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Biomedical subjects

Ian M Orme

Publications and source records attributed to Ian M Orme.

At least 37 records · Page 2Linked to original sources
PubMed2005

Interleukin-10 production by lung macrophages in CBA xid mutant mice infected with Mycobacterium tuberculosis.

Mice on the CBA inbred strain background expressing the well characterized mutation designated xid in the cytoplasmic signalling enzyme Bruton's protein kinase have been previously noted to illustrate shifts in T helper type 1 (Th1)/Th2 immunity which is underlined by an apparent failure to produce the regulatory cytokine interleukin-10. In the current study we examined if this extended to infection with Mycobacterium tuberculosis, which also depends on Th1 immunity. Contrary to expectations, xid mice showed evidence of a transient early susceptibility to pulmonary infection, changes in macrophage morphology, and decreased activation of lung natural killer cells, while showing evidence of substantial IL-10 production and accumulation in lung lesions macrophages, but paradoxically this did not influence the course of the chronic disease. In addition, macrophages from the lungs of xid mice also expressed high levels of CD14. These observations suggest that the xid mutation in cellular signalling has much wider effects on the immune system than previously thought.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed2005

Oral therapy using nanoparticle-encapsulated antituberculosis drugs in guinea pigs infected with Mycobacterium tuberculosis.

We evaluated the efficacy of nanoparticle-encapsulated antituberculosis drugs administered every 10 days versus that of daily nonencapsulated drugs against Mycobacterium tuberculosis aerosol infection in guinea pigs. Both treatments significantly reduced the bacterial count and lung histopathology, suggesting that the nanoparticle drug delivery system has potential in intermitted treatment of tuberculosis.

Administration, Inhalation↗
PubMed2005

Preclinical testing of the nitroimidazopyran PA-824 for activity against Mycobacterium tuberculosis in a series of in vitro and in vivo models.

This study extends earlier reports regarding the in vitro and in vivo efficacies of the nitroimidazopyran PA-824 against Mycobacterium tuberculosis. PA-824 was tested in vitro against a broad panel of multidrug-resistant clinical isolates and was found to be highly active against all isolates (MIC<1 microg/ml). The activity of PA-824 against M. tuberculosis was also assessed grown under conditions of oxygen depletion. PA-824 showed significant activity at 2, 10, and 50 microg/ml, similar to that of metronidazole, in a dose-dependent manner. In a short-course mouse infection model, the efficacy of PA-824 at 50, 100, and 300 mg/kg of body weight formulated in methylcellulose or cyclodextrin/lecithin after nine oral treatments was compared with those of isoniazid, rifampin, and moxifloxacin. PA-824 at 100 mg/kg in cyclodextrin/lecithin was as active as moxifloxacin at 100 mg/kg and isoniazid at 25 mg/kg and was slightly more active than rifampin at 20 mg/kg. Long-term treatment with PA-824 at 100 mg/kg in cyclodextrin/lecithin reduced the bacterial load below 500 CFU in the lungs and spleen. No significant differences in activity between PA-824 and the other single drug treatments tested (isoniazid at 25 mg/kg, rifampin at 10 mg/kg, gatifloxacin at 100 mg/kg, and moxifloxacin at 100 mg/kg) could be observed. In summary, its good activity in in vivo models, as well as its activity against multidrug-resistant M. tuberculosis and against M. tuberculosis isolates in a potentially latent state, makes PA-824 an attractive drug candidate for the therapy of tuberculosis. These data indicate that there is significant potential for effective oral delivery of PA-824 for the treatment of tuberculosis.

Animals↗
PubMed2005

Memory T lymphocytes generated by Mycobacterium bovis BCG vaccination reside within a CD4 CD44lo CD62 ligand(hi) population.

In the lungs of mice vaccinated with Mycobacterium bovis BCG, there was an accumulation of CD4 cells expressing the activated effector phenotype CD44hi CD62 ligandlo) (CD62Llo) which were capable of secreting gamma interferon. Upon cell transfer, however, cells expressing a resting/naïve phenotype (CD44lo CD62Lhi) were capable of protecting the recipients from a virulent challenge infection, suggesting the emergence of T-cell memory from within this subset.

Activated-Leukocyte Cell Adhesion Molecule↗
PubMed2005

Mice fed lipid-encapsulated Mycobacterium bovis BCG are protected against aerosol challenge with Mycobacterium tuberculosis.

Mice that consumed a single dose of 10(7) lipid-encapsulated Mycobacterium bovis BCG bacilli showed significant pulmonary and systemic protection against aerosol challenge with M. tuberculosis H37Rv. As an extension of previous challenge studies with virulent strains of M. bovis, this report describes a reduction in M. tuberculosis infection in mice vaccinated orally with lipid-encapsulated BCG comparable to that observed in mice vaccinated subcutaneously with BCG. These results are consistent with the induction of tuberculin-specific cell-mediated immune responses.

Administration, Oral↗
PubMed2005

Factors associated with severe granulomatous pneumonia in Mycobacterium tuberculosis-infected mice vaccinated therapeutically with hsp65 DNA.

Resistant C57BL/6 mice infected in the lungs with Mycobacterium tuberculosis and then therapeutically vaccinated with Mycobacterium leprae-derived hsp65 DNA develop severe granulomatous pneumonia and tissue damage. Analysis of cells accumulating in the lungs of these animals revealed substantial increases in T cells secreting tumor necrosis factor alpha and CD8 cells staining positive for granzyme B. Stimulation of lung cells ex vivo revealed very high levels of interleukin-10, some of which was produced by B-1 B cells. This was probably an anti-inflammatory response, since lung pathology was dramatically worsened in B-cell gene-disrupted mice.

Animals↗
PubMed2005

Tracking antigen-specific CD8 T lymphocytes in the lungs of mice vaccinated with the Mtb72F polyprotein.

This study used a major histocompatibility complex class I tetramer reagent to track antigen-specific CD8 T cells in the lungs of mice immunized with the tuberculosis vaccine candidate Mtb72F. The results show that CD8 T cells recognizing an immunodominant Mtb32-specific epitope could be detected in significant numbers over the course of infection in mice exposed to low-dose aerosol challenge with Mycobacterium tuberculosis and that prior vaccination substantially increased the numbers of these cells early in the lungs. The effector phenotype of the cells was shown by the demonstration that many secreted gamma interferon, but very few contained granzyme B. As the course of the infection progressed, many activated CD8 T cells down-regulated expression of CD45RB and upregulated expression of the interleukin-7 receptor alpha chain, indicating a transition of these cells to a state of memory. These data support the hypothesis that M. tuberculosis-specific CD8 T cells can be targeted by vaccination with the Mtb72F polyprotein.

Animals↗
PubMed2005

Use of specific rRNA oligonucleotide probes for microscopic detection of Mycobacterium tuberculosis in culture and tissue specimens.

Mycobacterium tuberculosis infections are a major global health problem. Fast and accurate detection of M. tuberculosis is clearly needed at both the clinical level and the research level. We report a rapid and reliable in situ hybridization technique using rRNA oligonucleotide probes for the identification of M. tuberculosis in tissues and cultures.

Animals↗
PubMed2005

Tuberculosis vaccines: current progress.

Tuberculosis continues to be a major cause of disease and death throughout the developing world. Chemotherapy is the current method of control but with the continuing emergence of drug resistance, coupled with the reticence of major drug companies to invest in drug discovery, the identification of new vaccines to combat tuberculosis is a pressing need. Rational vaccine design requires knowledge of the protective immune response and, while this is not fully understood, it is clear that induction of a T-helper-1 type of immunity is critical to host resistance. A variety of animal models, but especially the mouse and guinea pig, can be used to determine the protective efficacy of new vaccines. These mostly consist of relatively short-term prophylactic models in which animals are vaccinated and then challenged by the aerosol infection route to determine their capacity to reduce the lung bacterial load. Several promising vaccine types have emerged, including subunit vaccines, DNA vaccines and vaccines based upon living vectors, such as recombinant bacillus Calmette-Guérin (BCG) vaccines and auxotrophic or gene disrupted mutants of Mycobacterium tuberculosis. A few of these have already entered early stage clinical trials.

Animals↗
PubMed2004

Differential immune responses and protective efficacy induced by components of a tuberculosis polyprotein vaccine, Mtb72F, delivered as naked DNA or recombinant protein.

Key Ags of Mycobacterium tuberculosis initially identified in the context of host responses in healthy purified protein derivative-positive donors and infected C57BL/6 mice were prioritized for the development of a subunit vaccine against tuberculosis. Our lead construct, Mtb72F, codes for a 72-kDa polyprotein genetically linked in tandem in the linear order Mtb32(C)-Mtb39-Mtb32(N). Immunization of C57BL/6 mice with Mtb72F DNA resulted in the generation of IFN-gamma responses directed against the first two components of the polyprotein and a strong CD8(+) T cell response directed exclusively against Mtb32(C). In contrast, immunization of mice with Mtb72F protein formulated in the adjuvant AS02A resulted in the elicitation of a moderate IFN-gamma response and a weak CD8(+) T cell response to Mtb32c. However, immunization with a formulation of Mtb72F protein in AS01B adjuvant generated a comprehensive and robust immune response, resulting in the elicitation of strong IFN-gamma and Ab responses encompassing all three components of the polyprotein vaccine and a strong CD8(+) response directed against the same Mtb32(C) epitope identified by DNA immunization. All three forms of Mtb72F immunization resulted in the protection of C57BL/6 mice against aerosol challenge with a virulent strain of M. tuberculosis. Most importantly, immunization of guinea pigs with Mtb72F, delivered either as DNA or as a rAg-based vaccine, resulted in prolonged survival (>1 year) after aerosol challenge with virulent M. tuberculosis comparable to bacillus Calmette-Guérin immunization. Mtb72F in AS02A formulation is currently in phase I clinical trial, making it the first recombinant tuberculosis vaccine to be tested in humans.

Adjuvants, Immunologic↗
PubMed2004

Incorporation of CpG oligodeoxynucleotide fails to enhance the protective efficacy of a subunit vaccine against Mycobacterium tuberculosis.

Vaccines which offer better protection than BCG are now badly needed for controlling tuberculosis infection throughout the world. Immunological adjuvants capable of inducing a TH1 type of protective response are necessary to augment the immune response, particularly in the case of subunit vaccines. It is now well established that oligodeoxynucleotides (ODN) containing cytidine phosphate guanosine (CpG) motifs enhance cell-mediated responses in vivo by increasing the production of the TH1 cytokines IL-12 and interferon gamma (IFNgamma). To determine if this would improve subunit vaccination of mice CpG ODN were added to a subunit vaccine consisting of the culture filtrate proteins (CFP) of Mycobacterium tuberculosis H37Rv. It was observed that although adding CpG ODN to the vaccines promoted substantially increased IFNgamma production by lymph node cells draining sites of inoculation, this failed to translate after aerosol challenge into any degree of enhancement of bacterial clearance in the lungs, influx of IFN-positive T cells, or changes in histopathology. These data suggest that the vaccine enhancing effects of CpG ODN are relatively transient.

Animals↗
PubMed2004

The expression of early resistance to an infection with Mycobacterium tuberculosis by old mice is dependent on IFN type II (IFN-gamma) but not IFN type I.

Old mice can express a transient early resistance to infection with M. tuberculosis that requires the presence of CD8 T cells within the lungs. Further characterization of those CD8 T cells within the aged lung established that the majority of CD8 T cells from old mice expressed the IL-15 receptor (CD122) in combination with bright expression of CD44 (CD44(hi)), and were capable of producing IFN-gamma after T cell receptor cross-linking. It has been previously described that CD8 CD44(hi) T cells proliferate in response to IFN-I, acting via IL-15, and therefore we determined whether IFN-I signaling could be a participant in the response of CD8 T cells within the lungs of old mice infected with M. tuberculosis. We demonstrate here that IFN-I signaling was required for the expansion of CD8 T cells within the aging lung in response to infection with M. tuberculosis, but that IFN-I signaling had no influence on the capacity of old mice to express early resistance to an infection with M. tuberculosis. Resident CD8 T cells were still however capable of producing IFN-gamma, which we demonstrate here to be critical in the expression of early resistance, suggesting that the expression of early resistance requires the participation, but not expansion, of the CD8 T cell pool within the aging lung.

Aging↗
PubMed2004

Statistical limitations to the Cornell model of latent tuberculosis infection for the study of relapse rates.

The Cornell model has been extensively used as a mouse model for studying the latent stage of Mycobacterium tuberculosis infection. In this model mice are infected and then given a course of chemotherapy prior to reactivation of infection. We discuss here the importance of using adequate mouse numbers in a Cornell model for the study of relapse rates in order to obtain sufficient statistical power to confirm a hypothesis. Experiments with small sample sizes are useful for 'screening' experiments, but will have very little value in 'confirming' the objective. When the objective of the experiment is confirmation of an effect through establishment of statistical significance, power calculations are critical in order to assure that the sample size will be sufficient to meet that objective.

Animals↗
PubMed2004

The principal sigma factor sigA mediates enhanced growth of Mycobacterium tuberculosis in vivo.

The ability of Mycobacterium tuberculosis to grow in macrophages is central to its pathogenicity. We found previously that the widespread 210 strain of M. tuberculosis grew more rapidly than other strains in human macrophages. Because principal sigma factors influence virulence in some bacteria, we analysed mRNA expression of the principal sigma factor, sigA, in M. tuberculosis isolates during growth in human macrophages. Isolates of the 210 strain had higher sigA mRNA levels and higher intracellular growth rates, compared with other clinical strains and the laboratory strain H37Rv. SigA was also upregulated in the 210 isolate TB294 during growth in macrophages, compared with growth in broth. In contrast, H37Rv sigA mRNA levels did not change under these conditions. Overexpression of sigA enhanced growth of recombinant M. tuberculosis in macrophages and in lungs of mice after aerosol infection, whereas recombinant strains expressing antisense transcripts to sigA showed decreased growth in both models. In the presence of superoxide, sense sigA transformants showed greater resistance than vector controls, and the antisense sigA transformant did not grow. We conclude that M. tuberculosis sigA modulates the expression of genes that contribute to virulence, enhancing growth in human macrophages and during the early phases of pulmonary infection in vivo. This effect may be mediated in part by increased resistance to reactive oxygen intermediates.

Animals↗
PubMed2004

Stable T-cell population expressing an effector cell surface phenotype in the lungs of mice chronically infected with Mycobacterium tuberculosis.

Analysis of T-cell subsets accumulating in the lungs of C57BL/6 mice chronically infected with Mycobacterium tuberculosis revealed that both CD4 and CD8 T-cell populations expressed a cell surface phenotype consistent with that of effector T cells and that a significant proportion of these cells were in the process of secreting gamma interferon.

Animals↗
PubMed2004

Magnetic resonance imaging of pulmonary lesions in guinea pigs infected with Mycobacterium tuberculosis.

We utilized magnetic resonance imaging to visualize lesions in the lungs of guinea pigs infected by low-dose aerosol exposure to Mycobacterium tuberculosis. Lesions were prominent in such images, and colorized three-dimensional reconstructions of images revealed a very uniform distribution in the lungs. Lesion numbers after 1 month were approximately similar to the aerosol exposure algorithm, suggesting that each was established by a single bacterium. Numbers of lesions in unprotected and vaccinated animals were similar over the first month but increased thereafter in the control animals, indicating secondary lesion development. Whereas lesion sizes increased progressively in control guinea pigs, lesions remained small in BCG-vaccinated animals. A prominent feature of the disease pathology in unprotected animals was rapid and severe lymphadenopathy of the mediastinal lymph node cluster, which is paradoxical given the strong state of cellular immunity at this time. Further development of this technical approach could be very useful in tracking lesion size, number, and progression in the search for new tuberculosis vaccines.

Animals↗
PubMed2004

The protective effect of the Mycobacterium bovis BCG vaccine is increased by coadministration with the Mycobacterium tuberculosis 72-kilodalton fusion polyprotein Mtb72F in M. tuberculosis-infected guinea pigs.

A tuberculosis vaccine candidate consisting of a 72-kDa polyprotein or fusion protein based upon the Mtb32 and Mtb39 antigens of Mycobacterium tuberculosis and designated Mtb72F was tested for its protective capacity as a potential adjunct to the Mycobacterium bovis BCG vaccine in the mouse and guinea pig models of this disease. Formulation of recombinant Mtb72F (rMtb72F) in an AS02A adjuvant enhanced the Th1 response to BCG in mice but did not further reduce the bacterial load in the lungs after aerosol challenge infection. In the more stringent guinea pig disease model, rMtb72F delivered by coadministration with BCG vaccination significantly improved the survival of these animals compared to BCG alone, with some animals still alive and healthy in their appearance at >100 weeks post-aerosol challenge. A similar trend was observed with guinea pigs in which BCG vaccination was boosted by DNA vaccination, although this increase was not statistically significant due to excellent protection conferred by BCG alone. Histological examination of the lungs of test animals indicated that while BCG controls eventually died from overwhelming lung consolidation, the majority of guinea pigs receiving BCG mixed with rMtb72F or boosted twice with Mtb72F DNA had mostly clear lungs with minimal granulomatous lesions. Lesions were still prominent in guinea pigs receiving BCG and the Mtb72F DNA boost, but there was considerable evidence of lesion healing and airway remodeling and reestablishment. These data support the hypothesis that the coadministration or boosting of BCG vaccination with Mtb72F may limit the lung consolidation seen with BCG alone and may promote lesion resolution and healing. Collectively, these data suggest that enhancing BCG is a valid vaccination strategy for tuberculosis that is worthy of clinical evaluation.

Animals↗