Optimization of the flip angles of narrow-band editing pulses in J-difference edited MRS of lactate at 3T.

PURPOSE: Application of highly selective editing RF pulses provides a means of minimizing co-editing of contaminants in J-difference MRS (MEGA), but it causes reduction in editing yield. We examined the flip angles (FAs) of narrow-band editing pulses to maximize the lactate edited signal with minimal co-editing of threonine. METHODS: The effect of editing-pulse FA on the editing performance was examined, with numerical and phantom analyses, for bandwidths of 17.6-300 Hz in MEGA-PRESS editing of lactate at 3T. The FA and envelope of 46 ms Gaussian editing pulses were tailored to maximize the lactate edited signal at 1.3 ppm and minimize co-editing of threonine. The optimized editing-pulse FA MEGA scheme was tested in brain tumor patients. RESULTS: Simulation and phantom data indicated that the optimum FA of MEGA editing pulses is progressively larger than 180° as the editing-pulse bandwidth decreases. For 46 ms long 17.6 Hz bandwidth Gaussian pulses and other given sequence parameters, the lactate edited signal was maximum at the first and second editing-pulse FAs of 241° and 249°, respectively. The edit-on and difference-edited lactate peak areas of the optimized FA MEGA were greater by 43% and 25% compared to the 180°-FA MEGA, respectively. In-vivo data confirmed the simulation and phantom results. The lesions of the brain tumor patients showed elevated lactate and physiological levels of threonine. CONCLUSION: The lactate MEGA editing yield is significantly increased with editing-pulse FA much larger than 180° when the editing-pulse bandwidth is comparable to the lactate quartet frequency width.

Conjunctival fibrosis and the innate barriers to Chlamydia trachomatis intracellular infection: a genome wide association study.

Chlamydia trachomatis causes both trachoma and sexually transmitted infections. These diseases have similar pathology and potentially similar genetic predisposing factors. We aimed to identify polymorphisms and pathways associated with pathological sequelae of ocular Chlamydia trachomatis infections in The Gambia. We report a discovery phase genome-wide association study (GWAS) of scarring trachoma (1090 cases, 1531 controls) that identified 27 SNPs with strong, but not genome-wide significant, association with disease (5 × 10(-6) > P > 5 × 10(-8)). The most strongly associated SNP (rs111513399, P = 5.38 × 10(-7)) fell within a gene (PREX2) with homology to factors known to facilitate chlamydial entry to the host cell. Pathway analysis of GWAS data was significantly enriched for mitotic cell cycle processes (P = 0.001), the immune response (P = 0.00001) and for multiple cell surface receptor signalling pathways. New analyses of published transcriptome data sets from Gambia, Tanzania and Ethiopia also revealed that the same cell cycle and immune response pathways were enriched at the transcriptional level in various disease states. Although unconfirmed, the data suggest that genetic associations with chlamydial scarring disease may be focussed on processes relating to the immune response, the host cell cycle and cell surface receptor signalling.

Exposure to Chlamydia pneumoniae infection and age-related macular degeneration: the Blue Mountains Eye Study.

PURPOSE: To assess cross-sectional and longitudinal associations between exposure to Chlamydia pneumoniae infection and age-related macular degeneration (AMD) in the nested case-control sample drawn from the Blue Mountains Eye Study (BMES) cohort. METHODS: The BMES examined 3654 persons aged 49 to 97 years during 1992 through 1994 (BMES I survey). Survivors from this cohort (n = 2335; 75%) and 1174 persons who moved in this area or reached an eligible age were examined during 1997 through 2000 (BMES II survey, n = 3509). One hundred ninety-seven AMD cases and 433 control subjects matched for age, sex and smoking status, were drawn from the BMES II survey. Photographic macular grading followed the Wisconsin grading system. Plasma samples were analyzed with an enzyme-linked immunosorbent assay to determine antibody titers to the elementary bodies from C. pneumoniae AR39. Associations between seroreactivity to C. pneumoniae and prevalent and incident AMD were assessed by using logistic regression models. RESULTS: There were 159 early and 38 late AMD cases. Of them, 87 cases of early and 22 of late AMD developed between the baseline and follow-up examinations. After adjustment for age, gender, and smoking, no significant association was evident between C. pneumoniae antibody titer and any prevalent early or late AMD (OR 1.02, 95% CI 0.66-1.56 comparing upper with lower tertile of antibody titer). Findings were similar when early or late AMD was analyzed separately. Analysis confined to incident AMD also showed no significant association with the incidence of either early (OR 0.92, 95% CI 0.52-1.64) or late (OR 1.85, 95% CI 0.57-6.05) AMD. The results did not change after adjustment for family history of AMD and cardiovascular disease. CONCLUSIONS: In this nested case-control sample of an older Australian population we found no association between C. pneumoniae antibody titers and early AMD. The study has insufficient power to assess an association with late AMD.

The p47 GTPases Iigp2 and Irgb10 regulate innate immunity and inflammation to murine Chlamydia psittaci infection.

C57BL/6J mice were 10(5)-fold more resistant to Chlamydia psittaci infection than DBA/2J mice by LD(100) determinations. Linkage analysis using BXD recombinant inbred strains revealed a single effector locus at a 1.5-Mbp region on chromosome 11 encoding a cluster of three p47 GTPases (Irgb10, Igtp, and Iigp2). Western blots of infected tissue showed that Irgb10 was elevated in resistant mice and one of the two possible Iigp2 protein isoforms was preferentially expressed in susceptible mice. The BXD39 strain, susceptible at Irgb10 and resistant at Iigp2, had an intermediate phenotype implicating the nonredundant role of these p47 GTPases. C57BL/6J and DBA/2J exhibited a difference in IFN-gamma-dependent chlamydial control, which was reversible by Iigp2 small interfering RNA knockdown. Microarrays of infected peritoneal lavage revealed >10-fold up-regulation of neutrophil-recruiting chemokines in susceptible mice and >100-fold increase in macrophage differentiation genes in resistant mice, indicating that the susceptibility pattern involves the stimulation of different inflammatory cell-recruiting pathways. Massive neutrophil recruitment was seen in susceptible mice by histology and flow cytometry, and neutrophil chemokine receptor (CXCR2) knockout mice on a susceptible background survived a lethal challenge, confirming that neutrophil recruitment was required for susceptibility. Congenic Igtp knockout mice also susceptible at Irgb10 and Iigp2 on a resistant background recruited neutrophils and succumbed to infection. We conclude that Irgb10 and Iigp2 act together to confer differential susceptibility against murine chlamydial infection. Data indicate that these p47 GTPases have cell-autonomous effects that result in vastly different inflammatory stimulations, leading to either recovery or death.

Secondary outcomes of a pilot randomized trial of azithromycin treatment for asthma.

OBJECTIVES: The respiratory pathogen Chlamydia pneumoniae (C. pneumoniae) produces acute and chronic lung infections and is associated with asthma. Evidence for effectiveness of antichlamydial antibiotics in asthma is limited. The primary objective of this pilot study was to investigate the feasibility of performing an asthma clinical trial in practice settings where most asthma is encountered and managed. The secondary objectives were to investigate (1) whether azithromycin treatment would affect any asthma outcomes and (2) whether C. pneumoniae serology would be related to outcomes. This report presents the secondary results. DESIGN: Randomized, placebo-controlled, blinded (participants, physicians, study personnel, data analysts), allocation-concealed parallel group clinical trial. SETTING: Community-based health-care settings located in four states and one Canadian province. PARTICIPANTS: Adults with stable, persistent asthma. INTERVENTIONS: Azithromycin (six weekly doses) or identical matching placebo, plus usual community care. OUTCOME MEASURES: Juniper Asthma Quality of Life Questionnaire (Juniper AQLQ), symptom, and medication changes from baseline (pretreatment) to 3 mo posttreatment (follow-up); C. pneumoniae IgG and IgA antibodies at baseline and follow-up. RESULTS: Juniper AQLQ improved by 0.25 (95% confidence interval; -0.3, 0.8) units, overall asthma symptoms improved by 0.68 (0.1, 1.3) units, and rescue inhaler use decreased by 0.59 (-0.5, 1.6) daily administrations in azithromycin-treated compared to placebo-treated participants. Baseline IgA antibodies were positively associated with worsening overall asthma symptoms at follow-up (p = 0.04), but IgG was not (p = 0.63). Overall asthma symptom improvement attributable to azithromycin was 28% in high IgA participants versus 12% in low IgA participants (p for interaction = 0.27). CONCLUSIONS: Azithromycin did not improve Juniper AQLQ but appeared to improve overall asthma symptoms. Larger community-based trials of antichlamydial antibiotics for asthma are warranted.

Different growth rates of Chlamydia trachomatis biovars reflect pathotype.

BACKGROUND: Despite small genomic differences, Chlamydia trachomatis biovars exhibit diverse disease manifestations and different growth rates in vivo and in cell culture models. METHODS: Chlamydial inclusion-forming units were enumerated over time in HeLa cells, to evaluate the length of the developmental cycle for C. trachomatis strains A, B, C, and E/Bour (ocular strains) as well as D, E/UW5/Cx, F, and L2 (genital strains). Prototype strains A, D, and L2 were selected for detailed analysis of reticulate body growth, division, and genomic replication. The impact that changing host cells and that coinfection with different strains has on growth was also assessed. RESULTS: The genital strains completed the developmental cycle in 36-44 h, whereas the ocular strains lagged behind considerably. Differences were the result of a longer lag phase (entry plus differentiation) and generation time for the ocular strains. A prototype ocular strain grew faster in conjunctival cells than in cervical cells. Coinfection with genital (D or L2) and ocular strains expedited recovery of the ocular strain. CONCLUSIONS: Precise temporal evaluation of the chlamydial developmental cycle for selected genital and ocular C. trachomatis biovars provides a means for investigating genomic differences that define chlamydial pathotype.

Serological association between Chlamydia pneumoniae infection and age-related macular degeneration.

BACKGROUND: Age-related macular degeneration (ARMD) is a leading cause of blindness in the United States, but the mechanisms that initiate and promote the disease remain ill defined. There are several risk factors that ARMD shares with atherosclerosis, and these diseases may have similar pathogenic mechanisms that involve inflammation. Chlamydia pneumoniae, a prokaryotic pathogen that causes chronic inflammation is now emerging as a risk factor in the development of cardiovascular diseases. It is therefore plausible that this microorganism also contributes to the pathogenesis of ARMD. METHODS: To examine if C pneumoniae infection is associated with ARMD, serum samples from 25 consecutive patients with ARMD and from 18 without the disease were collected and assayed for the presence of the antibodies to C pneumoniae elementary bodies, Chlamydia trachomatis heat shock protein 60 (cHsp60), C trachomatis heat shock protein 10 (cHsp10), Escherichia coli GroEL, and E coli GroES. RESULTS: A serological association was found between ARMD and anti-C pneumoniae antibodies (P =.047) but not between ARMD and the anti-C trachomatis or anti-E coli heat shock protein antibodies. The association remained statistically significant after adjusting for age and smoking, both established risk factors for ARMD. CONCLUSIONS: These data indicate that C pneumoniae infection may be associated with ARMD. Further studies on larger cohorts of individuals are necessary to determine if this pathogen plays a role in the pathogenesis of ARMD.

Serum immunoglobulin G antibodies to chlamydial heat shock protein 60 but not to human and bacterial homologs are associated with coronary artery disease.

BACKGROUND: Evidence for an association between Chlamydia pneumoniae infection and coronary artery disease (CAD) has been reported by numerous studies, cross-reactive heat shock protein (Hsp) antibody responses have been causally linked to CAD, and the severity of chlamydial disease pathogenesis correlates with Hsp serology. Our aim was to determine if chlamydial Hsp (cHsp) antibody responses are predictive of CAD. METHODS AND RESULTS: Patients were recruited in a case-control study: 250 cases had angiographically significant CAD (stenosis > or =70%), and 250 controls had normal coronary arteries (stenosis <10%). Serum immunoglobulin G reactivity to Hsp10 and Hsp60 antigens (chlamydial, Escherichia coli, and human), and C pneumoniae whole organisms were measured by ELISA. Univariate analysis confirmed that classical CAD risk factors were predictors of CAD. Univariate analysis showed that cHsp60 (P= 0.001, OR 3.9), cHsp10 (P=0.045, OR 3.8), E coli Hsp60 (P=0.04, OR 1.5) and C pneumoniae (P=0.03, OR 1.8) ELISA optical density (OD) values were significantly different between cases and controls. Multivariate analysis found that only upper-quintile cHsp60 seroreactivity remained a significant predictor of CAD after controlling for classical CAD risk factors and seroreactivity to the other antigens (cHsp60 OD, P=0.005, OR 3.9 per OD unit; cHsp60 quintile, 5 versus 1 to 4; P=0.01, OR 2.1). CONCLUSIONS: The presence of elevated anti-cHsp60 immunoglobulin G antibodies, but not anti-human or anti-E coli homologs, was independently associated with CAD. This finding argues against previous suggestions that cross-reactive or autoimmune Hsp60 responses may contribute to disease progression. High anti-cHsp60 antibody response appears to identify the subset of patients with chlamydial infection and significant CAD.

Impact of host genetics on susceptibility to human Chlamydia trachomatis disease.

Evidence that host genetic factors play a major role in susceptibility or resistance to many infectious diseases is increasing, due to major advances in genetic epidemiological methodology. Recent human genome mapping information and the identification of a large number of candidate genes provide the tools for such studies. The information obtained is important for understanding the pathogenesis of disease and for the design of preventive and therapeutic strategies. In the study of Chlamydia trachomatis disease pathogenesis, much research focuses on how bacterial factors modulate the immune response and thus contribute to the disease process. It is likely, however, that host factors also play a role, and therefore susceptibility to disease is the result of an environmental effect set against a background of genetic factors. This review outlines the evidence for the contribution of host genetic factors to susceptibility to C. trachomatis disease in humans.