Dendritic cells (DCs) and leukemia-derived DC (DCleu) are potent stimulators of various immunoreactive cells and they play a pivotal role in the (re-) activation of the immune system. As a potential treatment tool for patients with acute myeloid leukemia, we developed and analyzed two new PGE1-containing protocols (Pici-PGE1, Kit M) to generate DC/DCleu ex vivo from leukemic peripheral blood mononuclear cells (PBMCs) or directly from leukemic whole blood (WB) to simulate physiological conditions. Pici-PGE1 generated significantly higher amounts of DCs from leukemic and healthy PBMCs when compared to control and comparable amounts as the already established protocol Pici-PGE2. The proportions of sufficient DC-generation were even higher after DC/DCleu-generation with Pici-PGE1. With Kits, it was possible to generate DCs and DCleu directly from leukemic and healthy WB without induction of blast proliferation. The average amounts of generated DCs and DCleu-subgroups were comparable with all Kits. The PGE1 containing Kit M generated significantly higher amounts of mature DCs when compared to the PGE2-containing Kit K and increased the anti-leukemic-activity. In summary PGE1-containing protocols were suitable for generating DC/DCleu from PBMCs as well as from WB, which reliably (re-) activated immunoreactive cells, improved the overall ex vivo anti-leukemic activity, and influenced cytokine-release-profiles.

Bacterial meningitis is a deadly disease most commonly caused by Streptococcus pneumoniae, leading to severe neurological sequelae including cerebral edema, seizures, stroke, and mortality when untreated. Meningitis is initiated by the transfer of S. pneumoniae from blood to the brain across the blood-cerebrospinal fluid barrier or the blood-brain barrier (BBB). The underlying mechanisms are still poorly understood. Current treatment strategies include adjuvant dexamethasone for inflammation and cerebral edema, followed by antibiotics. The success of dexamethasone is however inconclusive, necessitating new therapies for controlling edema, the primary reason for neurological complications. Since we have previously shown a general activation of hypoxia inducible factor (HIF-1α) in bacterial infections, we hypothesized that HIF-1α, via induction of vascular endothelial growth factor (VEGF) is involved in transmigration of pathogens across the BBB. In human, murine meningitis brain samples, HIF-1α activation was observed by immunohistochemistry. S. pneumoniae infection in brain endothelial cells (EC) resulted in in vitro upregulation of HIF-1α/VEGF (Western blotting/qRT-PCR) associated with increased paracellular permeability (fluorometry, impedance measurements). This was supported by bacterial localization at cell-cell junctions in vitro and in vivo in brain ECs from mouse and humans (confocal, super-resolution, electron microscopy, live-cell imaging). Hematogenously infected mice showed increased permeability, S. pneumoniae deposition in the brain, along with upregulation of genes in the HIF-1α/VEGF pathway (RNA sequencing of brain microvessels). Inhibition of HIF-1α with echinomycin, siRNA in bEnd5 cells or using primary brain ECs from HIF-1α knockout mice revealed reduced endothelial permeability and transmigration of S. pneumoniae. Therapeutic rescue using the HIF-1α inhibitor echinomycin resulted in increased survival and improvement of BBB function in S. pneumoniae-infected mice. We thus demonstrate paracellular migration of bacteria across BBB and a critical role for HIF-1α/VEGF therein and hence propose targeting this pathway to prevent BBB dysfunction and ensuing brain damage in infections.

Our results suggest that sTACI and sBCMA in the CSF are promising new biomarkers for diagnosis and therapy monitoring in PCNSL. However, our findings need to be validated in an independent cohort.

Previous studies have demonstrated that the radical scavenger superoxide dismutase completely blocked the increase of regional cerebral blood flow (rCBF), intracranial pressure (ICP), and brain water content during the early phase of experimental pneumococcal meningitis in the rat. To obtain information on the nature of the reactive oxygen species involved, the effect of catalase, a hydrogen peroxide scavenger, was tested. Rats injected intracisternally with live pneumococci were either untreated or received intravenous catalase. The increase of rCBF and brain water content in infected untreated rats was significantly attenuated by catalase 6 h after intracisternal challenge. ICP increased in both infected groups, with a trend toward lower ICP with catalase treatment. Cerebrospinal fluid white blood cell counts were not significantly different between infected groups. These results and previous experiments using superoxide dismutase suggest that the increase of rCBF, ICP, and brain water content is mainly caused by superoxide or superoxide reaction products.

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