Potent Tetrahydroquinolone Eliminates Apicomplexan Parasites

Apicomplexan infections cause substantial morbidity and mortality, worldwide. New, improved therapies are needed. Herein, we create a next generation anti-apicomplexan lead compound, JAG21, a tetrahydroquinolone, with increased sp3-character to improve parasite selectivity. Relative to other cytochrome b inhibitors, JAG21 has improved solubility and ADMET properties, without need for pro-drug. JAG21 significantly reduces Toxoplasma gondii tachyzoites and encysted bradyzoites in vitro, and in primary and established chronic murine infections. Moreover, JAG21 treatment leads to 100% survival. Further, JAG21 is efficacious against drug-resistant Plasmodium falciparum in vitro. Causal prophylaxis and radical cure are achieved after P. berghei sporozoite infection with oral administration of a single dose (2.5 mg/kg) or 3 days treatment at reduced dose (0.625 mg/kg/day), eliminating parasitemia, and leading to 100% survival. Enzymatic, binding, and co-crystallography/pharmacophore studies demonstrate selectivity for apicomplexan relative to mammalian enzymes. JAG21 has significant promise as a pre-clinical candidate for prevention, treatment, and cure of toxoplasmosis and malaria

The Bicarbonate Transporter Is Essential for Bacillus anthracis Lethality

In the pathogenic bacterium Bacillus anthracis, virulence requires induced expression of the anthrax toxin and capsule genes. Elevated CO2/bicarbonate levels, an indicator of the host environment, provide a signal ex vivo to increase expression of virulence factors, but the mechanism underlying induction and its relevance in vivo are unknown. We identified a previously uncharacterized ABC transporter (BAS2714-12) similar to bicarbonate transporters in photosynthetic cyanobacteria, which is essential to the bicarbonate induction of virulence gene expression. Deletion of the genes for the transporter abolished induction of toxin gene expression and strongly decreased the rate of bicarbonate uptake ex vivo, demonstrating that the BAS2714-12 locus encodes a bicarbonate ABC transporter. The bicarbonate transporter deletion strain was avirulent in the A/J mouse model of infection. Carbonic anhydrase inhibitors, which prevent the interconversion of CO2 and bicarbonate, significantly affected toxin expression only in the absence of bicarbonate or the bicarbonate transporter, suggesting that carbonic anhydrase activity is not essential to virulence factor induction and that bicarbonate, and not CO2, is the signal essential for virulence induction. The identification of this novel bicarbonate transporter essential to virulence of B. anthracis may be of relevance to other pathogens, such as Streptococcus pyogenes, Escherichia coli, Borrelia burgdorferi, and Vibrio cholera that regulate virulence factor expression in response to CO2/bicarbonate, and suggests it may be a target for antibacterial intervention

Analysis of Legionella Metabolism by Pathogen Vacuole Proteomics

The causative agent of Legionnaires' disease, Legionella pneumophila, replicates in free-living amoebae as well as in macrophages of the innate immune system within a distinct membrane-bound compartment, the "Legionella-containing-vacuole" (LCV). LCV formation is a complex process and requires the bacterial Icm/Dot type IV secretion system, which translocates approximately 300 different "effector" proteins. Intact LCVs from infected Dictyostelium discoideum amoebae or RAW 264.7 murine macrophages can be purified using a straightforward protocol. In the first step, the LCVs in cell homogenates are tagged with an antibody directed against an L. pneumophila effector protein specifically localizing to the pathogen vacuole membrane and isolated by immunomagnetic separation using a secondary antibody coupled to magnetic beads. In the second step, the LCVs are further enriched by density gradient centrifugation through a Histodenz cushion. LCVs thus purified are analyzed by mass spectrometry-based proteomics and characterized by biochemical and cell biological approaches