Background and current state of research
Infections with Neisseria gonorrhoeae, Chlamydia trachomatis and Ureaplasma urealyticum account for the majority of sexually transmitted infections (STIs) worldwide. Despite the huge clinical impact of ascending STI- infections in females leading to pelvic inflammatory diseases (PID), salpingitis and tubal infertility, the underlying mechanisms are poorly understood. Human and mice studies suggest that the micro-environment of the female urogenital tract (fUGT) exhibits particular characteristics that directly impair host immune functions against intra- and extracellular pathogens. Furthermore, there is mounting evidence that the female reproductive tract may be uniquely susceptible to infection at specific times during the menstrual cycle, due to hormonal regulation of both innate and adaptive immune responses [Shacklett. 2009]. We and others could show that environmental factors such as local oxygen availability or the presence of estrogen or progesterone directly or indirectly interfere with intracellular growth of C. trachomatis and the anti-bacterial efficacy of IFN-γ [Roth 2010; Hafner 2013]. Bacterial growth and host immune mechanisms are thereby directly connected to environmental and cellular metabolism that may support or inhibit the replication of the pathogen, but also hamper or strengthen cellular immune functions. The key factor in controlling the regulation of cellular homeostasis and metabolism and directly interfering with host immune functions via NF-kappa B interactions is the hypoxia-inducible factor-1 (HIF-1) [Rius 2009]. However, HIF-1 is not only involved in functions of the innate immunity but also directly interferes with the control of Treg and Th17 cells [Bollinger 2014; Dang 2012].
Based on the work of the first doctoral researcher on that project within the RTG1743 the data from the human microbiome studies in females with STIs will be applied to establish profound co-infection models in vitro (primary fallopian tube cells) and ex vivo (human fallopian tube model). This implies comprehensive achievements to optimize culture conditions of so far neglected bacterial species supposed to modify the course of female STIs. The second main goal is to analyze the STI- related pathology in the mice UGT in the context of microbial and metabolic changes that are connected to the HIF-1 signaling pathway.
How to get there
The doctoral researcher will follow-up the work on the mice infection model that has been established within the RTG1743 from the previous PhD. The major aim within the 1st year is to establish stable cultivation conditions for the most prominent indicator species linked to STIs that have been identified in the female cohorts. In parallel, the microbiome data will be particularly investigated for the in silico analysis of potential micro-environmental changes that might have an impact on the growth and pathogenicity of STIs. In initial experiments, the impact of different anti-microbial substances on the eradication/disturbance of the physiological flora in mice will be tested. In a second step, structured changes of the UGT microbiome of the mice will be conducted, applying bacterial species that have been linked to STI- infections and tested in in vitro and ex vivo co-infection models. Imaging of morphological changes will be performed by scanning electron microscopy (SEM) and 2-photon laser microscopy (PLM), which will be offered to all other members of the consortium. PLM imaging not only allows the direct monitoring of host-pathogen interactions in high temporal and spatial resolution, but also gives detailed insights into the metabolic activity of infected and non-infected cells/tissue on the basis of fluorescence lifetime imaging (FLIM) and determination of NAD(P)H- fluorescence intensity. The more functional analysis of metabolic and inflammatory changes to the affected UGT will be the focus of the 2nd year of the PhD. Thus, inflammatory cells of infected and non-infected cells under different structured changes to the UGT microbiome will be analyzed with respect to their mitochondrial and glycolytic activity using the Seahorse Bioanalyzer. The impact on differentiation of T-cell subsets and host-derived inflammation will be analyzed by FACS and RT-PCR/Western blot, respectively. Based on own data on the functional relevance of the HIF-1 signaling pathway the same experiments will be performed in conditional myeloid HIF knock-out mice in the 3rd year of the PhD. In a recent animal experiment application, this particular part was included in the work plan and has already been approved by the responsible ministry.
Applications are particularly encouraged for MSc or Dipl. graduates in the field of molecular life sciences, (infection) biology and/or biochemistry. A special interest in further training in computational science/bioinformatics is helpful.