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.

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.

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.

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.

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.

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 ≥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.

Failure to detect HLA-A*6802-restricted CD8+ T cells specific for Chlamydia trachomatis antigens in subjects from trachoma-endemic communities

The role of HLA-A*6802-restricted CD8+ T cells in chlamydial disease was investigated in human ocular infections. Peptides with predicted binding motifs for HLA-A*6802 were synthesized using sequences based on chlamydial antigens, major outer membrane protein (MOMP), macrophage infectivity potentiator (MIP) and heat shock protein (hsp70). Peptides were pooled according to Chlamydia trachomatis protein type and serovar, and were tested in 51Cr-release cytotoxic T lymphocyte (CTL) and enzyme-linked immunospot (ELISPOT) assays, using peripheral blood mononuclear cells (PBMC) isolated from subjects living in trachoma-endemic communities in The Gambia. Significant CTL activity or interferon-gamma release was not detected in any of the subjects, suggesting either that HLA-A*6802 CD8+ T cells may not be important in ocular infections or that the peptides chosen did not represent epitopes.

Polymorphisms in candidate genes and risk of scarring trachoma in a Chlamydia trachomatis--endemic population

Genes involved in regulating antimicrobial immunity and inflammation may modulate the risk of tissue scarring and fibrosis in chlamydial diseases such as trachoma. By use of a large case-control study of scarring trachoma in The Gambia, the importance of single-nucleotide polymorphisms in several candidate genes was investigated. Overall, no significant differences were found between patients and control subjects in genotype frequencies for polymorphisms in cytokine promoters interleukin (IL)-10 (positions -1082, -819, -592), IL-4 (-590), or tumor necrosis factor-alpha (-376) or for codon 57 of the mannose-binding protein. Among the ethnic groups in the study, Mandinkas had the highest frequency of the IL-10-1082G allele (0.36). Within this ethnic group, the IL-10-1082G homozygote genotype was significantly more common among case patients than control subjects (odds ratio, 5.10; 95% confidence interval, 1.24-24.2; P=.009). This single association is consistent with data indicating that the IL-10-1082G allele is associated with higher levels of IL-10 transcription and that Th2-type immune responses are associated with risk of chlamydial disease.

Transmission ecology of the fly Musca sorbens, a putative vector of trachoma

Recent evidence suggests that eye-seeking flies are important trachoma vectors. We conducted a series of investigations to identify which species of synanthropic flies are potential vector(s) of this blinding disease in The Gambia. Several species of fly were caught in fish-baited attractant traps placed in villages throughout the year (1997/98) but only 2 species, Musca sorbens and M. domestica, were caught from the eyes of children. M. sorbens comprised < 10% of the total number of flies caught with attractant traps but was responsible for > 90% of fly-eye contacts, the remainder were made by M. domestica. All fly species were more numerous in the wet season than the dry season. Eyes of young children are considered to be the main reservoir of Chlamydia trachomatis, the causative agent of trachoma. Collections of eye-seeking flies from children showed frequent fly-eye contacts (median [interquartile range], 3 [1.5-7] every 15 min). Children with potentially infective ocular or nasal discharge had twice as many fly-eye contacts than children with no discharge (P < 0.001). There was no difference in exposure to fly-eye contacts if a child sat inside or outside a house (P = 0.273). Female flies were more commonly caught from eyes than male (P < 0.001). The presence of Chlamydia DNA was demonstrated by PCR on 2 of 395 flies caught from the eyes of children with a current active trachoma infection. Both positive flies were M. sorbens, one male and the other female. Further elucidation of M. sorbens behavioural ecology and the development of sustainable strategies to control these flies should be a priority. It is likely that M. sorbens is the principal insect vector of trachoma in The Gambia.

Characterization of B-cell responses to Chlamydia trachomatis antigens in humans with trachoma

The circulating B-cell responses to Chlamydia trachomatis of 60 children and 34 adults in The Gambia were characterized in a cross-sectional study of different grades of trachoma, using the enzyme-linked immunospot (ELISPOT) assay. Antibody-secreting cells (ASCs) specific to chlamydial major outer membrane protein (MOMP), heat shock protein 60, and whole elementary bodies were detected in children with no evidence of ocular disease, and the immunoglobulin (IgA) response was significantly increased in those with follicular trachoma. In marked contrast, children with the most intense ocular inflammation paradoxically had an almost completely absent B-cell response of all isotypes and to all chlamydial antigens, but with normal serum IgG and IgA responses, which was even lower than in the group with no ocular inflammation. Adults with or without evidence of trachomatous scarring had equivalent numbers of circulating B cells, principally IgA, to all chlamydial antigens. Plasmablasts secreting antibodies to MOMP were present in the urine of children in the absence of urogenital infection detectable by PCR, and relative numbers were 8 to 25 times higher than in blood, suggesting site-specific homing within a common mucosal immune system. These results suggest that ELISPOT assay of ongoing B-cell responses detects suppression of chlamydia-specific IgA ASCs during the proinflammatory response to ocular chlamydial infection seen in intense trachoma, which may play a role in tissue damage leading to trachomatous scarring.

Scarring trachoma is associated with polymorphism in the tumor necrosis factor alpha (TNF-alpha) gene promoter and with elevated TNF-alpha levels in tear fluid

Tumor necrosis factor alpha (TNF-alpha) may play a central role in the disease pathogenesis which occurs as a consequence of chlamydial infection. To investigate the importance of TNF-alpha gene promoter polymorphisms and TNF-alpha levels in tear fluid in scarring trachoma, a large matched-pair case-control study was performed in The Gambia. The -308A allele was present in a higher proportion of patients (28.4%) than controls (18.4%), with an increasing association for homozygotes (chi2 for trend, P = 0.032; allele frequency, 0.163 in patients and 0.099 in controls; chi2, P = 0.025). For the -238A allele, the association was similar but not significant. The disease association was highly significant when the number of either -308A or -238A sites in an individual was considered (P = 0.003). TNF-alpha promoter alleles are tightly linked to some HLA class I and II alleles, but multivariate analysis confirmed that the disease associations were independent of HLA, although a class I allele, A*6802, is also associated with disease. TNF-alpha was more frequently detected in tear samples from patients (27.6%) than from controls (15.9%), increasingly so for higher levels of detectable TNF-alpha (P = 0.015). Among patients, detectable TNF-alpha in tears was highly associated with the presence of ocular chlamydial infection (P < 0.001). The results indicate that TNF-alpha plays a major role in the tissue damage and scarring which occurs as a consequence of Chlamydia trachomatis infection.