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

Assessing the Impact of TLR4 rs4986790 Polymorphism on Bacterial Meningitis Risk: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Toll-like receptor ( TLR2 ) gene plays an important role in the pathogenesis of bacterial meningitis (such as meningococcal meningitis and pneumococcal meningitis). The association between TLR4 rs4986790 polymorphism and the susceptibility to bacterial meningitis has been extensively studied. However, the results of these studies remain inconsistent. Therefore, we performed a meta-analysis to evaluate the association between TLR4 rs4986790 polymorphism and the susceptibility to meningococcal meningitis and pneumococcal meningitis.

METHODS

Google Scholar, Embase, and PubMed databases were searched for case-control studies on TLR4 polymorphisms and the risks of meningococcal meningitis and pneumococcal meningitis, published up to May 31, 2024. To assess the strength of the association between TLR4 polymorphism and meningococcal meningitis and pneumococcal meningitis, the odds ratios (ORs) with 95% confidence intervals (CIs) were used. The meta-analysis of the associations between the TLR4 rs4986790 polymorphism and meningococcal meningitis and pneumococcal meningitis was carried out under different genetic models. Meta-analyses were conducted using Cochrane RoB 2 tool and Metagenyo to calculate the ORs and 95% CIs. Fourteen published studies with 3599 cases and 7438 controls were included.

RESULTS

Overall, there was a strong correlation between TLR4 polymorphisms and meningococcal meningitis observed across three genetic models using a random-effects model: GG + GA vs. AA (OR: 0.34, 95% CI: 0.14-0.79, P = 0.01, I ² = 60%); GA vs. AA (OR: 0.34, 95% CI: 0.13-0.91, P = 0.03, I ² = 65%); and GG vs. AA (OR: 0.34, 95% CI: 0.14-0.78, P = 0.01, I ² = 59%). Conversely, a fixed-effects model also revealed a significant association in the G vs. A model (OR: 0.84, 95% CI: 0.73-0.96, P = 0.01, I ² = 38%). In pneumococcal meningitis, a fixed-effects model analysis demonstrated a significant association in the GG vs. AA model (OR: 0.35, 95% CI: 0.14-0.87, P = 0.02, I ² = 48%) respectively.

CONCLUSION

This meta-analysis showed a strong correlation between TLR4 rs4986790 polymorphism and susceptibility to meningococcal meningitis and pneumococcal meningitis. Further studies with diverse populations are needed to validate and strengthen these findings.

From Immunity to Neurogenesis: Toll-like Receptors as Versatile Regulators in the Nervous System

Toll-like receptors (TLRs) are among the main components of the innate immune system. They can detect conserved structures in microorganisms and molecules associated with stress and cellular damage. TLRs are expressed in resident immune cells and both neurons and glial cells of the nervous system. Increasing evidence is emerging on the participation of TLRs not only in the immune response but also in processes of the nervous system, such as neurogenesis and cognition. Below, we present a review of the literature that evaluates the expression and role of TLRs in processes such as neurodevelopment, behavior, cognition, infection, neuroinflammation, and neurodegeneration.

Gene polymorphisms of IL-17A and bacterial meningitis in Angolan children

Interleukin (IL)-17 A plays a crucial role in protecting hosts from invading bacterial pathogens. In this study, we investigated if single nucleotide polymorphisms (SNPs) in IL-17A are associated with susceptibility and outcome of bacterial meningitis (BM) in Angolan children. The study sample comprised 241 confirmed BM patients and 265 controls, which were matched for age and ethnicity. Three IL-17A SNPs - rs2275913 (-197G > A), rs8193036 (-737C > T) and rs4711998 (-877 A > G) - were determined by high-resolution melting analysis (HRMA). The frequency of variant genotype rs4711998 was significantly higher in patients with BM caused by Haemophilus influenzae (odds ratio [OR] 3.5; 95% confidence interval [CI] 1.49-8.23; P = 0.0025) than in controls. Also, patients with BM caused by Gram-negative bacteria and who carried the variant genotype rs2275913 had a lower glucose level (P = 0.0051) in cerebrospinal fluid (CSF). Patients with BM caused by Streptococcus pneumoniae who carried the variant type rs8193036 had a reduced risk for severe neurological sequelae (OR: 0.14; 95% CI: 0.029-0.68; P = 0.0079), blindness (OR: 0.012; 95% CI: 0.012-0.87; P = 0.017) and ataxia (OR: 0.28; 95% CI: 0.091-0.83; P = 0.023). This study suggests an association of IL-17A genetic variations with susceptibility and outcome of bacterial meningitis in Angolan children.

Gene polymorphisms of TLR10: effects on bacterial meningitis outcomes in Angolan children

This study examined whether gene polymorphisms for toll-like receptor 10 (TLR10) associated with the susceptibility to and outcomes of bacterial meningitis (BM) in Angolan children. The study cohort consisted of 190 BM patients and the determination of ten single-nucleotide polymorphisms (SNPs) by Sanger sequencing. Patients with BM caused by Streptococcus pneumoniae who carried the following variants of TLR10 SNPs exhibited an increased risk of coexisting pneumonia: rs10004195 (T > A) (p = 0.025), rs10856837 (G > A) (p = 0.018) or rs11096956 (G > T) (p = 0.010). Yet, TLR10 SNPs rs11466652 (A > G), rs10856837 (G > A) and rs11096956 (G > T) influenced the protein levels in the cerebrospinal fluid (CSF). Moreover, compared with the wild type, patients with pneumococcal meningitis carrying a variant genotype of TLR10 SNP rs11466648 (A > G) exhibited an increased risk of developing blindness (p = 0.025), whereas patients with TLR10 SNP rs10004195 (T > A) exhibited a lower risk of convulsions at admission (p = 0.039) and a lower risk of altered consciousness (p = 0.029). This study suggests a relationship exists between coexisting pneumonia, protein levels in CSF, blindness, convulsions and an altered consciousness with genetic variations of TLR10 in BM in Angolan children.

Genetic variations of toll-like receptors: Impact on susceptibility, severity and prognosis of bacterial meningitis

Bacterial meningitis (BM) is a serious infectious disease of the central nervous system，which is mainly caused by Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Group B Streptococcus and Listeria monocytogenes. Throughout the world, BM has become one of the most lethal diseases that commonly occurs in children. Toll like receptors (TLRs) are one of the most important immune defense lines in infectious diseases, and play an essential role in host defense. Accumulating evidence shows that genetic variations in TLRs are associated with host responses in BM. This review aims to summarize the role of different TLRs and their genetic variations in the susceptibility, severity and prognosis of BM and discuss the identified risk factors for better treatment and improvement of the course and outcome of BM.

Follow-up evaluation of the immunological status of children admitted for acute cerebral nervous system infections: a retrospective study

Background

Acute Cerebral Nervous System Infections (ACNS) may cause death or severe complications even to promptly treated children. The role of the immune system in influencing the course and the outcome of meningitis has been studied but it is not yet completely understood. The aim of the research is to ascertain whether children who experienced ACNS infection had a normal immune system.

Methods

Patients under 18 years of age admitted at Bambino Gesù Children from January 2006 till June 2016 for meningitis were asked to participate to the follow-up study. The immune status was evaluated both clinically and by laboratory investigations.

Results

Most of the patients over 3 years at follow up had at least one immunological alteration at follow-up evaluation (74%). Considering ACNS infection etiology, certain pathogens were almost exclusive of patients affected by some immunological alteration, regardless of their age.

Discussion

Our preliminary results indicate that sub-clinical immunological defects may be associated to ACNS pediatric infections. Moreover, to the best of our knowledges, this is the first study correlating pathogens to immune evaluation in ACNS infections. It is, however, important to underline the high frequency of persistent immunological alterations in the analyzed patients. Further studies are needed to confirm our conclusions.

Conclusions

We recommend an immunological assessment at follow up evaluation in children who experienced an ACNS infection.