Polymorphisms in lymphotoxin alpha and CD14 genes influence TNFalpha production induced by Gram-positive and Gram-negative bacteria

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.

The Role of Efferocytosis in Autoimmune Diseases

Apoptosis happens continuously for millions of cells along with the active removal of apoptotic debris in order to maintain tissue homeostasis. In this respect, efferocytosis, i.e., the process of dead cell clearance, is orchestrated through cell exposure of a set of "find me," "eat me," and "tolerate me" signals facilitating the engulfment of dying cells through phagocytosis by macrophages and dendritic cells. The clearance of dead cells via phagocytes is of utmost importance to maintain the immune system tolerance to self-antigens. Accordingly, this biological activity prevents the release of autoantigens by dead cells, thus potentially suppressing the undesirable autoreactivity of immune cells and the appearance of inflammatory autoimmune disorders as systemic lupus erythematous and rheumatoid arthritis. In the present study, the apoptosis pathways and their immune regulation were reviewed. Moreover, efferocytosis process and its impairment in association with some autoimmune diseases were discussed.

Lack of association of the caspase-12 long allele with community-acquired pneumonia in people of African descent

Community-acquired pneumonia (CAP) is a common cause of sepsis. Active full-length caspase-12 (CASP12L), confined to the people of African descent, has been associated with increased susceptibility to and mortality from severe sepsis. The objective of this study was to determine whether CASP12L was a marker for susceptibility and/or severity of CAP. We examined three CAP cohorts and two control populations: 241 adult Memphis African American CAP patients, 443 pediatric African American CAP patients, 90 adult South African CAP patients, 120 Memphis healthy adult African American controls and 405 adult Chicago African American controls. Clinical outcomes including mortality, acute respiratory distress syndrome (ARDS), septic shock or severe sepsis, need for mechanical ventilation, and S. pneumoniae bacteremia. Neither in the three individual CAP cohorts nor in the combined CAP cohorts, was mortality in CASP12L carriers significantly different from that in non-CASP12L carriers. No statistically significant association between genotype and any measures of CAP severity was found in any cohort. We conclude that the functional CASP12L allele is not a marker for susceptibility and/or severity of CAP.

Genetic predisposition to respiratory infection and sepsis

Genetic variations, in part, determine individual susceptibility to sepsis and pneumonia. Advances in genetic sequence analysis as well as high throughput platform analysis of gene expression has allowed for a better understanding of immunopathogenesis during sepsis. Differences in genes can also modulate immune and inflammatory response during sepsis thereby translating to differences in clinical outcomes. An increasing number of candidate genes have been implicated to play a role in sepsis susceptibility, most of which are controversial with few exceptions. This does not refute the significance of genetic polymorphisms in sepsis, but rather highlights the difficulties and pitfalls related to genetic association studies. These difficulties include differences in study design such as heterogeneous patient cohorts and differences in pathogenic organisms, linkage disequilibrium, and lack of power for detailed haplotype analysis or examination of gene-gene interactions. There is extensive diversity in the pathways of inflammation and immune response during sepsis making it even harder to prove the functional and clinical significance of one single genetic polymorphism which could be easily masqueraded or compensated by other upstream or downstream events of the pathway involved. The majority of studies have analysed candidate genes in isolation from other possible polymorphisms. It is likely that susceptibility to sepsis is the result of polymorphisms from multiple genes rather than one single mutation. Future studies should aim for multi-centered collaborative approach looking at genome wide association or gene profiling to provide a more complete appraisal of the key genetic players in determining genetic susceptibility to sepsis. This review paper will summarise the prominent candidate gene polymorphisms with known functional changes or those with haplotype data. In addition, a summary of the expanding research in the field of epigenetics and post-sepsis immunosuppression will be discussed.

TNF-α and TNF-β Polymorphisms are Associated with Susceptibility to Osteoarthritis in a Korean Population

BACKGROUND

The tumor necrosis factor (TNF) is believed to play an important role in the pathophysiology of osteoarthritis (OA). Evidence shows that genetic polymorphisms make substantial contributions to the etiology of OA.

METHODS

We investigated the genotypes TNF-α and TNF-β in 301 OA patients and 291 healthy subjects as controls. We employed a polymerase chain reaction-restriction fragment length polymorphism and a polymerase chain reaction-single strand conformation polymorphism assay to identify the genotypes TNFA -G308A and TNFB +G252A, respectively.

RESULTS

For TNFA -G308A, the percentages of genotypes GG, AG, and AA were 26.3% (79/301), 62.5% (188/301), and 11.3% (34/301) in OA patients and 88.7% (258/291), 11.3% (33/291), and 0% (0/291) in controls. For TNFB +G252A, the percentages of genotypes GG, AG, and AA were 15.3% (46/301), 41.9% (126/301), and 42.9% (129/301) in OA patients and 12% (35/291), 52.6% (153/291), and 35.4% (103/291) in controls. There were significant differences in genotypes and alleles of TNFA -308 between OA patients and controls (p<0.0001) and in alleles of TNFB +252 (p=0.0325). The risk of OA was significantly higher for carriers of the TNFA -308A allele and the TNFB +252 AA homozygote (p=0.0224).

CONCLUSIONS

The results suggest close relationships between TNFA -G308A and TNFB +G252A polymorphisms and individual susceptibility to OA in the Korean population.

Characterisation of TNF block haplotypes affecting the production of TNF and LTA

Polymorphisms in the central major histocompatibility complex (MHC) (particularly TNF and adjacent genes) associate with several immunopathological diseases and with susceptibility to pneumonia. The MHC is characterised by strong linkage disequilibrium (LD), so identification of loci affecting disease must be based on haplotypes. We have defined 31 tumour necrosis factor (TNF) block haplotypes (denoted FV1-31) in Caucasians, Asians and Australian Aboriginals. This study correlates the carriage of TNF block haplotypes with TNF and lymphotoxin alpha (LTA) protein production by peripheral blood mononuclear cells from 205 healthy Caucasian subjects, following in vitro stimulation with Streptococcus pneumoniae (S. pneumoniae; gram-positive bacteria), Escherichia coli (E. coli; gram-negative bacteria) or TNF over 4, 8 and 24 h. Fifteen haplotypes were present at >1%, accounting for 94.5% of the cohort. The haplotypes were grouped into five families based on common alleles. Following stimulation, cells from carriers of the FV10 haplotype (family 2) produced less LTA compared with non-FV10 carriers. Carriers of the FV18 haplotype (family 4) produced more LTA than other donors. Induction of TNF by S. pneumoniae following 24 h stimulation was also greater in donors with FV18. The FV18 haplotype associated with the 44.1 MHC ancestral haplotype (HLA-A2, -C5, -B44, -DRB1*0401 and -DQB1*0301) that has few disease associations. FV16 occurred in the 8.1 MHC haplotype (HLA-A2, B8, DR3) that is associated with multiple immunopathological diseases. FV16 did not affect TNF or LTA levels. The findings suggest that many genetic variations critical in vivo are not effectively modelled by short-term cultures.

Association between lymphotoxin-α intron +252 polymorphism and sepsis: a meta-analysis

BACKGROUND

We evaluated the association of lymphotoxin-α (LTA, also known as tumour necrosis factor-β) promoter +252 A/G polymorphism with sepsis.

METHODS

A systematic search was performed in MEDLINE, EMBASE, and Web of Science (for the period January 1966 to June 2010). Two reviewers independently selected studies on the genetic association of LTA +252 A/G polymorphism with sepsis and independently extracted data onto standardized forms.

RESULTS

Twenty-seven studies with 4399 septic patients were included based on predefined inclusion criteria. As compared to AG + GG, the LTA AA genotype was significantly associated with an increased development of sepsis in the overall population (odds ratio (OR) 1.33, 95% confidence interval (CI) 1.09-1.62; p = 0.006). An association between mortality from sepsis and AA genotype was also found in the overall population (OR 1.89, 95% CI 1.27-2.80; p = 0.002). Stratification by ethnicity indicated that the contribution to both sepsis susceptibility and mortality may be stronger in Caucasians (OR 1.44, 95% CI 1.08-1.91 and OR 2.47, 95% CI 1.52-4.00, respectively) than in other ethnicities.

CONCLUSIONS

The LTA +252 A/G polymorphism is associated with both susceptibility to and mortality from sepsis.

Genetic risk of acute pulmonary infections and sepsis

The focus of this review is the genetic influence on pneumonia and sepsis. A large number of polymorphisms in a diverse collection of genes have been identified as potential candidates to explain the genetic variability in susceptibility to acute pulmonary infection and its adverse outcomes. Unfortunately, apart from polymorphisms in mannose-binding lectin, CD14 and the IgG2 receptor, there is little consensus on which polymorphisms are truly important. As well as discussing some of the major published findings, this review will focus on the reasons for failure to make more progress. We will also address the issues for future research, particularly the need to address the limitations of past studies, including the grouping of patients with different pathogens, as the relationship between genotype and phenotype may be highly pathogen dependent. Finally, our approach to reporting genetic studies needs to change to minimize the number of publications of spurious findings.

Association between CD14 gene polymorphisms and disease phenotype in sarcoidosis

Although the etiology of sarcoidosis is unknown, genetic susceptibility has been demonstrated. Granuloma formation is a key feature in the pathophysiology of sarcoidosis and Crohn's Disease, raising the possibility that these diseases share common pathogenetic pathways. An association between sarcoidosis and the protein "CD14", a molecule that is part of the lipopolysaccharide (LPS) cell surface receptor complex, has been suggested. In the current study we evaluated the CD14 gene promoter 159 C-->T polymorphic site and soluble CD14 levels in a cohort of 74 sarcoidosis patients compared to 85 healthy controls. We further sought to identify correlations between clinical phenotype, specific genotypes and soluble CD14 levels. We found the TT genotype to be more prevalent in the sarcoidosis patient group than in controls (p=0.03). Serum levels of soluble CD14 were higher in the sarcoidosis patients (p=0.001). Within the patient cohort, CC homozygous patients presented at an older age with milder disease as assessed with the SAC score, longer time to diagnosis, and less impairment of pulmonary function tests. Our study suggests a role of CD14 in the pathogenesis of sarcoidosis, and a clinical phenotype-genotype association. Further mechanistic and epidemiologic studies are needed in order to establish the specific role of CD14 in the etiology, pathogenesis and clinical phenotype of sarcoidosis.

The neck-region polymorphism of DC-SIGNR in peri-centenarian from Han Chinese population

Background

DC-SIGNR (also called CD209L) has been extensively studied on its role in host genetic predisposition to viral infection. In particular, variable number tandem repeat (VNTR) of the neck-region of DC-SIGNR is highly polymorphic and the polymorphism has been investigated for genetic predisposition to various infectious diseases, though conflicting results had been reported. As infection is a major cause of human death and a mechanism of natural selection, we hypothesized that VNTR polymorphism of DC-SIGNR might have an effect on human life span.

Methods

Here we collected 361 peri-centenarian individuals (age ≥94 for female and age ≥90 for male) and 342 geographically matched controls (age 22-53, mean 35.0 ± 12.0) from Han Chinese. The VNTR polymorphism of the neck region was determined by PCR and genotype was called by separating the PCR products in agarose gel.

Results

A total of 11 genotypes and 5 alleles were found in our population. The genotype distribution, allele frequencies and homozygote proportion did not show a significant difference between peri-centenarian and control group. As gender differences in lifespan are ubiquitously observed throughout the animal kingdom, we then stratified the samples by gender. There was more 6/7 genotypes in female peri-centenarian group than that in female control group, at a marginal level of significance (5.56 vs. 1.28%, p = 0.041). The difference was not significant after correction by Bonferroni method. It suggests a possible differential effect of DC-SIGNR VNTR genotypes between sexes. Further studies are warranted to confirm our preliminary findings and investigate the mechanisms of the underlying functions.

Conclusions

Our study indicated that there was absence of association between the neck region polymorphism of DC-SIGNR and longevity in Han Chinese population. But the question of whether the DC-SIGNR could affect longevity in a gender-specific pattern remains open.

Genetic variation in heat shock protein 70 is associated with septic shock: narrowing the association to a specific haplotype

Heat shock protein 70 (HSP70) plays a major role in immune responses. Polymorphisms within the gene have been associated with development of septic shock. This study refines the region of the HSP70 gene associated with development of septic shock and confirms its functionality. Subjects (n = 31) were grouped into one of three haplotypes based on their HSPA1B-179C>T and HSPA1B1267A>G genotypes. Mononuclear cells from these subjects were stimulated with heat-killed bacteria (10(7 )colony-forming units/mL Escherichia coli or Streptococcus pneumoniae) for 8 and 21 h. HSP70 and tumour necrosis factor (TNF) mRNA and protein levels were measured by reverse transcriptase-polymerase chain reaction and ELISA, respectively. The HSPA1B-179*C:1267*A haplotype was associated with significantly lower levels of HSPA1B mRNA and protein and higher production of TNF mRNA and protein compared to the other haplotypes. Induction of HSP70 was TNF independent. These results suggest that the HSPA1B-179C>T:1267A>G haplotype is functional and may explain the association of the HSP70 gene with development of septic shock.

Bench-to-bedside review: Association of genetic variation with sepsis

Susceptibility and response to infectious disease is, in part, heritable. Initial attempts to identify the causal genetic polymorphisms have not been entirely successful because of the complexity of the genetic, epigenetic, and environmental factors that influence susceptibility and response to infectious disease and because of flaws in study design. Potential associations between clinical outcome from sepsis and many inflammatory cytokine gene polymorphisms, innate immunity pathway gene polymorphisms, and coagulation cascade polymorphisms have been observed. Confirmation in large, well conducted, multicenter studies is required to confirm current findings and to make them clinically applicable. Unbiased investigation of all genes in the human genome is an emerging approach. New, economical, high-throughput technologies may make this possible. It is now feasible to genotype thousands of tag single nucleotide polymorphisms across the genome in thousands of patients, thus addressing the issues of small sample size and bias in selecting candidate polymorphisms and genes for genetic association studies. By performing genome-wide association studies, genome-wide scans of nonsynonymous single nucleotide polymorphisms, and testing for differential allelic expression and copy number polymorphisms, we may yet be able to tease out the complex influence of genetic variation on susceptibility and response to infectious disease.

159C>T CD14 genotype--functional effects on innate immune responses in term neonates

Given the susceptibility of newborns to infection and the potential harm of overwhelming proinflammatory immune responses, the impact of genetic variation in innate immune molecules is of increasing interest for risk stratification and prevention. We studied the functional relevance of the 159C>T CD14 single nucleotide polymorphism in cord blood samples of n=135 healthy term neonates by investigation of sCD14, interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-alpha concentrations in whole-blood culture supernatants and intracellular assessment of IL-1beta, IL-6, and TNF-alpha expression by flow cytometry. The 159C>T CD14 genotype frequencies were n=42 (0.31) for homozygous CD14-159 CC, n=69 (0.51) for heterozygous CD14-159 CT, and n=24 (0.18) for homozygous CD14-159 TT. No genotype-associated differences were noted for ex vivo baseline expression of sCD14, IL-6, IL-10, and TNF-alpha. After in vitro stimulation of cord blood cultures with lipopolysaccharide, carriers of the CD14-159 T allele were determined to have higher levels of sCD14 compared with carriers of the CD14-159 C allele (p=0.04) and increased concentrations of IL-6 (p=0.009) in culture supernatants (one-way analysis of variance). The 159C>T CD14 polymorphism is associated with soluble CD14 expression and cytokine expression, which might influence the balance of pro- and anti-inflammatory immune responses in healthy term neonates. Further studies are needed to delineate whether the 159C>T CD14 genotype is a risk factor for severity of neonatal infection in the clinical setting and a potential target for prevention strategies.

Cytokine Profiling in Abacavir Hypersensitivity Patients

Background

Abacavir hypersensitivity in genetically susceptible individuals implicates an abacavir-specific T-cell response to either the parent drug or a metabolite generated in vivo. We have analysed the cytokine profile in antigen-presenting cells and the T-lymphocytes that are involved in the pathological immune response to abacavir.

Methods

In this study, we compared abacavir-specific cytokine responses in cultured peripheral blood mononuclear cells (PBMCs) from HIV-infected abacavir hypersensitive, tolerant and naive individuals. Cells were cultured in the presence or absence of abacavir. Cytokine expression was determined by microarray analysis, enzyme-linked immunosorbent assays and flow cytometry.

Results

We demonstrated using in vitro models of immune activation that the production of interferon-γwas specifically induced by abacavir treatment in PBMCs obtained from hypersensitive patients carrying the HLA-B*5701 allele (median 123.86 compared with -30.83 for tolerant controls, P=0.001).

Conclusion

These results provide further insight into the immunological and metabolic basis of abacavir hypersensitivity syndrome. In vitro assays could assist in the identification of susceptible loci by providing a surrogate marker for the hypersensitivity reaction. Such a marker could be studied in unexposed individuals to shed further light on the immunopathogenesis of the abacavir hypersensitivity syndrome.

Polymorphisms of CARD15/NOD2 and CD14 genes in New Zealand Crohn's disease patients

Polymorphisms in the CARD15/NOD2 gene, which encodes a cytosolic protein involved in bacterial recognition, are associated with development of Crohn's disease (CD). Other potential susceptibility genes such as CD14 may compound the risk of developing CD. We examined the frequency of the three major CARD15 risk alleles (3020insC/L1007fsinsC, G908R and R702W), and a functional polymorphism (-159C/T) in the promoter of the CD14 gene in 185 CD patients in New Zealand and 187 ethnically matched controls. The frequencies of the 3020insC (8.1 vs 0.8%, P < 0.0001), G908R (3.5 vs 2.4%, P = 0.37) and R702W (7.3 vs 5.1%, P = 0.21) alleles in CD patients and controls, respectively, were similar to those described in Australia, and the ancestral countries of Scotland, Ireland and the UK. Only the 3020insC polymorphism was found to be a significant risk factor for CD in our New Zealand cohort (odds ratio = 10.91 [95% confidence intervals 3.30-36.08]; P < 0.0001 for heterozygotes), but not a single patient was homozygous for the 3020insC polymorphism. The T allele (51 vs 50%, P = 0.77) and TT genotype (26 vs 24%, P = 0.84) frequencies of the -159C/T CD14 gene promoter polymorphism did not significantly differ between CD patients and controls. In summary, our findings provide evidence that the CARD15 3020insC risk allele influences disease susceptibility in a small proportion (<17%) of New Zealand CD patients, whereas there was no evidence that the CD14 -159C/T polymorphism is associated with CD.

The Genetics of Sepsis: The Promise, the Progress and the Pitfalls

Physicians are used to taking a family history of cardiovascular disease because of the known significant hereditary risk; yet the familial risk of dying from infection is even greater than that for atherosclerotic disease (Sorensen et al. 1988). There is certainly no doubt that genetic differences impact on the risk of developing or dying from infection. Obvious but rare examples include selective immunoglobulin deficiencies, complement deficiencies, and neutrophil function abnormalities. Genetic factors may also be protective, such as with sickle cell trait and malaria or mutations conferring resistance to human immunodeficiency virus infection.

Much more subtle differences in immune responses are now being described, usually as the result of one or more single nucleotide polymorphisms (SNP) in a gene. Rather than causing the failure of production of a protein or the production of a nonfunctional protein, SNPs are usually associated with changes in the rate of transcription, producing a much less severe phenotype than the classical examples of genetic defects mentioned above. It is now being appreciated that for many complex diseases, such as sepsis, the ultimate phenotype is the result of the interaction of genetic differences across many loci, not the dominant effect of a few key mutations.

As seen in Fig. 3.1, since the mid 1990s, an increasing body of literature has focused on the role that gene polymorphisms in key inflammatory genes play in sepsis. Indeed, with advances in knowledge of the human genome, greater understanding of the inflammatory response, and the development of high throughput genotyping technologies, so many genetic associations have been described that discussion of each one is well beyond the scope of this chapter. I will however summarize those findings that have been reported by multiple groups, as well as give an overview of the major groups of genes that have been implicated in genetic predisposition to sepsis and its adverse outcomes.

A diplotype in the lymphotoxin alpha gene is associated with differential expression of LTA mRNA induced by Gram-positive and Gram-negative bacteria

We sequenced the lymphotoxin alpha (LTA) promoter and identified LTA10G>A in strong linkage with LTA252G>A and LTA723C>A. Stimulated cells from LTA723AA: LTA252GG:LTA10AA individuals had significantly higher LTA mRNA levels than LTA723CC:LTA252AA:LTA10GG and LTA723AA:LTA252AG:LTA10GA individuals, suggesting that this diplotype may contain a functional polymorphism explaining the observed disease associations with LTA252G>A.

The tumor necrosis factor alpha -308 G/A polymorphism does not influence inflammation and coagulation response in human endotoxemia

Tumor necrosis factor (TNF)-alpha plays a major role in the immune system. Release of proinflammatory cytokines, such as TNF-alpha and interleukin 6, by macrophages and other cells occurs in response to bacterial products. It has been reported that the TNF-alpha -308 G/A polymorphism in the TNF-alpha gene determines basal TNF-alpha levels. We hypothesized that it may also be associated with the degree of inflammatory response in a well-standardized model of systemic inflammation. Eighty-seven young men (age range, 19-35 years) received 2 ng/kg i.v. endotoxin (lipopolysaccharide [LPS]). The TNF-alpha promoter genotype was analyzed on a TaqMan genomic analyzer. Inflammation markers (interleukin 6, TNF-alpha), temperature, and coagulation markers (prothrombin fragment F1+2, D-dimer) were measured at 0, 2, 6, and 24 h after LPS infusion. Tumor necrosis factor-alpha plasma concentrations increased from a baseline 1.3 ng/L (range, 0.8-3.1 ng/L) before LPS infusion to a peak of 57.5 ng/L (range, 10.8-131.4 ng/L) at 2 h after LPS and then decreased continually to 10.8 ng/L (range, 4.7-16.5 ng/L) after 6 h and returned to baseline values after 24 h (1.9 ng/L [range, 1.1-3.9 ng/L]). We observed no significant differences in TNF-alpha baseline levels or in response to LPS after stratification of the data according to TNF-alpha genotype. Basal and peak values of selected inflammatory and coagulation markers were not different between wild-type TNF-alpha -308 individuals (GG) and carriers of the TNF-alpha -308 mutant allele (GA and AA). The TNF-alpha -308 G/A polymorphism does not contribute significantly to the individual variability of systemic TNF-alpha plasma concentrations after endotoxin challenge. Thus, if any, the impact of the TNF-alpha -308 G/A polymorphism on systemic endotoxin-triggered inflammation seems to be limited.

Association between TNF and IL-1 bloc polymorphisms and plasma MCP-1 concentration

BACKGROUND

Circulating MCP-1 concentration was found to be increased in cardiovascular diseases and is of high interest in the list of biomarkers of atherosclerosis. TNF-alpha, LT-alpha, IL-1alpha and IL-1beta are four proinflammatory cytokines that regulate MCP-1 concentration in vitro. We hypothesized that specific genetic polymorphisms in TNF, LTA, IL-1A and IL-1B genes could modulate plasma MCP-1 concentration.

METHODS

Plasma MCP-1 concentration was quantified with a biochip array analyzer in 395 adults from the Stanislas family study. TNF -308G>A, LTA 252A>G (A=TNFB2, G=TNFB1), IL-1A -889C>T and IL-1B 3954C>T were genotyped with a prototypic multilocus genotyping assay.

RESULTS

Among the four polymorphisms studied only LTA 252A>G and TNF -308G>A were significantly associated with plasma MCP-1 concentration (p=0.005 and p=0.038, respectively) after adjustment for covariates (age, sex, smoking, monocyte count and hematocrit). Carriers of the 252A allele or the -308G had lower MCP-1 concentrations than carriers of the 252G or the -308A alleles, respectively. Moreover, as TNF and LTA genes were in linkage disequilibrium, the TNF bloc haplotypes were compared with respect to MCP-1 concentration, and a significant association (p=0.021) was observed, due only to the LTA polymorphism. This association remained significant even after adjustment for TNF-alpha and hs-CRP concentrations.

CONCLUSION

A functional polymorphism within the TNF bloc could modulate MCP-1 concentration and seems more likely to be near to the LTA 252A>G polymorphism than to the TNF -308G>A one. In addition, the association found in healthy French adults is independent of other actors of inflammation such as TNF-alpha and hs-CRP.

Genetic association studies in VLBW infants exemplifying susceptibility to sepsis--recent findings and implications for future research

CONTEXT

In recent years, tremendous effort has been carried out to study the genetic basis of susceptibility to development, progression and severity of complex diseases and response to therapy. The ultimate goal of these investigations is to find new tools for prevention and treatment of these complex diseases, such as sepsis in very-low-birth-weight (VLBW) infants. VLBW cohorts have a restricted clinical risk profile for the development of sepsis including immaturity of immune functions and antenatal/perinatal risk factors but also a significant event rate of sepsis within a short period of observational time. Therefore, prospective VLBW cohorts are advantageous for the investigation of candidate genetic risk factors of sepsis compared to adult cohorts. Furthermore, environmental factors are much better documented and highly controlled for VLBW infants in a standardized NICU setting compared to adult cohorts which are influenced by a variety of environmental risk factors, e.g. habits and comorbidities.

OBJECTIVE

The aim of this review is to discuss the value and limitations of genetic association studies in VLBW infant cohorts exemplifying recent findings for genetic susceptibility to neonatal sepsis.

DATA SOURCE

Published Medline articles reporting on studies of associations between genetic polymorphisms, neonatal sepsis and septic shock in VLBW infants.

CONCLUSIONS

Up-to-date, the classical approach to investigate the genetic component of susceptibility to sepsis in VLBW infants by means of twin and concordance studies has not been implemented yet. Regarding the interpretation of data from current genetic association studies, one should be aware of significant differences in cohort size, study design and definition of cases, controls and clinical end points. Furthermore, the contribution of genetic variants to susceptibility to sepsis may be specifically influenced by the immaturity of the immune response in VLBW infants, the selectivity of responsiveness to certain pathogens and the genotopyic/phenotypic variability of pathogens. We provide implications for the conduct and evaluation of future association studies with particular reference to methodological quality standards.

Functional variants in the lymphotoxin-alpha gene predict cardiovascular disease in dialysis patients

TNF-beta that is encoded by lymphotoxin-alpha gene (LTA) regulates adhesion molecules and IL-6. Previously, a genome-wide case-control study showed that LTA gene variants predisposed to cardiovascular disease (CVD). In a prospective study of 775 dialysis patients, LTA and IL-6 gene variants were tested as independent predictors of CVD risk. Four polymorphisms in the LTA gene and one in the IL-6 gene were genotyped. CVD events were ascertained from medical records. During a mean follow-up of 2.6 yr, 294 first-incident CVD events occurred. The LTA 26Asn variant predicted higher adjusted CVD risk (hazard ratio HR 1.33 for each additional copy of Asn allele; 95% confidence interval 1.14 to 1.55; P = 0.0003). Two other nonsynonymous polymorphisms in the LTA, 13Agr and 51Pro, were associated with lower inflammatory activity and CVD risk. LTA haplotypes (based on all four single-nucleotide polymorphisms) were associated with inflammatory markers and predicted CVD risk (P = 0.005) after adjustment. These LTA genotype associations were independent of the IL-6 -174G/C genotype association that was reported recently. LTA and IL-6 gene variants independently predicted risk for CVD among dialysis patients, suggesting that susceptibility in multiple inflammatory pathways contribute to the development of CVD.

Association of a maternal CD14 -159 gene polymorphism with preterm premature rupture of membranes and spontaneous preterm birth in multi-fetal pregnancies

CD14, the major receptor for bacterial lipopolysaccharide (LPS) as well as other microbial antigens, is a component of the innate immune system. We hypothesized that a single nucleotide C>T polymorphism at position -159 in the CD14 gene that results in elevated CD14 production would influence susceptibility to preterm premature rupture of membranes (PPROM) and spontaneous preterm birth (SPTB) in multi-fetal pregnancies. DNA from 107 mother-twin and three mother-triplet pairs was analyzed. Pregnancy outcomes were obtained after completion of testing. CD14*T homozygosity was present in 39.3% of 28 women whose pregnancies ended with PPROM, as opposed to 18.1% of 72 pregnancies without a SPTB (P=0.03). There was no relation between the fetal CD14 genotype and PPROM. The likelihood ratio (LR) for PPROM was 2.2 for women homozygous for CD14*T. The LR increased to 3.3 and 3.6 if the CD14 polymorphism was present in combination with previously determined maternal polymorphisms in the genes coding for the inducible 70kDa heat shock protein (hsp70-2) and the interleukin-1 receptor antagonist (IL1RN), respectively. Thus, an enhanced maternal pro-inflammatory immune response to LPS may increase susceptibility to PPROM in multi-fetal pregnancies.

Community-acquired pneumonia: pathophysiology and host factors with focus on possible new approaches to management of lower respiratory tract infections

The present understanding of the pathophysiology of community-acquired pneumonia (CAP) explains the mechanism for many specific manifestations, but does not address adequately why only some patients experience complications. Recent advances in under-standing the genetics of complex illnesses offer hope for a more complete insight into the pathogenesis of CAP. This article reviews genetic variation in the molecules involved in the known patho-genic mechanisms of CAP, including cough, bacterial recognition, inflammation and the compensatory anti-inflammatory response,and organ dysfunction.

TaqMan assays for genotyping of single nucleotide polymorphisms present at a disease susceptibility locus on chromosome 6

Multiple single-nucleotide polymorphisms in the

In vitro modulation of inflammatory cytokine production by three lipid emulsions with different fatty acid compositions

BACKGROUND AND AIMS

Studies have suggested that 100% long-chain triacylglycerols (LCTs) lipid emulsions exhibit immunosuppressive effects, sometimes suspected to favor infectious complications in patients receiving parenteral nutrition. Newer emulsions, in particular olive oil-based emulsions, seem to have lesser immunosuppressive effects. We studied the in vitro effect of 100% LCTs (Intralipide), 50% LCTs-50% medium chain triacylglycerols (Medialipide), and 80% olive oil-based lipid emulsions (ClinOleic) on inflammatory cytokines production by peripheral blood mononuclear cells (PBMCs).

METHODS

PBMCs separated by gradient centrifugation, or whole blood, were incubated with 0.001%, 0.01%, 0.1% and 1% of the three tested lipid emulsions during 24h in the presence or absence of activation by lipopolysaccharide and phytohemagglutinin. Then, supernatants were collected and cytokines measured (ELISA).

RESULTS

The three lipid emulsions reduced basal TNF-alpha and IL-1beta production in PBMCs and whole blood cultures. However, ClinOleic was significantly less powerful in TNF-alpha and IL-1beta inhibition by isolated PBMCs than Intralipide and Medialipide. Basal TNF-alpha production was equally inhibited by the three emulsions in whole blood, but IL-1beta production was not significantly modified by ClinOleic. Interleukin-6 and -8 were not affected. After cell activation, lipid emulsions exhibit no effect on cytokines production.

CONCLUSION

ClinOleic induces a significantly lower in vitro inhibition of TNF-alpha and IL-1beta production by PBMCs than 100% LCTs or 50% LCTs-50% MCTs emulsions, and therefore might be more immune neutral. These effects vary from one subject to another, and disappeared after cell activation. Therefore, caution must be taken before extrapolation in vivo. Provided information should be taken into account for future design of clinical trials studying the immune modulating properties of lipid emulsions.

Bioaerosols and innate immune responses in airway diseases

PURPOSE OF REVIEW

We review the role of bioaerosols in the pathogenesis of inflammatory airway disease. The focus is on recent discoveries in innate immune responses induced by common components of bioaerosols.

RECENT FINDINGS

Common components of bioaerosols include endotoxin, peptidoglycan and beta-glucan; all of which have been associated with inflammatory airway disease. Endotoxin signaling through toll-like receptor 4 is well characterized and updated. Peptidoglycan is now known to signal through three types of molecules: toll-like receptor 2; peptidoglycan recognition proteins; and nucleotide-binding oligomerization domain molecules. Beta-glucan, a common fungal cell wall component, signals through the newly discovered receptor, dectin-1. Emerging data indicate that genetic polymorphisms influence the response to bioaerosols.

SUMMARY

Activation of the innate immune system by bioaerosols is becoming better understood. This knowledge provides an opportunity to better prevent and treat airway diseases that result from environmental exposure.

Polymorphisms of the lipopolysaccharide-signaling complex in inflammatory bowel disease: association of a mutation in the Toll-like receptor 4 gene with ulcerative colitis

Genes encoding for receptors of the innate immune system are potential candidates for susceptibility to inflammatory bowel disease, e.g., mutations in the cytosolic receptor NOD2/CARD15 were associated with Crohn's disease. Herein, two mutations of the Toll-like receptor (TLR)-4 gene (Asp299Gly and Thr399Ile) resulting in impaired lipopolysaccharide signaling, the -159C/T promotor polymorphism of the CD14 gene, polymorphisms of the lipopolysaccharide binding protein gene and the bactericidal permeability increasing protein gene were evaluated in 102 patients with Crohn's disease, 98 patients with ulcerative colitis and 145 healthy controls. The allele and carrier frequencies for the Thr399Ile mutation in TLR4 gene were significantly increased in ulcerative colitis when compared to the controls (P = 0.014 and P = 0.018, respectively). None of the other five polymorphisms was associated with inflammatory bowel disease. In conclusion, a novel association between a functional polymorphism in TLR4 and ulcerative colitis is reported. This observation underscores the importance of impaired innate immunity in inflammatory bowel disease.

A CD14 promoter polymorphism is associated with CD14 expression and Chlamydia-stimulated TNFα production

CD14, a pattern recognition receptor on monocyte and macrophage, plays a central role in innate immunity through recognition of bacterial lipopolysaccharide and initiation of inflammatory response. Recently, CD14/-260C>T promoter gene polymorphism has been found to be related to a risk of inflammatory diseases. Our results showed that the C allele frequency among Chinese in Taiwan was lower than those in Western countries. The membrane CD14 expression was significantly higher in TT as compared with CT and CC genotypes (P=0.034, 0.044, respectively). There was a higher level of soluble CD14 in TT and CT genotypes than in CC genotypes. In addition, TNFalpha production in whole blood was significantly higher in TT genotype than in CC genotype after stimulation by Chlamydiae. In conclusion, the single base pair polymorphism of CD14 promoter gene is associated with CD14 expression and Chlamydia-stimulated TNFalpha production, and may thus play some role in the chlamydia-induced inflammatory response.

Predisposition to abacavir hypersensitivity conferred by HLA-B*5701 and a haplotypic Hsp70-Hom variant

Susceptibility to a clinically significant drug hypersensitivity syndrome associated with abacavir use seems to have a strong genetic component. We have previously shown that the presence of HLA-B*5701 strongly predicts abacavir hypersensitivity and have identified a potential susceptibility locus within a 300-kb region between the MEGT1 and C4A6 loci in the central MHC. We now report the results of fine recombinant genetic mapping in an expanded patient population of 248 consecutive, fully ascertained, abacavir-exposed individuals in the Western Australian HIV Cohort Study, in which 18 cases of definite abacavir hypersensitivity (7.3%) and 230 tolerant controls were identified. Haplotype mapping within patients with allelic markers of the 57.1 ancestral haplotype suggests a susceptibility locus within the 14-kb Hsp70 gene cluster. HLA-B*5701 was present in 94.4% of hypersensitive cases compared with 1.7% of controls (odds ratio, 960; P < 0.00001). A haplotypic nonsynonymous polymorphism of Hsp70-Hom (HspA1L, resulting from the substitution of residue M493T in the peptide-binding subunit) was found in combination with HLA-B*5701 in 94.4% of hypersensitive cases and 0.4% of controls (odds ratio, 3,893; P < 0.00001). Individuals with abacavir hypersensitivity demonstrated increased monocyte tumor necrosis factor expression in response to ex vivo abacavir stimulation, which was abrogated with CD8(+) T cell depletion. These data indicate that the concurrence of HLA-B*5701 and Hsp70-Hom M493T alleles is necessary for the development of abacavir hypersensitivity, which is likely to be mediated by an HLA-B*5701-restricted immune response to abacavir.

The Interleukin-6 G(−174)C Promoter Polymorphism Does Not Determine Plasma Interleukin-6 Concentrations in Experimental Endotoxemia in Humans

Background: Interleukin 6 (IL-6) is a pleiotropic cytokine that plays an essential role in the pathogenesis of acute and chronic infections. As the role of the IL-6 G(−174)C polymorphism in determining serum concentrations of IL-6 is controversial, we studied the genotype-specific IL-6 response in a well-standardized model of systemic inflammation.

Methods: A total of 76 healthy young males (age range, 19–35 years) received a single bolus of 2 ng/kg endotoxin [lipopolysaccharide (LPS)] intravenously. Plasma IL-6 was measured by enzyme immunoassay at 0, 2, 6, and 24 h after LPS infusion, and the IL-6 promoter genotype was analyzed by a mutagenic separated PCR assay.

Results: IL-6 increased 300-fold 2 h after LPS challenge and returned almost to normal within 24 h. Neither basal IL-6 nor the IL-6 response to LPS was significantly affected by the IL-6 promoter genotype.

Conclusions: The IL-6 G(−174)C promoter polymorphism does not significantly influence basal concentrations of IL-6 or peak IL-6 in human endotoxemia.

Alleles carried at positions -819 and -592 of the IL10 promoter affect transcription following stimulation of peripheral blood cells with Streptococcus pneumoniae

IL-10 inhibits the production of many pro-inflammatory cytokines. Polymorphisms in the IL10 gene promoter at positions -1082G-->A, -819C-->T and -592C-->A occur as three haplotypes, ATA, GCC and ACC. These influence several infectious and inflammatory diseases including community-acquired pneumonia, where a role for IL-10 is suggested by fluctuations in plasma levels of the cytokine. However, the effects of the haplotypes on IL-10 production are unclear. We stimulated peripheral blood mononuclear cells (PBMC) from at least five individuals homozygous for each of the three haplotypes with lipopolysaccharide (LPS, 10 microg/ml) or heat-killed Streptococcus pneumoniae (10(7)cfu/ml) and measured IL-10 mRNA by RT-PCR. Following S. pneumoniae stimulation, PBMC with the ATA haplotype had higher IL-10 mRNA levels than those with the GCC haplotype at 4 h (independent t-test; P=0.024), or the ACC haplotype at 4 h ( P<0.0001) and 8 h ( P=0.007). Following LPS stimulation, IL-10 mRNA levels were not significantly influenced by the IL10 haplotype, but similar trends were observed, consistent with the variable outcome of published studies. The results suggest that the -819 and/or -592 alleles affect transcription.

Genetics of sepsis and pneumonia

PURPOSE OF REVIEW

The genetic risk for pneumonia, sepsis, and other serious infections is generally unrecognized or underestimated. Although the strongest evidence for a genetic risk comes from an adoptee study, most evidence for a genetic role in infection involves association studies, which compare the incidence of specific mutations in a population with infection to a control population. Recent association studies in pneumonia and sepsis will be reviewed.

RECENT FINDINGS

Most positive association studies examine genes for important inflammatory molecules such as tumor necrosis factor, the interleukin-1 family, interleukin-10, and angiotensin converting enzyme, as well as molecules important in antigen recognition, such as the mannose-binding lectin, CD-14, and toll-like receptors.

SUMMARY

A genetic component to risk of sepsis and resultant complications clearly exists. Confirmation of the findings in this review and associations with other genetic polymorphisms await large-scale population studies and further validation of the physiologic significance of the variant alleles.