Mufadhal Al-Kuhlani

Transcription factor complex AP-1 mediates inflammation initiated by Chlamydia pneumoniae infection

Chlamydia pneumoniae is responsible for a high prevalence of respiratory infections worldwide and has been implicated in atherosclerosis. Inflammation is regulated by transcription factor (TF) networks. Yet, the core TF network triggered by chlamydiae remains largely unknown. Primary human coronary artery endothelial cells were mock‐infected or infected with C. pneumoniae to generate human transcriptome data throughout the chlamydial developmental cycle. Using systems network analysis, the predominant TF network involved receptor, binding and adhesion and immune response complexes. Cells transfected with interfering RNA against activator protein‐1 (AP‐1) members FOS, FOSB, JUN and JUNB had significantly decreased expression and protein levels of inflammatory mediators interleukin (IL)6, IL8, CD38 and tumour necrosis factor compared with controls. These mediators have been shown to be associated with C. pneumoniae disease. Expression of AP‐1 components wasregulated by MAPK3K8, a MAPK pathway component. Additionally, knock‐down of JUN and FOS showed significantly decreased expression of Toll‐like receptor (TLR)3 during infection, implicating JUN and FOS in TLR3 regulation. TLR3 stimulation led to elevated IL8. These findings suggest that C. pneumoniae initiates signalling via TLR3 and MAPK that activate AP‐1, a known immune activator in other bacteria not previously shown for chlamydiae, triggering inflammation linked to C. pneumoniae disease.

TRAIL-R1 Is a Negative Regulator of Pro-Inflammatory Responses and Modulates Long-Term Sequelae Resulting from Chlamydia trachomatis Infections in Humans

The immune system eliminates Chlamydia trachomatis infection through inflammation. However, uncontrolled inflammation can enhance pathology. In mice, TNF-related apoptosis-inducing ligand receptor (TRAIL-R), known for its effects on apoptosis, also regulates inflammation. In humans, the four homologues of TRAIL-R had never been investigated for effects on inflammation. Here, we examined whether TRAIL-R regulates inflammation during chlamydial infection. We examined TRAIL-R1 single nucleotide polymorphisms (SNPs) in an Ecuadorian cohort with and without C. trachomatis infections. There was a highly significant association for the TRAIL+626 homozygous mutant GG for infection vs no infection in this population. To confirm the results observed in the human population, primary lung fibroblasts and bone marrow-derived macrophages (BMDMs) were isolated from wildtype (WT) and TRAIL-R-deficient mice, and TRAIL-R1 levels in human cervical epithelial cells were depleted by RNA interference. Infection of BMDMs and primary lung fibroblasts with C. trachomatis strain L2, or the murine pathogen C. muridarum, led to higher levels of MIP2 mRNA expression or IL-1β secretion from TRAIL-R-deficient cells than WT cells. Similarly, depletion of TRAIL-R1 expression in human epithelial cells resulted in a higher level of IL-8 mRNA expression and protein secretion during C. trachomatis infection. We conclude that human TRAIL-R1 SNPs and murine TRAIL-R modulate the innate immune response against chlamydial infection. This is the first evidence that human TRAIL-R1 is a negative regulator of inflammation and plays a role in modulating Chlamydia pathogenesis.

Single-Cell Analysis of Murine Long-Term Hematopoietic Stem Cells Reveals Distinct Patterns of Gene Expression during Fetal Migration

Background Long-term hematopoietic stem cells (LT-HSCs) migrate from the fetal liver (FL) to the fetal bone marrow (FBM) during development. Various adhesion and chemotactic receptor genes have been implicated in the migration of adult LT-HSCs. However, their role in the migration of fetal LT-HSCs is not clearly understood due, in part, to the rare number of these cells in fetal tissues, which preclude classical gene expression analysis. The aim of this study is to characterize the expression of migration related genes in fetal LT-HSC across different anatomical locations during development. Methodology/Principal Findings We isolated fetal LT-HSC from different developmental stages, as well as different anatomical locations, and performed single-cell multiplex RT-qPCR and flow cytometry analysis of eight molecules involved in adult LT-HSC migration. Our results show that the gene expression of the chemokine receptor Cxcr4 in LT-HSC varies across developmental microenvironments and times, while the cadherin Cdh2 (Ncad) and the calcium receptor Casr show higher gene expression and variability only in FBM at 17.5 days post coitum (dpc). The cadherin Cdh5 (Vecad) maintains high expression variability only during fetal development, while the integrin subunit Itga5 (α5) increases its variability after 14.5 dpc. The integrin subunits Itga4 (α4) and Itgal (Lfa1), as well as the selectin ligand Selplg (Psgl1), did not show differences in their expression in single LT-HSCs irrespective of the developmental times or anatomical microenvironments studied. Conclusions/Significance Our data demonstrate that the expression pattern of phenotypically identical, single LT-HSCs fluctuates as a function of developmental stage and anatomical microenvironment. This is the first exhaustive gene expression comparison of migration-related molecules in fetal tissues across developmental times, enhancing the understanding of LT-HSC migration fate decisions during development.

CD8(+) T cells drive autoimmune hematopoietic stem cell dysfunction and bone marrow failure.

Bone marrow (BM) failure syndrome encompasses a group of disorders characterized by BM stem cell dysfunction, resulting in varying degrees of hypoplasia and blood pancytopenia, and in many patients is autoimmune and inflammatory in nature. The important role of T helper 1 (Th1) polarized CD4+ T cells in driving BM failure has been clearly established in several models. However, animal model data demonstrating a functional role for CD8+ T cells in BM dysfunction is largely lacking and our objective was to test the hypothesis that CD8+ T cells play a non-redundant role in driving BM failure. Clinical evidence implicates a detrimental role for CD8+ T cells in BM failure and a beneficial role for Foxp3+ regulatory T cells (Tregs) in maintaining immune tolerance in the BM. We demonstrate that IL-2-deficient mice, which have a deficit in functional Tregs, develop spontaneous BM failure. Furthermore, we demonstrate a critical role for CD8+ T cells in the development of BM failure, which is dependent on the cytokine, IFNγ. CD8+ T cells promote hematopoietic stem cell dysfunction and depletion of myeloid lineage progenitor cells, resulting in anemia. Adoptive transfer experiments demonstrate that CD8+ T cells dramatically expedite disease progression and promote CD4+ T cell accumulation in the BM. Thus, BM dysregulation in IL-2-deficient mice is mediated by a Th1 and IFNγ-producing CD8+ T cell (Tc1) response.

T cell and peripheral blood parameters define progression of autoimmune disease in the IL-2Rα KO model

IL-2Rα is required to generate the high affinity receptor for IL-2, a cytokine important in immune proliferation, activation, and regulation. Mice deficient in IL-2Rα (IL-2Rα-KO) develop systemic autoimmune disease and die from severe anemia between 18-80 days of age. These mice develop kinetically differing autoimmune disease, with approximately a quarter dying by 21 days of age and half dying after 30 days. This research aims to define immune parameters that distinguish cohorts of mice that develop early- and late-stage autoimmune disease in the IL-2Rα-KO genetic background. To investigate these differences, we evaluated complete blood counts (CBC), antibody binding of RBCs, T cell numbers and activation, and hematopoietic progenitor changes, to assess the extent of peripheral autoimmune hemolytic anemia and bone marrow failure. Early onset disease correlated with anti-RBC antibodies and lower hematocrit on day 19. We also found that predicted late stage-disease IL-2Rα-KO mice have higher numbers of developing memory CD4 and CD8 T cells and reduced AIHA at early ages. The expansion of CD8 T cells seen in IL-2R -KO mice is driven by unimpaired IL-2 signaling which correlated with increased IL-2RP expression. Using a simple CBC we were able to predict disease kinetics to explore mechanisms underlying early and late disease.

Th17/regulatory T cells balance is predictive of Coccidioides infection outcome in pediatric patients

Background Protective immunity against the fungal pathogen Coccidioides requires specific T helper responses. Mouse vaccine and infection studies have defined CD4+ T helper (Th)1 and Th17 cells in the resolution of infection and in effective protection. Patients with persistent Coccidioides infection demonstrate reduced cellular responses. Methods Peripheral blood and serum were collected from 30 pediatric Coccidioides-infected patients and 20 healthy controls in the California San Joaquin Valley. Samples were evaluated by flow cytometry for innate and adaptive immune populations and cytokines to define the early immune response and identify clinically useful biomarkers for predicting disease outcome. Clinical and flow data were evaluated according to disease outcome (resolved or persistent) using principal component analysis, high-dimensional flow cytometry analysis tools, chi-square automatic interaction detection, and individual cell population comparisons. Results Patients with persistent infection had lower Th17 and higher Treg frequencies, but similar Th1 responses, relative to patients that resolved disease. Treg frequency, eosinophil numbers and neutrophil numbers together distinguish patients that resolve infection from those that develop persistent infection. Conclusions The inability to resolve Coccidioides infection may be a result of elevated Treg frequency and functional capacity, and Treg frequency may predict patient disease outcome at diagnosis. In our study, Th1 responses were similar in persistent and resolved infection, in contrast to prior human studies. Instead, our data suggest that Th17 cells provide an effective protection during Coccidioides infection, and that elevated Treg frequency inhibits protective immunity.

CD8 Follicular T Cells Promote B Cell Antibody Class Switch in Autoimmune Disease.

CD8 T cells can play both a protective and pathogenic role in inflammation and autoimmune development. Recent studies have highlighted the ability of CD8 T cells to function as T follicular helper (Tfh) cells in the germinal center in the context of infection. However, whether this phenomenon occurs in autoimmunity and contributes to autoimmune pathogenesis is largely unexplored. In this study, we show that CD8 T cells acquire a CD4 Tfh profile in the absence of functional regulatory T cells in both the IL-2–deficient and scurfy mouse models. Depletion of CD8 T cells mitigates autoimmune pathogenesis in IL-2–deficient mice. CD8 T cells express the B cell follicle–localizing chemokine receptor CXCR5, a principal Tfh transcription factor Bcl6, and the Tfh effector cytokine IL-21. CD8 T cells localize to the B cell follicle, express B cell costimulatory proteins, and promote B cell differentiation and Ab isotype class switching. These data reveal a novel contribution of autoreactive CD8 T cells to autoimmune disease, in part, through CD4 follicular-like differentiation and functionality.