A glycosylphosphatidylinositol-anchored carbonic anhydrase-related protein of Toxoplasma gondii is important for rhoptry biogenesis and virulence

Carbonic anhydrase-related proteins (CARPs) have previously been described as catalytically inactive proteins closely related to α-carbonic anhydrases (α-CAs). These CARPs are found in animals (both vertebrates and invertebrates) and viruses as either independent proteins or domains of other proteins. We report here the identification of a new CARP (TgCA_RP) in the unicellular organism Toxoplasma gondii that is related to the recently described η-class CA found in Plasmodium falciparum. TgCA_RP is posttranslationally modified at its C terminus with a glycosylphosphatidylinositol anchor that is important for its localization in intracellular tachyzoites. The protein localizes throughout the rhoptry bulbs of mature tachyzoites and to the outer membrane of nascent rhoptries in dividing tachyzoites, as demonstrated by immunofluorescence and immunoelectron microscopy using specific antibodies. T. gondii mutant tachyzoites lacking TgCA_RP display a growth and invasion phenotype in vitro and have atypical rhoptry morphology. The mutants also exhibit reduced virulence in a mouse model. Our results show that TgCA_RP plays an important role in the biogenesis of rhoptries

Inappropriate use of vancomycin for preventing perinatal group B streptococcal (GBS) disease in laboring patients

Objective: The 2002 CDC guidelines for the prevention of perinatal group B streptococcus (GBS) stipulate that vancomycin is reserved for penicillin-allergic women at high risk for beta-lactam anaphylaxis with resistance to clindamycin or erythromycin. Our objective was to evaluate practitioner adherence to these guidelines. Methods: This is a retrospective chart review of patients admitted to labor and delivery who received vancomycin for GBS prophylaxis from January 1st, 2005 to June 1st, 2007. Identification and documentation of allergic reactions to beta lactams and performance of GBS sensitivities at the time of screening were recorded. Results: Eighty-seven patients reporting a penicillin allergy received vancomycin during labor. In 71 patients screened at 35–37 weeks, sensitivities were not performed for 55 patients, of which 10 reported an anaphylactic-like reaction to penicillin. Of 15 patients who had sensitivities performed at the time of screening and were resistant to clindamycin and/or erythromycin, only two patients, however, described an anaphylactic-like reaction to penicillin. Fourteen patients received vancomycin due to an unknown GBS status at <35 weeks of gestation and only three patients from this group reported an anaphylactic-like reaction to penicillin. There were deviations from the CDC protocol in 82 (94%) of 87 patients who received intrapartum vancomycin there were deviations in the CDC protocol. Conclusion: Most patients receiving intrapartum vancomycin for perinatal GBS prophylaxis either did not have a culture with sensitivities performed at the time of GBS screening due to a history of anaphylactic-like reactions to penicillin or received vancomycin for a mild or unknown allergy. Physician adherence to the CDC guidelines with regards to the use of vancomycin is far from optimal.Peer Reviewe

The Toxoplasma Vacuolar H+-ATPase Regulates Intracellular pH and Impacts the Maturation of Essential Secretory Proteins

Summary: Vacuolar-proton ATPases (V-ATPases) are conserved complexes that couple the hydrolysis of ATP to the pumping of protons across membranes. V-ATPases are known to play diverse roles in cellular physiology. We studied the Toxoplasma gondii V-ATPase complex and discovered a dual role of the pump in protecting parasites against ionic stress and in the maturation of secretory proteins in endosomal-like compartments. Toxoplasma V-ATPase subunits localize to the plasma membrane and to acidic vesicles, and characterization of conditional mutants of the a1 subunit highlighted the functionality of the complex at both locations. Microneme and rhoptry proteins are required for invasion and modulation of host cells, and they traffic via endosome-like compartments in which proteolytic maturation occurs. We show that the V-ATPase supports the maturation of rhoptry and microneme proteins, and their maturases, during their traffic to their corresponding organelles. This work underscores a role for V-ATPases in regulating virulence pathways. : Stasic et al. characterize the function of the vacuolar proton ATPase in the life cycle of Toxoplasma gondii, a widespread parasite that infects almost one-third of the world’s population. The work presents molecular evidence of the pump’s role in the synthesis of virulence factors of a highly successful pathogen. Keywords: toxoplasma, vacuolar-H+-ATPase, intracellular pH, proton transport, plant-like vacuole, VAC, rhoptries, micronemes, lytic cycle, lysosom