Relationship between toll-like receptor 2 Arg677Trp and Arg753Gln and toll-like receptor 4 Asp299Gly polymorphisms and cytomegalovirus infection

TLR2 and TLR4 Polymorphisms Are Not Associated with Dental Caries in Polish Children

The aim of the present study was to analyze the association of the TLR2 (Toll-like receptor 2 gene) 2258G>A (rs5743708), TLR4 (Toll-like receptor 4 gene) 896A>G (rs4986790), and TLR4 1196C>T (rs4986791) polymorphisms with dental caries in Polish children. The participants, 261 15-year-old children, were divided into two groups: 82 cases (i.e., children with DMFT (Decayed, Missing, and Filled Teeth) index >5, having either moderate or high caries experience, assigned as the "higher" caries experience group) and 179 controls (i.e., children with DMFT ≤ 5, having either low or very low caries experience, assigned as the "lower" caries experience group). Genomic DNA was isolated from buccal swabs, and genotyping was determined by means of real-time PCR (polymerase chain reaction). There were no significant differences in the genotype or allele distributions in all tested SNPs (single nucleotide polymorphisms) between children with "higher" caries experience and those with "lower" caries experience. TLR4 haplotype frequencies did not differ significantly between cases and controls. In an additional analysis with another case definition applied (subjects with DMFT ≥ 1 were assigned as "cases", whereas children with DMFT = 0 were assigned as "controls"), no significant differences in the TLR2 and TLR4 genotype, allele frequencies, and TLR4 haplotype frequencies were found between the case and the control groups. The results of the present study broaden our knowledge on the potential genetic factors that might affect caries risk and suggest that TLR2 rs5743708 and TLR4 rs4986790 and rs4986791 SNPs are not associated with dental caries susceptibility in Polish children.

Single Nucleotide Polymorphisms of Interleukins and Toll-like Receptors and Neuroimaging Results in Newborns with Congenital HCMV Infection

Congenital cytomegalovirus infection (cCMV) is the most common intrauterine infection with central nervous system (CNS) involvement. There is limited data on the associations between Single Nucleotide Polymorphisms (SNPs) in genes involving the first-line defense mechanism and the risk of CNS damage during cCMV. We investigated the associations between neuroimaging findings and SNPs in genes encoding the following cytokines and cytokine receptors in 92 infants with cCMV: interleukins (IL1B rs16944, IL12B rs3212227, IL28B rs12979860), C-C motif chemokine ligand 2 (CCL2 rs1024611), dendritic cell-specific intercellular adhesion grabbing non-integrin (DC-SIGN rs735240), Toll-like receptors (TLR2 rs5743708, TLR4 rs4986791, TLR9 rs352140). The SNP of IL1B rs16944 (G/A) was associated with a reduced risk of ventriculomegaly on MRI (OR = 0.46, 95% CI, 0.22-0.95; p = 0.03) and cUS (OR = 0.38, 95% CI, 0.0-0.93; p = 0.034). Infants carrying heterozygous (T/C) genotype at IL28B rs12979860 had an increased risk of cystic lesions on cUS (OR = 3.31, 95% CI, 1.37-8.01; p = 0.0064) and MRI (OR = 4.97, 95% CI, 1.84-13.43; p = 0.001), and an increased risk of ventriculomegaly on MRI (OR = 2.46, 95% CI, 1.03-5.90; p = 0.04). No other associations between genotyped SNPs and neuroimaging results were found. This is the first study demonstrating new associations between SNPs of IL1B and IL28B and abnormal neuroimaging in infants with cCMV.

Infection outcome needs two to tango: human host and the pathogen

Infectious diseases are potential drivers for human evolution, through a complex, continuous and dynamic interaction between the host and the pathogen/s. It is this dynamic interaction that contributes toward the clinical outcome of a pathogenic disease. These are modulated by contributions from the human genetic variants, transcriptional response (including noncoding RNA) and the pathogen’s genome architecture. Modern genomic tools and techniques have been crucial for the detection and genomic characterization of pathogens with respect to the emerging infectious diseases. Aided by next-generation sequencing (NGS), risk stratification of host population/s allows for the identification of susceptible subgroups and better disease management. Nevertheless, many challenges to a general understanding of host–pathogen interactions remain. In this review, we elucidate how a better understanding of the human host-pathogen interplay can substantially enhance, and in turn benefit from, current and future applications of multi-omics based approaches in infectious and rare diseases. This includes the RNA-level response, which modulates the disease severity and outcome. The need to understand the role of human genetic variants in disease severity and clinical outcome has been further highlighted during the Coronavirus disease 2019 (COVID-19) pandemic. This would enhance and contribute toward our future pandemic preparedness.

Cytomegalovirus Infection Downregulates Vitamin D Receptor in Patients Undergoing Hematopoietic Stem Cell Transplantation

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative option for patients with hematologic diseases but is associated with high mortality and morbidity. Cytomegalovirus (CMV) infection is common in HSCT patients and modulates vitamin D metabolism in vitro. We aimed at validating CMV-associated vitamin D metabolism in vivo in HSCT.

METHODS

Patients treated for significant CMV viremia after HSCT were evaluated for CMV load before, during, and after antiviral treatment. RNA was isolated from whole-blood samples to test for regulation of key components of the vitamin D receptor (VDR) pathway during different phases of CMV viremia.

RESULTS

CMV viremia developed a mean time of 102 (±34) d post-HSCT. Maximum levels of CMV-DNA reached a mean of 5668 (±7257) copies/mL. VDR expression was downregulated to a mean of 64.3% (±42.5%) relative to the VDR expression pre-CMV viremia (P = 0.035) and lagged in recovery following antiviral treatment. Toll-like receptor (TLR) 2 mRNA was upregulated to 225.4% during CMV viremia relative to the expression pre-CMV viremia (P = 0.012) but not TLR6/7/8 and the TLR-adaptor protein MyD88. Levels of 25-OH vitamin D were reduced in all viremic patients (48.0 ± 4.8 versus 25.1 ± 3.7 ng/mL) and were even lower after periods of CMV viremia compared with the control group (48.3 ± 3.5 versus 17.8 ± 1.8 ng/mL; P = 0.008).

CONCLUSIONS

CMV viremia is associated with significant dysregulation of vitamin D metabolism in HSCT patients.

Arg753Gln Polymorphisms in the Toll-Like Receptor 2 Gene are Associated with Cytomegalovirus Infection in Egyptian Bone Marrow Recipients

BACKGROUND

Previous studies have shown that cytomegalovirus (CMV) induced innate immune response via activation of Toll-like receptor 2 (TLR2). The association between CMV among specific single-nucleotide polymorphisms (SNPs) in the TLR2 gene was also investigated.

OBJECTIVE

This study investigated the relationship between specific SNPs in the TLR2 gene (G>A), TLR2-Arg753Gln (rs5743708), and CMV replication after bone marrow transplantation.

METHODS

The TLR2-Arg753Gln SNP was genotyped in 181 patients after bone marrow transplantation: 83 and 98 patients with and without CMV infection, respectively. CMV load was determined in serially collected blood samples using real-time PCR. Genotyping was performed using specific sequence primer PCR (SSP-PCR), and the results were confirmed by restriction fragment length polymorphism (RFLP) analysis of the PCR-amplified fragments for GG (wild type), GA and AA identification.

RESULTS

Roughly, 85% of the patients screened for the presence of the TLR2-Arg753Gln were GG homozygous, and 15% were GA heterozygous; no patients were homozygous for the mutant allele (A). The GA heterozygous allele was more frequent in the CMV-infected group after bone marrow transplantation.

CONCLUSION

To our knowledge, this is a novel observation that supports the notion that the functional missense mutation (TLR2-Arg753Gln polymorphism) is possibly associated with CMV replication after bone marrow transplantation. This suggests a role for TLR2 in the innate immune response of human CMV infection in Egyptian bone marrow recipients.

TLR4 896A/G and TLR9 1174G/A polymorphisms are associated with the risk of infectious mononucleosis

Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns and activate innate and adaptive immune responses. Single nucleotide polymorphisms (SNPs) within the TLR genes may influence host–pathogen interactions and can have an impact on the progression of infectious diseases. The present study aimed to investigate the genotype distribution of TLR2 (2029C/T, rs121917864; 2258G/A, rs5743708), TLR4 (896A/G, rs4986790), and TLR9 (− 1237T/C, rs5743836; − 1486T/C, rs187084; 1174G/A, rs352139; and 2848C/T, rs352140) polymorphisms in 149 children and adolescents with infectious mononucleosis (IM) and 140 healthy individuals. The potential association of TLR SNPs with the clinical manifestations of EBV infection was also studied. The presence of TLR2, TLR4, and TLR9 SNPs was identified by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP). EBV DNA loads were detected by quantitative real-time PCR assay. The TLR4 896 GG and the TLR9 1174 GA genotypes were associated with an increased risk of EBV-related IM in examined patients (p = 0.014 and p = 0.001, respectively). The heterozygous genotype of the TLR4 896A/G SNP was associated with an increased risk of elevated liver enzyme levels and leukocytosis (p < 0.05). Our preliminary study revealed that the TLR4 896A/G and the TLR9 1174G/A polymorphisms seem to be related to the course of acute EBV infection in children and adolescents.

Toll-Like 4 Receptor Expression on Peripheral Blood Mononuclear Cells in Renal Transplant Recipients Can Help to Indicate the Risk of Graft Deterioration in Patients Who Experienced an Episode of Symptomatic Cytomegalovirus Infection

Data binding the expression of Toll-like 4 receptor (TLR4), transplanted kidney (KT) function, and symptomatic CMV infection (CMV+) are scarcely available.

OBJECTIVE

To investigate the relationship between TLR4 expression (TLR4ex) in patients who had a relapse of CMV and transplant function.

MATERIALS AND METHODS

TLR4ex was measured in peripheral blood mononuclear cells of KT recipients. We compared TLR4ex among 30 CMV+ patients and 87 patients without CMV infection (CMVneg). At the beginning (day 0) TLR4ex, as well as concentrations of cyclosporin A and tacrolimus were determined. All patients, CMV+ and CMVneg patients were divided according to the respective median of TLR4ex into groups of low-TLR4 expression (L-TLR4ex) and high-TLR4 expression (H-TLR4ex). Estimated glomerular filtration rate (EGFR) was assessed on day 0 and after the follow-up (F-up). The magnitudes of EGFR change (ΔEGFR) were evaluated. Stable treatment along the F-up period (median 11.9 months) was applied.

RESULTS

TLR4ex of CMV+ in 67% was below median for all patients. For day 0, in CMV+: no link of TLR4ex with EGFR was found; TLR4ex was lower but day 0 EGFR did not differ from H-TLR4ex. In CMVneg, a GFR-TLR4ex link was present. Post F-up. In CMV+ with L-TLR4ex, EGFR declined, with no change in H-TLR4ex. In CMVneg with H-TLR4ex, EGFR increased, with no change in L-TLR4ex. Both regression and receiver operating characteristic curve analyses points out the impact of CMV+ and TLR4ex on eGFR and ΔEGFR.

CONCLUSION

In CMV+, low TLR4ex increases the risk of EGFR deterioration. In CMVneg, high TLR4ex raises the chance of EGFR improvement.

Treatment of Cytomegalovirus Anterior Uveitis at a North American Tertiary Center With Oral Valganciclovir

PURPOSE

Cytomegalovirus is an increasingly recognized cause of anterior uveitis. We present clinical features of cytomegalovirus anterior uveitis (CMVAU) and outcomes of oral valganciclovir treatment at a tertiary referral center in North America.

METHODS

This is a retrospective case series review (2002-2014) of immunocompetent patients with CMVAU treated with valganciclovir 900 mg BID and subsequent maintenance dosing of ≤450 mg BID. Most patients were prescribed topical corticosteroids concurrently. Diagnostic evaluations and clinical features at baseline and follow-up were reviewed. Resolution time, maintenance of quiescence, and adverse events were assessed.

RESULTS

Eighteen eyes of 16 patients were included. The mean age of diagnosis was 41 years. At diagnosis, mean best-corrected visual acuity was 0.30 LogMAR and mean intraocular pressure (IOP) was 18.4 mm Hg; 14 eyes (78%) had an active anterior chamber (AC) cell, 8 (44%) had circinate keratic precipitates, and 6 (33%) had iris atrophy. The mean follow-up duration was 48 months. Fourteen eyes of 12 patients were available for the 12-month follow-up; patients demonstrated improvement in best-corrected visual acuity (difference: -0.21 LogMAR, 95% CI -0.33 to -0.09; P = 0.003), AC cell (OR = 0.10, 95% CI 0.02-0.41; P = 0.002), and IOP (difference: -4.21 mm Hg, 95% CI -7.98 to -0.44; P = 0.03) compared with baseline. One patient experienced a serious adverse event likely due to valganciclovir. Thirteen eyes experienced recurrence of inflammation: 7 (54%) on prophylactic dose of valganciclovir and 6 (46%) after stopping.

CONCLUSIONS

Valganciclovir appears effective and safe for treating CMVAU in this retrospective case series. Long-term antiviral prophylaxis does not abolish recurrences, although it may possibly reduce their frequency when compared with no prophylaxis.

Host Genetics of Cytomegalovirus Pathogenesis

Human cytomegalovirus (HCMV) is a ubiquitous herpes virus (human herpes virus 5) with the highest morbidity and mortality rates compared to other herpes viruses. Risk groups include very young, elderly, transplant recipient, and immunocompromised individuals. HCMV may cause retinitis, encephalitis, hepatitis, esophagitis, colitis, pneumonia, neonatal infection sequelae, inflammatory, and age-related diseases. With an arsenal of genes in its large genome dedicated to host immune evasion, HCMV can block intrinsic cellular defenses and interfere with cellular immune responses. HCMV also encodes chemokines, chemokine receptors, and cytokines. Therefore, genes involved in human viral defense mechanisms and those encoding proteins targeted by the CMV proteins are candidates for host control of CMV infection and reactivation. Although still few in number, host genetic studies are producing valuable insights into biological processes involved in HCMV pathogenesis and HCMV-related diseases. For example, genetic variants in the immunoglobulin GM light chain can influence the antibody responsiveness to CMV glycoprotein B and modify risk of HCMV-related diseases. Moreover, CMV infection following organ transplantation has been associated with variants in genes encoding toll-like receptors (TLRs), programmed death-1 (PD-1), and interleukin-12p40 (IL-12B). A KIR haplotype (2DS4+) is proposed to be protective for CMV activation among hematopoietic stem cell transplant patients. Polymorphisms in the interferon lambda 3/4 (IFNL3/4) region are shown to influence susceptibility to CMV replication among solid organ transplant patients. Interestingly, the IFNL3/4 region is also associated with AIDS-related CMV retinitis susceptibility in HIV-infected patients. Likewise, interleukin-10 receptor 1 (IL-10R1) variants are shown to influence CMV retinitis development in patients with AIDS. Results from genome-wide association studies suggest a possible role for microtubule network and retinol metabolism in anti-CMV antibody response. Nevertheless, further genetic epidemiological studies with large cohorts, functional studies on the numerous HCMV genes, and immune response to chronic and latent states of infection that contribute to HCMV persistence are clearly necessary to elucidate the genetic mechanisms of CMV infection, reactivation, and pathogenesis.

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.

'From immunosenescence to immune modulation': a re-appraisal of the role of cytomegalovirus as major regulator of human immune function

In the year 2000, cytomegalovirus was identified as a risk factor for mortality in a seminal study of octogenarian residents in Sweden. This finding triggered a wave of additional epidemiological investigations, some of which supported this association whilst others observed no such effect. In addition, this increased risk of death in CMV-seropositive people was correlated with observed changes within the T-cell repertoire such that accelerated 'immunosenescence' became a de facto explanation, without strong evidence to this effect. Recent years have seen a re-appraisal of these findings. Interestingly, many studies show that cytomegalovirus acts to improve immune function, most clearly in younger donors. In addition, the excess mortality in older people that is observed in CMV-seropositive cohorts appears to be related primarily to an excess of vascular disease rather than impairment of immune function. CMV is an important member of the natural 'virome' of Homo sapiens and has an important, and generally positive, modulatory influence on human immune function throughout most of life. However, within certain populations, this influence can become negative and age, co-morbidity and environment all act as determinants of this effect. As such, it is important that new interventions are developed that can mitigate the damaging influence of CMV on human health in populations at risk.

Risk factors associated with the vertical transmission of cytomegalovirus in seropositive pregnant women

Congenital cytomegalovirus infection (cCMV) is the leading cause of childhood disabilities. More recent data indicates that cCMV following maternal nonprimary infection occurs frequently and can cause similar rates of sequelae as those following maternal primary infection. However, the risks associated with cCMV especially in CMV-seropositive women remain unclear. This review summarizes potential risk factors of cCMV in seropositive women with perspectives on the causal link including sociodemographic factors, virological characteristics, the host immune system, genomics, metabonomics and proteomics. These observations and some new molecular markers, although not yet validated as a reliable tool predictive of cCMV, could be the basis for designing future prospective studies.

Toll-like receptors genes polymorphisms and the occurrence of HCMV infection among pregnant women

Background

Human cytomegalovirus (HCMV) is the most common cause of intrauterine infections worldwide. The toll-like receptors (TLRs) have been reported as important factors in immune response against HCMV. Particularly, TLR2, TLR4 and TLR9 have been shown to be involved in antiviral immunity. Evaluation of the role of single nucleotide polymorphisms (SNPs), located within TLR2, TLR4 and TLR9 genes, in the development of human cytomegalovirus (HCMV) infection in pregnant women and their fetuses and neonates, was performed.

Methods

The study was performed for 131 pregnant women, including 66 patients infected with HCMV during pregnancy, and 65 age-matched control pregnant individuals. The patients were selected to the study, based on serological status of anti-HCMV IgG and IgM antibodies and on the presence of viral DNA in their body fluids. Genotypes in TLR2 2258 A > G, TLR4 896 G > A and 1196 C > T and TLR9 2848 G > A SNPs were determined by self-designed nested PCR-RFLP assays. Randomly selected PCR products, representative for distinct genotypes in TLR SNPs, were confirmed by sequencing. A relationship between the genotypes, alleles, haplotypes and multiple variants in the studied polymorphisms, and the occurrence of HCMV infection in pregnant women and their offsprings, was determined, using a logistic regression model.

Results

Genotypes in all the analyzed polymorphisms preserved the Hardy-Weinberg equilibrium in pregnant women, both infected and uninfected with HCMV (P > 0.050). GG homozygotic and GA heterozygotic status in TLR9 2848 G > A SNP decreased significantly the occurrence of HCMV infection (OR 0.44 95% CI 0.21–0.94 in the dominant model, P ≤ 0.050). The G allele in TLR9 SNP was significantly more frequent among the uninfected pregnant women than among the infected ones (χ² = 4.14, P ≤ 0.050). Considering other polymorphisms, similar frequencies of distinct genotypes, haplotypes and multiple-SNP variants were observed between the studied groups of patients.

Conclusions

TLR9 2848 G > A SNP may be associated with HCMV infection in pregnant women.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0730-8) contains supplementary material, which is available to authorized users.

Host genetics and susceptibility to congenital and childhood cytomegalovirus infection: a systematic review

Aim

To summarize available evidence on the role of host genetics in the susceptibility to congenital and childhood cytomegalovirus (CMV) infections by conducting a systematic review of published studies.

Methods

We searched online databases (PubMed, Web of Science, Scopus and HuGe Navigator) for relevant studies with well-defined inclusion and exclusion criteria and assessed the risk of bias using novel Confounding-Selection-Information bias score (CSI).

Results

5105 studies were initially identified, but only 5 met all the inclusion criteria and were analyzed in detail. Polymorphisms of the toll-like receptors (TLRs) and mannose-binding lectin (MBL) genes were shown to have an impact on the CMV infection in infants. Polymorphisms of the TLR2 (rs3804100, rs1898830), TLR4 (rs4986791), and TLR9 (rs352140) were shown to have a role in congenital CMV infection. Low MBL levels were associated with CMV infection in Chinese individuals, a finding that was not replicated in Caucasians. The overall credibility of evidence was weak.

Conclusions

Based on currently available very limited amount of evidence, it is uncertain whether congenital and childhood CMV infections are under host genetic control. Additional primary studies are needed with more specific research hypotheses that will enable gradual understanding of specific mechanisms of the CMV pathogenesis. More genetic studies in the future will facilitate better understanding of host susceptibility and likely enable novel preventative and curative measures.

The role of single nucleotide polymorphisms, contained in proinflammatory cytokine genes, in the development of congenital infection with human cytomegalovirus in fetuses and neonates

PURPOSE

The research project targeted the distribution of genotypes, alleles and haplotypes in single nucleotide polymorphisms (SNPs) within the interleukin (IL) 1A, IL1B, IL6, IL12B and TNFA genes, in fetuses and neonates, congenitally infected with human cytomegalovirus (HCMV), and among uninfected controls.

METHODS

The study included 20 fetuses and neonates with congenital HCMV infection and 31 control individuals. The genotypes in SNPs of the studied cytokine genes were identified by a self-designed nested PCR-RFLP assays. Selected genotypes, representing distinct variants in analyzed polymorphisms, were confirmed by sequencing. The relationship between the genetic status of the studied polymorphisms and congenital infection development was estimated, using a logistic regression model.

RESULTS

The CT haplotype, composed of C allele determined in IL1A -889 C > T and T allele in IL1B +3954 C > T SNP, increased the risk of congenital HCMV infection, as well as the onset of disease related symptoms (P ≤ 0.0001). Considering disease outcome, the risk of development of symptoms, was increased among the CT heterozygotes in IL1A -889 C > T polymorphism (OR 2.86, 95% CI 0.24-33.90; P = 0.045). Moreover, multiple-SNP variants CCGAG in the range of all the SNPs, analyzed in the study, increased the risk of congenital infection with HCMV (OR 7.94, 95% CI 1.38-45.69; P = 0.026).

CONCLUSIONS

Polymorphisms within the proinflammatory cytokine genes may contribute to the development of congenital infection with HCMV.

TLR2 2258 G>A single nucleotide polymorphism and the risk of congenital infection with human cytomegalovirus

BACKGROUND

Human cytomegalovirus (HCMV) is responsible for the most common intrauterine infections, which may be acquired congenitally from infected pregnant woman to fetus. The research was aimed to estimate the role of three single nucleotide polymorphisms (SNPs) located in TLR2 gene, and the common contribution of TLR2, and previously studied TLR4 and TLR9 SNPs, to the occurrence of congenital HCMV infection in fetuses and newborns.

METHODS

The study was performed in 20 Polish fetuses and newborns, congenitally infected with HCMV, and in 31 uninfected controls, as well as with participation of pregnant women, the mothers of 16 infected and 14 uninfected offsprings. Genotypes in TLR2 SNPs were determined, using self-designed nested PCR-RFLP assays, and confirmed by sequencing. The genotypes were tested for Hardy-Weinberg (H-W) equilibrium, and for their relationship with the development of congenital cytomegaly, using a logistic regression model. The common influence of TLR2, TLR4 and TLR9 SNPs on the occurrence of congenital disease was estimated by multiple-SNP analysis.

RESULTS

Distribution of the genotypes and alleles in TLR2 1350 T>C and 2029 C>T SNPs was similar between the studied groups of fetuses and neonates. In case of 2258 G>A polymorphism, the GA heterozygotic status was significantly more frequent in the infected cases than among the uninfected individuals (25.0% vs. 3.2%, respectively), and increased the risk of HCMV infection (OR 10.00, 95% CI 1.07-93.44; P ≤ 0.050). Similarly, the A allele within 2258 G>A polymorphism was significantly more frequent among the infected offsprings than in the uninfected ones (12.5% vs. 1.6%; P ≤ 0.050). Complex AA variants for both TLR2 2258 and TLR9 2848 G>A polymorphisms, were estimated to be at increased risk of congenital HCMV infection (OR 11.58, 95% CI 1.19-112.59; P ≤ 0.050). Additionally, significant relationships were observed between the occurrence of complex AA or GA variants for both TLR2 and TLR9 SNPs and the increased viral loads, determined in fetal amniotic fluids and in maternal blood or urine specimens (P ≤ 0.050).

CONCLUSIONS

Among various TLR2, TLR4 and TLR9 polymorphisms, TLR2 2258 G>A SNP seems to be an important factor associated with increased risk of congenital HCMV infection in Polish fetuses and neonates.

Association of TLR3 L412F Polymorphism with Cytomegalovirus Infection in Children

Intracellular Toll-like receptor 3 (TLR3) recognizes viral double-stranded RNA (dsRNA) and activates antiviral immune responses through the production of type I interferons (IFNs) and inflammatory cytokines. This receptor binds to dsRNA molecules produced during human cytomegalovirus (HCMV) replication. TLR7 senses viral single-stranded RNA (ssRNA) in endosomes, and it can interact with endogenous RNAs. We determined the genotype distribution of single-nucleotide polymorphisms (SNPs) within the TLR3 and TLR7 genes in children with HCMV infection and the relationship between TLR polymorphisms and viral infection. We genotyped 59 children with symptomatic HCMV infection and 78 healthy individuals for SNPs in the TLR3 (rs3775290, c.1377C>T, F459F; rs3775291, c.1234C>T, L412F; rs3775296, c.-7C>A) and TLR7 (rs179008, c.32A>T, Q11L; rs5741880, c.3+1716G>T) genes. SNP genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and capillary electrophoresis. The HCMV DNA load was quantified by real-time PCR. We found an increased frequency of the heterozygous genotype TLR3 L412F in children with HCMV infection compared with uninfected cases. In individuals with a mutation present in at least one allele of the L412F SNP, an increased risk of HCMV disease was found, and this result remained highly significant after Bonferroni’s correction for multiple testing (P^c < 0.001). The heterozygous genotype of this SNP was associated with the increased risk of HCMV disease in an adjusted model that included the HCMV DNA copy number in whole blood and urine (P < 0.001 and P = 0.008, respectively). Moreover, those with a heterozygous genotype of rs3775296 showed an increased relative risk of HCMV infection (P = 0.042), but this association did not reach statistical significance after correction for multiple testing. In contrast, the rs3775290 SNP of TLR3 and TLR7 SNPs were not related to viral infection. A moderate linkage disequilibrium (LD) was observed between the SNPs rs3775291 and rs3775296 (r² = 0.514). We suggest that the L412F polymorphism in the TLR3 gene could be a genetic risk factor for the development of HCMV disease.

Clinical significance of the single nucleotide polymorphism TLR2 R753Q in heart transplant recipients at risk for cytomegalovirus disease

BACKGROUND

The toll-like receptor 2 (TLR2) is a significant component of innate immunity against cytomegalovirus (CMV) infection but information on the clinical significance of the single nucleotide polymorphism (SNP) (R753Q) is conflicting.

OBJECTIVES

The inconsistent observations of the immunological and clinical significance of the TLR2 R753Q polymorphism for CMV infection indicates the influence of confounders.

STUDY DESIGN

The presence of the TLR2 polymorphism was determined by a genotyping assay of 175 HTX patients and 281 healthy blood donors and evaluated in relation to selected virological and clinical parameters.

RESULTS

Relative frequency of TLR2 polymorphism was similar in HTX patients and blood donors (homozygous wild-type, 94.3% vs. 94.0%; heterozygous, 5.1% vs. 5.7%; homozygous mutated, <1%). CMV viremia was detectable in 108 (61.7%) of HTX patients. The TLR2 polymorphism was neither associated with occurrence or level of CMV infection nor with survival, graft failure or rejection, or CMV serostatus of patient before transplantation. Nevertheless, CMV viremia occurred in 83.1% of R+/D+, 77.1% of R+/D-, and 64.3% of R-/D+ patients. Time of first CMV viremia was in R-/D+ patients later than in CMV-seropositive patients (median, 182days versus 23 days; P<0.001) corresponding to the duration of antiviral prophylaxis in R-/D+ patients.

CONCLUSIONS

The TLR2 R753Q polymorphism is extremely rare in the general population and HTX patients. Screening for this risk factor of CMV disease may not be cost-effective in contrast to testing for CMV viremia.

TLR9 -1486T/C and 2848C/T SNPs Are Associated with Human Cytomegalovirus Infection in Infants

Toll-like receptor 9 (TLR9) recognizes non-methylated viral CpG-containing DNA and serves as a pattern recognition receptor that signals the presence of human cytomegalovirus (HCMV). Here, we present the genotype distribution of single-nucleotide polymorphisms (SNPs) of the TLR9 gene in infants and the relationship between TLR9 polymorphisms and HCMV infection. Four polymorphisms (-1237T/C, rs5743836; -1486T/C, rs187084; 1174G/A, rs352139; and 2848C/T, rs352140) in the TLR9 gene were genotyped in 72 infants with symptomatic HCMV infection and 70 healthy individuals. SNP genotyping was performed by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Digested fragments were separated and identified by capillary electrophoresis. The HCMV DNA copy number was measured by a quantitative real-time PCR assay. We found an increased frequency of heterozygous genotypes TLR9 -1486T/C and 2848C/T in infants with HCMV infection compared with uninfected cases. Heterozygous variants of these two SNPs increased the risk of HCMV disease in children (P = 0.044 and P = 0.029, respectively). In infants with a mutation present in at least one allele of -1486T/C and 2848C/T SNPs, a trend towards increased risk of cytomegaly was confirmed after Bonferroni's correction for multiple testing (Pc = 0.063). The rs352139 GG genotype showed a significantly reduced relative risk for HCMV infection (Pc = 0.006). In contrast, the -1237T/C SNP was not related to viral infection. We found no evidence for linkage disequilibrium with the four examined TLR9 SNPs. The findings suggest that the TLR9 -1486T/C and 2848C/T polymorphisms could be a genetic risk factor for the development of HCMV disease.

The immune response to cytomegalovirus in allogeneic hematopoietic stem cell transplant recipients

Approximately, up to 70 % of the human population is infected with cytomegalovirus (CMV) that persists for life in a latent state. In healthy people, CMV reactivation induces the expansion of CMV-specific T cells up to 10 % of the entire T cell repertoire. On the contrary, CMV infection is a major opportunistic viral pathogen that remains a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Due to the delayed CMV-specific immune recovery, the incidence of CMV reactivation during post-transplant period is very high. Several methods are currently available for the monitoring of CMV-specific responses that help in clinical monitoring. In this review, essential aspects in the immune recovery against CMV are discussed to improve the better understanding of the immune system relying on CMV infection and, thereby, helping the avoidance of CMV disease or reactivation following hematopoietic stem cell transplantation with severe consequences for the transplanted patients.

The Putative Role of Viruses, Bacteria, and Chronic Fungal Biotoxin Exposure in the Genesis of Intractable Fatigue Accompanied by Cognitive and Physical Disability

Patients who present with severe intractable apparently idiopathic fatigue accompanied by profound physical and or cognitive disability present a significant therapeutic challenge. The effect of psychological counseling is limited, with significant but very slight improvements in psychometric measures of fatigue and disability but no improvement on scientific measures of physical impairment compared to controls. Similarly, exercise regimes either produce significant, but practically unimportant, benefit or provoke symptom exacerbation. Many such patients are afforded the exclusionary, non-specific diagnosis of chronic fatigue syndrome if rudimentary testing fails to discover the cause of their symptoms. More sophisticated investigations often reveal the presence of a range of pathogens capable of establishing life-long infections with sophisticated immune evasion strategies, including Parvoviruses, HHV6, variants of Epstein-Barr, Cytomegalovirus, Mycoplasma, and Borrelia burgdorferi. Other patients have a history of chronic fungal or other biotoxin exposure. Herein, we explain the epigenetic factors that may render such individuals susceptible to the chronic pathology induced by such agents, how such agents induce pathology, and, indeed, how such pathology can persist and even amplify even when infections have cleared or when biotoxin exposure has ceased. The presence of active, reactivated, or even latent Herpes virus could be a potential source of intractable fatigue accompanied by profound physical and or cognitive disability in some patients, and the same may be true of persistent Parvovirus B12 and mycoplasma infection. A history of chronic mold exposure is a feasible explanation for such symptoms, as is the presence of B. burgdorferi. The complex tropism, life cycles, genetic variability, and low titer of many of these pathogens makes their detection in blood a challenge. Examination of lymphoid tissue or CSF in such circumstances may be warranted.

TLR9 2848 GA heterozygotic status possibly predisposes fetuses and newborns to congenital infection with human cytomegalovirus

Background

Some single nucleotide polymorphisms (SNP), located in Toll-like receptor (TLR) genes, were reported to be associated with human cytomegalovirus (HCMV) infections. The study was aimed to assess the correlation of SNPs at TLR4 and TLR9 genes with the occurrence of congenital cytomegaly, based on available samples.

Methods

Reported case-control study included both HCMV infected and non-infected fetuses and newborns. The specimens were classified to the molecular analyses, based on serological features of the recent infection and HCMV DNAemia in body fluids. TLR SNPs were studied, using multiplex nested PCR-RFLP assay, and determined genotypes were confirmed by sequencing. Hardy-Weinberg equilibrium was assessed for the identified genotypes. The linkage disequilibrium was also estimated for TLR4 SNPs. A relationship between the status of TLR genotypes and congenital cytomegaly development was estimated, using a logistic regression model.

Results

Hardy Weinberg equilibrium was observed for almost all SNPs, both infected and non-infected patients, with exception of TLR4 896 A>G polymorphism in the control group (P≤0.050). TLR4 896 A>G and 1196 C>T SNPs were found in linkage disequilibrium in both study groups (P≤0.050). The CC genotype at TLR4 1196 SNP and the GA variant at TLR9 2848 G>A SNP were significantly associated with HCMV infection (P≤0.050). The risk of congenital cytomegaly was higher in heterozygotes at TLR9 SNP than in the carriers of other genotypic variants at the reported locus (OR 4.81; P≤0.050). The GC haplotype at TLR4 SNPs and GCA variants at TLR4 and TLR9 SNPs were significantly associated with HCMV infection (P≤0.0001). The ACA variants were more frequent among fetuses and neonates with symptomatic, rather than asymptomatic cytomegaly (P≤0.0001).

Conclusions

TLR4 and TLR9 polymorphisms may contribute to the development of congenital infection with HCMV in fetuses and neonates. The TLR9 2848 GA heterozygotic status possibly predisposes to HCMV infection, increasing the risk of congenital cytomegaly development.