Validation of the line-probe assay for rapid detection of rifampicin-resistant Mycobacterium tuberculosis in Vietnam.

BACKGROUND: Delays in identifying multidrug-resistant tuberculosis (MDR-TB) contribute to higher TB morbidity and mortality, and ongoing transmission. The line-probe assay (LiPA) is a rapid, commercially available polymerase chain reaction based assay that detects most mutations in the rpoB gene for rifampicin (RMP) resistance. We validated and compared this assay with conventional drug susceptibility testing (DST). METHODS: We re-cultured a random sample of stored isolates known to be either RMP-resistant or RMP-susceptible according to DST (proportion method). We performed a blinded comparison between LiPA and conventional DST. Genetic sequencing of the rpoB gene was performed on RMP-resistant isolates and discordant results. RESULTS: We tested 79 RMP-resistant and 64 RMP-susceptible strains. Concordance of LiPA with DST was 94%. For detecting RMP resistance, LiPA sensitivity was 90% and specificity was 100%. Molecular analysis of possible false-negative isolates by LiPA revealed an absence of mutations in the rpoB gene. RMP resistance was a good proxy for MDR-TB, as 66 (93%) of 71 RMP-resistant isolates were also isoniazid-resistant. CONCLUSION: The LiPA provided rapid results that were highly predictive of RMP resistance and MDR-TB. False-negatives occurred, but only among isolates with mutations in regions not assessed by LiPA. Performance and cost-effectiveness should be evaluated in patients during routine program conditions.

Comparison of tuberculosis surveillance systems in low-incidence industrialised countries.

The comparative analysis of National Tuberculosis Control Programmes (NTPs) in industrialised, low-tuberculosis-incidence countries is limited. Analysis of applied methods, function and accumulated experience contributes to improving global tuberculosis control. A questionnaire addressing NTP surveillance infrastructure and characteristics was completed in 19 industrialised countries, with populations of >3 million and annual notified tuberculosis incidence rates of <16 cases per 100,000 population (2003 data). All European countries surveyed adopted World Health Organization Collaborating Centre for the Surveillance of Tuberculosis in Europe (EuroTB) definitions. Surveillance information, which usually includes names, was transferred electronically to the national level in 17 out of the 19 countries. Surveillance systems capture process and social determinants. Case notification to the central level occurred within a median period of 7 days, independent of mandatory notification requirements. The mean completeness of tuberculosis case-reporting was estimated to be 93.5% (range 65-100%). Integration between HIV and tuberculosis registries was performed in two countries, and, in seven others, both databases were cross-matched periodically. National Tuberculosis Control Programme function in industrialised low-incidence countries utilises well-established infrastructure and relies upon centralised operations. Approaches are consistent with current World Health Organization surveillance recommendations. The present study lays collaborative groundwork for additional multinational analyses for the enhancement of global tuberculosis surveillance, which may assist policy-makers in countries moving from medium to low rates of incidence.

Capacity building for international tuberculosis control through operations research training.

SETTING: In resource-poor countries, few tuberculosis (TB) program staff at the national, provincial, and even district levels have the basic analytical and epidemiological skills necessary for collecting and analyzing quality data pertaining to national TB control program (NTP) improvements. This includes setting program priorities, operations planning, and implementing and evaluating program activities. OBJECTIVES: To present a model course for building capacity in basic epidemiology and operations research (OR). DESIGN: A combination of didactic lectures and applied field exercises were used to achieve the main objectives of the 6-day OR course. These were to increase the understanding of quantitative and qualitative research concepts, study design, and analytic methods, and to increase awareness of how these methods apply to the epidemiology and control of TB; and to demonstrate the potential uses of OR in answering practical questions on NTP effectiveness. As a final outcome, course participants develop OR proposals that are funded and later implemented. RESULTS: Since 1997, this OR course has been conducted nine times in five countries; 149 key NTP and laboratory staff have been trained in OR methods, and 44 OR protocols have been completed or are underway. CONCLUSION: This low-cost model course can be adapted to a wide range of public health issues.

Comparison of a whole-blood interferon gamma assay with tuberculin skin testing for detecting latent Mycobacterium tuberculosis infection.

CONTEXT: Identifying persons with latent tuberculosis infection (LTBI) is crucial to the goal of TB elimination. A whole-blood interferon gamma (IFN-gamma) assay, the QuantiFERON-TB test, is a promising in vitro diagnostic test for LTBI that has potential advantages over the tuberculin skin test (TST). OBJECTIVES: To compare the IFN-gamma assay with the TST and to identify factors associated with discordance between the tests. DESIGN AND SETTING: Prospective comparison study conducted at 5 university-affiliated sites in the United States between March 1, 1998 and June 30, 1999. PARTICIPANTS: A total of 1226 adults (mean age, 39 years) with varying risks of Mycobacterium tuberculosis infection or documented or suspected active TB, all of whom underwent both the IFN-gamma assay and the TST. MAIN OUTCOME MEASURE: Level of agreement between the IFN-gamma assay and the TST. RESULTS: Three hundred ninety participants (31.8%) had a positive TST result and 349 (28.5%) had a positive IFN-gamma assay result. Overall agreement between the IFN-gamma assay and the TST was 83.1% (kappa = 0.60). Multivariate analysis revealed that the odds of having a positive TST result but negative IFN-gamma assay result were 7 times higher for BCG-vaccinated persons compared with unvaccinated persons. The IFN-gamma assay provided evidence that among unvaccinated persons with a positive TST result but negative IFN-gamma assay result, 21.2% were responding to mycobacteria other than M tuberculosis. CONCLUSIONS: For all study participants, as well as for those being screened for LTBI, the IFN-gamma assay was comparable with the TST in its ability to detect LTBI, was less affected by BCG vaccination, discriminated responses due to nontuberculous mycobacteria, and avoided variability and subjectivity associated with placing and reading the TST.

Assessing excess deaths in St. Louis, Missouri: 1980 to 1994.

Excess deaths in the city of St. Louis from 1980 to 1994, their trends over time, and racial death patterns were assessed using the CDC's Wonder mortality database. Death rates in the city were compared with the three lowest statistically valid county death rates in the state of Missouri. The number and percent of preventable deaths in the city population also were estimated. Findings show that approximately 50 percent of city deaths from the nine leading causes may be preventable.

Interferon regulatory factor-2 is a transcriptional activator in muscle where It regulates expression of vascular cell adhesion molecule-1.

Previously, we have suggested that vascular cell adhesion molecule-1 (VCAM-1) and its integrin receptor alpha4beta1 mediate cell-cell interactions important for skeletal myogenesis. Expression of the receptors subsequently subsides in muscle after birth. Here, we examine the mechanism regulating VCAM-1 gene expression in muscle. An enhancer located between the TATA box and the transcriptional start site is responsible for VCAM-1 gene expression in muscle-this element is inactive in endothelial cells where VCAM-1 expression is dependent on nuclear factor kappaB sites and inflammatory cytokines. We identify interferon regulatory factor-2 (IRF-2), a member of the interferon regulatory factor family, as the enhancer-binding transcription factor and show that expression of IRF-2 parallels that of VCAM-1 during mouse skeletal myogenesis. IRF-2 is not dependent upon cytokines for expression or activity, and it has been shown to act as a repressor in other nonmuscle cell types. We show that the basic repressor motif located near the COOH-terminal of IRF-2 is not active in muscle cells, but instead an acidic region in the center of the molecule functions as a transactivating domain. Although IRF-2 and VCAM-1 expression diminishes on adult muscle fiber, they are retained on myogenic stem cells (satellite cells). These satellite cells proliferate and fuse to regenerate muscle fiber after injury or disease. We present evidence that VCAM-1 on satellite cells mediates their interaction with alpha4beta1(+) leukocytes that invade the muscle after injury or disease. We propose that VCAM-1 on endothelium generally recruits leukocytes to muscle after injury, whereas subsequent interaction with VCAM-1 on regenerating muscle cells focuses the invading leukocytes specifically to the sites of regeneration.

TNF-alpha and IL-4 synergistically increase vascular cell adhesion molecule-1 expression in cultured vascular smooth muscle cells.

Vascular cell adhesion molecule-1 (VCAM-1) is expressed on the endothelium and vascular smooth muscle in atherosclerosis, where it is thought to recruit alpha4 integrin-positive leukocytes, which play a role in disease progression. In this study, we show an increase of VCAM-1 expression on vascular smooth muscle cells (VSMC) results in increased adhesion of alpha4 integrin-positive lymphocytes. Additionally, we examine the regulation of VCAM-1 expression by cytokines in cultured VSMC. Previously in endothelial cells, we have demonstrated that TNF-alpha increases transcription of the VCAM-1 gene, whereas IL-4 acts to increase VCAM-1 mRNA stability. The combination of a cytokine that increases transcription with a cytokine that stabilizes mRNA results in a synergistic increase in VCAM-1 expression. In this study, we show that the combination of TNF-alpha with IL-4 also resulted in a synergistic increase in VCAM-1 expression on VSMC; however, the mechanism of cytokine activation differed. In contrast to endothelial cells, IL-4 stimulated VCAM-1 gene transcription in the VSMC, but there was little effect of TNF-alpha alone. Additionally, the synergy between TNF-alpha and IL-4 appears to result, at least in part, from a cooperative transcriptional mechanism.

Control of vascular cell adhesion molecule-1 gene promoter activity during neural differentiation.

Here we demonstrate that vascular cell adhesion molecule-1 (VCAM-1) is expressed in the developing central nervous system on neuroepithelial cells, which are the precursors of neurons and glia. As these cells differentiate, VCAM-1 is restricted to a subset of the glial population. An understanding of mechanisms responsible for this restricted pattern could provide insights into how lineage-specific gene expression is maintained during neural differentiation. As a model of neural differentiation, we turned to the P19 embryonic carcinoma cell line, which in response to retinoic acid will differentiate along a neural pathway. We show that VCAM-1 expression on the differentiating P19 cells resembles that in the central nervous system. Transfection of VCAM-1 gene promoter constructs into P19 cells revealed that the VCAM-1 gene is controlled sequentially by negative and positive elements during differentiation. We present evidence that early during differentiation, POU proteins block VCAM-1 gene activity; however, later in differentiation coincident with the appearance of VCAM-1 the pattern of POU proteins changes and the VCAM-1 gene promoter is activated. This activation is mediated through the NF kappa B/rel complex p50/p65, which forms during P19 cell differentiation.

Regulation of vascular cell adhesion molecule-1 expression by IL-4 and TNF-alpha in cultured endothelial cells.

Interaction between vascular cell adhesion molecule-1 (VCAM-1) on endothelial cells and alpha 4 integrins on leukocytes is thought to mediate the selective recruitment of eosinophils and lymphocytes that occurs in allergic diseases. IL-4 is associated with allergic conditions, and it has been shown to selectively increase expression of VCAM-1 on endothelial cells in vivo, suggesting that it could be responsible for VCAM-1 expression in allergic disease. Using a combination of immunofluorescence, flow cytometry, and Northern analysis, we compared the effect of TNF-alpha and IL-4 on VCAM-1 expression. TNF-alpha is also associated with allergic diseases, and it rapidly increases transcription of the VCAM-1 gene. The effect of IL-4 was relatively modest with prolonged kinetics: VCAM-1 was not detected until 72 h after treatment with IL-4. However, when TNF-alpha and IL-4 were combined, there was a synergistic increase in VCAM-1 expression and a dramatic prolongation of the appearance of VCAM-1 on the cell surface. This synergy results from a combination of transcriptional activation by TNF-alpha and the stabilization of resulting transcripts by IL-4. We propose that IL-4 allows subthreshold concentrations of TNF-alpha (concentrations that would not normally activate expression of adhesion molecules on the endothelium) to selectively increase VCAM-1 expression and to prolong its appearance on the surface of cells in allergic disease.

An intricate arrangement of binding sites for the Ets family of transcription factors regulates activity of the alpha 4 integrin gene promoter.

alpha 4 integrins mediate cell-cell and cell-extracellular matrix interactions that are critical for maturation and function of the immune system as well as differentiation of skeletal muscle. Here we examine molecular mechanisms controlling the pattern of alpha 4 expression. The activity of constructs containing 5' deletion mutants of the alpha 4 gene promoter was compared in transfection assays into cell lines that express alpha 4 and cell lines that do not. The sequence between position -42 and -76 base pairs (bp) was required for efficient transcription in cells that express alpha 4, but it showed no activity in HeLa cells, which do not express alpha 4. Three binding sites for the Ets family of transcription factors are found in this region: two adjacent sites at positions -50 and -54 bp and a more 5' site at position -67 bp. Using a series of constructs containing deletions and mutations in this region, we found that the 3'-most site alone was sufficient for binding GA-binding protein alpha (GABP alpha)/GABP beta and for a low level of transcriptional activation. When all three sites were present, a second complex "a" was detected, which contains an unknown member of the Ets family. Formation of complex a was cell-type specific and correlated with a high level of transcription. Deletion of the 5'-most Ets site had no effect on binding to GABP alpha/GABP beta, but it eliminated a. Concomitant with this loss of a, a new Ets-1-containing complex "c" appeared. Complex c substituted efficiently for complex a in transcriptional activation. We conclude that although neither of the two 5'-most Ets sites alone binds nuclear protein, they appear to act as modulators which control the pattern of Ets proteins that bind the alpha 4 gene promoter. This arrangement of Ets sites, coupled with the tissue- and developmental-specific expression of Ets members, likely play a key role in defining the pattern of alpha 4 integrin.

The integrin alpha 4 beta 1 and its counter receptor VCAM-1 in development and immune function.

The integrin alpha 4 beta 1 and its counter receptor vascular cell adhesion molecule-1 (VCAM-1) mediate well-described cell-cell interactions that are critical for immune function. However, these receptors also mediate cell-cell interactions that are important for skeletal muscle differentiation. We have found that contrasting transcriptional mechanisms control their patterns of expression in the immune system and in muscle. Recent studies indicate that alpha 4 beta 1 and VCAM-1 are also expressed in a number of developing tissues, implying that these receptors have a general role in facilitating cell-cell interactions during development.

Vascular cell adhesion molecule 1: contrasting transcriptional control mechanisms in muscle and endothelium.

Interaction between vascular cell adhesion molecule 1 (VCAM-1), which appears on the surface of endothelial cells in response to inflammation, and its integrin counter receptor, alpha 4 beta 1, on immune cells is responsible for targeting these immune cells to cytokine-stimulated endothelium. In addition to its role in the immune system, VCAM-1 is also expressed in a developmentally specific pattern on differentiating skeletal muscle, where it mediates cell-cell interactions important for myogenesis through interaction with alpha 4 beta 1. In contrast to endothelium, there is high basal expression of VCAM-1 in skeletal muscle cells and the expression is not cytokine-responsive. Here, we examine the molecular basis for these contrasting patterns of expression in muscle and endothelium, using VCAM-1 promoter constructs in a series of transfection assays. In endothelial cells, octamer binding sites act as silencers that prevent VCAM-1 expression in unstimulated cells. Tumor necrosis factor alpha overcomes the negative effects of these octamers and activates the promoter through two adjacent NF-kappa B binding sites. In muscle cells, a position-specific enhancer located between bp -21 and -5 overrides the effect of other promoter elements, resulting in constitutive VCAM-1 expression. A nuclear protein binds the position-specific enhancer in muscle but not endothelial cells; thus the pattern of expression of this protein could control enhancer activity.

Characterization of the promoter for vascular cell adhesion molecule-1 (VCAM-1).

Vascular cell adhesion molecule-1 (VCAM-1) was first identified as a protein that appears on the surface of endothelial cells after exposure to inflammatory cytokines. Through interaction with its integrin counter receptor VLA-4, VCAM-1 mediates cell-cell interactions important for immune function. We have cloned and begun characterization of the promoter for the VCAM-1 gene. In a series of transfection assays into human umbilical vein endothelial cells (HUVECs), we find that silencers between positions -1.641 kilobases and -288 base pairs restrict promoter activity, and that treatment with tumor necrosis factor-alpha overcomes this inhibition and activates the promoter through two NF kappa B sites located at positions -77 and -63 base pairs of the VCAM-1 gene. This responsiveness appears cell-specific since constructs containing the VCAM-1 NF kappa B sites are not responsive to tumor necrosis factor alpha in the T-cell line Jurkat. The two VCAM-1 NF kappa B sites, which differ slightly in their sequence, form distinct complexes in gel retardation assays, suggesting that they interact with different NF kappa B-site binding proteins. The distribution of these proteins could then control activity of the NF kappa B sites. We conclude that the pattern of VCAM-1 expression in HUVECs is controlled by a combination of these silencers and NF kappa B sites.