C. trachomatis is the most frequent sexually transmitted bacterial infection worldwide. The interplay between the vaginal microenvironment and host immunity seem to have a pivotal role in controlling infections with this obligate intracellular bacterium. In case of an ascending infection to the upper genital tract, ectopic pregnancy, pelvic inflammatory disease and infertility might occur as the most severe consequences of this often asymptomatic disease. In contrast to infections with extracellular bacteria, intracellular growth and progeny of C. trachomatis largely depends on host metabolism and immunity. Recent studies have thereby highlighted the role of T cells in the clearance of genital chlamydial infections, arguing for both CD4+ and CD8+ T-cells being involved in pathogen clearance but also pathology. The vaginal microenvironment that promotes protection against chlamydiae under physiological conditions is characterized by a typical microbial pattern, a low pH and low oxygen (hypoxia). The major molecular driver in a hypoxic milieu is the Hypoxia-inducible factor (HIF)-1α that mediates central metabolic and immunological host cell functions. Thus, HIF-1α is involved in the regulation of host glycolysis and glucose uptake via GLUT-1 and PDK-1 but also directly interferes with the control of Treg and Th17 cells. HIF-1α has been shown to be involved in the maintenance of host cells homeostasis of C. trachomatis infected cells in vitro, but its role in genital tract infections in vivo is completely unknown.
Within the previous two funding periods, an in vivo infection model using the chlamydial strains C. trachomatis and C. muridarum was established in our lab. Central techniques for the evaluation of host metabolic and immunological responses (e.g. FACS analysis, tissue PCR, histological and immunohistological staining) were set up, as well as the complete microbiota analysis of vaginal swabs/washes. Within this project we will now start comparing the host immune functions and metabolic signaling cascades with respect to chlamydial growth and pathogenicity in mice lacking the gene for HIF-1α in the myeloid cell lineage. Changes in the chlamydial clearance, the pathology score of affected mice, the composition of host immune cells and its functions will be analyzed in wild-type and in HIF-1α-/- mice assessing the role of HIF-1α during the course of infection.
Starting with molecular based methods in the lab, the new doctoral student will start detecting the stable knock-out via qPCR and Western Blot analysis. The aim for the first year will be to compare the infection with Chlamydia trachomatis and Chlamydia muridarum in HIF-1α-/- mice with the findings in wild-type with respect to bacterial shedding and pathology formation. Of particular interest will be the analysis of the commensal microbiota on the basis of 16S rRNA gene sequencing from murine vaginal washes. Within the 2nd year, the immune response of the HIF-1α-/- -mice will be analysed in detail as described above. Particular attention will be given the fact whether the ascending of the pathogens are altered, the time until eradication of the pathogen, and whether subsets of inflammatory cells are changed. A detailed mapping of the immune cell populations infiltrating the uterine tissue during the course of infection, especially T-cell subsets and its clonal structures by the analysis of the T-cell receptor (TCR) repertoire, will be the major task in the 3rd year of this project.
Requirements for the position:
Applicants have a Master certificate/ Diploma equivalent in Medical Life Sciences with a special interest in Infection Biology, Immunology, Cell Biology and/or Bioinformatics. The PhD-student will be integrated in an established team of PostDocs and technicians who set-up the infection model and have been involved in the RTG1743 right from the start.