immunology, IU School of MedicineThe importance of follicular T helper (TFH) cells and the germinal center (GC) reaction in the humoral immune response has become clear in recent years, however the role of TFH cells and the GC in an HIV vaccine strategy remains unclear. In this study, we primed mice with gp120-encoding DNA and boosted with gp120 protein, a regimen previously shown to induce high titers of high affinity and cross-reactive anti-gp120 Abs. Priming with gp120 DNA caused increased TFH cell differentiation, GC B cells, and antigen-specific antibody titers, compared with priming with gp120 protein. Priming with DNA also caused more activated CD4(+) T cells to become TFH cells and more GC B cells to become memory cells. Deletion of BCL6 midway through the vaccine regimen resulted in loss of TFH cells and GCs, and, unexpectedly, increased anti-gp120 IgG titers and avidity. Our data suggests vaccination with gp120-encoding DNA elicits a stronger and more rapid TFH and GC response than gp120 protein. Furthermore, we demonstrate that the GC reaction may actually limit antigen-specific IgG secretion in the context of repeated immunizations.