Multiplex testing for Factor II and Factor V mutations in thrombophilia: technical verification and clinical validation of the cobas® Factor II and Factor V test

Laboratory testing for thrombophilia is complicated but essential for diagnosis. In 2017, the cobas® Factor II and Factor V Test (cobas F2F5 test) was launched for use with the cobas z 480 analyzer. This qualitative polymerase chain reaction test enables multiplex Factor II and Factor V testing with flexible reporting and workflow efficiency. Here, we report the results from studies investigating the performance of the cobas F2F5 test. Technical performance verification, clinical validation, external laboratory performance, and workflow comparison studies were performed. Fresh and frozen whole-blood and genomic DNA (gDNA) samples were tested, and several manual and automated DNA isolation methods were used. Bidirectional Sanger sequencing was used to verify genotypes identified by the cobas F2F5 test. One hundred percent agreement between the cobas F2F5 test and Sanger sequencing was observed for all genotypes. An external laboratory using remnant clinical samples also yielded 100% agreement between cobas F2F5 test results and their routine testing method. The cobas F2F5 test reduced the total sample processing time compared with the LightCycler® 1.2 platform (98.6 vs 420.2 min; 96 samples). Hemoglobin, extraction buffer, and ethanol contamination of the gDNA sample can lead to invalid results. The cobas F2F5 test has a high degree of accuracy for identification of Factor II and Factor V genotypes. This multiplex testing with short sample processing time can reduce handling errors and increase efficiency. Both manual and automated DNA isolation methods can be used with the cobas F2F5 test.

The Mycobacterium bovis bacille Calmette-Guerin phagosome proteome

Mycobacterium tuberculosis and Mycobacterium bovis bacille Calmette-Guérin (BCG) alter the maturation of their phagosomes and reside within a compartment that resists acidification and fusion with lysosomes. To define the molecular composition of this compartment, we developed a novel method for obtaining highly purified phagosomes from BCG-infected human macrophages and analyzed the phagosomes by Western immunoblotting and mass spectrometry-based proteomics. Our purification procedure revealed that BCG grown on artificial medium becomes less dense after growth in macrophages. By Western immunoblotting, LAMP-2, Niemann-Pick protein C1, and syntaxin 3 were readily detectable on the BCG phagosome but at levels that were lower than on the latex bead phagosome; flotillin-1 and the vacuolar ATPase were barely detectable on the BCG phagosome but highly enriched on the latex bead phagosome. Immunofluorescence studies confirmed the scarcity of flotillin on BCG phagosomes and demonstrated an inverse correlation between bacterial metabolic activity and flotillin on M. tuberculosis phagosomes. By mass spectrometry, 447 human host proteins were identified on BCG phagosomes, and a partially overlapping set of 289 human proteins on latex bead phagosomes was identified. Interestingly, the majority of the proteins identified consistently on BCG phagosome preparations were also identified on latex bead phagosomes, indicating a high degree of overlap in protein composition of these two compartments. It is likely that many differences in protein composition are quantitative rather than qualitative in nature. Despite the remarkable overlap in protein composition, we consistently identified a number of proteins on the BCG phagosomes that were not identified in any of our latex bead phagosome preparations, including proteins involved in membrane trafficking and signal transduction, such as Ras GTPase-activating-like protein IQGAP1, and proteins of unknown function, such as FAM3C. Our phagosome purification procedure and initial proteomics analyses set the stage for a quantitative comparative analysis of mycobacterial and latex bead phagosome proteomes.

Malaria parasite invasion of the mosquito salivary gland requires interaction between the Plasmodium TRAP and the Anopheles saglin proteins

SM1 is a twelve-amino-acid peptide that binds tightly to the Anopheles salivary gland and inhibits its invasion by Plasmodium sporozoites. By use of UV-crosslinking experiments between the peptide and its salivary gland target protein, we have identified the Anopheles salivary protein, saglin, as the receptor for SM1. Furthermore, by use of an anti-SM1 antibody, we have determined that the peptide is a mimotope of the Plasmodium sporozoite Thrombospondin Related Anonymous Protein (TRAP). TRAP binds to saglin with high specificity. Point mutations in TRAP's binding domain A abrogate binding, and binding is competed for by the SM1 peptide. Importantly, in vivo down-regulation of saglin expression results in strong inhibition of salivary gland invasion. Together, the results suggest that saglin/TRAP interaction is crucial for salivary gland invasion by Plasmodium sporozoites.

Transmission of Plasmodium, the causative agent of malaria, requires the completion of a complex life cycle in the mosquito, which includes invasion of the salivary glands. This invasion depends on the recognition of mosquito salivary gland surface components by the parasite. This work demonstrates that interaction between the salivary-gland-specific surface protein saglin and the parasite surface protein TRAP is essential for invasion to occur. A better understanding of the mechanisms used by the parasite to develop in the mosquito may lead to novel approaches to intervene with the spread of the disease.

Proteomic analysis of plasma membrane and secretory vesicles from human neutrophils

Background

Polymorphonuclear neutrophils (PMN) constitute an essential cellular component of innate host defense against microbial invasion and exhibit a wide array of responses both to particulate and soluble stimuli. As the cells recruited earliest during acute inflammation, PMN respond rapidly and release a variety of potent cytotoxic agents within minutes of exposure to microbes or their products. PMN rely on the redistribution of functionally important proteins, from intracellular compartments to the plasma membrane and phagosome, as the means by which to respond quickly. To determine the range of membrane proteins available for rapid recruitment during PMN activation, we analyzed the proteins in subcellular fractions enriched for plasma membrane and secretory vesicles recovered from the light membrane fraction of resting PMN after Percoll gradient centrifugation and free-flow electrophoresis purification using mass spectrometry-based proteomics methods.

Results

To identify the proteins light membrane fractions enriched for plasma membrane vesicles and secretory vesicles, we employed a proteomic approach, first using MALDI-TOF (peptide mass fingerprinting) and then by HPLC-MS/MS using a 3D ion trap mass spectrometer to analyze the two vesicle populations from resting PMN. We identified several proteins that are functionally important but had not previously been recovered in PMN secretory vesicles. Two such proteins, 5-lipoxygenase-activating protein (FLAP) and dysferlin were further validated by immunoblot analysis.

Conclusion

Our data demonstrate the broad array of proteins present in secretory vesicles that provides the PMN with the capacity for remarkable and rapid reorganization of its plasma membrane after exposure to proinflammatory agents or stimuli.

Fetuin-A, a hepatocyte-specific protein that binds Plasmodium berghei thrombospondin-related adhesive protein: a potential role in infectivity

Malaria infection is initiated when the insect vector injects Plasmodium sporozoites into a susceptible vertebrate host. Sporozoites rapidly leave the circulatory system to invade hepatocytes, where further development generates the parasite form that invades and multiplies within erythrocytes. Previous experiments have shown that the thrombospondin-related adhesive protein (TRAP) plays an important role in sporozoite infectivity for hepatocytes. TRAP, a typical type-1 transmembrane protein, has a long extracellular region, which contains two adhesive domains, an A-domain and a thrombospondin repeat. We have generated recombinant proteins of the TRAP adhesive domains. These TRAP fragments show direct interaction with hepatocytes and inhibit sporozoite invasion in vitro. When the recombinant TRAP A-domain was used for immunoprecipitation against hepatocyte membrane fractions, it bound to alpha2-Heremans-Schmid glycoprotein/fetuin-A, a hepatocyte-specific protein associated with the extracellular matrix. When the soluble sporozoite protein fraction was immunoprecipitated on a fetuin-A-adsorbed protein A column, TRAP bound this ligand. Importantly, anti-fetuin-A antibodies inhibited invasion of hepatocytes by sporozoites. Further, onset of malaria infection was delayed in fetuin-A-deficient mice compared to that in wild-type C57BL/6 mice when they were challenged with Plasmodium berghei sporozoites. These data demonstrate that the extracellular region of TRAP interacts with fetuin-A on hepatocyte membranes and that this interaction enhances the parasite's ability to invade hepatocytes.

A mitogen-activated protein kinase regulates male gametogenesis and transmission of the malaria parasite Plasmodium berghei

Differentiation of malaria parasites into sexual forms (gametocytes) in the vertebrate host and their subsequent development into gametes in the mosquito vector are crucial steps in the completion of the parasite's life cycle and transmission of the disease. The molecular mechanisms that regulate the sexual cycle are poorly understood. Although several signal transduction pathways have been implicated, a clear understanding of the pathways involved has yet to emerge. Here, we show that a Plasmodium berghei homologue of Plasmodium falciparum mitogen-activated kinase-2 (Pfmap-2), a gametocyte-specific mitogen-activated protein kinase (MAPK), is required for male gamete formation. Parasites lacking Pbmap-2 are competent for gametocytogenesis, but exflagellation of male gametocytes, the process that leads to male gamete formation, is almost entirely abolished in mutant parasites. Consistent with this result, transmission of mutant parasites to mosquitoes is grossly impaired. This finding identifies a crucial role for a MAPK pathway in malaria transmission.

Genotoxicity associated with NO production in macrophages and co-cultured target cells

We previously used mouse macrophage-like RAW264.7 cells as an experimental system for the study of nitric oxide (NO)-associated genotoxicity under physiologically relevant conditions, and characterized genotoxic effects in the NO-producing cells. Here we report experiments utilizing a co-culture system enabling parallel studies of cytotoxic and genotoxic responses in co-cultured target cells as well as in macrophages stimulated to produce NO. We found that co-cultivation with macrophages stimulated to produce NO for 38-42 h resulted in significant increases in mutant fraction in the endogenous genes of target human TK6 and hamster CHO-AA8 cells and in the macrophages themselves, accompanied by a substantial decrease in cell viability. Addition of N-methyl-L-arginine, an NO synthase inhibitor, abrogated much of the cytotoxicity and genotoxicity in both target and macrophages cells, verifying the role of NO in the induction of these responses. We also showed that NO-associated genotoxic response in macrophages could be influenced by culture medium. Collectively, these results support the hypothesis that NO production by activated macrophages may contribute to genotoxic risks associated with chronic inflammation.

Functional reconstitution of a purified proline permease from Candida albicans: interaction with the antifungal cispentacin

We have purified proline permease to homogeneity from Candida albicans using an L-proline-linked agarose matrix as an affinity column. The eluted protein produced two bands of 64 and 67 kDa by SDS-PAGE, whereas it produced a single band of 67 kDa by native PAGE and Western blotting. The apparent Km for L-proline binding to the purified protein was 153 microM. The purified permease was reconstituted into proteoliposomes and its functionality was tested by imposing a valinomycin-induced membrane potential. The main features of L-proline transport in reconstituted systems, viz. specificity and sensitivity to N-ethylmaleimide, were very similar to those of intact cells, The antifungal cispentacin, which enters C. albicans cells via an inducible proline permease, competitively inhibited the L-proline binding and translocation in reconstituted proteoliposomes. However, the uptake of L-proline in proteoliposomes reconstituted with the purified protein displayed monophasic kinetics with an apparent Km of 40 microM.

Role of PM-ATPase, amino acid transport and free amino acid pool in the salt stress of, Candida membranefaciens

The salt tolerant yeast Candida membranefaciens exhibited a pleiotropic modification in response to high NaCl stress. The in vivo specific activity of Plasma Membrane-ATPase (PM-ATPase) of 1.35 M NaCl adapted cells was enhanced at the mid-log phase. The enhancement in the PM-ATPase activity was NaCl specific as cells stressed with identical concentration of KCl did not have any effect on PM-ATPase. The NaCl specific enhancement in the PM-ATPase activity was associated with decreased Km. Studies on H+ efflux correlated with the results of PM-ATPase. However, in vitro incubation of the enzyme with exogenously added salts like NaCl and KCl invariably inhibited enzyme activity by 70-90% in a dose dependent manner to suggest that in vivo effects of the salts on PM-ATPase were different from the in vitro effects. C. membranefaciens showed a higher intracellular levels of glutamate and aspartate in presence of 1.35 M NaCl which may impart osmoprotection to the stressed cells. It was interesting to observe that the transport activities of aspartate and glutamate were not enhanced according to their relative proportion in the total pool of free amino acids. Instead, transport of these and other amino acids (except lysine and arginine) showed a drastic reduction (upto 90%) in the 1.35 M NaCl grown cells.

Role of PM-ATPase, amino acid transport and free amino acid pool in the salt stress of, Candida membranefaciens

The salt tolerant yeast Candida membranefaciens exhibited a pleiotropic modification in response to high NaCl stress. The in vivo specific activity of Plasma Membrane-ATPase (PM-ATPase) of 1.35 M NaCl adapted cells was enhanced at the mid-log phase. The enhancement in the PM-ATPase activity was NaCl specific as cells stressed with identical concentration of KCl did not have any effect on PM-ATPase. The NaCl specific enhancement in the PM-ATPase activity was associated with decreased Km. Studies on H+ efflux correlated with the results of PM-ATPase. However, in vitro incubation of the enzyme with exogenously added salts like NaCl and KCl invariably inhibited enzyme activity by 70-90% in a dose dependent manner to suggest that in vivo effects of the salts on PM-ATPase were different from the in vitro effects. C. membranefaciens showed a higher intracellular levels of glutamate and aspartate in presence of 1.35 M NaCl which may impart osmoprotection to the stressed cells. It was interesting to observe that the transport activities of aspartate and glutamate were not enhanced according to their relative proportion in the total pool of free amino acids. Instead, transport of these and other amino acids (except lysine and arginine) showed a drastic reduction (upto 90%) in the 1.35 M NaCl grown cells.