Characterization of the public transit air microbiome and resistome reveals geographical specificity.

BACKGROUND: The public transit is a built environment with high occupant density across the globe, and identifying factors shaping public transit air microbiomes will help design strategies to minimize the transmission of pathogens. However, the majority of microbiome works dedicated to the public transit air are limited to amplicon sequencing, and our knowledge regarding the functional potentials and the repertoire of resistance genes (i.e. resistome) is limited. Furthermore, current air microbiome investigations on public transit systems are focused on single cities, and a multi-city assessment of the public transit air microbiome will allow a greater understanding of whether and how broad environmental, building, and anthropogenic factors shape the public transit air microbiome in an international scale. Therefore, in this study, the public transit air microbiomes and resistomes of six cities across three continents (Denver, Hong Kong, London, New York City, Oslo, Stockholm) were characterized. RESULTS: City was the sole factor associated with public transit air microbiome differences, with diverse taxa identified as drivers for geography-associated functional potentials, concomitant with geographical differences in species- and strain-level inferred growth profiles. Related bacterial strains differed among cities in genes encoding resistance, transposase, and other functions. Sourcetracking estimated that human skin, soil, and wastewater were major presumptive resistome sources of public transit air, and adjacent public transit surfaces may also be considered presumptive sources. Large proportions of detected resistance genes were co-located with mobile genetic elements including plasmids. Biosynthetic gene clusters and city-unique coding sequences were found in the metagenome-assembled genomes. CONCLUSIONS: Overall, geographical specificity transcends multiple aspects of the public transit air microbiome, and future efforts on a global scale are warranted to increase our understanding of factors shaping the microbiome of this unique built environment.

Prospective evaluation of quality of life in children treated in UKALL 2003 for acute lymphoblastic leukaemia: A cohort study.

BACKGROUND: Health-related quality of life (HRQoL) from diagnosis until end of treatment for children with acute lymphoblastic leukaemia was investigated, examining effects of age, gender, risk-stratified treatment regimen, and therapy intensity (one vs. two 'delayed intensifications' [DIs]). METHOD: In a multi-centre prospective study, parents reported their child's generic and disease-specific HRQoL and their own care-giving burden at five time points. From 1,428 eligible patients, 874 parents completed questionnaires at least once during treatment. RESULTS: At each time point, generic HRQoL was significantly lower than equivalent norm scores for healthy children. HRQoL decreased significantly at the start of treatment, before recovering gradually (but remained below pre-treatment levels). Parents reported that older children worried more about side effects and their appearance, but showed less procedural anxiety than younger children. Concern for appearance was greater among girls than boys. Compared to Regimen B (i.e. additional doxorubicin during induction and additional cyclophosphamide and cytarabine during consolidation chemotherapy), patients receiving Regimen A had fewer problems with pain and nausea. There were no statistically significant differences in HRQoL by number of DI blocks received. INTERPRETATION: HRQoL is compromised at all stages of treatment, and is partly dependent on age. The findings increase understanding of the impact of therapy on children's HRQoL and parental care-giving burden, and will contribute to the design of future trials.

Burden of illness in systemic lupus erythematosus: results from a UK patient and carer online survey.

Objective The objective of this study was to assess the impact of systemic lupus erythematosus (SLE) on patients and carers. Methods Adults with SLE and carers of SLE patients completed a UK-specific online survey covering many aspects of the disease. Surveys were developed in collaboration with an NHS lupus unit and a lupus patient organization. Results A total of 121 patients and 31 carers completed the surveys. Of the 70% of patients initially misdiagnosed with another condition, 59% received treatment for the misdiagnosis. Fatigue was the most debilitating symptom, experienced daily by 79% of patients. The proportion of patients not reporting flares to healthcare providers varied with flare severity: mild flares (43%), moderate flares (15%) and severe flares (5%). Most patients (89%) reported reduced ability to socialize, and 76% had changed employment; of these, 52% stopped working completely. Over one-half (52%) of carers in paid employment missed time from work, and 55% of carers reported a worsened financial status. Most carers (87%) experienced interference with social activities. Conclusion SLE is commonly misdiagnosed and has a considerable impact on the physical, social and financial status of patients and carers. Increased awareness of the disease among healthcare providers and employers of patients and their carers is needed.

High hyperdiploidy among adolescents and adults with acute lymphoblastic leukaemia (ALL): cytogenetic features, clinical characteristics and outcome.

High hyperdiploidy (HeH, 51-65 chromosomes) is an established genetic subtype of acute lymphoblastic leukaemia (ALL). The clinical and cytogenetic features as well as outcome of HeH among adolescents and adults have not been thoroughly investigated. Among 1232 B-cell precursor ALL patients (15-65 years) treated in the UKALLXII/ECOG2993 trial, 160 (13%) had a HeH karyotype, including 80 patients aged >24 years. The frequency of HeH was the same in Philadelphia chromosome (Ph)-positive and -negative cases, but Ph-positive patients were older. The cytogenetic profiles of Ph-positive and Ph-negative HeH cases were similar, although trisomy 2 was strongly associated with Ph-positive HeH. Overall, Ph-positive HeH patients did not have an inferior overall survival compared with Ph-negative patients (P=0.2: 50 vs 57% at 5 years). Trisomy of chromosome 4 was associated with a superior outcome in Ph-negative patients, whereas +5 and +20 were associated with an inferior outcome in Ph-positive and Ph-negative patients, respectively. All three markers retained significance in multivariate analysis adjusting for age and white cell count: hazard ratio for risk of death 0.47 (95% CI: 0.27-0.84) (P=0.01), 3.73 (1.51-9.21) (P=0.004) and 2.63 (1.25-5.54) (P=0.01), respectively. In conclusion, HeH is an important subtype of ALL at all ages and displays outcome heterogeneity according to chromosomal gain.

Proteomic analysis reveals differentially expressed proteins in macrophages infected with Leishmania amazonensis or Leishmania major.

CBA macrophages effectively control Leishmania major infection, yet are permissive to Leishmania amazonensis. Employing a transcriptomic approach, we previously showed the up-regulation of the genes involved in the classical pathway of macrophage activation in resistant mice. However, microarray analyses do not evaluate changes in gene expression that occur after translation. To circumvent this analytical limitation, we employed a proteomics approach to increase our understanding of the modulations that occur during infection and identify novel targets for the control of Leishmania infection. To identify proteins whose expression changes in CBA macrophages infected with L. major or L. amazonensis, protein extracts were obtained and digested and the peptides were characterized using multi-dimensional liquid chromatography coupled with tandem mass spectrometry analyses. A total of 162 proteins were selected as potentially modulated. Using biological network analyses, these proteins were classified as primarily involved in cellular metabolism and grouped into cellular development biological networks. This study is the first to use a proteomics approach to describe the protein modulations involved in cellular metabolism during the initial events of Leishmania-macrophage interaction. Based on these findings, we hypothesize that these differentially expressed proteins likely play a pivotal role in determining the course of infection.

Incidence of Vibrio vulnificus in estuarine waters of the south Texas Coastal Bend region.

AIMS: To determine the occurrence of the human pathogen, Vibrio vulnificus, in south Texas coastal waters. METHODS AND RESULTS: Coastal waters were sampled monthly between August 2006 and July 2007. Water temperature, dissolved oxygen, pH, salinity, conductivity and turbidity were measured during each sampling event. Culture-based techniques utilizing Vibrio vulnificus agar (VVA) and membrane-Enterococcus indoxyl-beta-D-glucoside agar (mEI) were used to assess the occurrence and levels of V. vulnificus and the faecal contamination indicator group, enterococci, respectively. Vibrio vulnificus isolates were confirmed using colony-blot hybridization with the species-specific VVAP probe. Vibrio vulnificus was isolated at all sites throughout the year even when the water temperature dropped to 9.71 degrees C. Significant correlations were found between concentrations of V. vulnificus and the abiotic factors, water temperature (P = 0.002) and dissolved oxygen (P = 0.028), as well as between concentrations of V. vulnificus and enterococci (P < 0.001). CONCLUSIONS: This study demonstrated the year-round presence of V. vulnificus in coastal waters of south Texas. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings indicate that the potential for human exposure to the pathogen, V. vulnificus, exists throughout the year. It also suggests that routinely monitored data might be used to predict the occurrence of the pathogen.

The scavenger receptor MARCO is involved in Leishmania major infection by CBA/J macrophages.

CBA/J mice are resistant to Leishmania major infection but are permissive to L. amazonensis infection. In addition, CBA/J macrophages control L. major but not L. amazonensis infection in vitro. Phagocytosis by macrophages is known to determine the outcome of Leishmania infection. Pattern recognition receptors (PRR) adorning antigen presenting cell surfaces are known to coordinate the link between innate and adaptive immunity. The macrophage receptor with collagenous structure (MARCO) is a PRR that is preferably expressed by macrophages and is capable of binding Gram-positive and Gram-negative bacteria. No research on the role of MARCO in Leishmania-macrophage interactions has been reported. Here, we demonstrate, for the first time, that MARCO expression by CBA/J macrophages is increased in response to both in vitro and in vivo L. major infections, but not to L. amazonensis infection. In addition, a specific anti-MARCO monoclonal antibody reduced L. major infection of macrophages by 30%-40% in vitro. The draining lymph nodes of anti-MARCO-treated mice displayed a reduced presence of immunolabelled parasite and parasite antigens, as well as a reduced inflammatory response. These results support the hypothesis that MARCO has a role in macrophage infection by L. major in vitro as well as in vivo.

A disattenuated correlation estimate when variables are measured with error: illustration estimating cross-platform correlations.

Previous cross-platform reproducibility studies have compared consistency of intensities as well as consistency of fold changes across different platforms using Pearson's correlation coefficient. In this study, we propose the use of measurement error models for estimating gene-specific correlations. Additionally, gene-specific reliability estimates are shown to be useful in prioritizing clones for sequence verification rather than selecting clones using a simple random sample. The proposed 'disattenuated' correlation may prove useful in a wide variety of studies when both X and Y are measured with error, such as in confirmation studies of microarray gene expression values, wherein more reliable laboratory assays such as real-time polymerase chain reaction are used.

Peritonitis after percutaneous endoscopic gastrostomy and jejunostomy: where there is smoke, there may not be fire.

Extensive reviews have been published regarding complications arising from percutaneous enteral access and ways of managing them. However, few data are available regarding unnecessary clinical interventions resulting from misinterpretation of benign postprocedural findings. We present here three representative cases of negative surgical abdominal cavity explorations for presumed peritonitis after percutaneous endoscopic gastrojejunostomy and jejunostomy.

Efficacy and safety of cholesterol-lowering treatment: prospective meta-analysis of data from 90,056 participants in 14 randomised trials of statins.

BACKGROUND: Results of previous randomised trials have shown that interventions that lower LDL cholesterol concentrations can significantly reduce the incidence of coronary heart disease (CHD) and other major vascular events in a wide range of individuals. But each separate trial has limited power to assess particular outcomes or particular categories of participant. METHODS: A prospective meta-analysis of data from 90,056 individuals in 14 randomised trials of statins was done. Weighted estimates were obtained of effects on different clinical outcomes per 1.0 mmol/L reduction in LDL cholesterol. FINDINGS: During a mean of 5 years, there were 8186 deaths, 14,348 individuals had major vascular events, and 5103 developed cancer. Mean LDL cholesterol differences at 1 year ranged from 0.35 mmol/L to 1.77 mmol/L (mean 1.09) in these trials. There was a 12% proportional reduction in all-cause mortality per mmol/L reduction in LDL cholesterol (rate ratio [RR] 0.88, 95% CI 0.84-0.91; p<0.0001). This reflected a 19% reduction in coronary mortality (0.81, 0.76-0.85; p<0.0001), and non-significant reductions in non-coronary vascular mortality (0.93, 0.83-1.03; p=0.2) and non-vascular mortality (0.95, 0.90-1.01; p=0.1). There were corresponding reductions in myocardial infarction or coronary death (0.77, 0.74-0.80; p<0.0001), in the need for coronary revascularisation (0.76, 0.73-0.80; p<0.0001), in fatal or non-fatal stroke (0.83, 0.78-0.88; p<0.0001), and, combining these, of 21% in any such major vascular event (0.79, 0.77-0.81; p<0.0001). The proportional reduction in major vascular events differed significantly (p<0.0001) according to the absolute reduction in LDL cholesterol achieved, but not otherwise. These benefits were significant within the first year, but were greater in subsequent years. Taking all years together, the overall reduction of about one fifth per mmol/L LDL cholesterol reduction translated into 48 (95% CI 39-57) fewer participants having major vascular events per 1000 among those with pre-existing CHD at baseline, compared with 25 (19-31) per 1000 among participants with no such history. There was no evidence that statins increased the incidence of cancer overall (1.00, 0.95-1.06; p=0.9) or at any particular site. INTERPRETATION: Statin therapy can safely reduce the 5-year incidence of major coronary events, coronary revascularisation, and stroke by about one fifth per mmol/L reduction in LDL cholesterol, largely irrespective of the initial lipid profile or other presenting characteristics. The absolute benefit relates chiefly to an individual's absolute risk of such events and to the absolute reduction in LDL cholesterol achieved. These findings reinforce the need to consider prolonged statin treatment with substantial LDL cholesterol reductions in all patients at high risk of any type of major vascular event.

Longitudinal study of babies born to mothers enrolled in a preconception prospective pregnancy study: study design and methodology, New York State Angler cohort study.

Persistent environmental chemicals such as organochlorine pesticides and polychlorinated biphenyls (PCBs) have been associated with alterations in fetal development and child health including subtle differences in developmental status. Previous prospective studies have ascertained prenatal or postnatal exposures but none have been designed to assess exposures at critical windows including preconception. To address this gap, we followed infants born to mothers recruited prior to conception in the New York State Prospective Pregnancy Study to assess feasibility issues including acceptability of a relatively invasive study protocol during the child's first 2 years of life. Longitudinal measurements on health, development, and growth were obtained from 53 live-born infants; 49 families consented to standardized in-home neurodevelopmental and psychosocial evaluations at 12 and 24 months of age. Nineteen participating parents consented to the collection of blood from infants for lead thyroid and PCB levels. Despite the intensive data collection protocol over 2 years coupled with the mothers having completed an intensive prospective pregnancy protocol, we found parents readily open to continued participation in a longitudinal study involving their children. Suggestions for conducting in-home assessments include use of a consistent contact nurse, comprehensive parent-friendly developmental assessment tools with some interim assessment by parent report, and periodic team visits.

Adverse impact of bone marrow transplantation on quality of life in acute myeloid leukaemia patients; analysis of the UK Medical Research Council AML 10 Trial.

The increasing success of intensive consolidation chemotherapy (CCT) as an alternative to bone marrow transplant (BMT) in acute myeloid leukaemia (AML) necessitates comparison of the impact on quality of life (QoL) of these two treatment modalities. Most QoL studies following BMT involve small patient numbers and provide ambivalent results. The present study examines QoL in a large number of patients 1 year from the end of treatment within the United Kingdom Medical Research Council (UK MRC) AML10 trial of BMT versus CCT. Allogeneic-BMT (Allo-BMT) was observed to have an adverse impact on most QoL dimensions compared with Autologous-BMT (A-BMT) and CCT. More patients receiving BMT had mouth dryness problems and worse sexual and social relationships, professional and leisure activities than CCT patients. QoL in A-BMT patients was less impacted than Allo-BMT. Intention-to-treat analysis showed similar results. These results indicate that a reconsideration of treatment strategies is warranted, and that further, good prospective studies are needed to evaluate more clearly the effects of these treatments in long-term survivors.

Association of erosive hand osteoarthritis with a single nucleotide polymorphism on the gene encoding interleukin-1 beta.

OBJECTIVE: Certain forms of primary osteoarthritis (OA), particularly those affecting hand joints, have a genetic component. Recent studies have shown suggestive evidence that hand and knee OA are linked with the interleukin-1 (IL-1) region on human chromosome 2q. This study was undertaken to assess the association of primary OA of the hand (hand OA) with IL-1 region markers. METHODS: Sixty-eight US Caucasoid cases and 51 US Caucasoid controls aged 60 years or older were recruited from the Mid-Atlantic region of the United States. Hand OA was classified by American College of Rheumatology (ACR) Clinical Criteria, and cases were subjected to radiographic examination for subgrouping. Genotyping was done for seven previously described single nucleotide polymorphisms (SNPs) of genes for IL-1alpha (encoded by IL1A), IL-1beta (IL1B), and the IL-1 receptor antagonist (IL1RN), as well as an IL1RN variable number of tandem repeat (VNTR) marker. Six microsatellite markers on other chromosomes (null loci) were also typed. RESULTS: The IL1B 5810 G>A SNP genotypes marker were not in Hardy-Weinberg equilibrium (p<0.05 in both non-erosive and erosive hand OA subgroups). Statistically significant association with the IL1B 5810 AA genotype was found in the erosive hand OA subgroup (relative risk 3.8, p=0.007). This IL1B 5810 AA genotype association was also significant between erosive and non-erosive hand OA subjects (relative risk 4.01, p=0.008). As expected, significant linkage disequilibrium was present between IL1B 5810 SNP and IL1A (-)889 SNP, other IL1B SNPs, and the nearest IL1RN SNP examined. The IL1B 5810A allele occurs most frequently on haplotypes with the SNP alleles IL1B 1423C, IL1B 1903T, IL1B 5887C, and IL1A (-)889C. Genotypes at null loci failed to show evidence suggesting population stratification that might account for spurious association. CONCLUSION: Statistical evidence shows association between erosive hand OA and a genomic region containing the IL1B 5810 SNP in a US Caucasoid population. This supports a potential role for IL-1 in the pathogenesis of a severe phenotype of hand OA.

Experience and extensions to the ASM2 family of models.

The development of ASM2 has created a complex model for biological phosphorus removal. Most of the published work on calibrating this model has focused on the design of experiments to maximise information with which to calibrate the model, or the use of hourly data collected around and within an aeration tank. But many sewage works do not collect such data, nor have such instrumentation. The application of ASM2 with sparse data collected at a low frequency, and mostly only input-output, is considered in this paper, based on data collected at a Swedish sewage works. This paper shows that ASM2 can be calibrated with such measurements. This paper also looks at a modification to ASM2d to better handle heterotrophic usage of volatile fatty acids, and the use of this model to study the effects of large increases in in-sewer storage on sewage treatment works. Concern about the generation of large quantities of VFAs, and their effect on the sewage treatment processes, was unfounded.

Genetic relatedness among Trypanosoma evansi stocks by random amplification of polymorphic DNA and evaluation of a synapomorphic DNA fragment for species-specific diagnosis.

In this study we employed randomly amplified polymorphic DNA patterns to assess the genetic relatedness among 14 Brazilian Trypanosoma evansi stocks from domestic and wild hosts, which are known to differ in biological characteristics. These akinetoplastic stocks were compared with one another, to three Old World (Ethiopia, China and Philippines) dyskinetoplastic stocks of T. evansi, and also with Trypanosoma equiperdum, Trypanosoma brucei brucei, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. Randomly amplified polymorphic DNA analysis showed limited heterogeneity in T. evansi stocks from different hosts and geographical regions of the world, or in other species of the subgenus Trypanozoon. However, minor variations generated random amplification of polymorphic DNA analysis disclosed a pattern consisting of a unique synapomorphic DNA fragment (termed Te664) for the T. evansi cluster that was not detected in any other trypanosome species investigated. Pulsed field gel electrophoresis analysis demonstrated that the Te664 fragment is a repetitive sequence, dispersed in intermediate and minichromosomes of T. evansi. Based on this sequence, we developed a conventional PCR assay for the detection of T. evansi using crude preparations of blood collected either on glass slides or on filter paper as template DNA. Our results showed that this assay may be useful as a diagnostic tool for field-epidemiological studies of T. evansi.

Trypanosoma vivax: characterization of the spliced-leader gene of a Brazilian stock and species-specific detection by PCR amplification of an intergenic spacer sequence.

The sequence of the spliced-leader gene repeat of a Brazilian Trypanosoma vivax stock from cattle showed high similarity to sequences of West African T. vivax in both intron and intergenic sequences. This is the first evidence based on DNA sequences of close-relatedness between Brazilian and West African T. vivax stocks. A T. vivax-specific diagnostic PCR assay based on spliced-leader gene intergenic sequences was able to amplify DNA from T. vivax stocks from South America (Brazil, Bolivia, and Colombia) and West Africa. Species-specificity of this method was confirmed by results obtained by testing 15 other trypanosomes, including other species and subspecies that can also infect cattle. The PCR assay developed presented high sensitivity, detecting the DNA content of only one parasite and also revealing T. vivax infection in asymptomatic animals without detectable parasitemia by microhematocrit or in Giemsa-stained blood smears. Use of crude preparations from field-blood samples collected on both filter paper and glass slides as DNA template suggested that this method could be useful for the diagnosis of T. vivax in large epidemiological studies.

Prediction of fetal anemia with Doppler measurement of the middle cerebral artery peak systolic velocity in pregnancies complicated by maternal blood group alloimmunization or parvovirus B19 infection.

OBJECTIVES: To confirm the relationship between the middle cerebral artery peak systolic velocity (MCA PSV) and hemoglobin values in fetuses at risk for anemia (due to maternal blood group alloimmunization or parvovirus B19 infection) and to investigate the clinical value of this method in the management of these pregnancies regardless of previous transfusions. SUBJECTS AND METHODS: Forty singleton pregnancies, 30 affected by alloimmunization and 10 by intrauterine parvovirus B19 infection, were referred to our tertiary center between 1998 and 2000. All cases underwent Doppler measurement of the MCA PSV immediately before fetal blood sampling and just before and after intrauterine transfusion. Hemoglobin determination was always performed after diagnostic cordocentesis, before starting and after terminating fetal transfusion. RESULTS: Overall, we performed 165 fetal blood samplings (hemoglobin values) and obtained 165 corresponding MCA PSV values, 140 in pregnancies complicated by red-cell alloimmunization and 25 by parvovirus B19 infection. In order to adjust for the effect of gestational age on the measurements, the data were expressed in multiples of the median (MoM). We found a good correlation between MCA PSV MoM and Hb MoM in both groups (alloimmunization, r2 = 0.6; y = 2.21 - 1.41 x + 0.24 x 2; parvovirus infection, r2 = 0.68; y = 2.09 - 0.58 x - 0.16 x 2). The reduction of post-transfusion MCA PSV values was statistically significant ( P < 0.0001). Using a threshold of 1.29 for MoM PSV, the sensitivity and the specificity of MCA pulsatility indices on pretransfusion values in predicting any degree of fetal anemia (Hb < or = 0.84 MoM) were 73.1% and 81.5% in the alloimmunization group and 100% and 100% in the parvovirus infection group, respectively. CONCLUSION: We can confirm the presence of an inverse correlation between MCA PSV measurements and hemoglobin values in fetuses at risk for anemia due to maternal blood group alloimmunization and fetal parvovirus B19 infection. The MCA PSV is a reliable method for the prediction of anemia not only in fetuses before the first intrauterine transfusion, but also in those which have undergone one or more transfusions, with good sensitivity and specificity in both groups of fetuses at risk.

Infecundity and consumption of polychlorinated biphenyl-contaminated fish.

Biologic capacity for reproduction, or fecundity, may be threatened by environmental contaminants, especially compounds capable of disrupting endocrine pathways. Telephone interviews that focused on reproductive events were conducted with female members of the New York State Angler Cohort Study who became pregnant between 1991 and 1993 and who reported known time to pregnancy (N = 895; 73%). Consumption of polychlorinated biphenyl-contaminated Lake Ontario sportfish and other factors were ascertained in 1991. The authors classified the women as follows: (a) fecund (time to pregnancy < or =12 cycles; n = 723); (b) having resolved infecundity (time to pregnancy > 12 cycles; n = 81); or (c) having unresolved infecundity (time to pregnancy > 12 cycles without pregnancy; n = 94). Adjusted odds ratios for duration of fish consumption for both resolved and unresolved infecundity were elevated (1.46 and 1.19, respectively), although confidence intervals included unity. Frequency of recent fish consumption was associated with an increased risk for select categories, although confidence intervals included one.

Trypanosoma cruzi: exogenously regulated gene expression.

A regulated expression vector would provide a strong tool for the dissection of gene function in Trypanosoma cruzi. Herein, we establish a system in which genes in T. cruzi expression vectors can be exogenously regulated by tetracycline. We first generated strains of T. cruzi that stably express the repressor of the bacterial tetracycline resistance gene and T7 RNA polymerase. Based on these strains, we developed two T. cruzi expression systems regulated by tetracycline--the first by use of a regulated rRNA promoter and the second by use of a regulated T7 promoter. In the former, we constructed an expression vector in which tetracycline resistance gene operators flank the transcription start point of the T. cruzi rRNA gene promoter. Reporter gene activity from this modified promoter was regulated up to 20-fold in the presence of different concentrations of tetracycline. In the T7 system, tetracycline resistance gene operators flank the transcription start point of the T7 promoter. Reporter gene activity from this modified promoter was regulated up to 150-fold in the presence of different concentrations of tetracycline. Expression in these systems was repressed when tetracycline was removed even after full induction for extended periods in the presence of tetracycline. We are now using these two systems to test protein function in T. cruzi.