Genes and their single nucleotide polymorphism involved in innate immune response in central nervous system in bacterial meningitis: review of literature data

Peripheral white blood cell patterns in children with hydrocephalus as a response to ventriculo-peritoneal shunt infection

Shunt infection is one of the most common complications of conventional hydrocephalus treatment. The route of invasion of a pathogen can modify the immune response of the CNS. The aim of the study is to analyze the immune response to shunt infection caused by S. epidermidis in children with hydrocephalus. The immune response to the pathogen will be analyzed on the basis of, inter alia, simple laboratory test results, such as changes in the pattern of white blood cells, including neutrophils, monocytes, and lymphocytes. The entire study analyzes changes in general parameters of the cerebrospinal fluid (pleocytosis, protein level, glucose level) and in levels of selected interleukins (IL-6, CXCL8 / IL-8, CCL3 / MIP-1a) in the cerebrospinal fluid. The clinical material analyzed in the study was collected in 2010-2014. The study group consisted of 30 patients, who were admitted to the hospital due to their first-ever episode of valve dysfunction caused by S. epidermidis infection. The control group consisted of 30 children who also suffered from congenital hydrocephalus but had not been operated on before. The most pronounced response to CSF infection in the study group was a significant increase in the counts of all investigated WBC lines in the samples collected immediately after the patients' admission to the ward. The earliest aberration of the CSF was a significant increase in protein level. An infection of a ventriculoperitoneal shunt caused by S. epidermidis evokes a very early peripheral blood response. In children affected by a ventriculoperitoneal valve infection, the humoral immune response detected in the cerebrospinal fluid precedes the increase in the level of pleocytosis. The highest level of cytokines in the cerebrospinal fluid is achieved when the pathogens are cleared. Phagocytes, and, in particular, monocytes, play an important role in the normalization of the cerebrospinal fluid parameters after the elimination of S. epidermidis. The local immune response of the central nervous system plays an important role in extinguishment of the inflammatory process.

Adjuvant Cannabinoid Receptor Type 2 Agonist Modulates the Polarization of Microglia Towards a Non-Inflammatory Phenotype in Experimental Pneumococcal Meningitis

Background

Microglia initiates and sustains the inflammatory reaction that drives the pathogenesis of pneumococcal meningitis. The expression of the G-protein cannabinoid receptor type 2 (CB2) in the brain is low, but is upregulated in glial cells during infection. Its activation down-regulates pro-inflammatory processes, driving microglia towards an anti-inflammatory phenotype. CB2 agonists are therefore therapeutic candidates in inflammatory conditions like pneumococcal meningitis. We evaluated the effects of JWH-133, a specific CB2 agonist on microglial cells, inflammation, and damage driven by S. pneumoniae in vitro and in experimental pneumococcal meningitis.

Materials/methods

Primary mixed glial cultures were stimulated with live or heat-inactivated S. pneumoniae, or lipopolysaccharide and treated with JWH-133 or vehicle. Nitric oxide and cytokines levels were measured in the supernatant. In vivo, pneumococcal meningitis was induced by intracisternal injection of live S. pneumoniae in 11 days old Wistar rats. Animals were treated with antibiotics (Ceftriaxone, 100 mg/kg, s.c. bid) and JWH-133 (1 mg/kg, i.p. daily) or vehicle (10% Ethanol in saline, 100 µl/25g body weight) at 18 h after infection. Brains were harvested at 24 and 42 h post infection (hpi) for histological assessment of hippocampal apoptosis and cortical damage and determination of cyto/chemokines in tissue homogenates. Microglia were characterized using Iba-1 immunostaining. Inflammation in brain homogenates was determined using membrane-based antibody arrays.

Results

In vitro, nitric oxide and cytokines levels were significantly lowered by JWH-133 treatment. In vivo, clinical parameters were not affected by the treatment. JWH-133 significantly lowered microglia activation assessed by quantification of cell process length and endpoints per microglia. Animals treated with JWH-133 demonstrated significantly lower parenchymal levels of chemokines (CINC-1, CINC-2α/β, and MIP-3α), TIMP-1, and IL-6 at 24 hpi, and CINC-1, MIP-1α, and IL-1α at 42 hpi. Quantitative analysis of brain damage did not reveal an effect of JWH-133.

Conclusions

JWH-133 attenuates microglial activation and downregulates the concentrations of pro-inflammatory mediators in pneumococcal infection in vitro and in vivo. However, we didn't observe a reduction in cortical or hippocampal injury. This data provides evidence that inhibition of microglia by adjuvant CB2 agonists therapy effectively downmodulates neuroinflammation but does not reduce brain damage in experimental pneumococcal meningitis.

Gene Polymorphisms of TLR4 and TLR9 and Haemophilus influenzae Meningitis in Angolan Children

Bacterial meningitis (BM) is a severe disease caused by various bacterial pathogens. Toll-like receptors (TLRs) protect humans from invading pathogens. In this study, we determined whether single nucleotide polymorphisms (SNPs) of TLR4 and TLR9 are associated with susceptibility to and outcome of BM in Angolan children. Samples were taken from 241 patients and 265 age-matched ethnic controls. The SNPs TLR4 rs4986790 (896A > G) and TLR9 rs187084 (−1486T > C) were determined by high-resolution melting analysis (HRMA). The frequency of variant genotypes in TLR4 was significantly higher in patients with Haemophilus influenzae meningitis than controls (odds ratio (OR), 2.5; 95% confidence interval (CI), 1.2–5.4; p = 0.021), whereas the frequency of variant genotypes in TLR9 was significantly lower in patients with H. influenzae meningitis than controls (OR, 0.4; 95% CI, 0.2–0.9; p = 0.036). No such differences were found with other causative pathogens, such as Streptococcus pneumoniae and Neisseria meningitidis. At the time of discharge, patients with meningitis caused by Gram-negative bacteria who were carriers of variant TLR4 genotypes had a higher risk of ataxia (OR, 12.91; 95% CI, 1.52–109.80; p = 0.019) and other neurological sequelae (OR, 11.85; 95% CI, 1.07–131.49; p = 0.044) than those with the wild-type TLR4 genotype. Our study suggests an association between H. influenzae meningitis and genetic variation between TLR4 and TLR9 in Angolan children.

Double deficiency of toll-like receptors 2 and 4 alters long-term neurological sequelae in mice cured of pneumococcal meningitis

Toll-like receptor (TLR) 2 and 4 signalling pathways are central to the body’s defence against invading pathogens during pneumococcal meningitis. Whereas several studies support their importance in innate immunity, thereby preventing host mortality, any role in protecting neurological function during meningeal infection is ill-understood. Here we investigated both the acute immunological reaction and the long-term neurobehavioural consequences of experimental pneumococcal meningitis in mice lacking both TLR2 and TLR4. The absence of these TLRs significantly impaired survival in mice inoculated intracerebroventricularly with Streptococcus pneumoniae. During the acute phase of infection, TLR2/4-deficient mice had lower cerebrospinal fluid concentrations of interleukin-1β, and higher interferon-γ, than their wild-type counterparts. After antibiotic cure, TLR2/4 double deficiency was associated with aggravation of behavioural impairment in mice, as shown by diurnal hypolocomotion throughout the adaptation phases in the Intellicage of TLR-deficient mice compared to their wild-type counterparts. While TLR2/4 double deficiency did not affect the cognitive ability of mice in a patrolling task, it aggravated the impairment of cognitive flexibility. We conclude that TLR2 and TLR4 are central to regulating the host inflammatory response in pneumococcal meningitis, which may mediate diverse compensatory mechanisms that protect the host not only against mortality but also long-term neurological complications.

Association between Proton Pump Inhibitor Use and CNS Infection Risk: A Retrospective Cohort Study

This study investigated the incidence of central nervous system (CNS) infection following the use of proton pump inhibitors (PPIs). A retrospective cohort study was conducted in Taiwan by using data from the National Health Insurance Research Database. We identified and enrolled 16,241 patients with CNS infection who used PPIs (PPI users). The patients were individually propensity score matched (1:1) according to age, sex, hypertension, hyperlipidemia, Charlson comorbidity index (CCI), H2 blocker, non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroid, and immunosuppressant use with 16,241 controls (PPI nonusers). A Cox proportional hazards model was used to estimate adjusted hazard ratio (aHR) for CNS infection in the PPI users and nonusers. After adjustment for other confounding factors, the incidence of CNS infection in the PPI users was 2.23-fold higher than that in the PPI nonusers (95% CI = 1.27⁻3.94). In addition, the PPI users exhibited a higher risk of CNS infection than the nonusers in the hypertension and CCI = 1 groups (aHR = 3.80, 95% CI = 1.40⁻10.32; aHR = 2.47, 95% CI = 1.07⁻5.70 in the PPI users and nonusers, respectively). In conclusions, according to these results, we concluded that the incidence of CNS infection was higher in the PPI users than in the nonusers.