Role of polymorphisms of toll-like receptor (TLR) 4, TLR9, toll-interleukin 1 receptor domain containing adaptor protein (TIRAP) and FCGR2A genes in malaria susceptibility and severity in Burundian children

The relationship between 896A/G (rs4986790) polymorphism of TLR4 and infectious diseases: A meta-analysis

Toll-like Receptors (TLRs), such as the TLR4, are genes encoding transmembrane receptors of the same name, which induce a pro- or anti-inflammatory response according to their expression as the host's first line of defense against pathogens, such as infectious ones. Single nucleotide polymorphisms (SNPs) are the most common type of mutation in the human genome and can generate functional modification in genes. The aim of this article is to review in which infectious diseases there is an association of susceptibility or protection by the TLR4 SNP rs4986790. A systematic review and meta-analysis of the literature was conducted in the Science Direct, PUBMED, MEDLINE, and SciELO databases between 2011 and 2021 based on the dominant genotypic model of this SNP for general and subgroup analysis of infectious agent type in random effect. Summary odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated for genotypic comparison. I² statistics were calculated to assess the presence of heterogeneity between studies and funnel plots were inspected for indication of publication bias. A total of 27 articles were included, all in English. Among the results achieved, the categories of diseases that were most associated with the SNP studied were in decreasing order of number of articles: infections by bacteria (29.63%); caused by viruses (22.23%); urinary tract infection-UTI (7.4%), while 11 studies (40.74%) demonstrated a nonsignificant association. In this meta-analysis, a total of 5599 cases and 5871 controls were finalized. The present meta-analysis suggests that there is no significant association between TLR4-rs4986790 SNP and infections (OR = 1,11; 95% CI: 0,75-1,66; p = 0,59), but in the virus subgroup it was associated with a higher risk (OR = 2,16; 95% CI: 1,09-4,30; p = 0,03). The subgroups of bacteria and parasites did not show statistical significance (OR = 0,86; 95% CI: 0,56-1,30; p = 0,47, and no estimate of effects, respectively). Therefore, it has been shown that a diversity of infectious diseases is related to this polymorphism, either by susceptibility or even severity to them, and the receptor generated is also crucial for the generation of cell signaling pathways and immune response against pathogens.

Toll-like receptor 9 and 4 gene polymorphisms in susceptibility and severity of malaria: a meta-analysis of genetic association studies

BACKGROUND

Malaria is still a major public health problem in sub-Saharan Africa and South-east Asia. The clinical presentations of malaria infection vary from a mild febrile illness to life-threatening severe malaria. Toll like receptors (TLRs) are postulated to be involved in the innate immune responses to malaria. Individual studies showed inconclusive findings. This study aimed to assess the role of TLR4 (D299G, T399I) and TLR9 (T1237C, T1486C) in severity or susceptibility of malaria by meta-analysis of data from eligible studies.

METHODS

Relevant case-control studies that assessed the association between TLR 4/9 and malaria either in susceptibility or progression were searched in health-related electronic databases. Quality of included studies was evaluated with Newcastle-Ottawa scale. Pooled analyses for specific genetic polymorphisms were done under five genetic models. Stratified analysis was done by age and geographical region (Asian countries vs non-Asian countries).

RESULTS

Eleven studies (2716 cases and 2376 controls) from nine endemic countries were identified. Five studies (45.4%) obtained high score in quality assessment. Overall, a significant association between TLR9 (T1486C) and severity of malaria is observed in allele model (OR: 1.26, 95% CI: 1.08-1.48, I² = 0%) or homozygous model (OR: 1.55, 95% CI: 1.08-2.28, I² = 0%). For TLR9 (T1237C), a significant association with severity of malaria is observed in in heterozygous model (OR:1.89, 95% CI: 1.11-3.22, I² = 75%). On stratifications, TLR9 (T1486C) is only significantly associated with a subgroup of children of non-Asian countries under allele model (OR: 1.25, 95% CI: 1.02-1.38), while 1237 is with a subgroup of adults from Asian countries under heterozygous model (OR: 2.0, 95% CI: 1.09-3.64, I² = 39%). Regarding the susceptibility to malaria, TLR9 (T1237C) is significantly associated only with the children group under recessive model (OR: 2.21, 95% CI: 1.06-4.57, I²⁼85%) and homozygous model (OR: 1.49, 95% CI: 1.09-2.0, I² = 0%). For TLR4 (D299G, T399I), none is significantly associated with either severity of malaria or susceptibility to malaria under any genetic models.

CONCLUSIONS

The findings suggest that TLR 9 (T1486C and T1237C) seems to influence the progression of malaria, under certain genetic models and in specific age group of people from specific geographical region. TLR 9 (T1237C) also plays a role in susceptibility to malaria under certain genetic models and only with children of non-Asian countries. To substantiate these, future well designed studies with larger samples across endemic countries are needed.

TLR4 and TLR9 polymorphism: Probable role in susceptibility among the population of Bihar for Indian visceral leishmaniasis

Genetic variations in the host TLRs genes play an important role in susceptibility and/or resistance to visceral leishmaniasis by altering the host-pathogen interaction. In this study, we investigated the association between polymorphisms of TLR4 (Asp299Gly, Thr399Ile) and TLR-9 (T-1237C), with susceptibility to visceral leishmaniasis. A bi-directional PCR amplification of specific alleles technique was used to characterize the distribution of TLR4 (Asp299Gly and Thr399Ile) and TLR9 (T-1237C) polymorphisms. A total of 60 samples were randomly selected from confirmed visceral leishmaniasis patients and 24 endemic healthy volunteers. The samples were genotyped and allele frequencies were determined. We observed that TLR4 Asp299Gly and Thr399Ile genotypes were more frequent in visceral leishmaniasis patients (10% and 15% respectively) compared to controls (4.2% and 8.3% respectively). However, the differences were not significant in TLR4 Asp299Gly and Thr399Ile alleles and genotypes. In the case of TLR9, we observed the frequency of T1237C genotype was higher in visceral leishmaniasis patients (43.3%) than in healthy controls (33.3%). Statistically significant differences were observed in TLR9 T1237C alleles and genotypes. We concluded that TLR9 T1237C, but not TLR4, gene polymorphisms can be regarded as contributors to visceral leishmaniasis susceptibility among the Indian population of Bihar state.

Germline Genetic Variants of Viral Entry and Innate Immunity May Influence Susceptibility to SARS-CoV-2 Infection: Toward a Polygenic Risk Score for Risk Stratification

The ongoing COVID-19 pandemic caused by the novel coronavirus, SARS-CoV-2 has affected all aspects of human society with a special focus on healthcare. Although older patients with preexisting chronic illnesses are more prone to develop severe complications, younger, healthy individuals might also exhibit serious manifestations. Previous studies directed to detect genetic susceptibility factors for earlier epidemics have provided evidence of certain protective variations. Following SARS-CoV-2 exposure, viral entry into cells followed by recognition and response by the innate immunity are key determinants of COVID-19 development. In the present review our aim was to conduct a thorough review of the literature on the role of single nucleotide polymorphisms (SNPs) as key agents affecting the viral entry of SARS-CoV-2 and innate immunity. Several SNPs within the scope of our approach were found to alter susceptibility to various bacterial and viral infections. Additionally, a multitude of studies confirmed genetic associations between the analyzed genes and autoimmune diseases, underlining the versatile immune consequences of these variants. Based on confirmed associations it is highly plausible that the SNPs affecting viral entry and innate immunity might confer altered susceptibility to SARS-CoV-2 infection and its complex clinical consequences. Anticipating several COVID-19 genomic susceptibility loci based on the ongoing genome wide association studies, our review also proposes that a well-established polygenic risk score would be able to clinically leverage the acquired knowledge.

Genetic variation in the immune system and malaria susceptibility in infants: a nested case-control study in Nanoro, Burkina Faso

BACKGROUND

Genetic polymorphisms in the human immune system modulate susceptibility to malaria. However, there is a paucity of data on the contribution of immunogenetic variants to malaria susceptibility in infants, who present differential biological features related to the immaturity of their adaptive immune system, the protective effect of maternal antibodies and fetal haemoglobin. This study investigated the association between genetic variation in innate immune response genes and malaria susceptibility during the first year of life in 656 infants from a birth cohort survey performed in Nanoro, Burkina Faso.

METHODS

Seventeen single nucleotide polymorphisms (SNPs) in 11 genes of the immune system previously associated with different malaria phenotypes were genotyped using TaqMan allelic hybridization assays in a Fluidigm platform. Plasmodium falciparum infection and clinical disease were documented by active and passive case detection. Case-control association analyses for both alleles and genotypes were carried out using univariate and multivariate logistic regression. For cytokines showing significant SNP associations in multivariate analyses, cord blood supernatant concentrations were measured by quantitative suspension array technology (Luminex).

RESULTS

Genetic variants in IL-1β (rs1143634) and FcγRIIA/CD32 (rs1801274)-both in allelic, dominant and co-dominant models-were significantly associated with protection from both P. falciparum infection and clinical malaria. Furthermore, heterozygote individuals with rs1801274 SNP in FcγRIIA/CD32 showed higher IL-1RA levels compared to wild-type homozygotes (P = 0.024), a cytokine whose production is promoted by the binding of IgG immune complexes to Fcγ receptors on effector immune cells.

CONCLUSIONS

These findings indicate that genetic polymorphisms in genes driving innate immune responses are associated to malaria susceptibility during the first year of life, possibly by modulating production of inflammatory mediators.

Association of variants in IL1B, TLR9, TREM1, IL10RA, and CD3G and Native American ancestry on malaria susceptibility in Colombian populations

Host genetics is an influencing factor in the manifestation of infectious diseases. In this study, the association of mild malaria with 28 variants in 16 genes previously reported in other populations and/or close to ancestry-informative markers (AIMs) selected was evaluated in an admixed 736 Colombian population sample. Additionally, the effect of genetic ancestry on phenotype expression was explored. For this purpose, the ancestral genetic composition of Turbo and El Bagre was determined. A higher Native American ancestry trend was found in the population with lower malaria susceptibility [odds ratio (OR) = 0.416, 95% confidence interval (95% CI) = 0.234-0.740, P = 0.003]. Three AIMs presented significant associations with the disease phenotype (MID1752, MID921, and MID1586). The first two were associated with greater malaria susceptibility (D/D, OR = 2.23, 95% CI = 1.06-4.69, P = 0.032 and I/D-I/I, OR = 2.14, 95% CI = 1.18-3.87, P = 0.011, respectively), and the latter has a protective effect on the appearance of malaria (I/I, OR = 0.18, 95% CI = 0.08-0.40, P < 0.0001). After adjustment by age, sex, municipality, and genetic ancestry, genotype association analysis showed evidence of association with malaria susceptibility for variants in or near IL1B, TLR9, TREM1, IL10RA, and CD3G genes: rs1143629-IL1B (G/A-A/A, OR = 0.41, 95% CI = 0.21-0.78, P = 0.0051), rs352139-TLR9 (T/T, OR = 0.28, 95% CI = 0.11-0.72, P = 0.0053), rs352140-TLR9 (C/C, OR = 0.41, 95% CI = 0.20-0.87, P = 0.019), rs2234237-TREM1 (T/A-A/A, OR = 0.43, 95% CI = 0.23-0.79, P = 0.0056), rs4252246-IL10RA (C/A-A/A, OR = 2.11, 95% CI = 1.18-3.75, P = 0.01), and rs1561966-CD3G (A/A, OR = 0.20, 95% CI = 0.06-0.69, P = 0.0058). The results showed the participation of genes involved in immunological processes and suggested an effect of ancestral genetic composition over the traits analyzed. Compared to the paisa population (Antioquia), Turbo and El Bagre showed a strong decrease in European ancestry and an increase in African and Native American ancestries. Also, a novel association of two single nucleotide polymorphisms with malaria susceptibility was identified in this study.

Paradoxical Roles of the MAL/Tirap Adaptor in Pathologies

Toll-like receptors (TLRs) are at the forefront of pathogen recognition ensuring host fitness and eliciting protective cellular and humoral responses. Signaling pathways downstream of TLRs are tightly regulated for preventing collateral damage and loss of tolerance toward commensals. To trigger effective intracellular signaling, these receptors require the involvement of adaptor proteins. Among these, Toll/Interleukin-1 receptor domain containing adaptor protein (Tirap or MAL) plays an important role in establishing immune responses. Loss of function of MAL was associated with either disease susceptibility or resistance. These opposite effects reveal paradoxical functions of MAL and their importance in containing infectious or non-infectious diseases. In this review, we summarize the current knowledge on the signaling pathways involving MAL in different pathologies and their impact on inducing protective or non-protective responses.

Maternal-Fetal Conflict During Infection: Lessons From a Mouse Model of Placental Malaria

Infections that reach the placenta via maternal blood can target the fetal-placental barrier and are associated with reduced birth weight, increased stillbirth, miscarriage and perinatal mortality. Malaria during pregnancy can lead to infection of the placental tissue and to adverse effects on the unborn child even if the parasite is successfully cleared, indicating that placental sufficiency is significantly compromised. Human samples and animal models of placental malaria have been used to unravel mechanisms contributing to this insufficiency and have implicated molecular pathways related to inflammation, innate immunity and nutrient transport. Remarkably, fetal TLR4 was found to take part in placental responses that protect the fetus, in contrast to maternal TLR4 responses that presumably preserve the mother‘s health but result in reduced fetal viability. We propose that this conflict of fetal and maternal responses is a determinant of the clinical outcomes of placental malaria and that fetally derived trophoblasts are on the front lines of this conflict.

Toll-like receptor polymorphism in host immune response to infectious diseases: A review

Immunopolymorphism is considered as an important aspect behind the resistance or susceptibility of the host to an infectious disease. Over the years, researchers have explored many genetic factors for their role in immune surveillance against infectious diseases. Polymorphic characters in the gene encoding Toll-like receptors (TLRs) play profound roles in inducing differential immune responses by the host against parasitic infections. Protein(s) encoded by TLR gene(s) are immensely important due to their ability of recognizing different types of pathogen associated molecular patterns (PAMPs). This study reviews the polymorphic residues present in the nucleotide or in the amino acid sequence of TLRs and their influence on alteration of inflammatory signalling pathways promoting either susceptibility or resistance to major infectious diseases, including tuberculosis, leishmaniasis, malaria and filariasis. Population-based studies exploring TLR polymorphisms in humans are primarily emphasized to discuss the association of the polymorphic residues with the occurrence and epidemiology of the mentioned infectious diseases. Principal polymorphic residues in TLRs influencing immunity to infection are mostly single nucleotide polymorphisms (SNPs). I602S (TLR1), R677W (TLR2), P554S (TLR3), D299G (TLR4), F616L (TLR5), S249P (TLR6), Q11L (TLR7), M1V (TLR8), G1174A (TLR9) and G1031T (TLR10) are presented as the major influential SNPs in shaping immunity to pathogenic infections. The contribution of these SNPs in the structure-function relationship of TLRs is yet not clear. Therefore, molecular studies on such polymorphisms can improve our understanding on the genetic basis of the immune response and pave the way for therapeutic intervention in a more feasible way.

MiRNA-146a polymorphism increases the odds of malaria in pregnancy

Background

Plasmodium falciparum infection during pregnancy is a major cause of poor maternal health, adverse foetal outcome and infant mortality in sub-Saharan Africa. Genetic disposition is involved in susceptibility to malaria in pregnancy and its manifestation. MicroRNAs (miRNAs) influence gene regulation including that of innate immune responses. A miRNA-146a rs2910164 G > C single nucleotide polymorphism (SNP) has been associated with increased risks of several diseases, but no data as to malaria are available.

Methods

The association between miRNA-146a rs2910164 and P. falciparum infection among 509 Ghanaian women attending antenatal care (ANC) and 296 delivering Ghanaian primiparae was investigated. Malaria parasites were diagnosed by microscopy and PCR. Leukocyte-associated hemozoin in placental samples was recorded as well. Proportions were compared between groups by Fisher’s exact test, and logistic regression models were used to adjust for possible confounders.

Results

By PCR, P. falciparum infection was detected in 63% and 67% of ANC attendees and delivering primiparae, respectively. In both groups, two in three women were either heterozygous or homozygous for miRNA-146a rs2910164. Among ANC attendees, homozygosity conferred increased odds of infection (adjusted odds ratio (aOR), 2.3; 95% CI, 1.3–4.0), which was pronounced among primigravidae (aOR, 5.8; 95% CI, 1.6–26) but only marginal in multigravidae. Likewise, homozygosity for miRNA-146a rs2910164 in primiparae increased the odds of past or present placental P. falciparum infection almost six-fold (aOR, 5.9; 95% CI, 2.1–18).

Conclusions

These results indicate that SNP rs2910164 G > C is associated with increased odds for P. falciparum infection in first-time pregnant women who are considered to lack sufficient acquired immune responses against pregnancy-specific strains of P. falciparum. These findings suggest that miRNA-146a is involved in protective malarial immunity, and specifically in the innate component.

Parasite Recognition and Signaling Mechanisms in Innate Immune Responses to Malaria

Malaria caused by the Plasmodium family of parasites, especially P.falciparum and P. vivax, is a major health problem in many countries in the tropical and subtropical regions of the world. The disease presents a wide array of systemic clinical conditions and several life-threatening organ pathologies, including the dreaded cerebral malaria. Like many other infectious diseases, malaria is an inflammatory response-driven disease, and positive outcomes to infection depend on finely tuned regulation of immune responses that efficiently clear parasites and allow protective immunity to develop. Immune responses initiated by the innate immune system in response to parasites play key roles both in protective immunity development and pathogenesis. Initial pro-inflammatory responses are essential for clearing infection by promoting appropriate cell-mediated and humoral immunity. However, elevated and prolonged pro-inflammatory responses owing to inappropriate cellular programming contribute to disease conditions. A comprehensive knowledge of the molecular and cellular mechanisms that initiate immune responses and how these responses contribute to protective immunity development or pathogenesis is important for developing effective therapeutics and/or a vaccine. Historically, in efforts to develop a vaccine, immunity to malaria was extensively studied in the context of identifying protective humoral responses, targeting proteins involved in parasite invasion or clearance. The innate immune response was thought to be non-specific. However, during the past two decades, there has been a significant progress in understanding the molecular and cellular mechanisms of host-parasite interactions and the associated signaling in immune responses to malaria. Malaria infection occurs at two stages, initially in the liver through the bite of a mosquito, carrying sporozoites, and subsequently, in the blood through the invasion of red blood cells by merozoites released from the infected hepatocytes. Soon after infection, both the liver and blood stage parasites are sensed by various receptors of the host innate immune system resulting in the activation of signaling pathways and production of cytokines and chemokines. These immune responses play crucial roles in clearing parasites and regulating adaptive immunity. Here, we summarize the knowledge on molecular mechanisms that underlie the innate immune responses to malaria infection.

Modulation of innate immune responses at birth by prenatal malaria exposure and association with malaria risk during the first year of life

BACKGROUND

Factors driving inter-individual differences in immune responses upon different types of prenatal malaria exposure (PME) and subsequent risk of malaria in infancy remain poorly understood. In this study, we examined the impact of four types of PME (i.e., maternal peripheral infection and placental acute, chronic, and past infections) on both spontaneous and toll-like receptors (TLRs)-mediated cytokine production in cord blood and how these innate immune responses modulate the risk of malaria during the first year of life.

METHODS

We conducted a birth cohort study of 313 mother-child pairs nested within the COSMIC clinical trial (NCT01941264), which was assessing malaria preventive interventions during pregnancy in Burkina Faso. Malaria infections during pregnancy and infants' clinical malaria episodes detected during the first year of life were recorded. Supernatant concentrations of 30 cytokines, chemokines, and growth factors induced by stimulation of cord blood with agonists of TLRs 3, 7/8, and 9 were measured by quantitative suspension array technology. Crude concentrations and ratios of TLR-mediated cytokine responses relative to background control were analyzed.

RESULTS

Spontaneous production of innate immune biomarkers was significantly reduced in cord blood of infants exposed to malaria, with variation among PME groups, as compared to those from the non-exposed control group. However, following TLR7/8 stimulation, which showed higher induction of cytokines/chemokines/growth factors than TLRs 3 and 9, cord blood cells of infants with evidence of past placental malaria were hyper-responsive in comparison to those of infants not-exposed. In addition, certain biomarkers, which levels were significantly modified depending on the PME category, were independent predictors of either malaria risk (GM-CSF TLR7/8 crude) or protection (IL-12 TLR7/8 ratio and IP-10 TLR3 crude, IL-1RA TLR7/8 ratio) during the first year of life.

CONCLUSIONS

These findings indicate that past placental malaria has a profound effect on fetal immune system and that the differential alterations of innate immune responses by PME categories might drive heterogeneity between individuals to clinical malaria susceptibility during the first year of life.

Influence of polymorphisms in toll-like receptors (TLRs) on malaria susceptibility in low-endemic area of the Atlantic Forest, São Paulo, Brazil

In low-endemic areas for malaria transmission, asymptomatic individuals play an important role as reservoirs for malarial infection. Understanding the dynamics of asymptomatic malaria is crucial for its efficient control in these regions. Genetic host factors such as Toll-like receptor (TLR) polymorphisms may play a role in the maintenance or elimination of infection. In this study, the effect of TLR polymorphisms on the susceptibility to malaria was investigated among individuals living in the Atlantic Forest of São Paulo, Southern Brazil. A hundred and ninety-five Brazilian individuals were enrolled and actively followed up for malaria for three years. Twenty-four polymorphisms in five toll-like receptor (TLR) genes were genotyped by RFLP, direct sequencing or fragment analysis. The genotypes were analyzed for the risk of malaria. Ongoing Plasmodium vivax or P. malariae infection, was identified by the positive results in PCR tests and previous P. vivax malaria, was assumed when antiplasmodial antibodies against PvMSP1₁₉ were detected by ELISA. An evaluation of genomic ancestry was conducted using biallelic ancestry informative markers and the results were used as correction in the statistical analysis. Nine SNPs and one microsatellite were found polymorphic and three variant alleles in TLR genes were associated to malaria susceptibility. The regression coefficient estimated for SNP TLR9.-1237.T/C indicated that the presence of at least one allele C increased, on average, 2.3 times the malaria odds, compared to individuals with no allele C in this SNP. However, for individuals with the same sex, age and household, the presence of at least one allele C in SNP TLR9.-1486.T/C reduced, on average, 1.9 times the malaria odds, compared to individuals with no allele C. Moreover, this allele C plus an S allele in TLR6.P249S in individuals with same sex, age and ancestry, reduced, on average, 4.4 times the malaria odds. Our findings indicate a significant association of TLR9.-1237.T/C gene polymorphism with malarial infection and contribute to a better knowledge of the role of TLRs in malaria susceptibility in an epidemiological setting different from other settings.

Role of rs4986790 Polymorphism of TLR4 Gene in Susceptibility towards Malaria Infection in the Pakistani Population

BACKGROUND

Toll-like receptors (TLRs) of the human immune mechanism play important role in the detection of invading pathogens. TLRs specifically recognize the pathogen-associated molecular patterns (PAMPs) from pathogens and start the effective response. Single nucleotide polymorphisms (SNPs) in the TLRs can mediate their functions. Present study evaluated the importance of rs4986790 polymorphism of TLR4 gene in susceptibility towards malaria, clinical outcomes of the disease and responsible species of malaria.

METHODS

Blood samples of 228 malaria patients and 226 healthy volunteers were selected for the study. Sample collection was completed during Sep 2013 to Sep 2015 from different hospitals of Punjab, Pakistan. Patient's samples were divided into P. vivax group and P. falciparum group on the basis of causative species of Plasmodium. Malaria samples were also divided into mild and severe malaria group based on clinical outcomes of the disease according to WHO criteria. Healthy individuals were placed in the control group. Whole blood was used for the isolation of DNA. Genomic DNA was isolated and amplification of targeted SNP was performed using allele-specific PCR.

RESULTS

Results indicate the protective role of AA genotype against the susceptibility of P. vivax infection, OR: 0.5, 95%CI: 0.285-0.876, P=0.038.

CONCLUSION

rs4986790 polymorphism of TLR4 gene modulates the susceptibility towards P. vivax infection. AA genotype is found to be protective against the development of P. vivax infection in the local population of Pakistan.

The potential role of toll-like receptor 4 Asp299Gly polymorphism and its association with recurrent cystic echinococcosis in postoperative patients

The study of pathogenesis mechanisms of larval stages in the Taeniidae has recently focused on host genetic factors, particularly toll-like receptor (TLR) variations. However, the potential role of TLR4 polymorphism in hydatidosis has not yet been sufficiently elucidated in postoperative patients. In this case-control investigation, 80 patients from Iran, including 40 with acute hydatidosis (AH) and 40 with recurrent hydatidosis (RH), and 80 ethnically matched controls were evaluated from February 2015 to February 2017. Hydatidosis patients were confirmed using radiological, immunological, and histopathological examinations. Genotyping of Asp299Gly and Thr399Ile of TLR4 single-nucleotide polymorphisms was determined by restriction fragment length polymorphism, sequencing, and phylogenetic strategies. The heterozygous mutant-type TLR4 Asp299Gly genotype indicated a tendency to be associated with the occurrence of RH (P = 0.060) and conferred a 3-fold risk for susceptibility. There was no difference in genotype frequency of Asp299Gly between patients with AH and healthy controls (P = 0.42; OR, 1.82; 95% CI, 0.11-30.1%). Interestingly, a frequency of the G allele (12%: Gly) was observed to be a risk factor for susceptibility to RH patients (P = 0.050; OR, 7.08; 95% CI, 0.97-51.5%). A relative genetic variability of TLR4 Asp299Gly was found in RH patients (haplotype diversity: 0.700) compared to AH patients and healthy controls (Hd: 0.000). The Asp299Gly genotype was dominantly identified in patients with hepatic hydatid cysts. The TLR4 Thr399Ile codon was not detected except in a patient with a pulmonary hydatid cyst. The current findings enhance our knowledge regarding the TLR4 Asp299Gly polymorphism potentially leading to the development of RH, by skewing the immune system towards a Th2 response. Identification of the Asp299Gly codon may be a diagnostic hallmark in RH patients who have undergone unsuccessful postoperative intervention. However, further studies with a higher case number are needed on ethnic population from various geographic regions, in order to confirm this hypothesis.

Beyond binding: antibody effector functions in infectious diseases

Antibodies play an essential role in host defence against pathogens by recognizing microorganisms or infected cells. Although preventing pathogen entry is one potential mechanism of protection, antibodies can control and eradicate infections through a variety of other mechanisms. In addition to binding and directly neutralizing pathogens, antibodies drive the clearance of bacteria, viruses, fungi and parasites via their interaction with the innate and adaptive immune systems, leveraging a remarkable diversity of antimicrobial processes locked within our immune system. Specifically, antibodies collaboratively form immune complexes that drive sequestration and uptake of pathogens, clear toxins, eliminate infected cells, increase antigen presentation and regulate inflammation. The diverse effector functions that are deployed by antibodies are dynamically regulated via differential modification of the antibody constant domain, which provides specific instructions to the immune system. Here, we review mechanisms by which antibody effector functions contribute to the balance between microbial clearance and pathology and discuss tractable lessons that may guide rational vaccine and therapeutic design to target gaps in our infectious disease armamentarium.

Role of MyD88-adaptor-like gene polymorphism rs8177374 in modulation of malaria severity in the Pakistani population

Introduction

The present study was designed to investigate the association between rs8177374 polymorphism and malaria symptoms due to exposure of Plasmodium vivax and Plasmodium falciparum.

Materials and methods

A total of 454 samples were included in the study (228 malaria patients and 226 healthy individuals). Malaria patients, divided into P. vivax and P. falciparum groups on the basis of the causative species of Plasmodium, were categorized into mild and severe on the basis of clinical outcomes according to WHO criteria. Healthy individuals were used as controls. Allele specific PCR based strategy was used for the identification of rs8177374 SNP.

Results

MyD88-adaptor-like gene polymorphism was associated with susceptibility to malaria (p < 0.001). C allele frequency (0.74) was higher in the population compared to T allele frequency (0.26). CT genotype increased the susceptibility of malaria (OR: 2.661; 95% CI: 1.722–4.113) and was positively associated with mild malaria (OR: 5.609; 95% CI: 3.479–9.044, p = 0.00). On the other hand, CC genotype was associated with severe malaria (OR: 3.116; 95% CI: 1.560–6.224, p = 0.00). P. vivax infection rate was higher in CT genotype carriers compared to other genotypes (OR: 3.616; 95% CI: 2.219–5.894, p < 0.001).

Conclusion

MyD88-adaptor-like/TIR domain containing adaptor protein polymorphism for single nucleotide polymorphism rs8177374 is related with the susceptibility of malaria.

Reciprocal translocation of small numbers of inbred individuals rescues immunogenetic diversity

Genetic rescue can reduce inbreeding depression and increase fitness of small populations, even when the donor populations are highly inbred. In a recent experiment involving two inbred island populations of the New Zealand South Island robin, Petroica australis, reciprocal translocations improved microsatellite diversity and individual fitness. While microsatellite loci may reflect patterns of genome-wide diversity, they generally do not indicate the specific genetic regions responsible for increased fitness. We tested the effectiveness of this reciprocal translocation for rescuing diversity of two immunogenetic regions: Toll-like receptor (TLR) and major histocompatibility complex (MHC) genes. We found that the relatively small number of migrants (seven and ten per island) effectively brought the characteristic TLR gene diversity of each source population into the recipient population. However, when migrants transmitted TLR alleles that were already present at high frequency in the recipient population, it was possible for offspring of mixed heritage to have decreased gene diversity compared to recipient population diversity prior to translocation. In contrast to TLRs, we did not observe substantial changes in MHC allelic diversity following translocation, with limited evidence of a decrease in differentiation, perhaps because most MHC alleles were observed at both sites prior to the translocation. Overall, we conclude that small numbers of migrants may successfully restore the diversity of immunogenetic loci with few alleles, but that translocating larger numbers of animals would provide additional opportunity for the genetic rescue of highly polymorphic immunity regions, such as the MHC, even when the source population is inbred.

Heterozygous mutants of TIRAP (S180L) polymorphism protect adult patients with Plasmodium falciparum infection against severe disease and mortality

Toll-interleukin-1 receptor domain containing adapter protein (TIRAP) plays a crucial role in TLR2 and TLR4 signaling pathways. Glycosylphospatidylinositol (GPI), considered a toxin molecule of Plasmodium falciparum, interacts with TLR2 and 4 to induce an immune inflammatory response. A single nucleotide polymorphism at coding region of TIRAP (S180L) has been reported to influence TLRs signaling. In the present study, we investigated the association of TIRAP (S180L) polymorphism with susceptibility/resistance to severe P. falciparum malaria in a cohort of adult patients from India. TIRAP S180L polymorphism was typed in 347 cases of severe malaria (SM), 232 uncomplicated malaria and 150 healthy controls. Plasma levels of TNF-α was quantified by ELISA. Heterozygous mutation (S/L) conferred significant protection against MOD (multi organ dysfunction), NCSM (non-cerebral severe malaria) as well as mortality. Interestingly, homozygous mutants (L/L) had 16 fold higher susceptibility to death. TIRAP mutants (S/L and L/L) were associated with significantly higher plasma TNF-α levels compared to wild type (S/S). The results of the present study demonstrate that TIRAP S180L heterozygous mutation may protect patients against severe malaria and mortality.

Genetic variation in pattern recognition receptors: functional consequences and susceptibility to infectious disease

Cells of the innate immune system are equipped with surface and cytoplasmic receptors for microorganisms called pattern recognition receptors (PRRs). PRRs recognize specific pathogen-associated molecular patterns and as such are crucial for the activation of the immune system. Currently, five different classes of PRRs have been described: Toll-like receptors, C-type lectin receptors, nucleotide-binding oligomerization domain-like receptors, retinoic acid-inducible gene I-like receptors and absent in melanoma 2-like receptors. Following their discovery, many sequence variants in PRR genes have been uncovered and shown to be implicated in human infectious diseases. In this review, we will discuss the effect of genetic variation in PRRs and their signaling pathways on susceptibility to infectious diseases in humans.

Genetic polymorphisms and the development of invasive bacterial infections in children

To evaluate the associations between single nucleotide polymorphisms (SNPs) of factors involved in the development of invasive bacterial disease (IBD) in children, 47 SNPs of 18 candidate genes were analysed in 49 children with IBD and 100 controls. The G/T genotype of TLR2 rs2149356 and the C genotype of LTA rs2229094 were associated with significantly reduced risk of developing IBD (P=0.04 and P=0.05, respectively), whereas the C/T genotype of RFP175 rs1585110 was associated with a significantly higher risk of developing IBD (P=0.02). These results support the evidence that some genetic variants of factors involved in innate immunity may influence IBD risk in children.

A Toll-like receptor-1 variant and its characteristic cellular phenotype is associated with severe malaria in Papua New Guinean children

Genetic factors are likely to contribute to low severe malaria case fatality rates in Melanesian populations, but association studies can be underpowered and may not provide plausible mechanistic explanations if significant associations are detected. In preparation for a genome-wide association study, 29 candidate single-nucleotide polymorphisms (SNPs) with minor allele frequencies >5% were examined in a case-control study of 504 Papua New Guinean children with severe malaria. In parallel, an immunological substudy was performed on convalescent peripheral blood mononuclear cells (PBMCs) from cases and controls. Following stimulation with a Toll-like receptor (TLR) 1/2 agonist, effector cytokines and chemokines were assayed. The only significant genetic association observed involved a nonsynonymous SNP (TLR1rs4833095) in the TLR1 gene. A recessive (TT) genotype was associated with reduced odds of severe malaria of 0.52 (95% confidence interval (0.29-0.90), P=0.006). Concentrations of pro-inflammatory cytokines interleukin-1β and tumour necrosis factor α were significantly higher in severe malaria cases compared with healthy controls, but lower in children with the protective recessive (TT) genotype. A genetic variant in TLR1 may contribute to the low severe malaria case fatality rates in this region through a reduced pro-inflammatory cellular phenotype.

The influence of genetic polymorphisms in TLR4 and TIRAP, and their expression levels in peripheral blood, on susceptibility to sepsis

The present study aimed to investigate whether genetic polymorphisms in the Toll-like receptor (TLR)-4 and Toll/interleukin-1 receptor (TIR)-associated protein (TIRAP) genes, and/or their expression levels, influence the susceptibility of a patient to sepsis. A total of 106 patients with sepsis were divided into two groups on the basis of their acute physiology and chronic health evaluation (APACHE) II scores: i) Sepsis group A (APACHE II <20) and ii) Sepsis group B (APACHE II >20). In addition, 100 healthy volunteers were enrolled into the control group. Polymerase chain reaction-restriction fragment length polymorphism assay was used to detect the following genetic polymorphisms: The Ser180Leu allele of the TIRAP gene and the Asp299Gly and Thr399I1e alleles of the TLR4 gene. Furthermore, the protein expression levels of TLR4 and TIRAP were analyzed using an enzyme-linked immunosorbent assay. Genetic polymorphisms were not detected for the TLR4 and TIRAP genes; however, the protein expression levels of TLR4 and TIRAP differed significantly between the control, sepsis A and sepsis B groups (P<0.01). An APACHE II score of 20 was used as a baseline in order to differentiate sepsis severity. Pearson analysis demonstrated that TLR4 and TIRAP protein expression levels were positively correlated with sepsis severity (r=0.931 and 0.972; P<0.05), and TLR4 protein expression levels were positively correlated with those of TIRAP (r=0.936; P<0.05). The results of the present study suggested that the protein expression levels of, but not genetic polymorphisms in, TLR4 and TIRAP were associated with the severity of sepsis.

Toll-like receptor (TLR4) Asp299Gly and Thr399Ile polymorphisms in relation to clinical falciparum malaria among Nigerian children: a multisite cross-sectional immunogenetic study in Lagos

INTRODUCTION

This study determined the association of TLR4 Asp299Gly and Thr399Ile with uncomplicated and severe malaria among Nigerian children of similar ethnic background in Lagos. The association of these SNPs with high parasite density, malnutrition, hyperpyrexia and anaemia was also investigated.

METHODS

Genomic DNA of the study participants was screened for the genotypes of TLR4 Asp299Gly and Thr399Ile by PCR-RFLP. Anthropometric measurement was performed on the Pf infected children stratified into asymptomatic malaria (control), uncomplicated and severe malaria (case). Parasites were detected by light microscopy and Hardy Weinberg Equilibrium (HWE) of SNP genotypes was also determined.

RESULTS

A total of 279 children comprising 182 children (62.1 % male; mean ± SEM age, 57.3 ± 1.7 months) with clinical falciparum malaria and 97 children (55.7 % male; mean ± SEM age, 55.6 ± 2.5 years) with asymptomatic falciparum malaria were enrolled. All the genotypes of both TLR4 SNPs were found in the study population with their minor alleles: 299Gly and 399Ile, found to be 17.6 % and 14.7 % in severe malaria children. Unlike in asymptomatic population, the genotype distribution of TLR4 Asp299Gly SNP was not in HWE in the clinical malaria group but did not condition susceptibility. However, Asp299Gly and Thr399Ile polymorphisms were found to increase the risk of severe malaria 3-fold and 8-fold respectively (P < 0.05). They also increased the risk of severe anaemia, high parasite density and severe malnutrition 3.8 -5.3-fold, 3.3 - 4.4-fold and 4-fold respectively.

CONCLUSIONS

Based on the above findings, we conclude that TLR4 Asp299Gly and Thr399Ile polymorphisms may modulate susceptibility to severe malaria among Nigerian children of Yoruba ethnic background.

Interferons and interferon regulatory factors in malaria

Malaria is one of the most serious infectious diseases in humans and responsible for approximately 500 million clinical cases and 500 thousand deaths annually. Acquired adaptive immune responses control parasite replication and infection-induced pathologies. Most infections are clinically silent which reflects on the ability of adaptive immune mechanisms to prevent the disease. However, a minority of these can become severe and life-threatening, manifesting a range of overlapping syndromes of complex origins which could be induced by uncontrolled immune responses. Major players of the innate and adaptive responses are interferons. Here, we review their roles and the signaling pathways involved in their production and protection against infection and induced immunopathologies.

Comparison of manual methods of extracting genomic DNA from dried blood spots collected on different cards: implications for clinical practice

Isolating genomic DNA from blood samples is essential when studying the associations between genetic variants and susceptibility to a given clinical condition, or its severity. This study of three extraction techniques and two types of commercially available cards involved 219 children attending our outpatient pediatric clinic for follow-up laboratory tests after they had been hospitalised. An aliquot of venous blood was drawn into plastic tubes without additives and, after several inversions, 80 microL were put on circles of common paper cards and Whatman FTA-treated cards. Three extraction methods were compared: the Qiagen Investigator, Gensolve, and Masterpure. The best method in terms of final DNA yield was Masterpure, which led to a significantly higher yield regardless of the type of card (p less than 0.001), followed by Qiagen Investigator and Gensolve. Masterpure was also the best in terms of price, seemed to be simple and reliable, and required less hands-on time than other techniques. These conclusions support the use of Masterpure in studies that evaluate the associations between genetic variants and the severity or prevalence of infectious diseases.

The role of TLR4 896 A>G and 1196 C>T in susceptibility to infections: a review and meta-analysis of genetic association studies

Background

Toll-like receptor 4 plays a role in pathogen recognition, and common polymorphisms may alter host susceptibility to infectious diseases.

Purpose

To review the association of two common polymorphisms (TLR4 896A>G and TLR4 1196C>T) with infectious diseases.

Data Sources

We searched PubMed and EMBASE up to March 2013 for pertinent literature in English, and complemented search with references lists of eligible studies.

Study Selection

We included all studies that: reported an infectious outcome; had a case-control design and reported the TLR4 896A>G and/or TLR4 1196C>T genotype frequencies; 59 studies fulfilled these criteria and were analyzed.

Data Extraction

Two authors independently extracted study data.

Data Synthesis

The generalized odds ratio metric (OR_G) was used to quantify the impact of TLR4 variants on disease susceptibility. A meta-analysis was undertaken for outcomes reported in >1 study. Eleven of 37 distinct outcomes were significant. TLR4 896 A>G increased risk for all parasitic infections (OR_G 1.59; 95%CI 1.05-2.42), malaria (1.31; 95%CI 1.04-1.66), brucellosis (2.66; 95%CI 1.66-4.27), cutaneous leishmaniasis (7.22; 95%CI 1.91-27.29), neurocysticercosis (4.39; 95%CI 2.53-7.61), Streptococcus pyogenes tonsillar disease (2.93; 95%CI 1.24-6.93) , typhoid fever (2.51; 95%CI 1.18-5.34) and adult urinary tract infections (1.98; 95%CI 1.04-3.98), but was protective for leprosy (0.36; 95%CI 0.22-0.60). TLR4 1196 C>T effects were similar to TLR4 896 A>G for brucellosis, cutaneous leishmaniasis, leprosy, typhoid fever and S. pyogenes tonsillar disease, and was protective for bacterial vaginosis in pregnancy (0.55; 95%CI 0.31-0.98) and Haemophilus influenzae tonsillar disease (0.42; 95%CI 0.17-1.00). The majority of significant associations were among predominantly Asian populations and significant associations were rare among European populations.

Conclusions

Depending on the type of infection and population, TLR4 polymorphisms are associated with increased, decreased or no difference in infectious disease. This may be due to differential functional expression of TLR4, the co-segregation of TLR4 variants or a favorable inflammatory response.

The genetics of innate immunity sensors and human disease

Since their discovery, innate immunity microbial sensors have been increasingly studied and shown to play a critical role in innate responses to microbes in several experimental in vitro, ex vivo, and animal models. However, their role in the human response to infection in natural conditions has just started to be deciphered, by means of clinical studies of primary immunodeficiencies and epidemiological genetic studies. Here, we summarize the major findings concerning the genetic diversity of the various families of microbial sensors in humans, and of other molecules involved in the signaling pathways they trigger. Specifically, we review the genetic associations, revealed by both clinical and epidemiological genetics studies, of microbial sensors from five different families: Toll-like receptors, C-type lectin receptors, NOD-like receptors, RIG-I-like receptors, and cytosolic DNA sensors. In particular, we consider the relationships between variation at the genes encoding these molecules and susceptibility to and the severity of infectious diseases and other clinical conditions associated with immune dysfunction, including autoimmunity, inflammation, allergy, and cancer. Despite the fact that the genetic links between innate immunity sensors and human disorders remain still limited, human genetics studies are increasingly improving our understanding of the genuine functions of microbial sensors and downstream signaling molecules in the natural setting.

TLR-9 promoter polymorphisms (T-1237C and T-1486C) are not associated with systemic lupus erythematosus: a case control study and meta-analysis

Toll like receptors (TLRs) are essential molecules implicated in both innate and adaptive immune response. Polymorphisms in TLR gene have been associated with various infectious diseases and autoimmune disorders. Role of TLR9 has been elegantly demonstrated in both human systemic lupus erythematosus (SLE) and mice model of lupus. In the present study we investigated association of TLR-9 promoter polymorphisms (T-1237C and T-1486C) with susceptibility/resistance to SLE in an Eastern Indian state which is endemic to parasitic diseases. 210 Female SLE patients who fulfilled the American College of Rheumatology criteria were enrolled along with matched healthy controls from Odisha, India. TLR-9 polymorphisms (T-1237C and T-1486C) were typed by polymerase chain reaction followed by restriction fragment length polymorphism. For meta-analysis, relevant literatures were searched from PubMed database and comprehensive meta-analysis V2 software was employed for analysis. Allele and genotype frequency of TLR-9 promoter polymorphisms (T-1237C and T-1486C) were comparable among SLE patients and controls. Further, meta-analysis of earlier reports and present study did not reveal a significant association of TLR-9 (T-1237C and T-1486C) polymorphisms with SLE. Data from the present study suggest that TLR-9 promoter polymorphisms are not associated with susceptibility to SLE in an area endemic to parasitic diseases.