Biology subjects

Stelzner, K.

Publications and source records attributed to Stelzner, K..

3 recordsLinked to original sources

bioRxiv2024

Infection of human organoids supports an intestinal niche for Chlamydia trachomatis

Several reports suggest that intestinal tissue may be a natural niche for Chlamydia trachomatis infection and a reservoir for persistent infections in the human body. Due to the human specificity of the pathogen and the lack of suitable host models, there is limited knowledge on this topic. In our study, we modelled the course of the chlamydial infection in human primary gastrointestinal (GI) epithelial cells originating from patient-derived organoids. We show that GI cells are resistant to apical infection and C. trachomatis needs access to the basolateral membrane to establish an infection. Transmission electron microscopy analysis reveals the presence of both normal as well as aberrant chlamydial developmental forms in the infected cells, suggesting a possible cell-type specific nature of the infection. Furthermore, we show that the plasmid-encoded Pgp3 is an important virulence factor for the infection of human GI cells. This is the first report of C. trachomatis infection in human primary intestinal epithelial cells supporting a possible niche for chlamydial infection in the human intestinal tissue. Author summaryChlamydial infection has a high global prevalence and is a major health concern. Untreated infections may cause complications and lead to serious health problems, especially in women. Although the infection is usually localized to the genital tract, experiments performed in a mouse infection model as well as the accumulating clinical data suggest that the human gastrointestinal (GI) tract might represent a hidden infection niche and a source of reinfections. In our study, we used the advantages of the organoid technology to model the chlamydial infection in patient-derived primary GI epithelial cells. We were able to show that these cells are resistant to the infection, however, Chlamydia could utilize a basolateral entry route for efficient infection. Chlamydia form either normal or persistent-like developmental forms in these GI epithelial cells. We also showed the importance of the plasmid-mediated virulence in the infection of human GI cells. The results obtained in the GI infection model replicated phenotypes predicted and expected for Chlamydia human intestinal infection, and therefore support a role of the human GI tract as a potential niche for chlamydial infection.

microbiology↗

bioRxiv2020

Intracellular Staphylococcus aureus perturbs the host cell Ca2+-homeostasis to promote cell death

The opportunistic human pathogen Staphylococcus aureus causes serious infectious diseases ranging from superficial skin and soft tissue infections to necrotizing pneumonia and sepsis. While classically regarded as extracellular pathogen, S. aureus is able to invade and survive within human cells. Host cell exit is associated with cell death, tissue destruction and spread of infection. The exact molecular mechanism employed by S. aureus to escape the host cell is still unclear. In this study, we performed a genome-wide shRNA screen and identified the calcium signaling pathway to be involved in intracellular infection. S. aureus induced a massive cytosolic Ca2+-increase in epithelial host cells after invasion and intracellular replication of the pathogen. This was paralleled by decrease in endoplasmic reticulum Ca2+-concentration. Additionally, calcium ions from the extracellular space contributed to the cytosolic Ca2+-increase. As a consequence, we observed that the cytoplasmic Ca2+-rise led to increase in mitochondrial Ca2+-concentration, the activation of calpains and caspases and eventually to cell lysis of S. aureus-infected cells. Our study therefore suggests that intracellular S. aureus disturbs the host cell Ca2+-homeostasis and induces cytoplasmic Ca2+-overload, which results in both apoptotic and necrotic cell death in parallel or succession. ImportanceDespite being regarded as an extracellular bacterium, the pathogen Staphylococcus aureus can invade and survive within human cells. The intracellular niche is considered as hide-out from the host immune system and antibiotic treatment and allows bacterial proliferation. Subsequently, the intracellular bacterium induces host cell death, which may facilitate spread of infection and tissue destruction. So far, host cell factors exploited by intracellular S. aureus to promote cell death are only poorly characterized. We performed a genome-wide screen and found the calcium signaling pathway to play a role in S. aureus invasion and cytotoxicity. The intracellular bacterium induces a cytoplasmic and mitochondrial Ca2+-overload, which results in host cell death. Thus, this study firstly showed how an intracellular bacterium perturbs the host cell Ca2+-homeostasis.

microbiology↗

bioRxiv2020

Intracellular Staphylococcus aureus employs the cysteine protease staphopain A to induce host cell death in epithelial cells

Staphylococcus aureus is a major human pathogen, which can invade and survive in non-professional and professional phagocytes. Intracellularity is thought to contribute to pathogenicity and persistence of the bacterium. Upon internalization by epithelial cells, cytotoxic S. aureus strains can escape from the phagosome, replicate in the cytosol and induce host cell death. Here, we identified a staphylococcal cysteine protease to induce cell death by intracellular S. aureus after translocation into the host cell cytoplasm. We demonstrated that loss of staphopain A function leads to delayed onset of host cell death and prolonged intracellular replication of S. aureus in epithelial cells. Overexpression of staphopain A in a non-cytotoxic strain facilitated intracellular killing of the host cell even in the absence of detectable intracellular replication. Moreover, staphopain A contributed to efficient colonization of the lung in a mouse pneumonia model. Our study suggests that staphopain A is utilized by S. aureus to mediate escape from the host cell and thus contributes to tissue destruction and dissemination of infection. Author SummaryStaphylococcus aureus is a well-known antibiotic-resistant pathogen that emerges in hospital and community settings and can cause a variety of diseases ranging from skin abscesses to lung inflammation and blood poisoning. The bacterium asymptomatically colonizes the upper respiratory tract and skin of about one third of the human population and takes advantage of opportune conditions, like immunodeficiency or breached barriers, to cause infection. Although S. aureus is not regarded as a professional intracellular bacterium, it can be internalized by human cells and subsequently exit the host cells by induction of cell death, which is considered to cause tissue destruction and spread of infection. The bacterial virulence factors and underlying molecular mechanisms involved in the intracellular lifestyle of S. aureus remain largely unknown. We identified a bacterial cysteine protease to contribute to host cell death mediated by intracellular S. aureus. Staphopain A induced killing of the host cell after translocation of the pathogen into the cell cytosol, while bacterial proliferation was not required. Further, the protease enhanced survival of the pathogen during lung infection. These findings reveal a novel, intracellular role for the bacterial protease staphopain A.

microbiology↗