Analysis of the polar lipids of Toxoplasma gondii by electrospray ionization tandem mass spectrometry provides a detailed picture of the lipid molecular species of this parasitic protozoan. Most notably, T. gondii contains a relatively high level, estimated to about 2% of the total polar lipid, of ceramide phosphoethanolamine. The ceramide phosphoethanolamine has a fatty amide profile with only 16-and 18-carbon species. Compared with the host fibroblasts in which it was grown, T. gondii also has higher levels of phosphatidylcholine, but lower levels of sphingomyelin and phosphatidylserine. Analysis at the molecular species level indicated that T. gondii has greater amounts of shorter-chain fatty acid in its polar lipid molecular species than the host fibroblasts. Shorter-chain fatty acids with a combined total of 30 or fewer acyl carbons make up 21% of Toxoplasma's, but only 3% of the host's, diacyl phosphatidylcholine. Furthermore, diacyl phosphatidylcholine with two saturated acyl chains with 12, 14, or 16 carbons make up over 11% of parasite phosphatidylcholine, but less than 3% of the host phosphatidylcholine molecular species. The distinctive T. gondii tachyzoite lipid profile may be particularly suited to the function of parasitic membranes and the interaction of the parasite with the host cell and the host's immune system. Combined with T. gondii genomic data, these lipidomic data will assist in elucidation of metabolic pathways for lipid biosynthesis in this important human pathogen. † This work was supported by NIH NIAID R01s AI27530, AI43228, AI071319, the Research to Prevent Blindness Foundation, and gifts from the Kieweit, Blackmon, Brennan, Koshland, Langel, Morel, Rosenstein, Cussen, Kapnick, and Rooney-Alden families. Work and instrument acquisition at the Kansas Lipidomics Research Center Analytical Laboratory were supported by grants from NSF (MCB 0455318 and DBI 0521587) and NSF's EPSCoR program (EPS-0236913), with matching support from the State of Kansas through Kansas Technology Enterprise Corporation and Kansas State University, as well from NIH grant P20 RR016475 from the INBRE program of the National Center for Research Resources. This is contribution 07-308-J from the Kansas Agricultural Experiment Station.*To whom correspondence should be addressed: Rima McLeod, M.D., The University of Chicago, AMBH S206; 5841 S Maryland Avenue, Chicago, Illinois 60637, Email: rmcleod@midway.uchicago.edu. 1 Abbreviations: ceramide, Cer; ceramide phosphoethanolamine, PE-cer; dihexosylceramide, Dihex-cer; electrospray ionization, ESI; mass spectrometry, MS; phosphatidic acid, PA; phosphatidylcholine, PC; (alkyl or alkenyl)/acyl glycerophosphocholine, ePC; phosphatidylethanolamine, PE; (alkyl or alkenyl)/acyl glycerophosphoethanolamine, ePE; phosphatidylinositol, PI; (alkyl or alkenyl)/ acyl glycerophosphoserine, ePS; Hexosyl ceramide, Hex-cer; phosphatidylserine, PS; sphingomyelin, SM; tandem mass spectrometry, MS/MS. Toxoplasma gondii infects 2-3 billion people throughout the world and is known ...

Improvements in neutrophil chemotaxis assays have advanced our understanding of the mechanisms of neutrophil recruitment; however, traditional methods limit biologic inquiry in important areas. We report a microfluidic technology that enables neutrophil purification and chemotaxis on-chip within minutes, using nanoliters of whole blood, and only requires a micropipette to operate. The low sample volume requirements and novel lid-based method for initiating the gradient of chemoattractant enabled the measurement of human neutrophil migration on a cell monolayer to probe the adherent and migratory states of neutrophils under inflammatory conditions; mouse neutrophil chemotaxis without sacrificing the animal; and both 2D and 3D neutrophil chemotaxis. First, the neutrophil chemotaxis on endothelial cells revealed 2 distinct neutrophil phenotypes, showing that endothelial cell-neutrophil interactions influence neutrophil chemotactic behavior. Second, we validated the mouse neutrophil chemotaxis assay by comparing the adhesion and chemotaxis of neutrophils from chronically inflamed and wild-type mice; we observed significantly higher neutrophil adhesion in blood obtained from chronically inflamed mice. Third, we show that 2D and 3D neutrophil chemotaxis can be directly compared using our technique. These methods allow for new avenues of research while reducing the complexity, time, and sample volume requirements to perform neutrophil chemotaxis assays. (Blood. 2012;120(14): e45-e53)

To eliminate apicomplexan parasites, inhibitory compounds must cross host cell, parasitophorous vacuole, and parasite membranes and cyst walls, making delivery challenging. Here, we show that short oligomers of arginine enter Toxoplasma gondii tachyzoites and encysted bradyzoites. Triclosan, which inhibits enoyl-ACP reductase (ENR), conjugated to arginine oligomers enters extracellular tachyzoites, host cells, tachyzoites inside parasitophorous vacuoles within host cells, extracellular bradyzoites, and bradyzoites within cysts. We identify, clone, and sequence T. gondii enr and produce and characterize enzymatically active, recombinant ENR. This enzyme has the requisite amino acids to bind triclosan. Triclosan released after conjugation to octaarginine via a readily hydrolyzable ester linkage inhibits ENR activity, tachyzoites in vitro, and tachyzoites in mice. Delivery of an inhibitor to a microorganism via conjugation to octaarginine provides an approach to transporting antimicrobials and other small molecules to sequestered parasites, a model system to characterize transport across multiple membrane barriers and structures, a widely applicable paradigm for treatment of active and encysted apicomplexan and other infections, and a generic proof of principle for a mechanism of medicine delivery.