Single nucleotide polymorphisms in pathogen recognition receptor genes are associated with susceptibility to meningococcal meningitis in a pediatric cohort

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.

Effect of TLR-4 gene polymorphisms on sepsis susceptibility in neonates: a systematic review and meta-analysis

Aim: To clarify the role of polymorphisms rs4986790 and rs4986791 in TLR-4 with susceptibility to neonatal sepsis. Methods: To evaluate the possible correlation of polymorphisms rs4986790 and rs4986791 with sepsis risk, odds ratios (ORs) were calculated. The heterogeneity was evaluated by χ²-based Q-test. Results: For rs4986790, ORs were 1.36 (95% CI: 1.05-1.79, p = 0.017) and 1.84 (95% CI: 0.04-7.9, p = 0.410) under AG+GG versus AA and G vs. A models, respectively. For rs4986791, ORs were 2.22 (95% CI: 1.25-3.94, p = 0.006) and 2.20 (95% CI: 1.26-3.85, p = 0.005) under CT+TT versus CC and of T versus C models, respectively. Conclusion: The rs4986790 and rs4986791 polymorphisms in TLR-4 could influence the sepsis susceptibility in neonates.

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.

Study protocol: The Dutch 20|30 Postmeningitis study: a cross-sectional follow-up of two historical childhood bacterial meningitis cohorts on long-term outcomes

Background

Bacterial meningitis (BM) is a serious, life-threatening infectious disease of the central nervous system that often occurs in young children. The most common severe to moderate sequelae following BM are sensorineural hearing loss, neuromotor disabilities and mental retardation, while subtle sequelae include academic and behavioral disabilities. It is largely unknown whether these more subtle sequelae persist into adolescence and adulthood. Therefore, this study will investigate the very long-term effects of childhood BM in later life. Better understanding of long-term effects and early identification of adverse outcomes after BM are essential for more timely interventions. Additionally, certain single nucleotide polymorphisms (SNPs) are associated with disease severity and might predict adverse sequelae. These include SNPs in genes encoding for pathogen recognition and immune response upon infection. Accordingly, a secondary objective of this study is to investigate the role of genetic variation in BM and use any insights to predict short- and long-term outcomes.

Methods

In the Dutch 20|30 Postmeningitis study, adolescents and young adults (n = 947) from two historical cohorts with a prior episode of BM during childhood will be enrolled into a cross-sectional follow-up investigation using mainly questionnaires that examine executive and behavioral functioning, health-related quality of life, subjective hearing, mood and sleeping disorders, academic performance, and economic self-sufficiency. The results will be compared to normative data by one-sample t-tests. Multivariable regression analysis will be used to assess for any associations with causative pathogens and severity of BM. Participants that complete the questionnaires will be approached to provide a swab for buccal DNA and subsequent sequencing analyses. Logistic regression models will be used to predict sequelae.

Discussion

The unique follow-up duration of this cohort will enable us to gain insights into the possible very long-term adverse effects of childhood BM and how these might impact on quality of life. The investigation of host genetic factors will contribute to the development of prediction models which will serve as prognostic tools to identify children who are at high risk of adverse outcome after BM.

Trial Registration

Dutch Trial Register NTR-6891. Retrospectively registered 28 December 2017.

Host genetic variability and pneumococcal disease: a systematic review and meta-analysis

Background

Pneumonia, sepsis, meningitis, and empyema due to Streptococcus pneumoniae is a major cause of morbidity and mortality. We provide a systemic overview of genetic variants associated with susceptibility, phenotype and outcome of community acquired pneumococcal pneumonia (CAP) and invasive pneumococcal disease (IPD).

Methods

We searched PubMed for studies on the influence of host genetics on susceptibility, phenotype, and outcome of CAP and IPD between Jan 1, 1983 and Jul 4, 2018. We listed methodological characteristics and when genetic data was available we calculated effect sizes. We used fixed or random effect models to calculate pooled effect sizes in the meta-analysis.

Results

We identified 1219 studies of which 60 studies involving 15,358 patients were included. Twenty-five studies (42%) focused on susceptibility, 8 (13%) on outcome, 1 (2%) on disease phenotype, and 26 (43%) on multiple categories. We identified five studies with a hypothesis free approach of which one resulted in one genome wide significant association in a gene coding for lincRNA with pneumococcal disease susceptibility. We performed 17 meta-analyses of which two susceptibility polymorphisms had a significant overall effect size: variant alleles of MBL2 (odds ratio [OR] 1·67, 95% confidence interval [CI] 1·04–2·69) and a variant in CD14 (OR 1·77, 95% CI 1·18–2·66) and none of the outcome polymorphisms.

Conclusions

Studies have identified several host genetics factors influencing risk of pneumococcal disease, but many result in non-reproducible findings due to methodological limitations. Uniform case definitions and pooling of data is necessary to obtain more robust findings.

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0572-x) contains supplementary material, which is available to authorized users.

The association between pneumococcal vaccination, ethnicity, and the nasopharyngeal microbiota of children in Fiji

BACKGROUND

Streptococcus pneumoniae is a significant global pathogen that colonises the nasopharynx of healthy children. Pneumococcal conjugate vaccines, which reduce nasopharyngeal colonisation of vaccine-type S. pneumoniae, may have broader effects on the nasopharyngeal microbiota; however, data are limited. In Fiji, nasopharyngeal carriage prevalence of S. pneumoniae and other colonising species differ between the two main ethnic groups. Here, we examined the association between the 7-valent pneumococcal conjugate vaccine (PCV7) and the nasopharyngeal microbiota of children in Fiji, including for each of the two main ethnic groups-indigenous Fijians (iTaukei) and Fijians of Indian descent (FID).

METHOD

The nasopharyngeal microbiota of 132 Fijian children was examined using nasopharyngeal swabs collected from 12-month-old iTaukei and FID children who were vaccinated (3 doses PCV7) or unvaccinated in infancy as part of a phase II randomised controlled trial. Microbiota composition was determined by sequencing the V4 region of the 16S rRNA gene. Species-specific carriage of S. pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus was determined using real-time quantitative PCR. Associations between microbiota composition and other host and environmental factors were considered in the analysis.

RESULTS

PCV7 had no overall impact on microbial diversity or composition. However, ethnic differences were observed in both diversity and composition with iTaukei children having higher relative abundance of Moraxella (p = 0.004) and Haemophilus (p = 0.004) and lower relative abundance of Staphylococcus (p = 0.026), Dolosigranulum (p = 0.004) and Corynebacterium (p = 0.003) compared with FID children. Further, when we stratified by ethnicity, associations with PCV7 could be detected: vaccinated iTaukei children had a lower relative abundance of Streptococcus and Haemophilus compared with unvaccinated iTaukei children (p = 0.022 and p = 0.043, respectively); and vaccinated FID children had a higher relative abundance of Dolosigranulum compared with unvaccinated FID children (p = 0.037). Children with symptoms of an upper respiratory tract infection (URTI) had a significantly different microbiota composition to children without symptoms. The microbiota composition of iTaukei children without URTI symptoms was most similar to the microbiota composition of FID children with URTI symptoms.

CONCLUSIONS

Associations between PCV7 and nasopharyngeal microbiota differed within each ethnic group. This study highlights the influence that ethnicity and URTIs have on nasopharyngeal microbiota.

Infection Complications in Hematopoietic Stem Cells Transplant Recipients: Do Genetics Really Matter?

Hematopoietic stem cell transplantation (HSCT) is a highly advanced technique that offers a potential cure for an increasing number of life-threatening diseases. Enormous progress achieved in the last decade, including the refinement of donor selection and advancements in patient supportive care, had significantly improved transplant outcomes; however, invasive infections, graft-vs.-host disease (GVHD) and other serious complications still represent a major source of morbidity and mortality in HSCT recipients. The damage of anatomical barriers due to pre-transplant conditioning, a severely damaged immune function and a profound disruption in the composition of gut microbial commensals (gut microbiota) are alterations inherent to the transplant procedure that are directly implicated in the development of invasive infections and other HSCT complications. Although HLA-matching represents the most important genetic predictor of transplant outcomes, genetic variants in non-HLA genes, especially single nucleotide polymorphisms (SNPs) of genes encoding proteins associated with the immune response to tissue injury and pathogen infection have also been proposed as additional risk factors implicated in the occurrence of HSCT complications. Furthermore, although the microbiota composition is affected by several factors, recent evidence suggests that certain host genetic variants are associated with an altered composition of the gut microbiome and may, therefore, predispose some individuals to invasive infectious complications. This article summarizes the current understanding of the influence that genetic variants in non-HLA genes have on the development of infectious complications in HSCT recipients.

Toll-Interleukin 1 Receptor Domain-Containing Adaptor Protein 180L Single-Nucleotide Polymorphism Is Associated With Susceptibility to Recurrent Pneumococcal Lower Respiratory Tract Infections in Children

Lower respiratory tract infections (LRTI) are often caused by Streptococcus pneumoniae (Spn) and can be recurrent in 8% of children older than 2 years of age. Spn is recognized by pattern-recognition receptors (PRRs) of the innate immune system, in particular toll-like receptors (TLRs) 2 and 4. To assess whether a defect somewhere along this TLR signaling pathway increases susceptibility to recurrent pneumococcal LRTI, we conducted a prospective case-control study with 88 healthy individuals and 45 children with recurrent LRTI aged 2-5 years old. We examined cell surface expression of TLR2 and TLR4, as well as eight genetic variants of these receptors or associated co-receptors TLR1 and TLR6. Interleukin-6 production was measured after whole blood stimulation assays with specific agonists and heat-killed Spn. Our findings reveal that single-nucleotide polymorphisms within toll-interleukin 1 receptor domain-containing adaptor protein (TIRAP) alone or in combination with TLR1 N248S, TLR1 I602S, or TLR6 S249P polymorphisms contributes to various degree of susceptibility to recurrent pneumococcal LRTI in children by modulating the inflammatory response. In that respect, carriage of the TIRAP S180L heterozygous trait increases the likelihood to protect against pneumococcal LRTI, whereas children carrying the mutant homozygous TIRAP 180L polymorphism might be more likely susceptible to recurrent pneumococcal LRTI.

Role of toll-like receptor 4 Asp299Gly polymorphism in the development of cardiovascular diseases in HIV-infected patients

OBJECTIVE

Cardiovascular diseases (CVDs) are one of the main causes of morbimortality in HIV-infected patients on suppressive antiretroviral therapy. The objective of this work was to evaluate the role of single nucleotide polymorphisms (SNPs) in lipopolysaccharide (LPS) Toll-like receptor 4 (TLR4) and CVDs occurrence in HIV-infected patients. Additionally, the functional consequences of carrying these SNPs were analyzed.

METHODS

The association of TLR4 SNPs, Asp299Gly/Thr399Ile with CVDs occurrence was analyzed using multivariate logistic regression models. Clinical, immunological, and traditional cardiovascular risk factors were used as covariates. The monocyte phenotype and response were assessed by multiparametric flow cytometry comparing carriers with noncarriers of this SNP.

RESULTS

Asp299Gly SNP, assayed in 253 HIV-infected patients, was independently associated with the occurrence of CVDs after adjusting for CD4+ T-cell nadir, HCV-coinfection, bacterial pneumonia, diabetes mellitus, and traditional cardiovascular risk factors [odds ratio (confidence interval 95%) = 3.672 (1.061-12.712), P = 0.04). Carriers of Asp299Gly SNP showed higher percentage of patrolling and intermediate monocytes producing a proinflammatory combination of cytokines compared with noncarriers (P = 0.037 and P = 0.046, respectively). Intermediate monocyte subset levels correlated with soluble interleukin-6 levels only in carriers (r = 0.89; P = 0.01).

CONCLUSION

TLR4 Asp299Gly polymorphism is independently associated with the occurrence of CVDs in HIV-infected patients. The proinflammatory profile associated to this variant could be involved in the development of atherosclerotic pathologies.

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

Background

There are many studies analysing the effect of SNPs in genes coding proteins which are involved in innate immune response on susceptibility to invasive bacterial disease. Many of them gave inconclusive results. Regarding the complexity of immune response and cooperation between particular elements, number of SNPs may have a cumulative effect on the susceptibility to bacterial meningitis.

Findings

In most studies cooccurrence of several SNPs was not analysed. These studies were performed on small groups of patients and usually only few SNPs were checked simultaneously. Additionally, comparison of the results across the studies is hard to conduct. We hypothesise that the number of variants of genes involved in innate immune response plays a role in susceptibility to bacterial meningitis. However, the role of toll-like receptors and other part of innate immune response in the eradication of bacteria, and initiation of the inflammatory response in CNS need further studies.

Conclusion

Large multicentre studies assessing multiple SNPs in patients with microbiologically proven pneumococcal or meningococcal meningitis are needed to find real genetic risk factors for developing bacterial meningitis. This is necessary to design more effective treatment and prevention strategies for severe infections.

Association between TLR2 + 2477G/A polymorphism and bacterial meningitis: a meta-analysis

Toll-like receptor 2 (TLR2) is a key member of TLRs, which is crucial in the initial inflammatory response against bacteria. TLR2, is also the initial barrier against bacterial infection and plays an important role in recognising a variety of bacterial lipoproteins. Several studies have been performed to investigate the TLR2 + 2477G/A polymorphism and bacterial meningitis susceptibility. Unfortunately, the results of previous studies were controversial. Therefore, we performed a meta-analysis to derive a more precise estimation of the association. The association between the TLR2 + 2477G/A polymorphism and bacterial meningitis susceptibility was assessed by odds ratios together with their 95% confidence intervals (CI). Six studies were enrolled in the present meta-analysis. Overall, no significant association between TLR2 + 2477G/A polymorphism and bacterial meningitis risk were found under allele contrast (A vs. G: OR = 1.15, 95% CI = 0.93-1.43, P = 0.202), recessive genetic model (AA vs. AG/GG: OR = 1.12, 95% CI = 0.90-1.41, P = 0.313). The significant association was found between TLR2 + 2477G/A polymorphism and pneumococcal meningitis risk under allele contrast (A vs. G: OR = 1.54, 95% CI = 1.01-2.36, P = 0.046), recessive genetic model (AA vs. AG/GG: OR = 1.63, 95% CI = 1.03-2.57, P = 0.035). We conclude that TLR2 + 2477G/A polymorphism is not associated with meningococcal meningitis risk but contributes an increased risk of pneumococcal meningitis.

How many single-nucleotide polymorphisms (SNPs) must be tested in order to prove susceptibility to bacterial meningitis in children? Analysis of 11 SNPs in seven genes involved in the immune response and their effect on the susceptibility to bacterial meningitis in children

The aim of this study is to describe the prevalence of single single-nucleotide polymorphisms (SNPs) as well as their combinations in genes encoding proteins involved in the immune response in children with bacterial meningitis. The prospective study group consisted of 39 children with bacterial meningitis and 49 family members surveyed between 2012 and 2016. Eleven SNPs in seven genes involved in immune response were analysed. The mean number of minor frequency alleles (MAF) of studied SNPs was lowest in the control group and highest in patients with pneumococcal meningitis. We found that carrying ≥6 MAF of studied SNPs was associated with an increased risk of pneumococcal meningitis. The prevalence of risky variants was noted to be higher in patients with pneumococcal meningitis as compared to the control group. In conclusion, genetic factors are a relevant factor in determining the susceptibility to bacterial meningitis. A statistically significant cumulative effect of mutated variants on increasing the risk of bacterial meningitis was detected. Combining all three SNPs in MBL2 improves the prediction of susceptibility to pneumococcal meningitis. Analysis of risky alleles can help indicate people prone to the disease who are ‘gene-immunocompromised’.

Toll-like receptor 4 polymorphism is associated with increased susceptibility to chronic obstructive pulmonary disease in Han Chinese patients with chronic periodontitis

The aim of the present study was to evaluate the association of single nucleotide polymorphisms (SNPs) in toll-like receptor 4 (TLR4) with chronic obstructive pulmonary disease (COPD) in Han Chinese patients with chronic periodontitis (CP). Six candidate SNPs of TLR4-rs10759930, rs10983755, rs11536879, rs1927907, rs11536889 and rs7873784-and 18 haplotype-tagging SNPs (tagSNPs) were genotyped in 339 patients with chronic periodontitis only (CP group), and 373 CP patients with COPD (CP with COPD group). The genotype distribution and allele frequencies of TLR4 rs1927907 among the CP (AA: 26, 8.5%, AG: 109, 35.5%, GG: 172, 56.0%) and CP with COPD (AA: 41, 12.0%, AG: 143, 41.7%, GG: 159, 46.4%) groups were significantly different (P = 0.039). After adjusting for age, sex, smoking status, and oral hygiene habits, CP patients carrying the AG polymorphism in TLR4 rs1927907 were found to be more susceptible to concomitant COPD than those carrying the GG genotype (P = 0.005, OR = 1.94, 95% CI for OR: 1.22-3.03). In conclusion, TLR4 gene polymorphism plays a role in the common pathophysiology of CP and COPD, indicating that CP patients with TLR4 gene rs1927907 polymorphism may be more susceptible to COPD.(J Oral Sci 58, 555-560, 2016).

Genetic predisposition to infection in a case of atypical hemolytic uremic syndrome

Most cases of hemolytic uremic syndrome (HUS) are caused by infection with enterohemorrhagic Escherichia coli (EHEC). Genetic defects causing uncontrolled complement activation are associated with the more severe atypical HUS (aHUS). Non-EHEC infections can trigger the disease, however, complement defects predisposing to such infections have not yet been studied. We describe a 2-month-old patient infected with different Gram-negative bacterial species resulting in aHUS. Serum analysis revealed slow complement activation kinetics. Rare variant R229C was found in complement inhibitor vitronectin. Recombinant mutated vitronectin showed enhanced complement inhibition in vitro and may have been a predisposing factor for infection. Our work indicates that genetic changes in aHUS can not only result in uncontrolled complement activation but also increase vulnerability to infections contributing to aHUS.

Analysis of TLR2, TLR4, and TLR9 single nucleotide polymorphisms in children with bacterial meningitis and their healthy family members

BACKGROUND

The aim was to analyse TLR2 rs5743708, TLR2 rs4696480, TLR4 rs4986790, TLR9 rs5743836, and TLR9 rs352140 single nucleotide polymorphisms (SNPs) in children with pneumococcal and meningococcal meningitis and their family members.

METHODS

The study group consisted of 39 children with bacterial meningitis (25 with meningococcal meningitis and 14 with pneumococcal meningitis) and 49 family members. Laboratory test results and the course of the diseases were analyzed. Genomic DNA was extracted from 1.2ml of peripheral blood in order to analyze the five SNPs.

RESULTS

Patients with pneumococcal and meningococcal meningitis showed a similar male/female ratio, mean age, and duration of symptoms. There were no statistically significant differences in biochemical markers between the two groups. All patients possessed at least one polymorphic variant of the analyzed SNPs. The most common SNP was TLR9 rs352140, detected in 89.7% of patients. No significant differences in SNP frequency were found between patients, family members, and the general population.

CONCLUSIONS

The allele frequencies in the population studied are in accordance with the literature data. The study did not find an association between the analyzed SNPs and susceptibility to bacterial meningitis. The role of SNPs in genes coding toll-like receptors and the interactions between them in controlling inflammation in the central nervous system needs further evaluation.

Innate immune recognition and inflammation in Neisseria meningitidis infection

Neisseria meningitidis (Nme) can cause meningitis and sepsis, diseases which are characterised by an overwhelming inflammatory response. Inflammation is triggered by host pattern recognition receptors (PRRs) which are activated by pathogen-associated molecular patterns (PAMPs). Nme contains multiple PAMPs including lipooligosaccharide, peptidoglycan, proteins and metabolites. Various classes of PRRs including Toll-like receptors, NOD-like receptors, C-type lectins, scavenger receptors, pentraxins and others are expressed by the host to respond to any given microbe. While Toll-like receptors and NOD-like receptors are pivotal in triggering inflammation, other PRRs act as modulators of inflammation or aid in functional antimicrobial responses such as phagocytosis or complement activation. This review aims to give an overview of the various Nme PAMPs reported to date, the PRRs they activate and their implications during the inflammatory response to infection.

Technologies for Proteome-Wide Discovery of Extracellular Host-Pathogen Interactions

Pathogens have evolved unique mechanisms to breach the cell surface barrier and manipulate the host immune response to establish a productive infection. Proteins exposed to the extracellular environment, both cell surface-expressed receptors and secreted proteins, are essential targets for initial invasion and play key roles in pathogen recognition and subsequent immunoregulatory processes. The identification of the host and pathogen extracellular molecules and their interaction networks is fundamental to understanding tissue tropism and pathogenesis and to inform the development of therapeutic strategies. Nevertheless, the characterization of the proteins that function in the host-pathogen interface has been challenging, largely due to the technical challenges associated with detection of extracellular protein interactions. This review discusses available technologies for the high throughput study of extracellular protein interactions between pathogens and their hosts, with a focus on mammalian viruses and bacteria. Emerging work illustrates a rich landscape for extracellular host-pathogen interaction and points towards the evolution of multifunctional pathogen-encoded proteins. Further development and application of technologies for genome-wide identification of extracellular protein interactions will be important in deciphering functional host-pathogen interaction networks, laying the foundation for development of novel therapeutics.

Is Toxoplasma gondii a Trigger of Bipolar Disorder?

Toxoplasma gondii, a ubiquitous intracellular parasite, has a strong tropism for the brain tissue, where it forms intracellular cysts within the neurons and glial cells, establishing a chronic infection. Although latent toxoplasmosis is generally assumed to be asymptomatic in immunocompetent individuals, it is now clear that it can induce behavioral manipulations in mice and infected humans. Moreover, a strong relation has emerged in recent years between toxoplasmosis and psychiatric disorders. The link between T. gondii and schizophrenia has been the most widely documented; however, a significant association with bipolar disorder (BD) and suicidal/aggressive behaviors has also been detected. T. gondii may play a role in the etiopathogenesis of psychiatric disorders affecting neurotransmitters, especially dopamine, that are implicated in the emergence of psychosis and behavioral Toxoplasma-induced abnormalities, and inducing brain inflammation by the direct stimulation of inflammatory cytokines in the central nervous system. Besides this, there is increasing evidence for a prominent role of immune dysregulation in psychosis and BD. The aim of this review is to describe recent evidence suggesting a link between Toxoplasma gondii and BD, focusing on the interaction between immune responses and this infectious agent in the etiopathogenesis of psychiatric symptoms.

Variation of 46 Innate Immune Genes Evaluated for their Contribution in Pneumococcal Meningitis Susceptibility and Outcome

Pneumococcal meningitis is the most common and severe form of bacterial meningitis. Early recognition of the pathogen and subsequent innate immune response play a vital role in disease susceptibility and outcome. Genetic variations in innate immune genes can alter the immune response and influence susceptibility and outcome of meningitis disease. Here we conducted a sequencing study of coding regions from 46 innate immune genes in 435 pneumococcal meningitis patients and 416 controls, to determine the role of genetic variation on pneumococcal meningitis susceptibility and disease outcome. Strongest signals for susceptibility were rs56078309 CXCL1 (p=4.8e-04) and rs2008521 in CARD8 (p=6.1e-04). For meningitis outcome the rs2067085 in NOD2 (p=5.1e-04) and rs4251552 of IRAK4 were the strongest associations with unfavorable outcome (p=6.7e-04). Haplotype analysis showed a haplotype block, determined by IRAK4 rs4251552, significantly associated with unfavorable outcome (p=0.004). Cytokine measurements from cerebrospinal fluid showed that with the IRAK4 rs4251552 G risk allele had higher levels of IL-6 compared to individuals with A/A genotype (p=0.04). We show that genetic variation within exons and flanking regions of 46 innate immunity genes does not yield significant association with pneumococcal meningitis. The strongest identified signal IRAK4 does imply a potential role of genetic variation in pneumococcal meningitis.

N. meningitidis and TLR Polymorphisms: A Fascinating Immunomodulatory Network

N. meningitidis infections represent a global health problem that can lead to the development of serious permanent sequelae. Although the use of antibiotics and prevention via vaccination have reduced the incidence of meningococcal disease, our understanding regarding N. meningitidis pathogenesis is still limited, especially of those mechanisms responsible for IMD and fulminant or deadly septic shock. These severe clinical presentations occur in a limited number of subjects, whereas about 10% of healthy individuals are estimated to carry the bacteria as a commensal. Since TLR activation is involved in the defense against N. meningitidis, several studies have highlighted the association between host TLR SNPs and a higher susceptibility and severity of N. meningitidis infections. Moreover, TLR SNPs induced variations in immunological responses and in their persistence upon vaccination against meningococcal disease. In the absence of mass vaccination programs, the early identification of risk factors for meningococcal disease would be recommended in order to start immunization strategies and antibiotic treatment in those subjects carrying the risk variants. In addition, it could allow us to identify individuals with a higher risk for severe disease and sequelae in order to develop a personalized healthcare of high-risk subjects based on their genomic profile. In this review, we have illustrated important preliminary correlations between TLR variants and meningococcal susceptibility/severity and with vaccine-induced immune responses.

Toxoplasma gondii exposure may modulate the influence of TLR2 genetic variation on bipolar disorder: a gene-environment interaction study

Background

Genetic vulnerability to environmental stressors is yet to be clarified in bipolar disorder (BD), a complex multisystem disorder in which immune dysfunction and infectious insults seem to play a major role in the pathophysiology. Association between pattern-recognition receptor coding genes and BD had been previously reported. However, potential interactions with history of pathogen exposure are yet to be explored.

Methods

138 BD patients and 167 healthy controls were tested for serostatus of Toxoplasma gondii, CMV, HSV-1 and HSV-2 and genotyped for TLR2 (rs4696480 and rs3804099), TLR4 (rs1927914 and rs11536891) and NOD2 (rs2066842) polymorphisms (SNPs). Both the pathogen-specific seroprevalence and the TLR/NOD2 genetic profiles were compared between patients and controls followed by modelling of interactions between these genes and environmental infectious factors in a regression analysis.

Results

First, here again we observed an association between BD and Toxoplasma gondii (p = 0.045; OR = 1.77; 95 % CI 1.01–3.10) extending the previously published data on a cohort of a relatively small number of patients (also included in the present sample). Second, we found a trend for an interaction between the TLR2rs3804099 SNP and Toxoplasma gondii seropositivity in conferring BD risk (p = 0.017, uncorrected).

Conclusions

Pathogen exposure may modulate the influence of the immunogenetic background on BD. A much larger sample size and information on period of pathogen exposure are needed in future gene–environment interaction studies.

Group B streptococcal meningitis in a previously healthy man

Group B Streptococcus (GBS) is an infrequent cause of meningitis in adults, usually affecting elderly patients and those with serious underlying disease. It is more commonly recognised as one of the leading aetiological agents of neonatal sepsis following maternally derived infection during pregnancy. We report a case of a previously healthy 26-year-old man who presented with fevers, confusion and headache. Lumbar puncture results were consistent with bacterial meningitis, and blood cultures grew GBS. To the best of our knowledge, our patient represents one of the few reported cases of GBS meningitis in a previously healthy young man. Interestingly, our patient had a significant family history of central nervous system infection including a son with herpes simplex virus encephalitis, a sister with meningococcal meningitis and a great-uncle with meningitis of unknown cause. We discuss genetic factors that may predispose certain people to develop meningitis with normally harmless microorganisms such as GBS.

Toll-like receptor 2 subfamily gene polymorphisms are associated with Bacillus Calmette-Guérin osteitis following newborn vaccination

AIM

Toll-like receptor (TLR) 1, 2, 6 and 10, the TLR2 subfamily, are known to be associated with immunity against tuberculosis. We evaluated whether polymorphisms in genes encoding TLR1, TLR2 and TLR6 were associated with osteitis in infants who received the Bacillus Calmette-Guérin (BCG) vaccination soon after birth.

METHODS

Blood samples from 132 adults aged 21-49 who had BCG osteitis in early childhood were analysed in a controlled study for TLR1 T1805G (rs5743618), TLR2 G2258A (rs5743708) and TLR6 C745T (rs5743810) gene single nucleotide polymorphisms.

RESULTS

The frequencies of the variant genotypes differed between the cases and controls: 11.4% versus 5.7% for TLR2 G2258A (p = 0.033) and 77.3% versus 61.6% for TLR6 C745T (p = 0.001). The TLR2 and TLR6 variant genotypes were associated with a higher risk of BCG osteitis, with adjusted odds ratios (aOR) of 2.154 (95%CI 1.026-4.521) and 1.907 (95%CI 1.183-3.075), respectively. The frequency of the TLR1 T1805G variant genotype was 19.7% in the cases and 33.6% in the controls (p = 0.003). The TLR1 variant genotype was associated with a lower risk of BCG osteitis (aOR 0.554, 95%CI 0.336-0.911).

CONCLUSION

Gene polymorphisms that regulate the function of the TLR2 subfamily play a role in the development of BCG osteitis in vaccinated infants.