Biomedical subjects

D N McMurray

Publications and source records attributed to D N McMurray.

At least 19 recordsLinked to original sources

PubMed2002

Dietary n-3 PUFA affect TcR-mediated activation of purified murine T cells and accessory cell function in co-cultures.

Diets enriched in n-3 polyunsaturated fatty acids (PUFA) suppress several functions of murine splenic T cells by acting directly on the T cells and/or indirectly on accessory cells. In this study, the relative contribution of highly purified populations of the two cell types to the dietary suppression of T cell function was examined. Mice were fed diets containing different levels of n-3 PUFA; safflower oil (SAF; control containing no n-3 PUFA), fish oil (FO) at 2% and 4%, or 1% purified docosahexaenoic acid (DHA) for 2 weeks. Purified (>90%) T cells were obtained from the spleen, and accessory cells (>95% adherent, esterase-positive) were obtained by peritoneal lavage. Purified T cells or accessory cells from each diet group were co-cultured with the alternative cell type from every other diet group, yielding a total of 16 different co-culture combinations. The T cells were stimulated with either concanavalin A (ConA) or antibodies to the T cell receptor (TcR)/CD3 complex and the costimulatory molecule CD28 (alphaCD3/alphaCD28), and proliferation was measured after four days. Suppression of T cell proliferation in the co-cultures was dependent upon the dose of dietary n-3 PUFA fed to mice from which the T cells were derived, irrespective of the dietary treatment of accessory cell donors. The greatest dietary effect was seen in mice consuming the DHA diet (P = 0.034 in the anova; P=0.0053 in the Trend Test), and was observed with direct stimulation of the T cell receptor and CD28 costimulatory ligand, but not with ConA. A significant dietary effect was also contributed accessory cells (P = 0.033 in the Trend Test). We conclude that dietary n-3 PUFA affect TcR-mediated by T cell activation by both direct and indirect (accessory cell) mechanisms.

Animals↗

PubMed2001

Tuberculosis vaccine development: recent progress.

Recent years have seen a renewed effort to develop new vaccines against tuberculosis. As a result, several promising avenues of research have developed, including the production of recombinant vaccines, auxotrophic vaccines, DNA vaccines and subunit vaccines. In this article we briefly review this work, as well as consider the pros and cons of the animal models needed to test these new vaccines. Screening to date has been carried out in mouse and guinea pig models, which have been used to obtain basic information such as the effect of the vaccine on bacterial load, and whether the vaccine can prevent or reduce lung pathology. The results to date lead us to be optimistic that new candidate vaccines could soon be considered for evaluation in clinical trials.

Animals↗

PubMed2001

Disease model: pulmonary tuberculosis.

In spite of a massive effort to apply the tools currently available for tuberculosis (TB) control, both in this country and abroad, it is clear that complicating factors [for example, HIV co-infection, drug resistance, lack of patient compliance with chemotherapy, variable efficacy of Bacille Calmette-Guerin (BCG) vaccine] will prevent disease control unless new drugs, vaccines and diagnostic tests are developed (1). The publication of the complete genome sequence of Mycobacterium tuberculosis in 1998 (2) has facilitated a directed search for virulence genes, new drug targets, and vaccine antigens. This research effort has been made possible by the availability of highly biologically relevant animal models of pulmonary TB ((3)).

Animals↗

PubMed2001

Respirable PLGA microspheres containing rifampicin for the treatment of tuberculosis: screening in an infectious disease model.

PURPOSE: Targeted delivery of rifampicin loaded microspheres to the alveolar macrophage, the host cell for Mycobacterium tuberculosis (MTB), may be an effective targeted approach to pulmonary tuberculosis therapy. A guinea pig infection model has been adopted as a post-treatment screening method for antimicrobial effect. Insufflation and nebulization methods of drug delivery were evaluated. METHODS: Rifampicin alone (RIF, 1.03-1.72 mg/kg), within poly(lactide-co-glycolide) microspheres (R-PLGA, equivalent to 1.03-1.72 mg/kg) or polymer microparticles alone (PLGA) were administered by insufflation or nebulization, 24 h before bacterial aerosol exposure. Animals were infected with an aerosol containing a small number (2 x 10(5) cfu/mL) of virulent H37Rv strain of MTB. Lung and spleen tissue samples were collected 28 days after infection for quantitative bacteriology and histopathological analysis. RESULTS: There was a dose-effect relationship between insufflated R-PLGA and burden of bacteria in the lungs. In addition, guinea pigs treated with R-PLGA had a significantly smaller number of viable bacteria (P < 0.05), reduced inflammation and lung damage than lactose or saline control, PLGA or RIF treated animals. CONCLUSIONS: These studies indicate the potential of R-PLGA, delivered by insufflation or nebulization directly to the lungs, to affect the early development of pulmonary TB.

Administration, Inhalation↗

PubMed2001

Dietary n-3 polyunsaturated fatty acids modulate purified murine T-cell subset activation.

Studies in humans and murine disease models have clearly shown dietary fish oil to possess anti-inflammatory properties, apparently mediated by the n-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). To determine the mechanisms by which dietary EPA and DHA modulate mouse T-cell activation, female C57BL/6 mice were fed diets containing either 2% safflower oil (SAF), 2% fish oil (FO), or a 2% purified EPA/DHA ethyl ester mixture for 14 days. Splenic CD4 T cells ( approximately 90% purity) or CD8 T cells ( approximately 85% purity) were incubated with agonists which act at the plasma membrane receptor level [anti(alpha)-CD3/anti(alpha)-CD28], the intracellular level (PMA/Ionomycin), or at both the receptor and intracellular levels (alphaCD3/PMA). CD4 T cells stimulated with alphaCD3/alphaCD28 or PMA/Ionomycin proliferated and produced principally IL-2 (i.e. a Th1 phenotype), whereas the proliferation of CD4 T cells stimulated with alphaCD3/PMA was apparently driven principally by IL-4 (i.e. a Th2 phenotype). The IL-4 driven proliferation of putative Th2 CD4 cells was enhanced by dietary n-3 fatty acids (P = 0.02). Conversely, IL-2 production by alphaCD3/alpha CD28-stimulated CD4 T cells was reduced in FO-fed animals (P < 0.0001). The alphaCD3/alphaCD28-stimulated CD8 cells cultured from FO-fed animals exhibited a significant decrease (P < 0.05) in proliferation. There were no dietary effects seen in alphaCD3/PMA-stimulated CD8 cells, which produced both IL-2 and IL-4, or in PMA/Ionomycin-stimulated CD8 cells, which produced principally IL-2. These data suggest that dietary n-3 fatty acids down-regulated IL-2 driven CD4 and CD8 activation, while up-regulating the activation of the Th2 CD4 T-cell subset. Thus, the anti-inflammatory effects of n-3 fatty acids may result in both the direct suppression of IL-2-induced Th1 cell activation and the indirect suppression of Th1 cells by the enhanced cross-regulatory function of Th2 cells.

Animals↗

PubMed2001

Immunological characterization of antigens encoded by the RD1 region of the Mycobacterium tuberculosis genome.

Development of immunoassays specific for the diagnosis of tuberculosis requires antigens unique to Mycobacterium tuberculosis. In a search for such antigens we tested six proteins encoded by RD1, a region present in M. tuberculosis and virulent M. bovis genomes but missing from the DNA of all substrains of M. bovis Bacillus Calmette-Guerin (BCG). The six proteins (Rv3871, Rv3872, Rv3873, MTSA-10, ESAT-6 and Rv3878) were purified to near-homogeneity from recombinant Escherichia coli. When tested for the ability to elicit antibody responses and delayed type hypersensitivity in tuberculous guinea pigs, only two of six antigens, ESAT-6 and MTSA-10, elicited strong skin reactions, while vigorous antibody responses were observed to all six proteins. When antibody responses to RD1 antigens were evaluated in sera from patients having pulmonary tuberculosis and from control subjects (patients having mycobacterioses other than tuberculosis, and healthy persons), a sizeable proportion (25%) of tuberculosis patients but none of the control subjects, had antibodies against MTSA-10 and/or ESAT-6. We conclude that MTSA-10 and ESAT-6 are promising candidates for immunodiagnostic assays specific for tuberculosis.

Animals↗

PubMed2001

A coordinated strategy for evaluating new vaccines for human and animal tuberculosis.

There is a remarkable convergence in the current efforts to develop and evaluate new tuberculosis (TB) vaccine candidates for use in humans, domestic animals, and wild animal reservoirs. It is quite likely that similar vaccination strategies will prove useful in these diverse host species. Many TB vaccine candidates are being screened for protective efficacy in conventional laboratory animals (e.g. mouse, guinea pig), in captive wild species under laboratory conditions (e.g. brushtail possum), and in the target hosts (e.g. cattle, deer). These systems share some important features, e.g. direct challenge infection of the lung by intratracheal or aerosol exposure, and the use of bacterial enumeration, and gross and microscopic histopathology, as the readouts. Some TB vaccine candidates have been tested in many models, yielding important insights into common mechanisms of resistance to Mycobacterium tuberculosis and M. bovis, and providing evidence of the vaccine's ability to induce protection under widely different circumstances. Coordination of this global search for better TB vaccines, irrespective of target species, would facilitate the rapid application of new technologies and maximize the sharing of materials and experiences between human and veterinary TB researchers. The creation of liaisons between TB vaccine research efforts of government-sponsored medical and agricultural research programs, international bodies such as the World Health Organization (WHO) and the European Community (EC), private foundations and the vaccine industry, will yield a high return.

Animals↗

PubMed2001

Determinants of vaccine-induced resistance in animal models of pulmonary tuberculosis.

A more effective vaccine will be essential if the global tuberculosis (TB) pandemic is ever to be controlled. A large number of new tuberculosis vaccines have been developed, representing the whole range of modern strategies for vaccine formulation and delivery. There is currently no alternative to testing these new vaccines in experimental animals challenged with virulent Mycobacteriurn tuberculosis in order to assess their protective efficacy. Although such testing is being carried out in several animal species (mice, guinea pigs, rabbits), all rational models include pulmonary challenge with a low dose of virulent mycobacteria. The quantitative measures for TB vaccines include increased survival, amelioration of clinical signs and symptoms (e.g. prevention of weight loss), decreased lesion size, reduction in bacillary loads in the lungs, and prevention of extrapulmonary dissemination and hematogenous reseeding of the lung. Although the ultimate objective of vaccination in humans is to prevent transmission to susceptible contacts, no such measurement is being used in animal studies of new vaccines. The validation of an immunological "correlate of protection" is urgently needed. Candidates for such a correlate include antigen-specific interferon-gamma production by T cells of the memory phenotype (CD45RB(high) or mycobacterial killing by macrophages co-cultured with immune T cells. Additional animal models must be developed for vaccines designed to prevent endogenous reactivation or exogenous reinfection, or to be used as a adjunct to chemotherapy.

Animals↗

PubMed2001

Airways delivery of rifampicin microparticles for the treatment of tuberculosis.

A Mycobacterium tuberculosis (H37Rv)-infected guinea pig model was used to screen for targeted delivery to the lungs by insufflation (with lactose excipient) or nebulization, of either rifampicin alone, rifampicin within poly(lactide-co-glycolide) microspheres (R-PLGA) or polymer microparticles alone (PLGA). Animals treated with single and double doses of R-PLGA microspheres exhibited significantly reduced numbers of viable bacteria, inflammation and lung damage compared with lactose-, PLGA- or rifampicin-treated animals 28 days post-infection (P < 0.05). Two doses of R-PLGA resulted in reduced splenic enlargement. These studies support the potential of R-PLGA delivered to the lung to treat pulmonary tuberculosis.

Animals↗

PubMed2001

Docosahexaenoic acid suppresses function of the CD28 costimulatory membrane receptor in primary murine and Jurkat T cells.

(n-3) polyunsaturated fatty acids (PUFA) have been widely documented to reduce inflammation in diseases such as rheumatoid arthritis. This study sought to elucidate the mechanism whereby (n-3) PUFA downregulate T-cell proliferation. We hypothesized that membrane incorporation of dietary PUFA would alter membrane structure and consequently membrane receptor function. Female C57BL/6 mice were fed for 14 d one of three diets containing arachidonic acid (AA), fish oil or docosahexaenoic acid (DHA) that varied in lipid composition only. Spleens were harvested and T cells ( approximately 90% purity) were activated with agonists that stimulated proliferation at the receptor level [anti-CD3 (alphaCD3)/anti-CD28 (alphaCD28)], intracellularly [phorbol-12-myristate-13-acetate (PMA)/ionomycin] or with a combined receptor/intracellular agonist (alphaCD3/PMA). Although there was no significant difference (P > 0.05) in proliferative response across dietary groups within each agonist set, interleukin (IL)-2 secretion was significantly reduced (P = 0.05) in cells from DHA-fed mice stimulated with alphaCD3/alphaCD28. In parallel in vitro experiments, Jurkat T cells were incubated with 50 micromol/L linoleic acid, AA, or DHA. Similar agonists sets were employed, and cells incubated with DHA and AA had a significantly reduced (P < 0.05) IL-2 secretion in three of the agonist sets. However, only when the CD28 receptor was stimulated was there a significant difference (P < 0.05) between DHA and AA. The results of this study suggest the involvement of the CD28 receptor in reducing IL-2 secretion in DHA-fed mice and DHA-incubated Jurkat cells and that purified T cells from DHA-fed mice require accessory cells to modulate proliferative suppression.

Animals↗

PubMed2001

Stable transfection of the bovine NRAMP1 gene into murine RAW264.7 cells: effect on Brucella abortus survival.

Genetically based natural resistance to brucellosis in cattle provides for novel strategies to control zoonotic diseases. Bovine NRAMP1, the homologue of a murine gene (Bcg), has been identified as a major candidate for controlling the in vivo resistant phenotype. We developed an in vitro model for expression of resistance- and susceptibility-associated alleles of bovine NRAMP1 as stable transgenes under the regulatory control of the bovine NRAMP1 promoter in the murine RAW264.7 macrophage cell line (Bcg(s)) to analyze the regulation of the NRAMP1 gene and its role in macrophage function. We demonstrated that the 5'-flanking region of bovine NRAMP1, despite the lack of TATA and CAAT boxes, has a functional promoter capable of driving the expression of a transgene in murine macrophages. A polymorphism within a microsatellite in the 3' untranslated region critically affects the expression of bovine NRAMP1 and the control of in vitro replication of Brucella abortus but not Salmonella enterica serovar Dublin. We did not observe any differences in the production of NO by resting or gamma interferon (IFN-gamma)- and IFN-gamma-lipopolysaccharide (LPS)-treated transfected cell lines, yet the resistant transfected cell lines produced significantly less NO than other cell lines, following stimulation with LPS at 24 and 48 h.

3' Untranslated Regions↗

PubMed2000

A small-molecule nitroimidazopyran drug candidate for the treatment of tuberculosis.

Mycobacterium tuberculosis, which causes tuberculosis, is the greatest single infectious cause of mortality worldwide, killing roughly two million people annually. Estimates indicate that one-third of the world population is infected with latent M. tuberculosis. The synergy between tuberculosis and the AIDS epidemic, and the surge of multidrug-resistant clinical isolates of M. tuberculosis have reaffirmed tuberculosis as a primary public health threat. However, new antitubercular drugs with new mechanisms of action have not been developed in over thirty years. Here we report a series of compounds containing a nitroimidazopyran nucleus that possess antitubercular activity. After activation by a mechanism dependent on M. tuberculosis F420 cofactor, nitroimidazopyrans inhibited the synthesis of protein and cell wall lipid. In contrast to current antitubercular drugs, nitroimidazopyrans exhibited bactericidal activity against both replicating and static M. tuberculosis. Lead compound PA-824 showed potent bactericidal activity against multidrugresistant M. tuberculosis and promising oral activity in animal infection models. We conclude that nitroimidazopyrans offer the practical qualities of a small molecule with the potential for the treatment of tuberculosis.

Animals↗

PubMed2000

A nonhuman primate model for preclinical testing of new tuberculosis vaccines.

Nonhuman primates appear to have significant advantages over conventional laboratory animals in terms of modeling pulmonary tuberculosis for purposes of vaccine evaluation. Primates are quite susceptible to infection by the aerosol route, develop a humanlike disease, exhibit antigen-induced T lymphocyte reactivity both in vitro and in vivo, and can be protected quite effectively by bacille Calmette-Guérin vaccination. There are fewer than a dozen published studies of experimental tuberculosis in primates, and all of the available data on the response of primates to vaccination have been generated in rhesus monkeys (Macaca mulatta). There have been no modern immunologic studies of primate tuberculosis. Thus, responses to tuberculosis vaccines in primates are only minimally characterized, and much additional baseline work remains to be done before the responses to new vaccines can be placed in the proper biological context.

Animals↗

PubMed2000

Effects of dietary n-3 fatty acids on T cell activation and T cell receptor-mediated signaling in a murine model.

A short-term feeding paradigm in mice, with diets enriched with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), was used to study the modulation of T cell activation via the T cell receptor (TcR) and the downstream pathways of intracellular signaling. Diets enriched in EPA and DHA suppressed antigen-specific delayed hypersensitivity reactions and mitogen-induced proliferation of T cells. Cocultures of accessory cells and T cells from mice given different diets revealed that purified fatty acid ethyl esters acted directly on the T cell, rather than through the accessory cell. The loss of proliferative capacity was accompanied by reductions in interleukin (IL)-2 secretion and IL-2 receptor alpha chain mRNA transcription, suggesting that dietary EPA and DHA act, in part, by interrupting the autocrine IL-2 activation pathway. Dietary EPA and DHA blunted the production of intracellular second messengers, including diacylglycerol and ceramide, following mitogen stimulation in vitro. Dietary effects appear to vary with the agonist employed (i.e., anti-CD3 [TcR], anti-CD28, exogenous IL-2, or phorbol myristate acetate and ionomycin).

Animals↗

PubMed2000

Pathologic findings and association of Mycobacterium bovis infection with the bovine NRAMP1 gene in cattle from herds with naturally occurring tuberculosis.

OBJECTIVE: To determine necropsy and Mycobacterium bovis culture results in cattle from herds with tuberculosis, the role of the bovine NRAMP1 gene in resistance and susceptibility to infection with M bovis, and the association between magnitude of the tuberculous lesions and various types of M bovis isolates. ANIMALS: 61 cattle from herds with tuberculosis in Texas and Mexico. PROCEDURE: 61 cattle were evaluated by necropsy; 59 had positive and 2 had negative caudal fold tuberculin intradermal test (CFT) results. Thirty-three cattle with positive CFT results were genotyped to evaluate polymorphism of the 3' untranslated region of the bovine NRAMP1 gene, using single-stranded conformational analysis, 9 were resistant to M bovis with no tuberculous lesions and negative M bovis culture results, and 24 were susceptible with tuberculous lesions and positive M bovis culture results. Isolates of M bovis were analyzed by restriction fragment length polymorphism (RFLP) on the basis of IS6110 sequences and direct-repeat fingerprinting patterns. RESULTS: 21 (35.6%; 21/59) cattle with positive CFT results had tuberculous lesions or positive culture results; in addition, 1 of 2 cattle with negative CFT results had tuberculous lesions and positive culture results. Tuberculous lesions were most common in the thorax (35/63; 55.5%) and lymphoid tissues of the head (10/63; 15.9%). Tuberculous lesions varied from 1 to 11/animal; 8 of 21 (38.1%) had solitary lesions. Associations were not found between resistance or susceptibility to infection with M bovis and polymorphism in the NRAMP1 gene or between the magnitude of the lesions and various RFLP types of M bovis isolates. CONCLUSIONS AND CLINICAL RELEVANCE: The NRAMP1 gene does not determine resistance and susceptibility to infection with M bovis in cattle.

Alleles↗

PubMed2000

[Protective efficacy of BCG Tokyo 172 in the guinea pig model of pulmonary tuberculosis].

BCG Tokyo 172 strain was examined for its protective efficacy against pulmonary tuberculosis in a guinea pig model. Guinea pigs were vaccinated with an intradermal injection of 10(3) CFU of BCG Tokyo 172 strain. BCG Copenhagen 1331 was employed as a control strain. Eight weeks after the vaccination, the animals were infected with about 10 CFU of M. tuberculosis H37Rv by a respiratory route in an aerosol chamber. Five weeks after infection, the animals were euthanized and their spleens, lungs and livers were obtained for enumeration of M. tuberculosis H37Rv and histopathological examinations. The mean log10 CFU of M. tuberculosis H37Rv recovered from right lower lung lobes of guinea pigs vaccinated with BCG Tokyo 172 (frozen), BCG Tokyo 172 (freeze-dried), BCG Copenhagen 1331 (freeze-dried) and placebo were 4.72, 4.23, 4.35 and 5.76, respectively. The mean log10 CFU of the bacteria recovered from spleens were 2.11, 1.51, 1.37 and 5.90, respectively. There was a significant difference in bacterial recovery from both lung and spleen between the vaccinated and the non-vaccinated groups. No significant difference was seen among the groups vaccinated with different strains of BCG in any organ. The lungs exhibited just small granulomatous nodules and the spleens showed no granulomatous nodules in the BCG-vaccinated guinea pigs. On the other hand, the lungs and spleens from non-vaccinated guinea pigs showed much larger granulomatous nodules with central necrosis. These histopathological difference between the vaccinated and the non-vaccinated guinea pigs was consistent with the difference of bacterial growth between them. The results of this study have clearly indicated that BCG Tokyo 172 strain possesses a significant protective efficacy against M. tuberculosis as well as BCG Copenhagen 1331 strain. These results have also shown that the respiratory infection model in guinea pigs is very useful to evaluate efficacy of vaccines against pulmonary tuberculosis.

Animals↗

PubMed2000

Recent advances in improved tuberculosis vaccines.

Tuberculosis continues to be a major infectious cause of global morbidity and mortality, both in children and adults, in spite of widespread vaccination of infants with Bacille Calmette-Guerin (BCG) and the availability of effective antibiotics. The failure of BCG to significantly affect disease incidence in adults in many endemic countries, combined with the growing HIV epidemic and the appearance of multidrug resistant strains of Mycobacterium tuberculosis, threatens to overwhelm current tuberculosis control strategies. This unfortunate state of affairs has driven an intensive search for better tuberculosis vaccines. This article reviews the various vaccine development strategies which are being used e.g., purification or synthesis of protein peptide and non-peptide antigens from M. tuberculosis, creation of rationally-attenuated mutants of BCG and M. tuberculosis, development of DNA vaccines based upon the published genome sequence, the cloning of mycobacterial genes into living vaccine carrier strains (e.g., attenuated Salmonella, vaccinia virus, etc), or the use of naturally attenuated mycobacterial species (e.g., M. vaccae, M. microti). The animal models in which these vaccine candidates are being screened for protective efficacy (e.g., the mouse, guinea pig, rabbit, primate) will be discussed briefly. Finally, some of the challenges inherent in the eventual clinical evaluation of new tuberculosis vaccines are reviewed.

Adult↗

PubMed1999

The M cell as a portal of entry to the lung for the bacterial pathogen Mycobacterium tuberculosis.

M. tuberculosis accesses the terminal lung and is phagocytosed by alveolar macrophages. Utilizing a mouse intratracheal challenge model, we demonstrate that M. tuberculosis rapidly enters through M cells as well. From there, bacilli are deposited within associated intraepithelial leukocytes and subsequently conveyed to the draining lymph nodes early after infection. Osteopetrotic (Csfm(op)/Csfm(op)) mice, null mutants for macrophage colony-stimulating factor, possess diminished numbers of circulating monocytes and tissue macrophages. Csfm(op)/Csfm(op) mice were highly susceptible to challenge with M. tuberculosis. In contrast to controls, tubercle bacilli were not conveyed to draining lymph nodes early after infection but were instead retained within the mucosa. These results indicate that M cells represent an alternate portal of entry for M. tuberculosis, which may contribute to the rapid development of protective lung immune responses.

Animals↗