A polymorphism in human MR1 is associated with mRNA expression and susceptibility to tuberculosis.

The MR1 antigen-presenting system is conserved among mammals and enables T cells to recognize small molecules produced by bacterial pathogens, including Mycobacterium tuberculosis (M.tb). However, it is not known whether MR1-mediated antigen presentation is important for protective immunity against mycobacterial disease. We hypothesized that genetic control of MR1 expression correlates with clinical outcomes of tuberculosis infection. We performed an MR1 candidate gene association study and identified an intronic single-nucleotide polymorphism (rs1052632) that was significantly associated with susceptibility to tuberculosis in a discovery and validation cohort of Vietnamese adults with tuberculosis. Stratification by site of disease revealed that rs1052632 genotype GG was strongly associated with the development of meningeal tuberculosis (odds ratio=2.99; 95% confidence interval (CI) 1.64-5.43; P=0.00006). Among patients with meningeal disease, absence of the G allele was associated with an increased risk of death (hazard ratio=3.86; 95% CI 1.49-9.98; P=0.005). Variant annotation tools using public databases indicate that rs1052632 is strongly associated with MR1 gene expression in lymphoblastoid cells (P=0.004) and is located within a transcriptional enhancer in epithelial keratinocytes. These data support a role for MR1 in the pathogenesis of human tuberculosis by revealing that rs1052632 is associated with MR1 gene expression and susceptibility to tuberculosis in Vietnam.

MARCO variants are associated with phagocytosis, pulmonary tuberculosis susceptibility and Beijing lineage.

Macrophage receptor with collagenous structure (MARCO) has an important role in the phagocytosis of Mycobacterium tuberculosis (M. tuberculosis). We hypothesized that MARCO polymorphisms are associated with phagocytosis, tuberculosis (TB) disease susceptibility and presentation, and infecting lineage. We used a human cellular model to examine how MARCO genotype mediates the immune response; a case-control study to investigate tuberculosis host genetic susceptibility; and a host-pathogen genetic analysis to study host-pathogen interactions. Two MARCO heterozygous (AG) genotypes (single-nucleotide polymorphisms rs2278589 and rs6751745) were associated with impaired phagocytosis of M. tuberculosis trehalose 6,6'-dimycolate-cord factor and ß-glucan-coated beads in macrophages. The heterozygous genotypes of rs2278589 and rs6751745 were also associated with increased risk of pulmonary TB (PTB; rs2278589, P=0.001, odds ratio (OR)=1.6; rs6751745, P=0.009, OR=1.4), and with severe chest X-ray abnormalities (P=0.007, OR=1.6). These two genotypes were also associated with the Beijing lineage (rs2278589, P=0.001, OR=1.7; rs6751745, P=0.01, OR=1.5). Together, these results suggest that MARCO polymorphisms may regulate phagocytosis of M. tuberculosis and susceptibility and severity of PTB. They also suggest MARCO genotype and Beijing strains may interact to increase the risk of PTB.

TLR9 gene region polymorphisms and susceptibility to tuberculosis in Vietnam.

Humans exposed to Mycobacterium tuberculosis (Mtb) show variation in susceptibility to infection and differences in tuberculosis (TB) disease outcome. Toll-like receptor 9 (TLR9) is a pattern recognition receptor that mediates recognition of Mtb and modulates Mtb-specific T-cell responses. Using a case-population design, we evaluated whether single nucleotide polymorphisms (SNPs) in the TLR9 gene region are associated with susceptibility to pulmonary or meningeal TB as well as neurologic presentation and mortality in the meningeal TB group. In a discovery cohort (n = 352 cases, 382 controls), three SNPs were associated with TB (all forms, p < 0.05) while three additional SNPs neared significance (0.05 < p < 0.1). When these six SNPs were evaluated in a validation cohort (n = 339 cases, 367 controls), one was significant (rs352142) while another neared significance (rs352143). When the cohorts were combined, rs352142 was most strongly associated with meningeal tuberculosis (dominant model; p = 0.0002, OR 2.36, CI 1.43-3.87) while rs352143 was associated with pulmonary tuberculosis (recessive model; p = 0.006, OR 5.3, CI 1.26-31.13). None of the SNPs were associated with mortality. This is the first demonstration of an association between a TLR9 gene region SNP and tuberculous meningitis. In addition, this extends previous findings that support associations of TLR9 SNPs with pulmonary tuberculosis.

Tissue integrity signals communicated by high-molecular weight hyaluronan and the resolution of inflammation.

The extracellular matrix polysaccharide hyaluronan (HA) exerts size-dependent effects on leukocyte behavior. Low-molecular weight HA is abundant at sites of active tissue catabolism and promotes inflammation via effects on Toll-like receptor signaling. Conversely, high-molecular weight HA is prevalent in uninjured tissues and is anti-inflammatory. We propose that the ability of high-molecular weight but not low-molecular weight HA to cross-link CD44 functions as a novel form of pattern recognition that recognizes intact tissues and communicates "tissue integrity signals" that promote resolution of local immune responses.

A polymorphism in human CD1A is associated with susceptibility to tuberculosis.

CD1 proteins are antigen-presenting molecules that evolved to present lipids rather than peptides to T cells. However, unlike major histocompatibility complex genes, CD1 genes show low rates of polymorphism and have not been clearly associated with human disease. We report that an intronic polymorphism in CD1A (rs411089) is associated with susceptibility to tuberculosis in two cohorts of Vietnamese adults (combined cohort odds ratio 1.78; 95% confidence interval: 1.24-2.57; P=0.001). These data strengthen the hypothesis that CD1A-mediated lipid antigen presentation is important for controlling tuberculosis in humans.

A TLR6 polymorphism is associated with increased risk of Legionnaires' disease.

Legionella pneumophila (Lp), the etiologic agent of Legionnaires' disease (LD), is an important cause of community-acquired and nosocomial pneumonia. However, the host immune and genetic determinants of human susceptibility to Lp are poorly understood. Here we show that both TLR6 and TLR1 cooperate with TLR2 to recognize Lp in transfected HEK293 cells. We also perform a human genetic association study of 14 candidate single-nucleotide polymorphisms in Toll-like receptors (TLRs) 1, 2 and 6 in 98 LD cases and 268 controls from the Netherlands. No polymorphisms in TLR1 or TLR2 were associated with LD. A TLR6 polymorphism, 359T>C (rs5743808), was associated with an elevated risk of LD in genotypic and dominant (odds ratio (OR) 5.83, P=7.9 × 10(-5)) models. The increased risk in persons with 359 TC or CC genotypes was further enhanced among smokers. In a multivariate model, 359T>C was associated with a higher risk of LD (OR 4.24, P=0.04), than any other variable, including age and smoking. Together, these data suggest that the human TLR6 variant, 359T>C, is an independent risk factor for LD.

Epiregulin (EREG) variation is associated with susceptibility to tuberculosis.

Although host genetics influences susceptibility to Mycobacterium tuberculosis, the human genes regulating pathogenesis remain largely unknown. We used M. tuberculosis-stimulated macrophage gene expression profiling in conjunction with a case-control genetic association study to discover epiregulin (EREG), as a novel candidate tuberculosis (TB) susceptibility gene. Using a genome-wide association study dataset, we found that among the 21 genes with greater than 50-fold induction, EREG had the most polymorphisms associated with TB. We genotyped haplotype-tagging polymorphisms in discovery (N = 337 cases, N = 380 controls) and validation (N = 332 cases) datasets and an EREG polymorphism (rs7675690) was associated with susceptibility to TB (genotypic comparison; corrected P = 0.00007). rs7675690 was also associated more strongly with infections caused by the Beijing lineage of M. tuberculosis when compared with non-Beijing strains (controls vs Beijing, OR 7.81, P = 8.7 × 10(-5); non-Beijing, OR 3.13, P = 0.074). Furthermore, EREG expression was induced in monocytes and peripheral blood mononuclear cells stimulated with M. tuberculosis as well as TLR4 and TLR2/1/6 ligands. In murine macrophages, EREG expression induced by M. tuberculosis was MYD88- and TLR2-dependent. Together, these data provide the first evidence for an important role for EREG as a susceptibility gene for human TB.

Toll-like receptor 4 region genetic variants are associated with susceptibility to melioidosis.

Melioidosis is a tropical infection caused by the Gram-negative soil saprophyte Burkholderia pseudomallei. Despite broad exposure of northeastern Thais, disease develops in only a small proportion of individuals. Although diabetes is a risk factor, the mechanisms of host susceptibility to melioidosis are still poorly understood. We postulated that Toll-like receptors (TLRs) regulate host susceptibility to disease, and that genetic variation in TLRs is associated with melioidosis. We analyzed the frequency of eight previously described TLR pathway polymorphisms in 490 cases compared with 950 non-hospitalized controls or 458 hospitalized controls. Based on these results, we then analyzed the frequency of additional TLR4 or TLR6-1-10 region polymorphisms in cases and controls. We found that the TLR4(1196C>T) variant was associated with protection from melioidosis when compared with non-hospitalized controls. The TLR1(742A>G) and TLR1(-7202A>G) variants were associated with melioidosis when compared with hospitalized controls. In further analyses, we found that two additional TLR4 region polymorphisms were associated with disease. In diabetics, three other TLR6-1-10 region polymorphisms were associated with disease when compared with hospitalized controls. We conclude that TLR genetic variants may modulate host susceptibility to melioidosis. Confirmation of these findings and further investigation of the mechanisms are required.

Single nucleotide polymorphisms in toll-like receptor 6 are associated with altered lipopeptide- and mycobacteria-induced interleukin-6 secretion.

Toll-like receptors (TLRs) are critical mediators of the immune response to pathogens. The influence of human TLR6 polymorphisms on susceptibility to infection is only partially understood. Most microbes contain lipopeptides recognized by TLR2/1 or TLR2/6 heterodimers. Our aim was to determine whether single nucleotide polymorphisms in TLR6 are associated with altered immune responses to lipopeptides and whole mycobacteria. We sequenced the TLR6 coding region in 100 healthy South African adults to assess genetic variation and determined associations between polymorphisms and lipopeptide- and mycobacteria-induced interleukin (IL)-6 production in whole blood. We found two polymorphisms, C745T and G1083C, that were associated with altered IL-6 secretion. G1083C was associated with altered IL-6 levels in response to lipopeptides, Mycobacterium tuberculosis lysate (Mtb lysate, P=0.018) and Bacille Calmette-Guerin (BCG P=0.039). The 745T allele was also associated with lower NF-κB signaling in response to di-acylated lipopeptide, PAM2 (P=0.019) or Mtb (P=0.026) in an HEK293 cell line reconstitution assay, compared with the 745C allele. We conclude that TLR6 polymorphisms may be associated with altered lipopeptide-induced cytokine responses and recognition of Mtb. These studies provide new insight into the role of TLR6 variation and the innate immune response to human infection.

Prospective cohort study of microbial and inflammatory events immediately preceding Escherichia coli recurrent urinary tract infection in women.

BACKGROUND: A prospective cohort study was conducted to characterize the temporal sequence of microbial and inflammatory events immediately preceding Escherichia coli recurrent urinary tract infection (rUTI). METHODS: Women with acute cystitis and a history of UTI within the previous year self-collected periurethral and urine samples daily and recorded measurements of urine leukocyte esterase, symptoms, and sexual intercourse daily for 3 months. rUTI strains were characterized by pulsed-field gel electrophoresis and genomic virulence profiling. Urinary cytokine levels were measured. RESULTS: There were 38 E. coli rUTIs in 29 of 104 women. The prevalence of periurethral rUTI strain carriage increased from 46% to 90% during the 14 days immediately preceding rUTI, with similar increases in same-strain bacteriuria (from 7% to 69%), leukocyte esterase (from 31% to 64%), and symptoms (from 3% to 43%), most notably 2-3 days before rUTI (P<.05 for all comparisons). Intercourse with periurethral carriage of the rUTI strain also increased before rUTI (P=.008). Recurrent UTIs preceded by bacteriuria, pyuria, and symptoms were caused by strains less likely to have P fimbriae than other rUTI strains (P=.002). CONCLUSIONS: Among women with frequent rUTIs, the prevalences of periurethral rUTI strain carriage, bacteriuria, pyuria, and intercourse dramatically increase over the days preceding rUTI. A better understanding of the pathogenesis of rUTI will lead to better prevention strategies.

Polymorphisms in Toll-like receptor 4 (TLR4) are associated with protection against leprosy.

Accumulating evidence suggests that polymorphisms in Toll-like receptors (TLRs) influence the pathogenesis of mycobacterial infections, including leprosy, a disease whose manifestations depend on host immune responses. Polymorphisms in TLR2 are associated with an increased risk of reversal reaction, but not susceptibility to leprosy itself. We examined whether polymorphisms in TLR4 are associated with susceptibility to leprosy in a cohort of 441 Ethiopian leprosy patients and 197 healthy controls. We found that two single nucleotide polymorphisms (SNPs) in TLR4 (896G>A [D299G] and 1196C>T [T399I]) were associated with a protective effect against the disease. The 896GG, GA and AA genotypes were found in 91.7, 7.8 and 0.5% of leprosy cases versus 79.9, 19.1 and 1.0% of controls, respectively (odds ratio [OR] = 0.34, 95% confidence interval [CI] 0.20-0.57, P < 0.001, additive model). Similarly, the 1196CC, CT and TT genotypes were found in 98.1, 1.9 and 0% of leprosy cases versus 91.8, 7.7 and 0.5% of controls, respectively (OR = 0.16, 95% CI 0.06--.40, P < 0.001, dominant model). We found that Mycobacterium leprae stimulation of monocytes partially inhibited their subsequent response to lipopolysaccharide (LPS) stimulation. Our data suggest that TLR4 polymorphisms are associated with susceptibility to leprosy and that this effect may be mediated at the cellular level by the modulation of TLR4 signalling by M. leprae.

A polymorphism in human TLR2 is associated with increased susceptibility to tuberculous meningitis.

Tuberculous meningitis (TBM) results from the haematogenous dissemination of Mycobacterium tuberculosis from the lung to the brain. Dissemination is believed to occur early during infection, before the development of adaptive immunity. Toll-like receptor 2 (TLR2) mediates recognition of M. tuberculosis and initiates the innate immune response to infection. We hypothesized that polymorphisms in the TLR2 gene influence bacterial dissemination and the development of TBM. A case-control study was designed to test the hypothesis. Cases of bacteriologically confirmed pulmonary tuberculosis (TB) (n=183) and TBM (n=175), and cord blood controls (n=389) were enrolled in Vietnam. TLR2 genotype 597CC was associated with susceptibility to TB (odds ratio (OR)=2.22, 95% confidence interval (CI): 1.23-3.99). The association was found with meningeal rather than pulmonary TB (TBM vs control, OR=3.26, 95% CI: 1.72-6.18), and was strongest when miliary TB was found on chest radiography (controls vs TBM with miliary TB, OR=5.28, 95% CI: 2.20-12.65). Furthermore, the association increased with the severity of neurologic symptoms (grade I TBM, OR=1.93, 95% CI: 0.54-6.92; grade II, OR=3.32, 95% CI: 0.84-13.2; and grade III, OR=5.70, 95% CI: 1.81-18.0). These results demonstrate a strong association of TLR2 SNP T597C with the development of TBM and miliary TB and indicate that TLR2 influences the dissemination of M. tuberculosis.

The innate immune response to bacterial flagellin is mediated by Toll-like receptor 5.

The innate immune system recognizes pathogen-associated molecular patterns (PAMPs) that are expressed on infectious agents, but not on the host. Toll-like receptors (TLRs) recognize PAMPs and mediate the production of cytokines necessary for the development of effective immunity. Flagellin, a principal component of bacterial flagella, is a virulence factor that is recognized by the innate immune system in organisms as diverse as flies, plants and mammals. Here we report that mammalian TLR5 recognizes bacterial flagellin from both Gram-positive and Gram-negative bacteria, and that activation of the receptor mobilizes the nuclear factor NF-kappaB and stimulates tumour necrosis factor-alpha production. TLR5-stimulating activity was purified from Listeria monocytogenes culture supernatants and identified as flagellin by tandem mass spectrometry. Expression of L. monocytogenes flagellin in non-flagellated Escherichia coli conferred on the bacterium the ability to activate TLR5, whereas deletion of the flagellin genes from Salmonella typhimurium abrogated TLR5-stimulating activity. All known TLRs signal through the adaptor protein MyD88. Mice challenged with bacterial flagellin rapidly produced systemic interleukin-6, whereas MyD88-null mice did not respond to flagellin. Our data suggest that TLR5, a member of the evolutionarily conserved Toll-like receptor family, has evolved to permit mammals specifically to detect flagellated bacterial pathogens.

Developmentally regulated localization and phosphorylation of SmIrV1, a Schistosoma mansoni antigen with similarity to calnexin.

Potential molecular targets of a protective humoral immune response against schistosomiasis have previously been identified based on their enhanced immunogenicity in mice vaccinated with irradiated cercaria as compared to chronically infected mice. One of these antigens, IrV1, has been molecularly cloned and its sequence shown to be similar to the molecular chaperone calnexin. In this investigation, we partially characterized IrV1 from different developmental stages of the schistosome. Immunoprecipitation studies with antibodies raised against a portion of recombinant IrV1 demonstrated its presence in cercaria, schistosomula, and adult worms with an apparent molecular mass on SDS-polyacrylamide gel electrophoresis of 90 kDa. There was an approximate 6-fold increase in protein expression level during the cercaria to schistosomula transformation. Consistent with a potential role as a molecular chaperone, IrV1 was associated with several metabolically labeled proteins in co-immunoprecipitation studies with the adult worm tegumental fraction. Similar to calnexin, IrV1 was metabolically labeled with 32P in adult worms on serine and threonine residues and was one of the major phosphoproteins of this stage. This phosphorylation was developmentally regulated and coincided with the transformation of cercaria into schistosomula. The localization was also stage-specific as IrV1 was transported from internal regions of cercaria to the outer tegumental layer of schistosomula. The presence of IrV1 on the surface of schistosomula, an unprecedented localization for this family of endoplasmic reticulum proteins, supports additional studies of the immunoprophylactic potential of this molecule.

Detection and partial characterization of glycosylphosphatidylinositol-specific phospholipase activities from Fasciola hepatica and Schistosoma mansoni.

The tegument of trematodes serves as a dynamic host-parasite interface where surface antigens are shed in a process of immune evasion. Phospholipases, which could provide an enzymatic mechanism for release of glycosylphosphatidylinositol (GPI)-anchored proteins, were detected in detergent extracts of adult worms of Fasciola hepatica and cercaria and adult worms of Schistosoma mansoni. The enzymatic activities were partially characterized from both adult worm species and demonstrated a preference for [3H]GPI substrate over [3H]PI. Lipase activities from both species were sensitive to sulfhydryl-modifying reagents and the detergents CHAPS and n-octylglucoside. The presence of 1 M ammonium sulfate increased the enzyme activity in adult worms of both species by 8-11-fold and in cercaria by 146-fold, whereas other conditions of high ionic strength were inhibitory. Such stimulation suggested dissociation of a negative inhibitor which is prominent in the cercarial stage. The schistosome extract, which was partially sensitive to cation chelators and o-phenanthroline, contained a GPI-phospholipase D activity. In contrast, the F. hepatica extract contained a cation-independent phospholipase C activity which was partially purified and shown by gel filtration to have a molecular mass of 30,000-80,000.

Molecular cloning and expression of SmIrV1, a Schistosoma mansoni antigen with similarity to calnexin, calreticulin, and OvRal1.

Protective immunity against schistosomiasis induced by vaccination of mice with irradiated cercaria can be passively transferred to uninfected mice with sera or IgG. Antigens that are uniquely or more strongly recognized by such protective sera compared with sera from infected unprotected mice have been identified previously. Two genes, SmIrV1 and SmIrV5, were selected from an adult worm cDNA library by screening with antibodies raised against these candidate vaccine proteins. Active immunization with the SmIrV5 protein induces high levels of protection in mice. We report here the molecular cloning and sequencing of SmIrV1 which contains a deduced amino acid sequence of 582 residues with similarity to three proteins: calnexin, calreticulin, and OvRal1, a surface antigen of the filarial nematode Onchocerca volvulus. SmIrV1 can be divided into three regions: a neutral N-terminal region with a putative signal sequence, followed by a proline- and tryptophan-rich P region in which two sets of sequences are repeated four times and a C-terminal region which is highly acidic with an isoelectric point of 4.7. We expressed the P and C regions of SmIrV1 and showed that this polypeptide reacts with sera of immunized as well as chronically infected mice.