Emerging molecular targets in the treatment of bacterial meningitis

Transcriptome profiling of avian pathogenic Escherichia coli and the mouse microvascular endothelial cell line bEnd.3 during interaction

Background

Avian pathogenic Escherichia coli (APEC), an important extraintestinal pathogenic E. coli, causes colibacillosis, an acute and mostly systemic disease involving multiple organ lesions such as meningitis. Meningitis-causing APEC can invade the host central nervous system by crossing the blood–brain barrier (BBB), which is a critical step in the development of meningitis. However, the bacteria-host interaction mechanism in this process remains unclear.

Methods

In this study, we examined E. coli and bEnd.3 cells transcriptomes during infection and mock infection to investigate the global transcriptional changes in both organisms using RNA sequencing approach.

Results

When APEC infected the bEnd.3 cells, several significant changes in the expression of genes related to cell junctional complexes, extracellular matrix degradation, actin cytoskeleton rearrangement, immune activation and the inflammatory response in bEnd.3 cells were observed as compared to the mock infection group. Thus, the immune activation of bEnd.3 cells indicated that APEC infection activated host defenses. Furthermore, APEC may exploit cell junction degradation to invade the BBB. In addition, amino acid metabolism and energy metabolism related genes were downregulated and the protein export pathway related genes were upregulated in APEC cultured with bEnd.3 cells, compared to that in control. Thus, APEC may encounter starvation and express virulence factors during incubation with bEnd.3 cells.

Conclusion

This study provides a comprehensive overview of transcriptomic changes that occur during APEC infection of bEnd.3 cells, and offers insights into the bacterial invasion strategies and the subsequent host defense mechanism.

Differential Gene Expression Associated with Meningeal Injury in Acute Mild Traumatic Brain Injury

Injury to the meninges is not uncommon after traumatic brain injury (TBI), yet minimal research has been directed toward understanding the relevant biology. After a concussive event, the meninges are observed to abnormally enhance on post-contrast magnetic resonance imaging (MRI) in some patients, but not all. The aim of this work is to identify genes differentially expressed in patients with meningeal injury. Patients presenting to the emergency room with suspected TBI received a standard research MRI and blood draw within 48 h of injury. Two groups of patients were included: those with and without abnormal enhancement of the meninges on post-contrast MRI, both without other imaging findings. Groups were compared on microarray gene expression in peripheral blood samples using Affymetrix (Santa Clara, CA) and Partek Genomics Suite (Partek, Inc., St. Louis, MO) software (false discovery rate, <0.05). Forty patients were enrolled with a time from injury to MRI/blood draw of 16.8 h (interquartile range, 7.5-24.1). We observed 76 genes to be differentially expressed in patients with meningeal injury compared to those without, such as receptor for Fc fragment of IgA, multiple C2 domains, transmembrane 2, and G-protein-coupled receptor 27, which have been previously associated with initiating inflammatory mediators, phagocytosis, and other regulatory mechanisms. Post-contrast MRI is able to detect meningeal injury and has a unique biological signature observed through gene expression. These findings suggest that an acute inflammatory response occurs in response to injury to the meninges following a concussion.

Chemotaxis of T-cells after infection of human choroid plexus papilloma cells with Echovirus 30 in an in vitro model of the blood-cerebrospinal fluid barrier

Enterovirus is the most common pathogen causing viral meningitis especially in children. Besides the blood-brain barrier (BBB) the choroid plexus, which forms the blood-cerebrospinal-fluid (CSF) barrier (BCSFB), was shown to be involved in the pathogenesis of enteroviral meningitis. In a human in vitro model of the BCSFB consisting of human choroid plexus papilloma cells (HIBCPP), the permissiveness of plexus epithelial cells for Echovirus 30 (EV30) was analyzed by immunoblotting and quantitative real-time PCR (Q-PCR). HIBCPP could be directly infected by EV30 from the apical as well as from the physiological relevant basolateral side. During an infection period of 5h no alterations of barrier function and cell viability could be observed. Analysis of the cytokine/chemokine-profile following enteroviral infection with a cytometric bead array (CBA) and Q-PCR revealed an enhanced secretion of PanGRO (CXCL1, CXCL2 and CXCL3), IL8 and CCL5. Q-PCR showed a significant upregulation of CXCL1, CXCL2 and CXCL3 in a time dependant manner. However, there was only a minor effect of HIBCPP-infection with EV30 on transepithelial T lymphocyte migration with or without the chemoattractant CXCL12. Moreover, CXCL3 did not significantly enhance T cell migrations. Therefore additional factors must be involved for the in vivo reported enhanced T cell migration into the CNS in the context of enteroviral meningitis. As HIBCPP are permissive for infection with EV30, they constitute a valuable human in vitro model to study viral infection at the BCSFB.