Molecular cloning and characterization of Tap, a putative multidrug efflux pump present in Mycobacterium fortuitum and Mycobacterium tuberculosis

A recombinant plasmid isolated from a Mycobacterium fortuitum genomic library by selection for gentamicin and 2-N'-ethylnetilmicin resistance conferred low-level aminoglycoside and tetracycline resistance when introduced into M. smegmatis. Further characterization of this plasmid allowed the identification of the M. fortuitum tap gene. A homologous gene in the M. tuberculosis H37Rv genome has been identified. The M. tuberculosis tap gene (Rv1258 in the annotated sequence of the M. tuberculosis genome) was cloned and conferred low-level resistance to tetracycline when introduced into M. smegmatis. The sequences of the putative Tap proteins showed 20 to 30% amino acid identity to membrane efflux pumps of the major facilitator superfamily (MFS), mainly tetracycline and macrolide efflux pumps, and to other proteins of unknown function but with similar antibiotic resistance patterns. Approximately 12 transmembrane regions and different sequence motifs characteristic of the MFS proteins also were detected. In the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP), the levels of resistance to antibiotics conferred by plasmids containing the tap genes were decreased. When tetracycline accumulation experiments were carried out with the M. fortuitum tap gene, the level of tetracycline accumulation was lower than that in control cells but was independent of the presence of CCCP. We conclude that the Tap proteins of the opportunistic organism M. fortuitum and the important pathogen M. tuberculosis are probably proton-dependent efflux pumps, although we cannot exclude the possibility that they act as regulatory proteins.

An epitope delivery system for use with recombinant mycobacteria

We have developed a novel epitope delivery system based on the insertion of peptides within a permissive loop of a bacterial superoxide dismutase molecule. This system allowed high-level expression of heterologous peptides in two mycobacterial vaccine strains, Mycobacterium bovis bacille Calmette-Guérin (BCG) and Mycobacterium vaccae. The broader application of the system was analyzed by preparation of constructs containing peptide epitopes from a range of infectious agents and allergens. We report detailed characterization of the immunogenicity of one such construct, in which an epitope from the Der p1 house dust mite allergen was expressed in M. vaccae. The construct was able to stimulate T-cell hybridomas specific for Der p1, and it induced peptide-specific gamma interferon responses when used to immunize naive mice. This novel expression system demonstrates new possibilities for the use of mycobacteria as vaccine delivery vehicles.

Molecular cloning and functional analysis of a novel tetracycline resistance determinant, tet(V), from Mycobacterium smegmatis

The nucleotide sequence and mechanism of action of a tetracycline resistance gene from Mycobacterium smegmatis were determined. Analysis of a 2.2-kb sequence fragment showed the presence of one open reading frame, designated tet(V), encoding a 419-amino-acid protein (molecular weight, 44,610) with at least 10 transmembrane domains. A database search showed that the gene is homologous to membrane-associated antibiotic efflux pump proteins but not to any known tetracycline efflux pumps. The steady-state accumulation level of tetracycline by M. smegmatis harboring a plasmid carrying the tet(V) gene was about fourfold lower than that of the parental strain. Furthermore, the energy uncoupler carbonyl cyanide m-chlorophenylhydrazone blocked tetracycline efflux in deenergized cells. These results suggest that the tet(V) gene codes for a drug antiporter which uses the proton motive force for the active efflux of tetracycline. By primer-specific amplification the gene appears to be restricted to M. smegmatis and M. fortuitum.

Self-Regulation Behaviors in Underprepared (Developmental) and Regular Admission College Students

Although there is evidence that self-regulated learning processes, such as self-efficacy and goal setting, are significantly related to academic success most studies have not included participants from the one third of the entering college students who must take remedial college courses. The purpose of our research was to examine the differences between the self regulation reported by regular admission students and by underprepared students. We hypothesized that self regulating behaviors could predict developmental, that is underprepared, status or regular admission status among postsecondary students. Self regulation processes in randomly selected developmental and regular admission college students were identified using a structured interview. A discriminant function analysis tested the predictive ability of three measures of self regulating behavior. Developmental and regular admission students differed significantly in their self regulatory strategy deployment. The results suggest that self regulation may be a distinguishing characteristic between some developmental and regular admission students. Copyright 1998 Academic Press.

Circular YAC vectors containing a small mammalian origin sequence can associate with the nuclear matrix

Three different mammalian origins of DNA replication, 343, S3, and X24, have been cloned into a 15.8 kb circular yeast vector pYACneo. Subsequent transfection into HeLa cells resulted in the isolation of several stably maintained clones. Two cell lines, C343e2 and CS3e1, were found to have sequences maintained as episomes in long-term culture with a stability per generation of approximately 80%. Both episomes also contain matrix attachment region (MAR) sequences which mediate the binding of DNA to the nuclear skeleton and are thought to play a role in DNA replication. Using high salt extraction of the nucleus and fluorescent in situ hybridization, we were able to demonstrate an association of the 343 episome with the nuclear matrix, most probably through functional MAR sequences that allow an association with the nuclear matrix and associated regions containing essential replication proteins. The presence of functional MARs in small episomal sequences may facilitate the replication and maintenance of transfected DNA as an episome and improve their utility as small episomal constructs, potential microchromosomes.

IKK-1 and IKK-2: cytokine-activated IkappaB kinases essential for NF-kappaB activation

Activation of the transcription factor nuclear factor kappa B (NF-kappaB) is controlled by sequential phosphorylation, ubiquitination, and degradation of its inhibitory subunit IkappaB. A large multiprotein complex, the IkappaB kinase (IKK) signalsome, was purified from HeLa cells and found to contain a cytokine-inducible IkappaB kinase activity that phosphorylates IkappaB-alpha and IkappaB-beta. Two components of the IKK signalsome, IKK-1 and IKK-2, were identified as closely related protein serine kinases containing leucine zipper and helix-loop-helix protein interaction motifs. Mutant versions of IKK-2 had pronounced effects on RelA nuclear translocation and NF-kappaB-dependent reporter activity, consistent with a critical role for the IKK kinases in the NF-kappaB signaling pathway.

Reduction in renin release and renal vascular resistance by H(+)-K(+)-ATPase inhibition

Results from previous experiments in our laboratory suggested that a H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase) was present in vascular smooth muscle. Here we analyzed the effects on regulation of renal vascular function in anesthetized dogs of inhibition of the H(+)-K(+)-ATPase by a highly specific inhibitor, NC-1300-B. The compound was injected intravenously, 15 mg/kg (5.8 x 10(-5) mol wt/kg), into one group of six dogs, whereas saline was given to a control group of eight. Renal function was measured at controlled levels of renal perfusion pressure ranging from 110 to 60 mmHg. Renal blood flow (RBF) was higher in the treated group at all levels of perfusion pressure; at 70 mmHg, the treated group RBF was 5.85 +/- 1.00 ml.min-1.g kidney wt-1, 71% greater than that of the control group. Glomerular filtration rate (GFR) mean values of the two groups were not significantly different at any perfusion pressure level. Renin release was inhibited (P < 0.01) by H(+)-K(+)-ATPase inhibition; at 90 mmHg, the control group mean was 14.3 +/- 4.3 units, 4.47 times greater than the treated group mean of 3.2 +/- 1.6 units. H(+)-K(+)-ATPase inhibition with NC-1300-B causes profound renal vasodilation and inhibition of renin release without affecting regulation of GFR.

p38-2, a novel mitogen-activated protein kinase with distinct properties

Mitogen-activated protein (MAP) kinases are involved in many cellular processes. Here we describe the cloning and characterization of a new MAP kinase, p38-2. p38-2 belongs to the p38 subfamily of MAP kinases and shares with it the TGY phosphorylation motif. The complete p38-2 cDNA was isolated by polymerase chain reaction. It encodes a 364-amino acid protein with 73% identity to p38. Two shorter isoforms missing the phosphorylation motif were identified. Analysis of various tissues demonstrated that p38-2 is differently expressed from p38. Highest expression levels were found in heart and skeletal muscle. Like p38, p38-2 is activated by stress-inducing signals and proinflammatory cytokines. The preferred upstream kinase is MEK6. Although p38-2 and p38 phosphorylate the same substrates, the site specificity of phosphorylation can differ as shown by two-dimensional phosphopeptide analysis of Sap-1a. Additionally, kinetic studies showed that p38-2 appears to be about 180 times more active than p38 on certain substrates such as ATF2. Both kinases are inhibited by a class of pyridinyl imidazoles. p38-2 phosphorylation of ATF2 and Sap-1a but not Elk1 results in increased transcriptional activity of these factors. A sequential kinetic mechanism of p38-2 is suggested by steady state kinetic analysis. In conclusion, p38-2 may be an important component of the stress response required for the homeostasis of a cell.

Both A type and B type Epstein-Barr virus nuclear antigen 6 interact with RBP-2N

Using the yeast two-hybrid system, Epstein-Barr virus nuclear antigen 6A (EBNA6A) was found to interact with the RBP-2N isoform of RBP-J kappa. The interaction of EBNA6A and EBNA6B with RBP-2N was compared and the results indicated that EBNA6B was less efficient at interacting with RBP-2N than was EBNA6A. Deletion mutation analysis of EBNA6A identified a region involved in the interaction with RBP-2N, while analysis of RBP-2N identified a domain which interacts with EBNA6A. The region of RBP-2N to which EBNA6A binds has previously been shown to interact with EBNA2.

Production of tumor necrosis factor and nitric oxide by macrophages infected with live and dead mycobacteria and their suppression by an interleukin-10-secreting recombinant

We have analyzed mycobacterium-induced cytokine secretion in the J774A.1 macrophage-like cell line. Tumor necrosis factor alpha (TNF-alpha) was preferentially induced by live organisms, both slow and rapid growing. Expression of interleukin-10 by a recombinant strain of Mycobacterium smegmatis caused reduced production of TNF-alpha and nitric oxide during the early stages of infection.

Induction of a type 1 immune response to a recombinant antigen from Mycobacterium tuberculosis expressed in Mycobacterium vaccae

A 19-kDa lipoprotein from Mycobacterium tuberculosis was expressed as a recombinant antigen in the nonpathogenic mycobacterial host strain M. vaccae. Immunization of mice with the recombinant M. vaccae resulted in induction of a strong type 1 immune response to the 19-kDa antigen, characterized by immunoglobulin G2a (IgG2a) antibodies and gamma interferon (IFN-gamma) production by splenocytes. Immunization with the same antigen in incomplete Freund's adjuvant induced a strong IgG1 response with only low levels of IFN-gamma. Subsequent intravenous and aerosol challenges of immunized mice with virulent M. tuberculosis demonstrated no evidence of protection associated with the response to the 19-kDa antigen; in fact, the presence of the recombinant 19-kDa antigen abrogated the limited protection conferred by M. vaccae (vector control). The recombinant M. vaccae system is a convenient approach to induction of type 1 responses to M. tuberculosis antigens. However, the unexpected reduction in protective efficacy of M. vaccae expressing the 19-kDa antigen highlights the complexity of testing recombinant subunit vaccines and the need for a better understanding of the immune mechanisms required for effective vaccination against tuberculosis.

Rapid detection of multidrug-resistant tuberculosis

Transmission of multidrug-resistant strains of Mycobacterium tuberculosis (MDR-TB) presents a serious problem for infection control in hospitals, particularly in the context of co-infection with the human immunodeficiency virus (HIV). We report on the use of molecular genetic tools to allow rapid assessment of samples from patients potentially infected with MDR-TB. Sputum and bronchoalveolar lavage samples were obtained from two HIV-positive patients with suspected tuberculosis, who had previous contact with a known MDR-TB index case. Polymerase chain reaction (PCR) was used directly on clinical samples to amplify genetic loci associated with rifampicin resistance (rpoB), and strain-specific polymorphisms (the direct repeat (DR) region). Drug resistance was determined using a commercially available kit for detection of point mutations in the rpoB gene (Inno-Lipa RifTB; Innogenetics, Belgium), and confirmed by nucleotide sequencing. Strain variation was determined using the spoligotyping method, based on the presence or absence of variable linker sequences within the DR region. In one patient, infection with a MDR strain identical to that of a known index case was demonstrated. A second patient, although positive for M. tuberculosis, was found to be infected with a rifampicin-sensitive strain. Results were obtained within 48 h, allowing appropriate treatment to be initiated and infection control measures to be implemented. PCR-based tests for strain-typing and for identification of rifampicin resistance provide important tools for identifying patients with MDR-TB and for rapid monitoring of potential nosocomial spread of MDR-TB. Prompt confirmation or exclusion of possible transmission allows early clinical intervention to prevent future outbreaks of multidrug-resistant M. tuberculosis.

Differentiation of Mycobacterium tuberculosis isolates by spoligotyping and IS6110 restriction fragment length polymorphism

Mycobacterium tuberculosis isolates from 167 patients attending three London hospitals were analyzed by two techniques for strain differentiation. A significant number of isolates that appeared identical with the recently developed spoligotyping system could be distinguished from each other by IS6110 restriction fragment length polymorphism analysis, with the latter technique demonstrating a generally higher level of discrimination. Spoligotyping, on the other hand, was particularly useful for analysis of isolates with low IS6110 copy numbers, and use of the two techniques in tandem provided an optimal approach to the identification of clusters with epidemiological evidence consistent with recent transmission. Spoligotyping can be applied directly to clinical samples by PCR and provides an important tool for the rapid detection of nosocomial transmission of individual strains.

Differential responses to challenge with live and dead Mycobacterium bovis Bacillus Calmette-Guérin

Bacillus Calmette-Guérin (BCG) vaccination has been shown to protect against challenge with virulent Mycobacterium tuberculosis in a range of experimental animal models: in each case, protective efficacy requires vaccination with live bacteria. With the goal of moving to a new generation of safer, nonliving vaccines, efforts have been made to identify the factors that determine the efficacy of live vaccination. We show that injection of live, but not dead, BCG induces localized swelling in the mouse footpad model. Live and dead bacteria induce similar responses during the first week after vaccination as determined by immunohistochemical analysis of the site of injection and of the draining lymph node. The subsequent differential response is characterized by migration of acid-fast bacilli to the draining lymph node in the case of the live vaccine. This is accompanied by an increase in mononuclear cells in the lymph node and by expression of inducible nitric oxide synthase (iNOS) both in the lymph node and at the site of injection. The ability of the bacteria to migrate to the lymph node may be an important element in the efficacy of live BCG vaccination.

Differential responses to challenge with live and dead Mycobacterium bovis Bacillus Calmette-Guérin

Bacillus Calmette-Guérin (BCG) vaccination has been shown to protect against challenge with virulent Mycobacterium tuberculosis in a range of experimental animal models: in each case, protective efficacy requires vaccination with live bacteria. With the goal of moving to a new generation of safer, nonliving vaccines, efforts have been made to identify the factors that determine the efficacy of live vaccination. We show that injection of live, but not dead, BCG induces localized swelling in the mouse footpad model. Live and dead bacteria induce similar responses during the first week after vaccination as determined by immunohistochemical analysis of the site of injection and of the draining lymph node. The subsequent differential response is characterized by migration of acid-fast bacilli to the draining lymph node in the case of the live vaccine. This is accompanied by an increase in mononuclear cells in the lymph node and by expression of inducible nitric oxide synthase (iNOS) both in the lymph node and at the site of injection. The ability of the bacteria to migrate to the lymph node may be an important element in the efficacy of live BCG vaccination.

Epstein-Barr nuclear antigen-3 and -4 interact with RBP-2N, a major isoform of RBP-J kappa in B lymphocytes

The Epstein-Barr nuclear antigen (EBNA)-3 and EBNA-4 proteins are thought to act as transcriptional transactivators. The yeast two-hybrid system and coimmunoprecipitation were used to demonstrate that EBNA-3 and -4 associate with the DNA-binding protein RBP-2N, an isoform of RBP-J kappa. A comparison between EBNA-3, EBNA-4, and EBNA-6 binding to RBP-2N indicated that EBNA-3 enhanced beta-galactosidase activity 4-fold more than EBNA-6 and 30-fold more than EBNA-4. Assay of RBP-2N deletion mutants demonstrated that EBNA-3 binds to regions of RBP-2N which are distinct from those to which EBNA-2 and -6 interact, whereas EBNA-4 binds to the same region of RBP-2N as EBNA-2 and -6 (amino acids 159-331 of RBP-2N). Interaction of both A- and B-type EBNA-3 with RBP-2N was also demonstrated by immunoprecipitation. RT-PCR analysis of a panel of B cell lymphomas and lymphoblastoid cell lines demonstrated that higher levels of RBP-2N were expressed, in comparison to RBP-J kappa, indicating that RBP-2N is a major isoform expressed in B cells. These results suggest that all the EBNA-3 family proteins lead to transcriptional regulation via interaction with RBP-2N.

Roles of prostaglandins and nitric oxide in the effect of endothelin-1 on renal hemodynamics

It is known that endothelin-1 stimulates the release of nitric oxide and prostaglandins in various vascular beds. We designed the present study to analyze the roles of prostaglandins and nitric oxide in the effect of endothelin-1 on the regulation of renal hemodynamics and renin release. We used N omega-nitro-L-arginine methyl ester (L-NAME) and meclofenamic acid to inhibit the production of nitric oxide and prostaglandins, respectively. With a nonfiltering kidney model, renal blood flow was reduced 21% in dogs treated with L-NAME and 18% in dogs treated with meclofenamic acid. Inhibition of nitric oxide and prostaglandins, however, produced opposite effects on estimated glomerular hydraulic pressure: L-NAME increased glomerular hydraulic pressure from 63.1 +/- 0.9 to 64.6 +/- 1.3 mm Hg (P < .01), and meclofenamic acid reduced glomerular hydraulic pressure from 63.3 +/- 1.4 to 59.8 +/- 1.6 mm Hg (P < .01). Endothelin-1 infusion produced a dose-dependent reduction in renal blood flow after blockade of nitric oxide and prostaglandins. The responses of glomerular hydraulic pressure were different in the two groups during endothelin-1 infusion. Endothelin-1 progressively reduced glomerular hydraulic pressure in a dose-dependent fashion in the meclofenamic acid group. However, endothelin-1 slightly increased glomerular hydraulic pressure until the infusion rate reached 5.0 ng/kg per minute. At that rate, endothelin-1 reduced glomerular hydraulic pressure from 63.3 +/- 1.4 to 47.0 +/- 1.4 mm Hg in the meclofenamic acid group (P < .01), a more than 25% reduction, whereas at the same dose, endothelin-1 reduced glomerular hydraulic pressure only less than 2% in the L-NAME group. In addition, blockade of nitric oxide and prostaglandins did not alter the inhibitory effect of endothelin-1 on renin release in the non-filtering kidney. Therefore, the present study demonstrates that the release of nitric oxide and prostaglandins might modulate the effects of endothelin-1 on the renal circulation. The present findings suggest that the differential vasoconstrictive effects of endothelin-1 on preglomerular and postglomerular vessels are associated with its stimulation of nitric oxide and prostaglandin production.

Investigation of deaths related to electrical injury

Even though the use of electricity is an integral part of our lives, the number of accidents and deaths related to electricity is on the decline. This is due to increased awareness of electrical hazards and, in large part, to increased inclusion of safety mechanisms by manufacturers. However rare, electrical injury and related death can present a complicated case in the emergency department and for death investigators. Sometimes the circumstances of the physical scene are unclear because of intentional or accidental alterations or the investigator's inability to reconstruct events leading to the injury. This may hinder the initial clinical assessment. We present cases of typical and atypical deaths from electrical injury and review clinical and investigative procedures to assist in the treatment of patients with electrical injuries.

Bacterial glycoproteins: a link between glycosylation and proteolytic cleavage of a 19 kDa antigen from Mycobacterium tuberculosis

Protein glycosylation has an important influence on a broad range of molecular interactions in eukaryotes, but is comparatively rare in bacteria. Several antigens from Mycobacterium tuberculosis, the causative agent of human tuberculosis, have been identified as glycoproteins on the basis of lectin binding, or by detailed structural analysis. By production of a set of alkaline phosphatase (PhoA) hybrid proteins in a mycobacterial expression system, the peptide region required for glycosylation of the 19 kDa lipoprotein antigen from M.tuberculosis was defined. Mutagenesis of two threonine clusters within this region abolished lectin binding by PhoA hybrids and by the 19 kDa protein itself. Substitution of the threonine residues also resulted in generation of a series of smaller forms of the protein as a result of proteolysis. In a working model to account for these observations, we propose that the role of glycosylation is to regulate cleavage of a proteolytically sensitive linker region close to the acylated N-terminus of the protein.