Glutamine metabolism inhibition has dual immunomodulatory and antibacterial activities against Mycobacterium tuberculosis.

As one of the most successful human pathogens, Mycobacterium tuberculosis (Mtb) has evolved a diverse array of determinants to subvert host immunity and alter host metabolic patterns. However, the mechanisms of pathogen interference with host metabolism remain poorly understood. Here we show that a glutamine metabolism antagonist, JHU083, inhibits Mtb proliferation in vitro and in vivo.

Imaging Tumor-Targeting Bacteria Using 18F-Fluorodeoxysorbitol Positron Emission Tomography.

Background: Microbial-based cancer treatments are an emerging field, with multiple bacterial species evaluated in animal models and some advancing to clinical trials. Noninvasive bacteria-specific imaging approaches can potentially support the development and clinical translation of bacteria-based cancer treatments by assessing the tumor and off-target bacterial colonization.

Methods: 18F-Fluorodeoxysorbitol (18F-FDS) positron emission tomography (PET), a bacteria-specific imaging approach, was used to visualize an attenuated strain of Yersinia enterocolitica, currently in clinical trials as a microbial-based cancer treatment, in murine models of breast cancer.

Glutamine metabolism inhibition has dual immunomodulatory and antibacterial activities against .

As one of the most successful human pathogens, () has evolved a diverse array of determinants to subvert host immunity and alter host metabolic patterns. However, the mechanisms of pathogen interference with host metabolism remain poorly understood. Here we show that a novel glutamine metabolism antagonist, JHU083, inhibits proliferation in vitro and in vivo.

Effective Host-Directed Therapy for Tuberculosis by Depletion of Myeloid-Derived Suppressor Cells and Related Cells Using a Diphtheria Toxin Fusion Protein.

Myeloid-derived suppressor cells (MDSCs) are present in elevated numbers in tuberculosis patients and have been found to be permissive for Mycobacterium tuberculosis proliferation. To determine whether depletion of MDSCs may improve host control of tuberculosis, we used a novel diphtheria toxin-based fusion protein DABIL-4 that targets and depletes interleukin 4 (IL-4) receptor-positive cells. We show that DABIL-4 depletes both polymorphonuclear MDSCs and monocytic MDSCs, increases interferon-γ + T cells, and reduces the lung bacillary burden in a mouse tuberculosis model.

Host-Directed Therapies: Modulating Inflammation to Treat Tuberculosis.

Following infection with , the causative agent of tuberculosis (TB), most human hosts are able to contain the infection and avoid progression to active TB disease through expression of a balanced, homeostatic immune response. Proinflammatory mechanisms aiming to kill, slow and sequester the pathogen are key to a successful host response. However, an excessive or inappropriate pro-inflammatory response may lead to granuloma enlargement and tissue damage, which may prolong the TB treatment duration and permanently diminish the lung function of TB survivors.

Therapeutic targeting with DABIL-4 depletes myeloid suppressor cells in 4T1 triple-negative breast cancer model.

In many solid tumors including triple-negative breast cancer (TNBC), upregulation of the interleukin-4 receptor (IL-4R) has been shown to promote cancer cell proliferation, apoptotic resistance, metastatic potential, and a Th2 response in the tumor microenvironment (TME). Since immunosuppressive cells in the TME and spleen including myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) also express the IL-4R, we hypothesized that selective depletion of IL-4R-bearing cells in TNBC would result in the direct killing of tumor cells and the depletion of immunosuppressive cells and lead to an enhanced antitumor response. To selectively target IL-4R cells, we employed DABIL-4, a fusion protein toxin consisting of the catalytic and translocation domains of diphtheria toxin fused to murine IL-4.

Recent advances with Treg depleting fusion protein toxins for cancer immunotherapy.

T regulatory cells (Tregs) are an important T cell population for immune tolerance, prevention of autoimmune diseases and inhibition of antitumor immunity. The tumor-promoting role played by Tregs in cancer has prompted numerous approaches to develop immunotherapeutics targeting Tregs. One approach to depletion of Treg cells is retargeting the highly potent cytotoxic activity of bacterial toxins.

: Diphtheria Toxin, the Operon, and Its Regulation by Fe2 Activation of apo-DtxR.

Diphtheria is one of the most well studied of all the bacterial infectious diseases. These milestone studies of toxigenic along with its primary virulence determinant, diphtheria toxin, have established the paradigm for the study of other related bacterial protein toxins. This review highlights those studies that have contributed to our current understanding of the structure-function relationships of diphtheria toxin, the molecular mechanism of its entry into the eukaryotic cell cytosol, the regulation of diphtheria expression by holo-DtxR, and the molecular basis of transition metal ion activation of apo-DtxR itself.

Structural and mechanistic insights into EchAMP: A antimicrobial protein from the Echidna milk.

Background: Antibiotic resistance is a problem that necessitates the identification of new antimicrobial molecules. Milk is known to have molecules with antimicrobial properties (AMPs). Echidna Antimicrobial Protein (EchAMP) is one such lactation specific AMP exclusively found in the milk of Echidna, an egg-laying mammal geographically restricted to Australia and New Guinea.

Second-generation IL-2 receptor-targeted diphtheria fusion toxin exhibits antitumor activity and synergy with anti-PD-1 in melanoma.

Denileukin diftitox (DAB-IL-2, Ontak) is a diphtheria-toxin-based fusion protein that depletes CD25-positive cells including regulatory T cells and has been approved for the treatment of persistent or recurrent cutaneous T cell lymphoma. However, the clinical use of denileukin diftitox was limited by vascular leak toxicity and production issues related to drug aggregation and purity. We found that a single amino acid substitution (V6A) in a motif associated with vascular leak induction yields a fully active, second-generation biologic, s-DAB-IL-2(V6A), which elicits 50-fold less human umbilical vein endothelial cell monolayer permeation and is 3.

Identification of YfiH (PgeF) as a factor contributing to the maintenance of bacterial peptidoglycan composition.

Peptidoglycan (PG) is an essential, envelope-fortifying macromolecule of eubacterial cell walls. It is a large polymer with multiple glycan strands interconnected by short peptide chains forming a sac-like structure around cytoplasmic membrane. In most bacteria, the composition of the peptide chain is well-conserved and distinctive; in E.

Regulated proteolysis of a cross-link-specific peptidoglycan hydrolase contributes to bacterial morphogenesis.

Bacterial growth and morphogenesis are intimately coupled to expansion of peptidoglycan (PG), an extensively cross-linked macromolecule that forms a protective mesh-like sacculus around the cytoplasmic membrane. Growth of the PG sacculus is a dynamic event requiring the concerted action of hydrolases that cleave the cross-links for insertion of new material and synthases that catalyze cross-link formation; however, the factors that regulate PG expansion during bacterial growth are poorly understood. Here, we show that the PG hydrolase MepS (formerly Spr), which is specific to cleavage of cross-links during PG expansion in Escherichia coli, is modulated by proteolysis.