Tb H37Rv Research Articles

OL-033 Etambutol-mediated changes in rat liver cytochrome P-450 isoforms expression and DNA-fragmentation processes

source for most antibiotics on the market today, including the first-line and salvage TB regimens, including rifampin, streptomycin, amikacin and etc. A set of Microbial Natural Product Library (MNPL) containing secondary metabolites from a unique collection of actinomycetes and fungal strains from unor under-explored ecological niches in China has been constructed. A pilot screen for potential anti-TB compounds was conducted with a selection of 5,000 extracts samples from this MNPL, utilizing a GFP labeled M. bovis BCG based HTS model (Z’-factor 0.8, CV 90% inhibition against logarithmically growing BCG were further evaluated on M. tb H37Rv strains at Broad Institute, as a dilution series ranging from 1× to 1/128×. The results showed that 46 extracts demonstrated anti-H37Rv activity, with 8 showing activity at 1/16×, and 1 showing activity at 1/128×. The following large scale fermentation and bioactivity guided compound isolation work lead to the discovery of diversified class of anti-TB compounds, including actinomycins (MIC 1 4 ug/ml), quinomycins (MIC 0.5 ug/ml), nanaomycins (MIC 8 ug/ml), cyclopeptides (MIC 2 8 ug/ml), anthraquinones (MIC 4 8 ug/ml), oligomycins, part of which were new compounds (not listed).

T Cells from Programmed Death-1 Deficient Mice Respond Poorly to Mycobacterium tuberculosis Infection

BackgroundProgrammed Death-1 (PD-1; CD279) receptor molecule is widely believed to be a negative regulator predominantly expressed by exhausted/activated mouse T cells. Upon interaction with its ligands, PD-L1 and PD-L2, PD-1 inhibits activation of T cells and cytokine production, which has been documented in various viral and fungal infections as well as in vitro studies. Therefore, inhibition of T cell responses by PD-1 resulted in disease resistance in a variety of mouse infection models studied heretofore.Methodology/Principal FindingsHere, we report that PD-1 deficient (PD-1−/−) mice infected with Mycobacterium tuberculosis (M. tb) H37Rv by the aerosol route have increased susceptibility as compared with their wild type littermates. Surprisingly, M. tb antigen-specific T cell proliferation was dramatically reduced in PD-1 deficient animals compared with wild-type littermates, and this was due to increased numbers of regulatory T cells (Tregs) and recruitment of mesenchymal stem cells. Furthermore, PD-1−/− mice exhibited decreases in the autophagy-induced LC3-B marker protein in macrophages.Conclusions/SignificanceOur findings suggest that PD-1 does not play an inhibitory role during M. tb infection and instead promotes mycobacterial clearance in mice.

An attenuated Salmonella-vectored vaccine elicits protective immunity against Mycobacterium tuberculosis

There is a need to develop protective vaccines against tuberculosis (TB) that elicit full immune responses including mucosal immunity. Here, a live attenuated Salmonellatyphimurium aroA SL7207 vector TB vaccine, namely SL(E6-85B), harboring the Mycobacterium tuberculosis (M. tb) H37Rv ESAT6-Ag85B fusion gene was developed. The experimental data demonstrated that this SL(E6-85B) vaccine, or when it is combined with BCG vaccination, induced the strongest TB Ag-specific mucosal, humoral, and cellular immune responses comprised of increased proliferation of T cells, IFN-gamma expression, granzyme B production, as well as the greatest IFN-gamma production of effector-memory T (TEM) or effector CD8+ T cell responses and exerted high protective efficacy in mice against virulent M. tb H37Rv challenge compared to the other vaccinated groups (mice immunized with SL(Ag85B), a DNA vaccine or BCG only). This strategy may represent a novel promising mucosal vaccine candidate for the prevention of TB which are inexpensive to produce, efficacious, and able to be given orally rather than by injection.

Pentacyclo-undecane derived cyclic tetra-amines: Synthesis and evaluation as potent anti-tuberculosis agents

As part of an ongoing effort to develop highly potent anti-tuberculosis agents, fourteen pentacyclo-undecane (PCU) tetra-amine compounds were synthesized and screened for their in vitro anti- mycobacterial activity against two TB strains, H37Rv and XDR 194 [an extensively drug-resistant strain of tuberculosis]. Using the broth macrodilution method, nitrofuranylamide based compounds ( 6a and 6b) showed almost similar activities against the H37Rv strain of Mycobacterium tuberculosis when compared with the control drug, ethambutol. N-Geranyl piperazine PCU ( 8a) and trans– trans farnesyl piperazine PCU ( 8b) were 3.2 and 3.7 times more potent than commercially available ethambutol. Both isoprenyl PCU tetra-amine derivatives and N-decyl piperazine PCU ( 9a) were highly active against the XDR 194 strain of tuberculosis with MICs in the range of 0.63–3.02 μM. Cytotoxicities (IC 50) of isoprenyl based compounds ( 8a, 8b) and compound 9a were tested on a mammalian cell line [MDBK (Madin Darby bovine kidney epithelium)] with values of 30, 24 and 25 μM respectively.

Characterization of Immune Responses to Mycobacterium tuberculosis Rv2041c Protein

Tuberculosis, which is caused by Mycobacterium tuberculosis (M. tb), is one of the most important infectious diseases in the world. Although many functional studies have been conducted on M. tb proteins in the post-genomic era, little is known about the function of many proteins expressed specifically during latency. Previously, we reported that Rv2041c from M. tb H37Rv is highly expressed under conditions of low pH and hypoxia, which represent the in vitro mimicry of latent tuberculosis. In the present study, increased expression levels of Rv2041c under hypoxia and low pH in vitro culture was confirmed by RT-PCR. Interestingly, Rv2041c showed significantly increased expression among genes of the same operon and genes belonging to the same functional group. Finally, the immune responses elicited by the recombinant (r) Rv2041c protein were investigated using ex vivo and in vivo models of M. tb infection. A significantly high level of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-12p40 was detected in a dose-dependent manner by treatment of murine bone marrow-derived macrophages with rRv2041c protein. In addition, IFN-γ and TNF-α secretion increased after stimulation with purified Rv2041c protein to lymphocytes from latent and active TB mice in a modified Cornell model. In conclusion, our findings suggest that Rv2041c is a new T-cell antigen and could be a potential vaccine candidate against M. tb infection by inducing a strong cellular immune response.

Synthesis and Biological Evaluation of Naphthalene-1,4-dione Derivatives as Potent Antimycobacterial Agents

The recent increase in the incidence of tuberculosis with the emergence of multi-drug resistant (MDR) cases has lead to the search for new drugs that are effective against MDR strains of Mycobacterium tuberculosis (M. tb) and can augment the potential of existing drugs against tuberculosis. In the present study a series of naphthalene-1,4-dione derivatives were synthesized and evaluated for their in vitro antimycobacterial activity against M. tb H37Rv strain. Preliminary results indicated that most of the compounds demonstrated significant antimycobacterial activities. The most effective compounds of the series 7, 8 and 10 have MIC values of 3.13 microg/mL and growth inhibition of 99%. Compound 7 has an IC50 value of 0.49 microg/mL. Compounds 1, 3 and 18 with MIC values of 3.13 microg/mL also showed 96-98% growth inhibition. The objective of our study is to generate new leads through different mode of action and to optimize their structure to display the potent efficacy.

Overexpression of Mycobacterium tuberculosis manB, a phosphomannomutase that increases phosphatidylinositol mannoside biosynthesis in Mycobacterium smegmatis and mycobacterial association with human macrophages

Mycobacterium tuberculosis (M. tb) pathogenesis involves the interaction between the mycobacterial cell envelope and host macrophage, a process mediated, in part, by binding of the mannose caps of M. tb lipoarabinomannan (ManLAM) to the macrophage mannose receptor (MR). A presumed critical step in the biosynthesis of ManLAM, and other mannose-containing glycoconjugates, is the conversion of mannose-6-phosphate to mannose-1-phosphate, by a phosphomannomutase (PMM), to produce GDP-mannose, the primary mannose-donor in mycobacteria. We have identified four M. tb H37Rv genes with similarity to known PMMs. Using in vivo complementation of PMM and phosphoglucomutase (PGM) deficient strains of Pseudomonas aeruginosa, and an in vitro enzyme assay, we have identified both PMM and PGM activity from one of these genes, Rv3257c (MtmanB). MtmanB overexpression in M. smegmatis produced increased levels of LAM, lipomannan, and phosphatidylinositol mannosides (PIMs) compared with control strains and led to a 13.3 +/- 3.9-fold greater association of mycobacteria with human macrophages, in a mannan-inhibitable fashion. This increased association was mediated by the overproduction of higher order PIMs that possess mannose cap structures. We conclude that MtmanB encodes a functional PMM involved in the biosynthesis of mannosylated lipoglycans that participate in the association of mycobacteria with macrophage phagocytic receptors.