settings was observed. To gain more information towards possible cell stress signaling due to irradiation, well-known molecular markers of cytotoxicity were evaluated in irradiated HeLa cells by Western blot analysis. HeLa cells exposed to irradiation for 20 min at a dose of 3700 W/m2 were investigated for the presence of phosphorylated forms of the stress kinases Akt, p38 and ERK 1/2, at 0, 15 and 30 min after irradiation. We observed no difference between irradiated and non-irradiated cells regarding the phosphorylation status of Akt, p38 and ERK 1/2 protein. Samples were also collected 2, 4, 6 and 24 h after treatment and examined for autophagy and apoptosis induction. If not stated differently, all results are displayed as means 6 standard deviation or as means 6 standard error of the mean of the indicated number of experiments. The significance of differences was estimated by t test, and a p-value of,0.05 was considered significant. wIRA/VIS Inhibits Chlamydia and 12695532 9). Irradiation did not induce either apoptosis or autophagy marker regardless time post-irradiation in HeLa cells. A single dose of irradiation reduces the number of chlamydial inclusions within host cells After cytotoxic effects on host cells due to irradiation were precluded, we investigated the effect of a single dose of irradiation applied to infected cell monolayers. We aimed to determine whether irradiation has an effect on mature inclusions containing EBs and RBs within the host cell. We infected HeLa monolayers with C. trachomatis and irradiated them at 40 hpi for 20 min at a dose of 3700 W/m2. Parallel non-irradiated but infected HeLa cultures were used as controls. Similar to previous experiments, cultures were either collected for sub-passage titer analysis, or fixed and directly immunolabelled. Again, the frequency of chlamydial inclusions per nucleus was reduced in irradiated cells compared to non-irradiated C. trachomatisinfected HeLa cells . These findings were confirmed by sub-passage titer analysis showing that the IFU/mL of irradiated cultures was 62.88%68.41% compared 14642775 to the control. The reduction of inclusions per nucleus in Vero cells infected with C. pecorum was confirmed in parallel experiments and was similar . It was possible that irradiation of Chlamydia-infected host cells induces premature rupture of intracytoplasmic chlamydial inclu- sions, leading to loss of intact inclusions and subsequent release of EBs into the supernatant. Therefore, we assessed shedding of EBs into the supernatant by collecting the supernatant and the infected cell monolayer as separate fractions and analyzing them individually by sub-passage titer analysis. IFU was similarly reduced up to 50% by irradiation in both cells and 
supernatant and 59.58%613.27% in supernatants ). Irradiation of chlamydial inclusions at 40 hpi might also reduce chlamydial infectivity by influencing chlamydial maturation or inducing persistence/stress, which is characterized by alteration of the chlamydial developmental cycle and the presence of aberrant bodies. Therefore, the ultrastructure of irradiated chlamydial inclusions at 43 hpi was evaluated and compared to that of the infected but non-irradiated controls by transmission electron microscopy. Vero cells were infected with C. pecorum, irradiated and processed as purchase CX-4945 described before. First, ten inclusions for each condition were picked and the total number of bacteria was counted and allocated to the different developmental stages according