Comparison of the breadth and complexity of bovine viral diarrhea (BVDV) populations circulating in 34 persistently infected cattle generated in one outbreak

Exposure to bovine viral diarrhea viruses (BVDV) results in acute and persistent infections. Persistent infections result from in utero exposure during the first trimester of gestation. Clinical presentation, in persistently infected cattle (PI), is highly variable. The reasons for this variation is largely unknown. The BVDV circulating in PI exist as quasispecies (swarms of individual viruses). An outbreak resulting in 34 PI cattle presented an opportunity to compare a large number of PI׳s. Methods were developed to compare the circulating viral populations within PI animals. It was found that PI animals generated in the same outbreak carry circulating viral populations that differ widely in size and diversity. Further, it was demonstrated that variation in PI viral populations could be used as a quantifiable phenotype. This observation makes it possible to test the correlation of this phenotype to other phenotypes such as growth rate, congenital defects, viral shed and cytokine expression.

The ongoing challenge of latent tuberculosis

The global health community has set itself the task of eliminating tuberculosis (TB) as a public health problem by 2050. Although progress has been made in global TB control, the current decline in incidence of 2% yr⁻¹ is far from the rate needed to achieve this. If we are to succeed in this endeavour, new strategies to reduce the reservoir of latently infected persons (from which new cases arise) would be advantageous. However, ascertainment of the extent and risk posed by this group is poor. The current diagnostics tests (tuberculin skin test and interferon-gamma release assays) poorly predict who will develop active disease and the therapeutic options available are not optimal for the scale of the intervention that may be required. In this article, we outline a basis for our current understanding of latent TB and highlight areas where innovation leading to development of novel diagnostic tests, drug regimens and vaccines may assist progress. We argue that the pool of individuals at high risk of progression may be significantly smaller than the 2.33 billion thought to be immune sensitized by Mycobacterium tuberculosis and that identifying and targeting this group will be an important strategy in the road to elimination.

The development and validation of The Inquiry Science Observation Coding Sheet

Evaluation reports increasingly document the degree of program implementation, particularly the extent to which programs adhere to prescribed steps and procedures. Many reports are cursory, however, and few, if any, fully portray the long and winding path taken when developing evaluation instruments, particularly observation instruments. In this article, we describe the development of an observational method for evaluating the degree to which K-12 inquiry science programs are implemented, including the many steps and decisions that occurred during the development, and present evidence for the reliability and validity of the data that we collected with the instrument. The article introduces a method for measuring the adherence of inquiry science implementation and gives evaluators a full picture of what they might expect when developing observation instruments for assessing the degree of program implementation.

Frequency and implications of pyrazinamide resistance in managing previously treated tuberculosis patients

OBJECTIVE

To determine the extent of pyrazinamide (PZA) resistance in isolates from previously treated patients from the Western Cape, South Africa.

DESIGN

Drug-resistant isolates, isolates resistant to one or more drugs other than PZA (PZA resistance is not routinely determined) (n = 127), and drug-susceptible (n = 47) clinical isolates of Mycobacterium tuberculosis from previously treated patients from the Western Cape were phenotypically (BACTEC MGIT 960) and genotypically (pncA gene sequencing) analysed for PZA resistance.

RESULTS

MGIT analysis found that 68 of the 127 drug-resistant isolates were PZA-resistant. Nearly all (63/68) PZA-resistant isolates had diverse nucleotide changes scattered throughout the pncA gene, and five PZA-resistant isolates had no pncA mutations. Of the 47 phenotypically susceptible isolates, 46 were susceptible to PZA, while one isolate was PZA-monoresistant (OR = 53.0, 95% CI = 7.1-396.5). A pncA polymorphism (Thr114Met) that did not confer PZA resistance was also identified. PZA resistance was strongly associated with multidrug-resistant tuberculosis (MDR-TB).

CONCLUSION

An alarmingly high proportion of South African drug-resistant M. tuberculosis isolates are PZA-resistant, indicating that PZA should not be relied upon in managing patients with MDR-TB in the Western Cape. A method for the rapid detection of PZA resistance would be beneficial in managing patients with suspected drug resistance.

Lower limb landmine injuries

The medical records of 186 patients seeking treatment for landmine injuries in the authors' region between 1993 and 2001 were evaluated. Of these patients 13 died of accompanying complications. Ten (10) patients with general body trauma and upper limb trauma were excluded from the study. Of 163 patients with lower-limb injuries included in the study, 21 with traumatic amputation underwent surgical amputation at different levels. Patients without traumatic amputation were divided into 2 groups. There were 41 patients (29%) in Group I who were treated by limb salvage procedures. Treatments used in Group I including wound debridement, tendon repair, skin approximation, minimal osteosynthesis, external fixation of long bones and secondary wound coverage. In Group II, there were 101 patients (71%) with primary amputation. Trans-tibial amputation was performed in 52 cases (51.4%), ankle disarticulation in 24 (23.7%), trans-femoral amputation in 9 (8.9%), partial foot amputation in 8 (7.9%), knee disarticulation in 7 (6.9%) and hip disarticulation in 1 case. In Group I, there was infection in 21 patients (51.2%), revision in 27 (65.8%), and amputation in 15 (36.5%). In Group II, there was infection in 28 patients (27.7%), revision in 17 (16.8%), and amputation at a higher level in 8 (7%). In crush injuries such as those resulting from landmines, soft tissue, vascular, and neurological assessment must be performed with utmost care. Even so, the desired success in interventions intended to save a limb is complicated by a high infection rate, soft tissue complications, and high revision amputation rates. Therefore, a decision to amputate in the early term based on an accurate preoperative assessment is crucial.

Koch's bacillus - a look at the first isolate of Mycobacterium tuberculosis from a modern perspective

Using molecular methods the authors have studied mycobacterial DNA taken from a 19th century victim of tuberculosis. This was the case from which Robert Koch first isolated and cultured the organism responsible for tuberculosis. The mycobacteria were preserved within five glass culture tubes as abundant bacterial colonies on slopes of a gelatinous culture medium of unknown composition. Originally presented by Koch to surgical laryngologist Walter Jobson Horne in London in 1901, the relic has, since 1983, been in the care of the Royal College of Surgeons of England. Light and electron microscopy established the presence of acid-fast mycobacteria but showed that morphological preservation was generally poor. Eleven different genomic loci were successfully amplified by PCR. This series of experiments confirmed that the organisms were indeed Mycobacterium tuberculosis and further showed that the original strain was in evolutionary terms similar to 'modern' isolates, having undergone the TB D1 deletion. Attempts to determine the genotypic group of the isolate were only partially successful, due in part to the degraded nature of the DNA and possibly also to a truncation in the katG gene, which formed part of the classification scheme. Spoligotyping resulted in amplification of DR spacers consistent with M. tuberculosis but with discrepancies between independent extracts, stressing the limitations of this typing method when applied to poorly preserved material.

The effect of mycobacterial virulence and viability on MAP kinase signalling and TNF alpha production by human monocytes

SETTING

The success of Mycobacterium tuberculosis as a human pathogen depends on its ability to tolerate and perhaps manipulate host defense mechanisms.

OBJECTIVE

To determine the induction of tumour necrosis factor-alpha (TNF alpha), a central mediator of immunity, by human monocytes infected with virulent M. tuberculosis, M. leprae and attenuated M. bovis BCG.

DESIGN

Mycobacteria-induced cellular activation pathways of TNF alpha production was investigated using an inhibitor of protein tyrosine kinase (PTKs) and an inhibitor of mitogen-activated protein (MAP) kinases.

RESULTS

TNF alpha production was significantly lower during infection with virulent M. tuberculosis than with BCG and this differential response was independent of mycobacterial viability. TNF alpha production involved the PTK and MAP kinase pathways. Reduced TNF alpha induction by M. tuberculosis was associated with a reduction in the extent and duration of phosphorylation of extracellular-signal regulated kinases (ERK 1/2). Infection with M. leprae triggered low and transient ERK 1/2 activation as well as low TNF alpha production.

CONCLUSION

Maintenance of the differential response in both live and heat-killed preparations suggests that the reduced TNF alpha response associated with virulent mycobacteria is due to differences in the presence of components capable of triggering host pattern recognition receptors, rather than events associated with phagosome trafficking or the active release of intracellular modulators.

Novel strategies for intervention targeted at mycobacterial persistence

Effective global control of tuberculosis is likely to require intervention at multiple points in the course of infection. In addition to existing approaches based on treatment of active disease and preventive vaccination of unexposed individuals, current research on the biology of mycobacterial persistence suggests the potential for the development of novel disease-control strategies targeted at infected asymptomatic populations.

Genetic diversity among Mycobacterium bovis isolates: a preliminary study of strains from animal and human sources

Mycobacterium bovis has the broadest host range of species in the Mycobacterium tuberculosis complex and is responsible for disease in humans and diverse animal species. We report on genotypic differences at multiple loci among 13 isolates derived from a range of human and animal infections. All isolates were classified as M. bovis by phenotypic analysis but could be subdivided into five distinct genotypes based on polymorphisms at the pncA and oxyR loci, the status of the RD5 deletion region, and the spoligotype pattern. These findings suggest the existence of a spectrum of strains with genotypic characteristics between those of M. tuberculosis and M. bovis.

Enhanced antimycobacterial response to recombinant Mycobacterium bovis BCG expressing latency-associated peptide

With a view to exploring the role of transforming growth factor beta (TGF-beta) during mycobacterial infection, recombinant clones of bacillus Calmette-Guérin (BCG) were engineered to express the natural antagonist of TGF-beta, latency-activated peptide (LAP). Induction of TGF-beta activity was reduced when macrophages were infected with BCG expressing the LAP construct (LAP-BCG). There was a significant reduction in the growth of LAP-BCG in comparison to that of control BCG following intravenous infection in a mouse model. The enhanced control of mycobacterial replication was associated with an increase in the production of gamma interferon by splenocytes challenged during the acute stage of infection but with a diminished recall response assessed after 13 weeks. Organ weight and hydroxyproline content, representing tissue pathology, were also lower in mice infected with LAP-BCG. The results are consistent with the hypothesis that TGF-beta has a detrimental effect on mycobacterial immunity. While a reduction in TGF-beta activity augments the initial response to BCG vaccination, early bacterial clearance may adversely affect the induction of a long-term memory response by LAP-BCG.

Elevated potassium intake inhibits neointimal proliferation in the swine coronary artery

BACKGROUND

Previously, we reported that elevated extracellular potassium concentration in vitro inhibited proliferation and migration of vascular smooth muscle cells, formation of free radical compounds by macrophages, and reduced platelet sensitivity to agonists. More recently, we described a reduction in neointimal proliferation after balloon angioplasty injury in the carotid arteries of rats associated with an elevation of dietary potassium intake during a 4-week experiment. In the present study we conducted a similar investigation in the swine coronary artery balloon angioplasty model.

PROCEDURES

Two groups of seven castrated male swine were studied; for 28 days the normal potassium group consumed a diet containing 0.25% potassium and the high potassium group ate diet containing 2.0% potassium. After 14 days on the diet, balloon angioplasty was performed. After an additional 14 days on the same diets the hearts were removed, and normal and lesioned sections of the artery were analyzed histologically.

RESULTS

The neointimal area was markedly less in the high potassium group than in the normal potassium group, 0.33+/-0.04 mm2 v 0.74+/-0.10 mm2 (P < .004). Neointimal area-to-total wall area ratio in the normal potassium group averaged 0.199+/-0.018, significantly greater than the ratio computed for the elevated potassium group, 0.120+/-0.015 (P < .006).

CONCLUSION

These results support the hypothesis that a high level of dietary potassium intake inhibits neointimal proliferation after balloon angioplasty in the swine coronary artery.

Overexpression of heat-shock proteins reduces survival of Mycobacterium tuberculosis in the chronic phase of infection

Elevated expression of heat-shock proteins (HSPs) can benefit a microbial pathogen struggling to penetrate host defenses during infection, but at the same time might provide a crucial signal alerting the host immune system to its presence. To determine which of these effects predominate, we constructed a mutant strain of Mycobacterium tuberculosis that constitutively overexpresses Hsp70 proteins. Although the mutant was fully virulent in the initial stage of infection, it was significantly impaired in its ability to persist during the subsequent chronic phase. Induction of microbial genes encoding HSPs might provide a novel strategy to boost the immune response of individuals with latent tuberculosis infection.

Deletion of the 19kDa antigen does not alter the protective efficacy of BCG

Expression of the Mycobacterium tuberculosis 19kDa lipoprotein in saprophytic mycobacteria has been found to reduce their ability to prime a protective response to subsequent virulent challenge in the mouse model. The present study was designed to test whether 19kDa expression has an analogous detrimental effect on the efficacy of BCG vaccination. In contrast to the results in saprophytes, neither overexpression of the 19kDa antigen, nor deletion of the endogenous 19kDa gene altered the ability of BCG to protect against M. tuberculosis challenge in a mouse model.

Is there stereoelectronic control in hydrolysis of cyclic guanidinium ions?

To assess stereoelectronic effects in the cleavage of tetrahedral intermediates, a series of five-, six-, and seven-membered cyclic guanidinium salts was synthesized. If stereoelectronic control by antiperiplanar lone pairs is operative, these are expected to hydrolyze with endocyclic C-N cleavage to acyclic ureas. However, hydrolysis in basic media produces mixtures of cyclic and acyclic products, as determined by 1H NMR analysis. The results show that in the six-membered ring antiperiplanar lone pairs provide a weak acceleration of the breakdown of the tetrahedral intermediate, but in five- and seven-membered rings there is no evidence for such acceleration, which instead can be provided by syn lone pairs.

Stereoelectronic control in addition of nucleophiles to an amidinium ion

Nucleophilic addition to 1,3-dimethyl-5-phenyl-1,4,5,6-tetrahydropyrimidinium ion provides a quantitative measure of stereoelectronic control. This amidinium ion presents the nucleophile with two distinct paths for attack. Axial attack is favored by interaction between the orbital of the developing bond and antiperiplanar lone pairs on the nitrogens. Reaction of the amidinium salt with diverse nucleophiles (D(-), H3C(-), n-Bu(-), PhCH2(-), allyl(-), Ph(-), C5F6(-), CH2=CH(-), HC triple bond C(-), PhC triple bond C(-), CN(-)) produces mixtures of cis and trans stereoisomers. Both kinetic and thermodynamic product distributions were measured by 1H NMR, before and after acid-catalyzed equilibration. The values provide insight into the roles of steric and stereoelectronic forces at the transition state and in products. Stereoelectronic effects on reactivity are found to be weak (ca. 1 kcal/mol).

Paleopathological and biomolecular study of tuberculosis in a medieval skeletal collection from England

Nine human skeletons of medieval date from a rural English burial site show signs of skeletal tuberculosis. They were subject to polymerase chain reaction (PCR) assays aimed at detecting traces of DNA from infecting mycobacteria, with the purpose both of confirming the paleopathological diagnosis of tuberculosis and determining in individual cases whether disease was due to M. tuberculosis or M. bovis. In all nine cases, evidence for M. tuberculosis complex DNA was found, and in all instances it appeared that disease was due to M. tuberculosis rather than M. bovis. The significance of the findings for understanding tuberculous infection in rural agrarian communities in medieval England is discussed.

Analysis of recombinant mycobacteria as T helper type 1 vaccines in an allergy challenge model

The potential for development of mycobacteria as T helper type 1 (Th1) vaccines capable of induction of Th1 responses to recombinant antigens was explored in a model system based on an immunodominant peptide from house dust mite. Different recombinant mycobacterial preparations were compared for their ability to induce a Th1 response to the peptidea. It was found that mycobacterial viability was not a prerequisite for Th1 immunogenicity. A dominant interferon-gamma (IFN-gamma) response to peptide was observed in splenocytes from C57BL/6J mice immunized with live or heat-killed preparations of recombinant Mycobacterium vaccae or with live attenuated bacillus Calmette-Guèrin (BCG) vaccine expressing the antigen. Interleukin-5 (IL-5), a marker of a Th2 response, was detected only in mice receiving live M. vaccae. A similar pattern was observed in BALB/b mice, although the magnitude of the IFN-gamma response was much lower. Control and immunized mice were subsequently exposed to allergen using a Th2-inducing challenge protocol. A significant shift from a Th2 to a Th1 response was observed in immunized mice, as judged by cytokine expression by splenocytes and by subclass of circulating antibody. The effect was seen in three inbred mouse strains differing in their innate bias towards Th1 or Th2 responses. It was dependent on the presence of specific antigen in the mycobacterial preparation and, under the immunization conditions tested, was more pronounced with dead M. vaccae than with live BCG as carrier vaccine. The results demonstrate the potency of killed mycobacteria as Th1 adjuvants and suggest a potential application for recombinant mycobacteria in antigen-specific immune modulation.

Mycobacterium tuberculosis 19-kilodalton lipoprotein inhibits Mycobacterium smegmatis-induced cytokine production by human macrophages in vitro

Vaccination of mice with Mycobacterium vaccae or M. smegmatis induces some protection against M. tuberculosis challenge. The 19-kDa lipoprotein of M. tuberculosis, expressed in M. vaccae or M. smegmatis (M. smeg19kDa), abrogates this protective immunity. To investigate the mechanism of this suppression of immunity, human monocyte-derived macrophages (MDM) were infected with M. smeg19kDa. Infection resulted in reduced production of tumor necrosis factor alpha (TNF-alpha) (P < 0.01), interleukin-12 (IL-12) (P < 0.05), IL-6 (P < 0.05), and IL-10 (P < 0.05), compared to infection with M. smegmatis vector (M. smegV). Infection with M. smeg19kDa and with M. smegV had no differential effect on expression of costimulatory molecules on MDM, nor did it affect the proliferation of presensitized T cells cocultured with infected MDM. When MDM were infected with M. smegmatis expressing mutated forms of the 19-kDa lipoprotein, including non-O-glycosylated (M. smeg19NOG), nonsecreted (M. smeg19NS), and nonacylated (M. smeg19NA) variants, the reduced production of TNF-alpha or IL-12 was not observed. When the purified 19-kDa lipoprotein was added directly to cultures of infected monocytes, there was little effect on either induction of cytokine production or its inhibition. Thus, the immunosuppressive effect is dependent on glycosylated and acylated 19-kDa lipoprotein present in the phagosome containing the mycobacterium. These results suggest that the diminished protection against challenge with M. tuberculosis seen in mice vaccinated with M. smegmatis expressing the 19-kDa lipoprotein is the result of reduced TNF-alpha and IL-12 production, possibly leading to reduced induction of T-cell activation.

Contribution of Th1 and Th2 cells to protection and pathology in experimental models of granulomatous lung disease

Mice that had received adoptive transfer of DO11.10 TCR transgenic T cells polarized toward a Th1 or a Th2 phenotype were challenged with Ag-coated beads or with recombinant Mycobacterium tuberculosis expressing the OVA determinant. The resulting bead-induced pulmonary granulomas reflected the phenotype of the adoptively transferred T cells, with the Th2 cells promoting a fibrotic reaction. Mice receiving Th1 cells mounted an epitope-specific protective response to challenge with recombinant M. tuberculosis. Th2 recipients were characterized by enhanced weight loss and lung fibrosis during acute high-dose infection. The combination of TCR transgenic T cells and epitope-tagged mycobacteria provides a novel experimental model for investigation of the pathogenesis of tuberculosis.

Leprosy lipid provides the key to Schwann cell entry

A recent study has demonstrated that the species-specific phenolic glycolipid of Mycobacterium leprae triggers uptake into Schwann cells by interaction with laminin-2 and the alpha-dystroglycan receptor. This finding emphasizes the importance of lipids in the biology of mycobacterial infection and suggests possible strategies to combat nerve damage in leprosy.

Investigation and control of a large outbreak of multi-drug resistant tuberculosis at a central Lisbon hospital

An increase in the number of new cases of tuberculosis (TB) combined with poor clinical outcome was identified among HIV-infected injecting drug users attending a large HIV unit in central Lisbon. A retrospective epidemiological and laboratory study was conducted to review all newly diagnosed cases of TB from 1995 to 1996 in the HIV unit. Results showed that from 1995 to 1996, 63% (109/173) of the Mycobacterium tuberculosis isolates from HIV-infected patients were resistant to one or more anti-tuberculosis drugs; 89% (95) of these were multidrug-resistant, i.e., resistant to at least isoniazid and rifampicin. Eighty percent of the multidrug-resistant strains (MDR) available for restriction fragment length polymorphism (RFLP) DNA fingerprinting clustered into one of two large clusters. Epidemiological data support the conclusion that the transmission of MDR-TB occurred among HIV-infected injecting drug users exposed to infectious TB cases on open wards in the HIV unit. Improved infection control measures on the HIV unit and the use of empirical therapy with six drugs once patients were suspected to have TB, reduced the incidence of MDR-TB from 42% of TB cases in 1996 to 11% in 1999.

A post-genomic perspective

The complete genome sequence of Mycobacterium tuberculosis, along with novel genetic tools, provides the foundation for a new era of post-genomic research. The challenge is now to translate these opportunities into an improved understanding of the complex biology of tuberculosis infection.

Diagnostic assays for leprosy based on T-cell epitopes

To date, only a limited number of antigens have been described as specific for Mycobacterium leprae, and in many cases, homologues have subsequently been shown to exist in mycobacteria such as M. avium and M. intracellulare. A Leprosy Synthetic Peptide Skin Test Initiative was established by the Steering Committee on the Immunology of Mycobacteria of the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, to investigate the potential of synthetic peptides that encode T-cell epitopes as diagnostic tools, which could be used to develop a skin-test reagent specific for leprosy. Such M. leprae-specific peptides should have unique amino acid sequences, or significant sequence-dissimilarity from those in other mycobacteria. Synthetic peptides, 15 amino acids long, were synthesised from 33 genes or open reading frames within the M. leprae genome. Tuberculoid leprosy patients from four leprosy-endemic countries, Brazil, Ethiopia, Nepal and Pakistan, were tested as subjects known to have been infected with M. leprae, and to make good T-cell responses to antigens of M. leprae; UK blood donors were used as non-exposed or non-infected subjects. Peptides inducing potentially specific responses in leprosy patients and not in UK controls, and those inducing cross-reaction responses, present in both leprosy patients and non-exposed, non-infected controls, were identified. A difference from the equivalent M. tuberculosis sequence of five or more amino acid residues did not, by itself, identify peptides that were M. leprae-specific, suggesting that many of these peptides may have homologues in environmental mycobacteria. To date, this approach has identified a number of peptides with greater than 90% specificity and 19-47% sensitivity, which are undergoing further specificity-testing. Such peptides would have great potential as T-cell reagents with which to monitor exposure to M. leprae within communities, formulated either as skin-test reagents, or as antigens for tests in vitro.

Human herpesvirus 8 LANA interacts with proteins of the mSin3 corepressor complex and negatively regulates Epstein-Barr virus gene expression in dually infected PEL cells

The human herpesvirus 8 (HHV-8) latency-associated nuclear antigen (LANA) is expressed in all latently HHV-8 infected cells and in HHV-8-associated tumors, including primary effusion lymphoma (PEL). To better understand the contribution of LANA to tumorigenesis and to the PEL phenotype, we performed a yeast two-hybrid screen which identified the corepressor protein SAP30 as a LANA binding protein. SAP30 is a constituent of a large multicomponent complex that brings histone deacetylases to the promoter. Glutathione S-transferase affinity assays confirmed interaction between LANA and SAP30 and also demonstrated interactions between LANA and two other members of the corepressor complex, mSin3A and CIR. The corepressors bound to the amino-terminal 340-amino-acid domain of LANA. In transient expression assays, this same domain of LANA mediated repression when targeted to a 5xGal4tk-CAT reporter as a GAL4-LANA fusion. PEL cells have the unusual feature that they are frequently dually infected with both HHV-8 and Epstein-Barr virus (EBV). We found that EBV EBNA-1 expression is downregulated in PEL cells at both the RNA and protein levels. In transient expression assays, LANA repressed activated expression from the EBV Qp and Cp latency promoters. Reduction of endogenous Qp activity could also be demonstrated in EBV-infected Rael cells transfected with a LANA expression plasmid. In contrast to the effect of LANA on EBV latency promoters, LANA activated expression from its own promoter. The data indicate that LANA can mediate transcriptional repression through recruitment of an mSin3 corepressor complex and further that LANA-mediated repression is likely to contribute to the low level of EBV latency gene expression seen in dually infected PEL cells.

Increased potassium concentration inhibits stimulation of vascular smooth muscle proliferation by PDGF-BB and bFGF

The effects of changes in extracellular potassium concentration on the rate of vascular smooth muscle cell proliferation stimulated by cytokines and serum were analyzed in vitro. To analyze the DNA synthesis response, cells from swine coronary artery were grown in DMEM medium containing 3, 4, 5, or 6 mmol/L potassium together with 20 ng/mL platelet-derived growth factor BB (PDGF-BB), 25 ng/mL basic fibroblast growth factor (bFGF), or 5% fetal bovine serum (FBS), with [methyl 3H] thymidine added, for 24 h. Proliferation responses were analyzed in cells grown in medium with potassium concentrations of 3, 4, 5, or 6 mmol/L, together with either 20 ng/mL PDGF-BB, 25 ng/mL bFGF, or 5% FBS, for 7 days, then harvested and counted. Highly significant inverse relationships were observed between potassium concentration and 3H-thymidine incorporation stimulated by each of the three agonists (P < .01 for each, ANOVA), and between potassium concentration and proliferation (all P < .01, ANOVA). Elevation of potassium concentration within the physiologic range inhibits vascular smooth muscle cell DNA synthesis and proliferation.

A postgenomic approach to identification of Mycobacterium leprae-specific peptides as T-cell reagents

To identify Mycobacterium leprae-specific human T-cell epitopes, which could be used to distinguish exposure to M. leprae from exposure to Mycobacterium tuberculosis or to environmental mycobacteria or from immune responses following Mycobacterium bovis BCG vaccination, 15-mer synthetic peptides were synthesized based on data from the M. leprae genome, each peptide containing three or more predicted HLA-DR binding motifs. Eighty-one peptides from 33 genes were tested for their ability to induce T-cell responses, using peripheral blood mononuclear cells (PBMC) from tuberculoid leprosy patients (n = 59) and healthy leprosy contacts (n = 53) from Brazil, Ethiopia, Nepal, and Pakistan and 20 United Kingdom blood bank donors. Gamma interferon (IFN-gamma) secretion proved more sensitive for detection of PBMC responses to peptides than did lymphocyte proliferation. Many of the peptides giving the strongest responses in leprosy donors compared to subjects from the United Kingdom, where leprosy is not endemic, have identical, or almost identical, sequences in M. leprae and M. tuberculosis and would not be suitable as diagnostic tools. Most of the peptides recognized by United Kingdom donors showed promiscuous recognition by subjects expressing differing HLA-DR types. The majority of the novel T-cell epitopes identified came from proteins not previously recognized as immune targets, many of which are cytosolic enzymes. Fifteen of the tested peptides had > or =5 of 15 amino acid mismatches between the equivalent M. leprae and M. tuberculosis sequences; of these, eight gave specificities of > or =90% (percentage of United Kingdom donors who were nonresponders for IFN-gamma secretion), with sensitivities (percentage of responders) ranging from 19 to 47% for tuberculoid leprosy patients and 21 to 64% for healthy leprosy contacts. A pool of such peptides, formulated as a skin test reagent, could be used to monitor exposure to leprosy or as an aid to early diagnosis.

Evaluation of human antimycobacterial immunity using recombinant reporter mycobacteria

A novel in vitro whole blood model was developed to study human antimycobacterial immunity. Recombinant reporter mycobacteria were used to enumerate the bacteria, and interactions between host immune cells and mycobacteria were studied using whole blood rather than cell fractions. The ability of healthy tuberculin-positive and tuberculin-negative individuals to restrict mycobacterial growth was compared. Growth of luminescent mycobacteria was significantly lower in blood samples of tuberculin-positive individuals than in blood samples of tuberculin-negative individuals (P=.005). Restricted mycobacterial growth was associated with significantly higher production of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma (P=.01 and.004, respectively). Inhibition of the TNF-alpha and IFN-gamma response pathways by neutralizing monoclonal antibodies increased mycobacterial growth in whole blood. This model is the first functional assay in which individual variations in cell-mediated immunity are shown to correlate with differences in ability to control mycobacterial growth. It provides a new tool for studying human mycobactericidal mechanisms and, potentially, for the evaluation of improved vaccines.

High potassium intake inhibits neointima formation in the rat carotid artery balloon injury model

Recently, we reported that elevated extracellular potassium concentration in vitro inhibited proliferation and migration of vascular smooth muscle cells, formation of free radical compounds by macrophages, and reduced platelet sensitivity to agonists. In the present study we analyzed the effects of long-term, in vivo elevation of extracellular potassium concentration resulting from changes in dietary potassium intake on the vascular response to injury. The rat carotid artery balloon injury model was employed in 70 adult Sprague Dawley rats assigned to three groups. Beginning 14 days before surgical placement of the carotid lesion and continuing until death, the animals were fed diets containing either low (0.1% potassium, n = 25), normal (1.5% potassium, n = 19), or high potassium (4.0% potassium, n = 26). Fourteen days postsurgery the animals were killed and the arteries were analyzed to determine quantitatively the ratio of neointimal to medial area. Dietary potassium had a significant effect on arterial plasma potassium concentration (one-way analysis of variance, P < .01). Group mean and standard errors were 4.26+/-0.12 mmol/L for the low-potassium group, 5.22+/-0.19 mmol/L for normal, and 5.80+/-0.23 mmol/L for the high-intake group. Increases in dietary potassium attenuated neointima formation significantly (P < .05, one-way analysis of variance), with the mean ratio of neointimal area to medial area being 0.447+/-0.106 for the low-intake animals, 0.384+/-.116 for normal, and 0.240+/-.046 for the high-intake group. These results are consistent with a hypothesis that a high level of potassium intake is effective in inhibiting neointima formation in vivo.

Current tuberculosis vaccine development

Information derived from the complete genome sequence of Mycobacterium tuberculosis makes it possible to develop a range of new vaccine candidates. Strategies currently under investigation include construction of whole cell live attenuated mycobacterial vaccines, as well as the use of individual antigens delivered by a variety of subunit vaccination procedures. Fundamental questions associated with the rational design, preclinical testing, and future application of new tuberculosis vaccines are reviewed.

The 19-kD antigen and protective immunity in a murine model of tuberculosis

The 19-kD antigen is a cell wall-associated lipoprotein present in Mycobacterium tuberculosis and in bacille Calmette-Guérin (BCG) vaccine strains. Expression of the 19-kD antigen as a recombinant protein in two saprophytic mycobacteria-M. vaccae and M. smegmatis-resulted in abrogation of their ability to confer protection against M. tuberculosis in a murine challenge model, and in their ability to prime a DTH response to cross-reactive mycobacterial antigens. Induction of an immune response to the 19-kD antigen by an alternative approach of DNA vaccination had no effect on subsequent M. tuberculosis challenge. These results are consistent with a model in which the presence of the 19-kD protein has a detrimental effect on the efficacy of vaccination with live mycobacteria. Targeted inactivation of genes encoding selected antigens represents a potential route towards development of improved vaccine candidates.

Tumour necrosis factor-alpha production in human alveolar macrophages: modulation by inhaled corticosteroid

Using an ex vivo alveolar macrophage model, the hypothesis that inhaled preparations of corticosteroids might have important anti-inflammatory effects on cells of the peripheral airway was tested. The tumour necrosis factor (TNF)-alpha-inducing potential of three glycolipid preparations from nonpathogenic (arabinofuranasyl lipoarabinomannan (LAM (Ara-LAM)) and virulent (mannase LAM (ManLAM)) mycobacteria and Gram-negative bacteria (lipopolysaccharide (LPS)), in primary alveolar macrophage preparations was investigated. A novel inhaled chlorofluorocarbon (CFC)-free preparation of beclomethasone dipropionate (hydrofluoroalkane 134a (HFA)-BDP) with increased peripheral lung deposition was investigated for its ability to modulate glycolipidinduced TNF-alpha production by human alveolar macrophages, in comparison with a CFC-containing preparation and placebo. Compared to the basal TNF-alpha bioactivity of 0.72 ng x mL-1 (geometric mean), the TNF-alpha bioactivity in the macrophage preparation increased following incubation with LPS (138 ng x mL-1, p<0.001), AraLAM (12.6 ng-mL-1, p<0.001) and ManLAM (1.42 ng x mL-1, p=0.02). HFA-BDP, administered in vivo, significantly reduced LPS- and ManLAM-induced TNF-alpha production by alveolar macrophages cultured ex vivo. No change in glycolipid-induced TNF-alpha production was observed following in vivo administration of CFC-BDP or HFA-placebo. This is the first demonstration of an immunomodulatory effect on alveolar cells of corticosteroid delivered via metered dose inhaler. The present findings suggest that alveolar deposition of beclomethasone dipropionate is capable of modulating the inflammatory potential of the alveolar macrophage population.

Inhibition of vascular smooth muscle cell migration by elevation of extracellular potassium concentration

The effect of potassium on the migration of vascular smooth muscle cells was analyzed in media made with extracellular potassium concentrations of 3, 4, 5, and 6 mmol/L. The migration of cultured porcine coronary artery cells was stimulated with platelet-derived growth factor (PDGF)-BB. In the first study, cells were exposed to PDGF-BB at concentrations of 0, 10, or 20 ng/mL for 5 hours with the use of a Boyden chamber. Cells were quiescent overnight in 0.5% fetal bovine serum in Dulbecco's modified Eagle's medium with an extracellular potassium concentration of 4 mmol/L. With increasing potassium concentration, migration was significantly inhibited (P<0. 02, 2-way ANOVA). In the cells exposed to 10 ng/mL PDGF-BB, migration ranged from 500+/-86% to 294+/-44% (value in wells with 0 ng/mL PDGF-BB and 4 mmol/L potassium concentration=100%) in medium containing 3 to 6 mmol/L extracellular potassium concentration (P<0. 03). Long-term potassium exposure was investigated in cells grown in 5% serum in Dulbecco's modified Eagle's medium with an extracellular potassium concentration of 3, 4, 5, or 6 mmol/L for 3 to 4 weeks. Migration was assessed with 0 or 20 ng/mL PDGF-BB. Migration was significantly inhibited by the elevation of extracellular potassium concentration (P<0.01, 2-way ANOVA). With 20 ng/mL PDGF-BB, the migration rates ranged from 152+/-11% in medium with 3 mmol/L potassium to 69+/-5% in 6 mmol/L potassium (P<0.01). Increases in extracellular potassium concentration within the physiological range significantly and directly inhibit vascular smooth muscle cell migration.

Bacille Calmette-Guérin (BCG)-associated inflammation and fibrosis: modulation by recombinant BCG expressing interferon-gamma (IFN-gamma)

Immunization with existing BCG vaccines has failed to confer consistent protection against tuberculosis. One of the ways to improve the efficacy of BCG is by enhancing its ability to induce a type-1 T cell response. However, this approach carries the risk that enhanced immunoreactivity may exacerbate tissue pathology associated with vaccination. The aim of the present study was to determine whether use of a recombinant BCG expressing IFN-gamma (BCG-IFN) would result in an alteration in the pattern of inflammation and local tissue fibrosis. A murine intravenous BCG infection model was used in which there was a time- and dose-dependent increase in the weight and number of granulomas in the liver. Infection was associated with increased inflammatory activity in the liver, as shown by the increase in expression of inducible nitric oxide synthase (iNOS) assessed by immunochemistry and by measurement of specific mRNA, and in fibrosis measured by hydroxyproline content of the liver and percentage of granuloma cells staining positively for type 1 procollagen. Infection with BCG-IFN resulted in a reduction in organ weight and bacterial load on day 21 compared with infection with control BCG transformed with vector alone (BCG-plasmid). By day 21, there was also a reduction in iNOS mRNA and iNOS+ cells in granulomas in mice infected with BCG-IFN compared with infection with BCG-plasmid, and a similar reduction in both total number of granulomas and liver hydroxyproline content. These results demonstrate that the granulomas in the areas of mycobacterial infection are active sites of both inflammation and fibrosis, and that the local expression of IFN-gamma by the recombinant BCG results in more efficient bacterial clearance which is accompanied by a reduction in tissue pathology.

Comparison of Mycobacterium tuberculosis genomes reveals frequent deletions in a 20 kb variable region in clinical isolates

The Mycobacterium tuberculosis complex is associated with a remarkably low level of structural gene polymorphism. As part of a search for alternative forms of genetic variation that may act as a source of biological diversity in M. tuberculosis, we have identified a region of the genome that is highly variable amongst a panel of unrelated clinical isolates. Fifteen of 24 isolates examined contained one or more copies of the M. tuberculosis-specific IS6110 insertion element within this 20 kb variable region. In nine of the isolates, including the laboratory-passaged strain H37Rv, genomic deletions were identified, resulting in loss of between two and 13 genes. In each case, deletions were associated with the presence of a copy of the IS6110 element. Absence of flanking tri- or tetra-nucleotide repeats identified homologous recombination between adjacent IS6110 elements as the most likely mechanism of the deletion events. IS6110 insertion into hot-spots within the genome of M. tuberculosis provides a mechanism for generation of genetic diversity involving a high frequency of insertions and deletions.

Identification of a Mycobacterium tuberculosis gene that enhances mycobacterial survival in macrophages

Intracellular survival plays a central role in the pathogenesis of Mycobacterium tuberculosis. To identify M. tuberculosis genes required for intracellular survival within macrophages, an M. tuberculosis H37Rv plasmid library was constructed by using the shuttle vector pOLYG. This plasmid library was electroporated into Mycobacterium smegmatis 1-2c, and the transformants were used to infect the human macrophage-like cell line U-937. Because M. smegmatis does not readily survive within macrophages, any increased intracellular survival is likely due to cloned M. tuberculosis H37Rv DNA. After six sequential passages of M. smegmatis transformants through U-937 cells, one clone (p69) was enriched more than 70% as determined by both restriction enzyme and PCR analyses. p69 demonstrated significantly enhanced survival compared to that of the vector control, ranging from 2.4- to 5.3-fold at both 24 and 48 h after infection. DNA sequence analysis revealed three open reading frames (ORFs) in the insert of p69. ORF2 (1.2 kb) was the only one which contained a putative promoter region and a ribosome-binding site. Deletion analysis of the p69 insert DNA showed that disruption of ORF2 resulted in complete loss of the enhanced intracellular survival phenotype. This gene was named the enhanced intracellular survival (eis) gene. By using an internal region of eis as a probe for Southern analysis, eis was found in the genomic DNA of various M. tuberculosis strains and of Mycobacterium bovis BCG but not in that of M. smegmatis or 10 other nonpathogenic mycobacterial species. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis showed that all M. smegmatis eis-containing constructs expressed a unique protein of 42 kDa, the predicted size of Eis. The expression of this 42-kDa protein directly correlated to the enhanced survival of M. smegmatis p69 in U-937 cells. These results suggest a possible role for eis and its protein product in the intracellular survival of M. tuberculosis.

Assessment of immunity to mycobacterial infection with luciferase reporter constructs

Protective immunity to mycobacterial infection is incompletely understood but probably involves the coordinated interaction of multiple cell types and cytokines. With the aim of developing assays that might provide a surrogate measure of protective immunity, we have investigated the use of recombinant mycobacteria carrying luciferase reporter enzymes to assess the effectiveness of antimycobacterial immunity in model systems. Measurement of luminescence was shown to provide a rapid and simple alternative to the counting of CFU as a means of monitoring mycobacterial viability. We describe optimization of a luciferase reporter strain of Mycobacterium tuberculosis and demonstrate its application for the study of mycobacterial interactions with host cells in tissue culture and the rapid assessment of vaccine efficacy in a murine model.

Vascular protective effects of potassium

Potential mechanisms responsible for the cardiovascular protection associated with high levels of dietary potassium were investigated in in vitro and in vivo studies. Elevation of extracellular potassium concentration within the physiological range inhibited free radical formation from macrophages and endothelial cells, inhibited proliferation and thymidine incorporation of vascular smooth muscle cells, and reduced platelet sensitivity to thrombin and other agonists. The effects of potassium on several well-characterized animal models of vascular pathology were also studied. Acute elevation of plasma potassium concentration inhibited thrombus formation in the coronary artery of the dog and the carotid artery of the rabbit. In cholesterol-fed rabbits, 6 weeks of diet containing low potassium content increased by approximately 50% (compared with control rabbits) the number of arteries in the myocardium showing signs of arteriosclerotic lesion formation. And in rats and pigs, 4 weeks of eating high potassium-content diet reduced the severity compared with control animals of neointimal proliferation associated with balloon angioplasty. We propose that high levels of dietary potassium provide cardiovascular protection by inhibiting the function of the cells that are responsible for vascular lesion formation.

Inverse relationship between potassium intake and coronary artery disease in the cholesterol-fed rabbit

We tested the hypothesis that a low level of dietary potassium intake would exacerbate the severity of vascular lesion formation in rabbit coronary arteries during high cholesterol intake. Two groups of nine rabbits were studied for 6 weeks while eating a diet containing 2% cholesterol and 0.9% sodium. The normal potassium group consumed a diet containing 1.5% potassium and the low potassium group consumed a diet containing 0.4% potassium. After 6 weeks the animals were killed, the hearts were removed, and blood samples were withdrawn from the abdominal aorta immediately before removing the heart. The hearts were sectioned and slides were prepared and fixed with hematoxylin and eosin. The numbers of normal and abnormal vessels, and those with foam cells in the subintima, were counted in selected sections. Plasma potassium concentration in the normal and low potassium intake groups averaged 4.27 +/- 0.27 mmol/L and 3.90 +/- 0.11 mmol/L, respectively. No differences between the groups were observed in plasma cholesterol or body weight gain. The percentages of abnormal arteries in the groups were 4.20 +/- 0.35 in the normal intake group and 6.36 +/- 0.50 in the low intake group, 51% greater in the normal intake group (P < .001). These results support the hypothesis that low potassium intake exacerbates the severity of subintimal lesion development in the coronary arteries.

Identification of a novel protein antigen encoded by a Mycobacterium tuberculosis-specific RD1 region gene

A genomic DNA region, designated RD1, that is present in virulent and clinical strains of Mycobacterium tuberculosis and M. bovis, has been shown to be deleted in bacillus Calmette Guérin (BCG). The DNA segments corresponding to three open reading frames (ORFs: ORF-10, ORF-14 and ORF-15) of the RD1 region, that are deleted in BCG strains, were amplified from M. tuberculosis genomic DNA by polymerase chain reaction (PCR), subcloned into pGEX-4T vector system and expressed in Escherichia coli as fusion proteins with glutathione-S-transferase (GST). The recombinant proteins appeared as major cellular proteins in SDS-PAGE gels at the expected molecular mass. The identity of each fusion protein was confirmed by reactivity with anti-GST antibodies in Western immunoblots. When pooled human sera from 11 tuberculosis (TB) patients were used as the source of antibodies, only GST-ORF-14 fusion protein reacted in Western immunoblots. The protein corresponding to ORF-14 was then purified to near homogeneity and isolated free of its fusion partner (GST) by treating the purified GST-ORF-14 fusion protein with thrombin protease. In Western immunoblots, the purified ORF-14 protein reacted with antibodies in 26 of 57 human sera (46%) from TB patients while no reactivity was seen with 11 sera from M. bovis BCG-vaccinated healthy subjects. Interestingly, sera from nine of 15 (60%) long-term contacts of TB patients also had antibodies reactive to the ORF-14 protein. These results suggest that the ORF-14 protein in combination with other immunodominant proteins could be useful in the serodiagnosis of individuals infected with M. tuberculosis.

Construction and murine immunogenicity of recombinant Bacille Calmette Guérin vaccines expressing the B subunit of Escherichia coli heat labile enterotoxin

Three recombinant strains of Mycobacterium bovis Bacille Calmette Guerin (rBCG) were prepared in which the immunogenic B subunit of human Escherichia coli heat labile enterotoxin (LT-Bh) was expressed either as a cytoplasm protein, a cell wall associated lipoprotein or a secreted protein. Intraperitoneal immunisation of mice with these rBCG induced IgG and IgA antibodies to LT-Bh and shifted the serum IgG subclass response to subsequent challenge with purified LT-Bh from IgG1 to an IgG2a. Oral administration of recombinant BCG induced mucosal and serum IgA antibodies to LT-Bh which peaked four months after immunisation. Antibody responses were greater when LT-Bh was expressed as a secreted protein or lipoprotein rather than in the cytoplasm. Oral vaccination with recombinant BCG may be an effective approach, particularly to induce mucosal IgA and prime for a serum TH1 recall response.

Intron retention may regulate expression of Epstein-Barr virus nuclear antigen 3 family genes

The nuclear antigen 3 family genes (EBNA-3, EBNA-4, and EBNA-6) of Epstein-Barr virus (EBV) are important for EBV-induced immortalization and survival of B lymphocytes. However, little is known about how the expression of these genes is regulated. Each of the EBNA-3, EBNA-4, and EBNA-6 genes consists of two exons separated by a small intron. Reverse transcriptase PCR assays revealed that the vast majority of the EBNA-3, EBNA-4, and EBNA-6 mRNA, expressed in transfected and EBV-infected B cells, retained intron sequences. Northern blot and S1 protection assays confirmed that most of the EBNA-3 mRNA contained intron. Examination of deletion mutants of EBNA-3 indicated that the EBNA-3 protein was not necessary for intron retention and that there was no splicing silencing element encoded in the EBNA-3 mRNA. Cell fractionation and RNA gradient analysis revealed that the unspliced EBNA 3 family mRNAs were transported into the cytoplasm and associated with the polysomes. However, Western blot analysis of FLAG-epitope tagged EBNA-3 gave no indication of the presence of splice variant protein forms of EBNA-3. In contrast, transiently transfected cells expressing EBNA-3 revealed a sixfold increase in EBNA-3 protein expression from the genomic EBNA-3 gene compared to EBNA-3 cDNA. These data show that the intronic sequences can influence EBNA-3 protein expression and suggest that intron retention may provide a means for the fine-tuning of expression of the individual EBNA 3 family genes.

IkappaB kinase (IKK)-associated protein 1, a common component of the heterogeneous IKK complex

Activation of the transcription factor NF-kappaB is controlled by the sequential phosphorylation, ubiquitination, and degradation of its inhibitory subunit, IkappaB. We recently purified a large multiprotein complex, the IkappaB kinase (IKK) signalsome, which contains two regulated IkappaB kinases, IKK1 and IKK2, that can each phosphorylate IkappaBalpha and IkappaBbeta. The IKK signalsome contains several additional proteins presumably required for the regulation of the NFkappaB signal transduction cascade in vivo. In this report, we demonstrate reconstitution of IkappaB kinase activity in vitro by using purified recombinant IKK1 and IKK2. Recombinant IKK1 or IKK2 forms homo- or heterodimers, suggesting the possibility that similar IKK complexes exist in vivo. Indeed, in HeLa cells we identified two distinct IKK complexes, one containing IKK1-IKK2 heterodimers and the other containing IKK2 homodimers, which display differing levels of activation following tumor necrosis factor alpha stimulation. To better elucidate the nature of the IKK signalsome, we set out to identify IKK-associated proteins. To this end, we purified and cloned a novel component common to both complexes, named IKK-associated protein 1 (IKKAP1). In vitro, IKKAP1 associated specifically with IKK2 but not IKK1. Functional analyses revealed that binding to IKK2 requires sequences contained within the N-terminal domain of IKKAP1. Mutant versions of IKKAP1, which either lack the N-terminal IKK2-binding domain or contain only the IKK2-binding domain, disrupt the NF-kappaB signal transduction pathway. IKKAP1 therefore appears to mediate an essential step of the NF-kappaB signal transduction cascade. Heterogeneity of IKK complexes in vivo may provide a mechanism for differential regulation of NF-kappaB activation.

CIR, a corepressor linking the DNA binding factor CBF1 to the histone deacetylase complex

CBF1 is a member of the CSL family of DNA binding factors, which mediate either transcriptional repression or transcriptional activation. CSL proteins play a central role in Notch signaling and in Epstein-Barr virus-induced immortalization. Notch is a transmembrane protein involved in cell-fate decisions, and the cytoplasmic domain of Notch (NotchIC) targets CBF1. The Epstein-Barr virus-immortalizing protein EBNA2 activates both cellular and viral gene expression by targeting CBF1 and mimicking NotchIC. We have examined the mechanism of CBF1-mediated repression and show that CBF1 binds to a unique corepressor, CBF1 interacting corepressor (CIR). A CIR homolog is encoded by Caenorhabditis elegans, indicating that CIR is evolutionarily conserved. Two CBF1 mutants that were unable to bind CIR did not function as repressors, suggesting that targeting of CIR to CBF1 is an important component of repression. When expressed as a Gal4 fusion protein, CIR repressed reporter gene expression. CIR binds to histone deacetylase and to SAP30 and serves as a linker between CBF1 and the histone deacetylase complex.