Vertebrate host protective immunity drives genetic diversity and antigenic polymorphism in Schistosoma mansoni.

Schistosomes are gonochoric blood parasites with a complex life cycle responsible for a disease of considerable medical and veterinary importance in tropical and subtropical regions. Understanding the evolution of schistosome genetic diversity is clearly of fundamental importance to interpreting schistosomiasis epidemiology and disease transmission patterns of this parasite. In this article, we investigated the putative role of the host immune system in the selection of male genetic diversity. We demonstrated the link between genetic dissimilarity and the protective effect among male worms. We then compared the proteomes of three male clones with different genotypes and differing by their capacity to protect against reinfection. The identified differences correspond mainly to antigens known or supposed to be involved in the induction of protective immunity. These results underline the role played by host immune system in the selection of schistosome genetic diversity that is linked to antigenic diversity. We discuss the evolutionary consequences in the context of schistosome infection.

Changes in brain morphology in patients with obstructive sleep apnoea.

BACKGROUND: Obstructive sleep apnoea (OSA) is a common disease that leads to daytime sleepiness and cognitive impairment. Attempts to investigate changes in brain morphology that may underlie these impairments have led to conflicting conclusions. This study was undertaken to aim to resolve this confusion, and determine whether OSA is associated with changes in brain morphology in a large group of patients with OSA, using improved voxel-based morphometry analysis, an automated unbiased method of detecting local changes in brain structure. METHODS: 60 patients with OSA (mean apnoea hypopnoea index 55 (95% CI 48 to 62) events/h, 3 women) and 60 non-apnoeic controls (mean apnoea hypopnoea index 4 (95% CI 3 to 5) events/h, 5 women) were studied. Subjects were imaged using T1-weighted 3-D structural MRI (69 subjects at 1.5 T, 51 subjects at 3 T). Differences in grey matter were investigated in the two groups, controlling for age, sex, site and intracranial volume. Dedicated cerebellar analysis was performed on a subset of 108 scans using a spatially unbiased infratentorial template. RESULTS: Patients with OSA had a reduction in grey matter volume in the right middle temporal gyrus compared with non-apnoeic controls (p<0.05, corrected for topological false discovery rate across the entire brain). A reduction in grey matter was also seen within the cerebellum, maximal in the left lobe VIIIb close to XI, extending across the midline into the right lobe. CONCLUSION: These data show that OSA is associated with focal loss of grey matter that could contribute to cognitive decline. Specifically, lesions in the cerebellum may result in both motor dysfunction and working memory deficits, with downstream negative consequences on tasks such as driving.

The feasibility of using auto-titrating continuous positive airway pressure to treat obstructive sleep apnoea after acute tetraplegia.

STUDY DESIGN: A prospective cohort with acute tetraplegia. OBJECTIVES: Obstructive sleep apnoea (OSA) is common within weeks of tetraplegia. This study aimed at determining the feasibility of auto-titrating continuous positive airway pressure (CPAP) to treat OSA after acute tetraplegia. SETTING: The Victorian Spinal Cord Service, Melbourne, Australia. METHODS: Participants underwent full, portable polysomnography. Those with an apnoea hypopnoea index of more than 10 events per hour were defined as having OSA and were offered treatment with CPAP. Treatment adherence was objectively monitored, and measures of quality of life, sleepiness and functional outcomes were determined at enrollment and 3 months later at study conclusion. RESULTS: A total of 44 patients were admitted to our Spinal Cord Service over 9 months, and 19 participated. Fourteen of them had OSA and seven were adherent with therapy for 3 months. Compared with those who did not have OSA, and with those with OSA who were not adherent with CPAP, those who adhered to CPAP were older (mean (s.d.) age 54 years (13) versus non-adherent 28 years (15) and no OSA 29 years (10)) and heavier (body mass index (BMI) 32.5 (11.7), 24.1 (3.7) and 20.6 (3.1), respectively). CPAP-adherant patients and those without OSA showed a 50% or greater improvement in their state sleepiness over the 3 months. Patients with OSA who did not tolerate CPAP had no improvement in sleepiness. CONCLUSION: Auto-titrating CPAP is a feasible treatment for OSA in acute tetraplegia. Intensive clinical support was required initially, and a tolerance of therapy for at least 4 h for one of the first 3 days was predictive of good CPAP usage. SPONSORSHIP: Transport Accident Commission.

Nocturnal non-invasive nasal ventilation in stable hypercapnic COPD: a randomised controlled trial.

BACKGROUND: Sleep hypoventilation has been proposed as a cause of progressive hypercapnic respiratory failure and death in patients with severe chronic obstructive pulmonary disease (COPD). A study was undertaken to determine the effects of nocturnal non-invasive bi-level pressure support ventilation (NIV) on survival, lung function and quality of life in patients with severe hypercapnic COPD. METHOD: A multicentre, open-label, randomised controlled trial of NIV plus long-term oxygen therapy (LTOT) versus LTOT alone was performed in four Australian University Hospital sleep/respiratory medicine departments in patients with severe stable smoking-related COPD (forced expiratory volume in 1 s (FEV1.0) <1.5 litres or <50% predicted and ratio of FEV1.0 to forced vital capacity (FVC) <60% with awake arterial carbon dioxide tension (PaCO2) >46 mm Hg and on LTOT for at least 3 months) and age <80 years. Patients with sleep apnoea (apnoea-hypopnoea index >20/h) or morbid obesity (body mass index >40) were excluded. Outcome measures were survival, spirometry, arterial blood gases, polysomnography, general and disease-specific quality of life and mood. RESULTS: 144 patients were randomised (72 to NIV + LTOT and 72 to LTOT alone). NIV improved sleep quality and sleep-related hypercapnia acutely, and patients complied well with therapy (mean (SD) nightly use 4.5 (3.2) h). Compared with LTOT alone, NIV (mean follow-up 2.21 years, range 0.01-5.59) showed an improvement in survival with the adjusted but not the unadjusted Cox model (adjusted hazard ratio (HR) 0.63, 95% CI 0.40 to 0.99, p = 0.045; unadjusted HR 0.82, 95% CI 0.53 to 1.25, p = NS). FEV1.0 and PaCO2 measured at 6 and 12 months were not different between groups. Patients assigned to NIV + LTOT had reduced general and mental health and vigour. CONCLUSIONS: Nocturnal NIV in stable oxygen-dependent patients with hypercapnic COPD may improve survival, but this appears to be at the cost of worsening quality of life. TRIAL REGISTRATION NUMBER: ACTRN12605000205639.

Continuous positive airway pressure reduces daytime sleepiness in mild to moderate obstructive sleep apnoea: a meta-analysis.

BACKGROUND: Obstructive sleep apnoea syndrome (OSAS) affects an estimated 2-4% of the middle aged population. Meta-analyses of randomised controlled trials have shown that the severe presentation of the syndrome (apnoea hypopnoea index (AHI) >30/hour) is effectively treated with continuous positive airway pressure (CPAP). Until recently there have been insufficient data to determine whether CPAP improves sleepiness in the larger subgroup with mild to moderate OSAS (AHI 5-30/hour). METHODS: A systematic search of Medline and a hand search identified seven randomised controlled trials where CPAP was compared with either a placebo or with conservative management in the treatment of mild to moderate OSAS (AHI 5-30/hour). All trials used the Epworth Sleepiness Scale (ESS), four used the Multiple Sleep Latency Test (MSLT), and three used the Maintenance of Wakefulness Test (MWT) to measure sleepiness. RESULTS: Meta-analyses indicated that CPAP significantly reduced subjective daytime sleepiness (ESS) by 1.2 points (95% CI 0.5 to 1.9, p = 0.001), improved objective daytime wakefulness (MWT) by 2.1 minutes (95% CI 0.5 to 3.7, p = 0.011), but did not affect objective daytime sleepiness (MSLT, mean benefit -0.2 minutes, 95% CI -1.0 to 0.6, p = 0.6). The two significant effects were small (effect size <0.30). CONCLUSIONS: CPAP elicits small improvements in subjective sleepiness and objective wakefulness in people with mild to moderate OSAS. However, the effects on sleepiness are of limited clinical significance.

A conserved retinoid X receptor (RXR) from the mollusk Biomphalaria glabrata transactivates transcription in the presence of retinoids.

Retinoid X receptors (RXR) are members of the nuclear receptor superfamily of ligand-activated transcription factors that have been characterized in a wide variety of metazoan phyla. They act as heterodimer partners of other nuclear receptors, and in vertebrates also activate transcription as homodimers in the presence of a ligand, 9-cis retinoic acid. In order to test the hypothesis that retinoic acid signaling pathways involving RXRs are present in the Lophotrochozoa, we have sought to isolate conserved members of this family from the platyhelminth parasite Schistosoma mansoni and its intermediate host, the mollusk Biomphalaria glabrata. Here we report that an RXR ortholog from B. glabrata (BgRXR) is better conserved, compared with mouse RXRalpha, both in the DNA-binding domain (89% identity) and in the ligand-binding domain (LBD) (81% identity), than are arthropod homologs. In EMSA, BgRXR binds to the direct repeat response element DR1 as a homodimer or as a heterodimer with mammalian RARalpha, LXR, FXR or PPARalpha. When transfected alone into mammalian cell lines, BgRXR transactivated transcription of a reporter gene from the Apo-A1 promoter in the presence of 9-cis retinoic acid or DHA. Constructs with the Gal4 DNA binding domain fused to the hinge and LBDs of BgRXR were used to show that ligand-dependent activation of transcription by BgRXR required its intact AF-2 activation domain, and that the LBD can form homodimers. Finally, the binding of 9-cis retinoic acid preferentially protected the LBD of BgRXR from degradation by trypsin in a proteolysis protection assay. Our results show that BgRXR binds and is activated by retinoids and suggest that retinoid signaling pathways are conserved in the Lophotrochozoa. The nucleotide sequence reported in this paper has been submitted to the GenBank/EBI Data Bank with accession no. AY048663.

Sleep hypoventilation in hypercapnic chronic obstructive pulmonary disease: prevalence and associated factors.

Sleep hypoventilation (SH) may be important in the development of hypercapnic respiratory failure in chronic obstructive pulmonary disease (COPD). The prevalence of SH, associated factors, and overnight changes in waking arterial blood gases (ABG), were assessed in 54 stable hypercapnic COPD patients without concomitant sleep apnoea or morbid obesity. Lung function assessment, anthropomorphic measurements, and polysomnography with ABG measurement before and after sleep were conducted in all patients. Transcutaneous carbon dioxide tension (Pt,CO2) was measured in sleep, using simultaneous arterial carbon dioxide tension (Pa,CO2) for in vivo calibration and to correct for drift in the sensor. Of the patients, 43% spent > or = 20% of sleep time with Pt,CO2 > 1.33 kPa (10 mmHg) above waking baseline. Severity of SH was best predicted by a combination of baseline Pa,CO2, body mass index and per cent rapid-eye movement (REM) sleep. REM-related hypoventilation correlated significantly with severity of inspiratory flow limitation in REM, and with apnoea/hypopnoea index. Pa,CO2 increased mean+/-SD 0.70+/-0.65 kPa (5.29+/-4.92 mmHg) from night to morning, and this change was highly significant. The change in Pa,CO2 was strongly correlated with severity of SH. Sleep hypoventilation is common in hypercapnic chronic obstructive pulmonary disease, and related to baseline arterial carbon dioxide tension, body mass index and indices of upper airway obstruction. Sleep hypoventilation is associated with significant increases in arterial carbon dioxide tension night-to-morning, and may contribute to long-term elevations in arterial carbon dioxide tension.

The Victorian CPAP program: is there a need for additional education and support?

BACKGROUND: The Victorian Continuous Positive Airways Pressure (CPAP) Program provides CPAP services to financially disadvantaged individuals with moderate to severe sleep apnoea. AIMS: To evaluate health outcomes in patients referred to the pilot program in order to: (i) assess the magnitude of health benefit from treatment in this highly selected population and (ii) identify patient characteristics or factors related to service provision that may influence outcome. METHODS: We adopted a simple before-after research design. Patients who were referred to the program were recruited from five sleep centres. Questionnaires were administered at baseline and 1 and 3 months after commencing CPAP. Generic and disease-specific quality of life were assessed using the MOS 36-Item Short-form Health Survey and the Sleep Apnoea Quality-of-life Index, respectively. Subjective daytime sleepiness was measured using the Epworth Sleepiness Scale and the Sleep-Wake Activity Inventory. RESULTS: Of the 68 subjects enrolled in the study, 59 were available for follow up. There were significant improvements in daytime sleepiness (P < 0.0005). Treatment-related symptoms had a negative impact on overall disease-specific quality of life, however there were significant improvements in all other domains of disease-specific quality of life (P < 0.0005). Improvements in generic quality of life were small but statistically significant (P < 0.05). Hospital, disease severity, baseline sleepiness, gender and CPAP-machine type were not predictors of outcome (P > 0.05). CONCLUSION: This review of the Victorian CPAP Program identified significant improvements in subjective daytime sleepiness and quality of life, despite the negative impact of treatment-related symptoms. Future research should explore whether services can be modified to help reduce the impact of treatment-related side-effects.

Measurement variability in sleep disorders medicine: the Victorian experience.

BACKGROUND: Surveys of laboratories in North America have documented significant diversity in the working definitions used for reporting respiratory events in sleep studies. AIM: To assess sources of variability in the measurement of sleep-disordered breathing (as defined by the Apnoea-Hypopnoea Index) between sleep laboratories in Victoria, Australia. METHODS: A self-complete written questionnaire was constructed following literature review and interviews with staff at three separate sleep laboratories. The survey was sent to all laboratories listed in Victoria by the Australasian Sleep Association. The first part of the survey related to the type of equipment used to record sleep and other variables during overnight polysomnography and the second part related to the definitions and methods used to report results. RESULTS: Seventeen out of 18 laboratories returned the surveys. There were variations identified in the types of sensors used to measure particular signals. There were also inconsistencies identified in the criteria used to score arousals, apnoeas and hypopnoeas by different laboratories. The variability was greatest for hypopnoea definitions. CONCLUSIONS: There is considerable variation in the methods used to measure and define sleep-disordered breathing between sleep laboratories in Victoria. The extent to which these variations influence the comparability of reported results between laboratories requires further evaluation. The survey findings may assist the process of developing and implementing local guidelines for the performance and reporting of polysomnography.

Impact of different criteria for defining hypopneas in the apnea-hypopnea index.

OBJECTIVES: To explore the effect of using different scoring criteria for hypopneas in the scoring of polysomnographic studies: (1) by estimating the level of agreement between apnea-hypopnea index (AHI) scores derived from different scoring methods, and (2) by examining the effect on the point prevalence of disease using different threshold values of the AHI. DESIGN: Retrospective analysis of 48 diagnostic polysomnographic records. SETTING: Tertiary-hospital sleep-disorders clinic. MEASUREMENTS: AHIs were derived from three different methods for scoring hypopneas. The hypopnea definitions used incorporated different combinations and threshold values of respiratory signal changes in addition to differences in the requirement for associated oxygen desaturation or arousal. The level of agreement between different scoring methods was assessed by constructing Bland-Altman plots and calculating intraclass correlation coefficients (ICCs). kappa statistics were used to assess agreement between the different methods using varying thresholds of AHI to categorize sleep apnea (AHI > 5, AHI > 15, and AHI > 20). RESULTS: The random-effects ICC for the three methods was 0.89, suggesting that the different scoring methods tended to rank patients fairly consistently. However, the point prevalence of disease estimated by using different thresholds of AHI was found to vary depending on the method used to score sleep studies (kappa, 0.30 to 0.95). CONCLUSIONS: These findings have implications for case finding, population-prevalence estimates, and grading of disease severity for access to government-funded continuous positive airway pressure services. Guidelines for standardizing the measurement and reporting of sleep studies in clinical practice should be implemented.

Hormones and nuclear receptors in schistosome development.

A substantial but disparate body of evidence suggests that hormones affect the development of schistosomes within their definitive hosts. Here, Raymond Pierce and colleagues review such evidence for host steroid and thyroid hormones, and for ecdysteroids, and link this to the expanding knowledge of the nuclear receptors for these hormones. Phylogenetic analysis of the nuclear receptor superfamily and the characterization of the first schistosome nuclear receptors suggest that steroids and thyroid hormone probably act indirectly, or by pathways not involving the control of gene transcription. However, the probability that schistosome nuclear receptors exist for a variety of unique ligands opens up exciting possibilities for targeted drug development.

Structural and functional divergence of a nuclear receptor of the RXR family from the trematode parasite Schistosoma mansoni.

We describe the cloning and functional characterization of Schistosoma mansoni retinoid-X-receptor (SmRXR; NR2B4-B), a novel member of the nuclear receptor superfamily from S. mansoni, a homologue of vertebrate retinoid-X-receptor. The DNA-binding C domain of SmRXR shows 80% sequence identity to both human RXRalpha and Drosophila ultraspiracle (USP), but a much lower level of conservation of the ligand-binding E domain (22-25% identity). Phylogenetic analysis places SmRXR within the RXR group as an early offshoot of this clade. SmRXR mRNA is expressed at all life-cycle stages but at higher levels in the free-living larval stages. However, the SmRXR protein is expressed at markedly different levels, being almost absent from eggs while present at the highest concentration in schistosomula. Recombinant SmRXR fails to bind to the consensus direct repeat response elements, either alone, or as a heterodimer with mouse retinoic acid receptor alpha or the Drosophila ecdysone receptor. However, the use of chimaeric constructions shows that the C domain of SmRXR will bind to conventional response elements as a heterodimer, and that its specificity is modified by the presence of the D and E domains. In accordance with these results, native SmRXR failed to transactivate the transcription of a reporter gene after cotransfection of mammalian cell lines.

Construction and characterization of a Schistosoma mansoni bacterial artificial chromosome library.

A bacterial artificial chromosome (BAC) library has been established from genomic DNA isolated from the trematode parasite of human, Schistosoma mansoni. This library consists of more than 21,000 recombinant clones carrying inserts in the pBeloBAC11 vector. The mean insert size was 100 kb, representing an approximate 7.95-fold genome coverage. Library screening with eight chromosome-specific or single-copy gene probes yielded between 1 and 9 positive clones, and none of those tested was absent from the library. End sequences were obtained for 93 randomly selected clones, and 37 showed sequence identity to S. mansoni sequences (ESTs, genes, or repetitive sequences). A preliminary analysis by fluorescence in situ hybridization localized 8 clones on schistosome chromosomes 1 (2 clones), 2, 3, 5, Z, and W (3 clones). This library provides a new resource for the physical mapping and sequencing of the genome of this important human pathogen.

Tetanus toxin fragment C expressed in live Salmonella vaccines enhances antibody responses to its fusion partner Schistosoma haematobium glutathione S-transferase.

Tetanus toxoid has been used widely as an adjuvant. The atoxic fragment C from tetanus toxin (TetC) is potently immunogenic when expressed in Salmonella vaccine strains and has been used as a fusion partner for antigens (Ag). However, there has been no formal comparison of the immunomodulatory impact of TetC on its fusion partners. In this study, we have addressed this important issue. The protective 28-kDa glutathione S-transferase (GST) from Schistosoma haematobium (Sh28GST) was expressed either as a fusion to TetC or as the full-length Sh28GST alone in a nonvirulent aroA-attenuated strain of Salmonella enterica serovar Typhimurium. The Sh28GST proteins were soluble and stably expressed in Salmonella, as evaluated by Western blotting with TetC and/or Sh28GST antisera. Mice were immunized orally with a single dose of the live recombinant Salmonella. The constructs were stable in mice but, dramatically, only the strain expressing the TetC-Sh28GST fusion elicited significant antibody (Ab) responses directed against Sh28GST as determined by enzyme-linked immunosorbent assay. An analysis of the isotype profiles showed that these mice also produced anti-Sh28GST immunoglobulin A and GST-neutralizing assays revealed high levels of neutralizing Abs in sera. These are important correlates of protection in schistosomiasis. In addition, stimulation of spleen cells from immunized mice with Sh28GST Ag showed that both strains, expressing Sh28GST alone or the TetC-Sh28GST fusion, were able to stimulate the secretion of Th1-related cytokines (gamma interferon and interleukin 2) to comparable levels. Thus, TetC has modulated the immune responses generated against its fusion partner, Sh28GST, by markedly enhancing the Ab responses elicited. These results have important implications in the rational development of live vaccines.

Flow-volume curve changes in patients with obstructive sleep apnoea and brief upper airway dysfunction.

OBJECTIVE: Patients with obstructive sleep apnoea (OSA) and those with brief upper airway dysfunction (BUAD) have been reported to have abnormalities of maximal flow-volume curves. This study was designed to assess the ability of flow-volume curves to predict the presence of OSA or BUAD. METHODOLOGY: Four maximal flow-volume manoeuvres performed by 33 OSA patients and 16 BUAD patients were compared with those of 36 normal subjects. Flow-volume indices, their variability, saw-toothing in the curve and an algorithm based on the flow ratios and shape of the curves were assessed. RESULTS: When the confounding factors, body mass index (BMI), age, gender and smoking status were taken into account, there was no significant difference in a variety of indices derived from the flow-volume curves between OSA and normal subjects. No BUAD patient had normal flow-volume curves as determined with the algorithm. After BMI, age, gender and smoking status were accounted for, decreased forced expiratory volume in 1 s (FEV1), and increased variability of peak expiratory flow (PEF)/peak inspiratory flow (PIF) and FEV1/PEF remained significantly associated with BUAD. CONCLUSIONS: These findings suggest that flow-volume curve indices have no value in predicting OSA. Some abnormalities are found in patients with BUAD; a normal flow-volume curve makes the diagnosis of BUAD unlikely.

Upper airway function and dysfunction in respiration.

1. The upper airway not only provides a passage for air to be breathed in and out of the lungs, but it also heats, humidifies and filters the air and is involved in cough, swallowing and speech. 2. The complex muscle structure of the upper airway that produces speech and swallowing in humans also modulates respiratory airflow throughout the respiratory cycle, but is vulnerable to functional problems that may compromise respiration. 3. Even in normals, there is some collapse of the upper airway and increased upper airway resistance during sleep. 4. A substantial proportion of people suffer from obstructive sleep apnoea, in which the collapse of the upper airway is so great that respiration is compromised to the extent that arousal from sleep is required to restore adequate ventilation; the resulting disturbed sleep and hypoxia produce daytime sleepiness and neuropsychological and cardiorespiratory morbidity. 5. Functional abnormalities of the larynx can also occur, including prolonged inspiratory laryngeal dysfunction, brief upper airway dysfunction and expiratory laryngeal dysfunction or factitious asthma.

Vaccine potential of a recombinant glutathione S-transferase cloned from Schistosoma haematobium in primates experimentally infected with an homologous challenge.

Patas monkeys were twice immunized with a Schistosoma haematobium-derived recombinant glutathione S-transferase (Sh28GST) then challenged with an homologous calibrated challenge. BCG and Freund's Complete Adjuvant (FCA) were used as adjuvants in two distinct protocols. Specific IgG and IgA antibody responses were intense and homogeneous in the animals receiving Sh28GST in the presence of FCA, whereas BCG could only induce moderate and heterogeneous antibody titres. No significant effect on worm burdens was evidenced 36 weeks post-infection in either group of Sh28GST-immunized animals compared to their matched controls receiving an irrelevant protein. Although not significant, 50% reductions in the numbers of eggs located in all tissues (FCA group) and in the urogenital system (BCG group) were noted. Moreover, the total number of excreted eggs was dramatically diminished by 60% and 77% in the BCG and FCA groups, respectively. These reductions reached 75% and 80% in the urines of vaccinated monkeys. Bladder pathology was also reduced in the animals displaying the lowest urinary egg excretions. There was no clear positive or negative correlate between antibody responses and individual levels of protection. Taken as a whole, our results show that Sh28GST was capable of significantly reducing S. haematobium worm fecundity in experimentally infected primates. Although FCA induced higher levels of protection, the efficacy of BCG as an adjuvant appeared sufficient to justify consideration of the future application of this new formulation as a vaccine against human urogenital schistosomosis.