Medicine and Health Sciences Commons^™

Mast Cell–Derived Particles Deliver Peripheral Signals To Remote Lymph Nodes, Christian A. Kunder, Ashley L. St. John, Guojie Li, Kam W. Leong, Brent Berwin, Herman F. Staats, Soman N. Abraham

Dartmouth Scholarship

During infection, signals from the periphery are known to reach draining lymph nodes (DLNs), but how these molecules, such as inflammatory cytokines, traverse the significant distances involved without dilution or degradation remains unclear. We show that peripheral mast cells, upon activation, release stable submicrometer heparin-based particles containing tumor necrosis factor and other proteins. These complexes enter lymphatic vessels and rapidly traffic to the DLNs. This physiological drug delivery system facilitates communication between peripheral sites of inflammation and remote secondary lymphoid tissues.

Statistical Hypothesis Testing For Postreconstructed And Postregistered Medical Images, Eugene Demidenko

Dartmouth Scholarship

Postreconstructed and postregistered medical images are typically treated as the raw data, implicitly assuming that those operations are error free. We question this assumption and explore how the precision of reconstruction and affine registration can be assessed by the image covariance matrix and confidence interval, called the confidence eigenimage, using a statistical model-based approach. Various hypotheses may be tested after image reconstruction and registration using classical statistical hypothesis testing vehicles: Is there a statistically significant difference between images? Does the intensity at a specific location or area of interest belong to the “normal” range? Is there a tumor? Does the …

Phosphoinositides And Snare Chaperones Synergistically Assemble And Remodel Snare Complexes For Membrane Fusion, Joji Mima, William Wickner

Dartmouth Scholarship

Yeast vacuole fusion requires 4 SNAREs, 2 SNARE chaperone systems (Sec17p/Sec18p/ATP and the HOPS complex), and 2 phosphoinositides, phosphatidylinositol 3-phosphate [PI(3)P] and phosphatidylinositol 4,5-bisphosphate [PI(4,5)P₂]. By reconstituting proteoliposomal fusion with purified components, we now show that phosphoinositides have 4 distinct roles: PI(3)P is recognized by the PX domain of the SNARE Vam7p; PI(3)P enhances the capacity of membrane-bound SNAREs to drive fusion in the absence of SNARE chaperones; either PI(3)P or PI(4,5)P₂ can activate SNARE chaperones for the recruitment of Vam7p into fusion-competent SNARE complexes; and either PI(3)P or PI(4,5)P₂ strikingly promotes synergistic SNARE complex remodeling …

Long-Term Immunity To Lethal Acute Or Chronic Type Ii Toxoplasma Gondii Infection Is Effectively Induced In Genetically Susceptible C57bl/6 Mice By Immunization With An Attenuated Type I Vaccine Strain, Jason P. Gigley, Barbara A. Fox, David J. Bzik

Dartmouth Scholarship

C57BL/6 (B6) mice are genetically highly susceptible to chronic type II Toxoplasma gondii infections that invariably cause lethal toxoplasmic encephalitis. We examined the ability of an attenuated type I vaccine strain to elicit long-term immunity to lethal acute or chronic type II infections in susceptible B6 mice. Mice immunized with the type I cps1-1 vaccine strain were not susceptible to a lethal (100-cyst) challenge with the type II strain ME49. Immunized mice challenged with 10 ME49 cysts exhibited significant reductions in brain cyst and parasite burdens compared to naive mice, regardless of the route of challenge infection. Remarkably, cps1-1 strain-immunized …

Microbial Nad Metabolism: Lessons From Comparative Genomics, Francesca Gazzaniga, Rebecca Stebbins, Sheila Z. Chang, Mark A. Mcpeek, Charles Brenner

Dartmouth Scholarship

NAD is a coenzyme for redox reactions and a substrate of NAD-consuming enzymes, including ADP-ribose transferases, Sir2-related protein lysine deacetylases, and bacterial DNA ligases. Microorganisms that synthesize NAD from as few as one to as many as five of the six identified biosynthetic precursors have been identified. De novo NAD synthesis from aspartate or tryptophan is neither universal nor strictly aerobic. Salvage NAD synthesis from nicotinamide, nicotinic acid, nicotinamide riboside, and nicotinic acid riboside occurs via modules of different genes. Nicotinamide salvage genes nadV and pncA, found in distinct bacteria, appear to have spread throughout the tree of life …

Ras Activity Levels Control The Development Of Pancreatic Diseases, Baoan Ji, Lilian Tsou, Huamin Wang, Sebastian Gaiser, David Chang, Jaroslaw Daniluk, Yan Bi, Tobias Grote, Daniel Longnecker, Craig Logsdon

Dartmouth Scholarship

Differentiated pancreatic acinar cells expressing endogenous levels of mutant K-Ras do not spontaneously develop pancreatic ductal adenocarcinoma (PDAC). However, we hypothesized that acinar cells would develop PDAC in the presence of Ras activity levels mimicking those of human tumor cells.We measured Ras activity in PDAC cells from mice and humans using a Raf pull-down assay. We compared the effects of acinar cell expression of mutant K-Ras at endogenous and elevated levels on Ras activity and on the development of PDAC.

Characterization Of Two Outer Membrane Proteins, Flgo And Flgp, That Influence Vibrio Cholerae Motility, Raquel M. Martinez, Madushini N. Dharmasena, Thomas J. Kirn, Ronald K. Taylor

Dartmouth Scholarship

Vibrio cholerae is highly motile by the action of a single polar flagellum. The loss of motility reduces the infectivity of V. cholerae, demonstrating that motility is an important virulence factor. FlrC is the sigma-54-dependent positive regulator of flagellar genes. Recently, the genes VC2206 (flgP) and VC2207 (flgO) were identified as being regulated by FlrC via a microarray analysis of an flrC mutant (D. C. Morris, F. Peng, J. R. Barker, and K. E. Klose, J. Bacteriol. 190:231-239, 2008). FlgP is reported to be an outer membrane lipoprotein required for motility that functions as a colonization factor. The study reported …

Low-Dose Arsenic Compromises The Immune Response To Influenza A Infection In Vivo, Courtney D. Kozul, Kenneth H. Ely, Richard I. Enelow, Joshua W. Hamilton

Dartmouth Scholarship

Background:

Arsenic exposure is a significant worldwide environmental health concern. We recently reported that 5-week exposure to environmentally relevant levels (10 and 100 ppb) of As in drinking water significantly altered components of the innate immune response in mouse lung, which we hypothesize is an important contributor to the increased risk of lung disease in exposed human populations.

Objectives:

We investigated the effects of As exposure on respiratory influenza A (H1N1) virus infection, a common and potentially fatal disease.

Methods:

In this study, we exposed C57BL/6J mice to 100 ppb As in drinking water for 5 weeks, followed by intranasal …

Distinction Of The Memory B Cell Response To Cognate Antigen Versus Bystander Inflammatory Signals, Micah J. Benson, Raul Elgueta, William Schpero, Michael Molloy, Weijun Zhang, Edward Usherwood, Randolph J. Noelle

Dartmouth Scholarship

The hypothesis that bystander inflammatory signals promote memory B cell (B_MEM) self- renewal and differentiation in an antigen-independent manner is critically evaluated herein. To comprehensively address this hypothesis, a detailed analysis is presented examining the response profiles of B-2 lineage B220 + IgG + B_MEM toward cognate protein antigen in comparison to bystander inflammatory signals. After in vivo antigen encounter, quiescent B_MEM clonally expand. Surprisingly, proliferating B_MEM do not acquire germinal center (GC) B cell markers before generating daughter B_MEM and differentiating into plasma cells or form structurally identifiable GCs. In striking contrast to …

Disruption Of Histone Modification And Carm1 Recruitment By Arsenic Represses Transcription At Glucocorticoid Receptor-Regulated Promoters, Fiona D. Barr, Lori J. Krohmer, Joshua W. Hamilton, Lynn A. Sheldon

Dartmouth Scholarship

Chronic exposure to inorganic arsenic (iAs) found in the environment is one of the most significant and widespread environmental health risks in the U.S. and throughout the world. It is associated with a broad range of health effects from cancer to diabetes as well as reproductive and developmental anomalies. This diversity of diseases can also result from disruption of metabolic and other cellular processes regulated by steroid hormone receptors via aberrant transcriptional regulation. Significantly, exposure to iAs inhibits steroid hormone-mediated gene activation. iAs exposure is associated with disease, but is also used therapeutically to treat specific cancers complicating an understanding …

Urogenital Abnormalities In Men Exposed To Diethylstilbestrol In Utero: A Cohort Study, Julie R. Palmer, Arthur L. Herbst, Kenneth L. Noller, Deborah A. Boggs, Rebecca Troisi, Linda Titus-Ernstoff, Elizabeth E. Hatch, Lauren A. Wise, William C. Strohsnitter, Robert N. Hoover

Dartmouth Scholarship

Background: Diethylstilbestrol (DES), a synthetic estrogen widely prescribed to pregnant women during the 1940s70s, has been shown to cause reproductive problems in the daughters. Studies of prenatally-exposed males have yielded conflicting results.

Methods: In data from a collaborative follow-up of three U.S. cohorts of DES-exposed sons, we examined the relation of prenatal DES exposure to occurrence of male urogenital abnormalities. Exposure status was determined through review of prenatal records. Mailed questionnaires (1994, 1997, 2001) asked about specified abnormalities of the urogenital tract. Risk ratios (RR) were estimated by Cox regression with constant time at risk and control for year of …

Aging And Environmental Exposures Alter Tissue-Specific Dna Methylation Dependent Upon Cpg Island Context, Brock C. Christensen, E Andres Houseman, Carmen J. Marsit, Shichun Zheng, Margaret R. Wrensch, Joseph L. Wiemels, Heather H. Nelson, Margaret R. Karagas

Dartmouth Scholarship

Epigenetic control of gene transcription is critical for normal human development and cellular differentiation. While alterations of epigenetic marks such as DNA methylation have been linked to cancers and many other human diseases, interindividual epigenetic variations in normal tissues due to aging, environmental factors, or innate susceptibility are poorly characterized. The plasticity, tissue-specific nature, and variability of gene expression are related to epigenomic states that vary across individuals. Thus, population-based investigations are needed to further our understanding of the fundamental dynamics of normal individual epigenomes. We analyzed 217 non-pathologic human tissues from 10 anatomic sites at 1,413 autosomal CpG loci …

Real Time Pcr Detection Of The Pi*Z And Pi*S Mutations Associated With Alpha-1 Antitrypsin Deficiency, Claudine L. Bartels, Angela L. Marchetti, W. Edward Highsmith, Gregory J. Tsongalis

Dartmouth Scholarship

Alpha-1 antitrypsin (A1AT or AAT) is a serine protease inhibitor (PI) which, when present at low levels, can cause chronic obstructive pulmonary disease (COPD) and liver disease in both children and adults. Several mutations within the SERPINA1 gene have been found to cause this deficiency. The most common variants are PI*Z and PI*S, each caused by a single nucleotide polymorphism (SNP). We describe a real time polymerase chain reaction (PCR) assay for the rapid genotyping of these polymorphisms. DNA was extracted from fourteen EDTA-anticoagulated whole blood samples using the Qiagen EZ1 blood extraction kit. SNP genotyping was performed using primer/probe …

Uncoupling Scavenger Receptor A-Mediated Phagocytosis Of Bacteria From Endotoxic Shock Resistance, Eyal Amiel, Julie L. Acker, Ryan M. Collins, Brent Berwin

Dartmouth Scholarship

Unresolved infection by gram-negative bacteria can result in the potentially lethal condition known as endotoxic shock, whereby uncontrolled inflammation can lead to multiple organ failure and death of the infected host. Previous results have demonstrated that animals deficient in class A scavenger receptor (SRA), a trafficking receptor for bacteria and bacterium-derived molecules, are more susceptible to endotoxic shock. This has been proposed to be a result of impaired SRA-dependent phagocytic clearance of bacteria resulting in stronger proinflammatory stimuli. In this report, we test the hypothesis that there is an obligate reciprocal relationship between SRA-mediated phagocytosis of bacteria and susceptibility to …

Flagellum-Mediated Biofilm Defense Mechanisms Of Pseudomonas Aeruginosa Against Host-Derived Lactoferrin, Jeff G. Leid, Mathias Kerr, Candice Selgado, Chelsa Johnson, Gabriel Moreno, Alyssa Smith, Mark E. Shirtliff, Georg A. O'Toole, Emily K. Cope

Dartmouth Scholarship

Chronic infection with the gram-negative organism Pseudomonas aeruginosa is a leading cause of morbidity and mortality in human patients, despite high doses of antibiotics used to treat the various diseases this organism causes. These infections are chronic because P. aeruginosa readily forms biofilms, which are inherently resistant to antibiotics as well as the host's immune system. Our laboratory has been investigating specific mutations in P. aeruginosa that regulate biofilm bacterial susceptibility to the host. To continue our investigation of the role of genetics in bacterial biofilm host resistance, we examined P. aeruginosa biofilms that lack the flgK gene. This mutant …

A Functional Difficulty And Functional Pain Instrument For Hip And Knee Osteoarthritis, Alan M. Jette, Christine M. Mcdonough, Pengsheng Ni, Stephen M. Haley

Dartmouth Scholarship

The objectives of this study were to develop a functional outcome instrument for hip and knee osteoarthritis research (OA-FUNCTION-CAT) using item response theory (IRT) and computer adaptive test (CAT) methods and to assess its psychometric performance compared to the current standard in the field.

Suppression Of Rhog Activity Is Mediated By A Syndecan 4–Synectin–Rhogdi1 Complex And Is Reversed By Pkcα In A Rac1 Activation Pathway, Arye Elfenbein, John M. Rhodes, Julia Meller, Martin A. Schwartz, Michiyuki Matsuda, Michael Simons

Dartmouth Scholarship

Fibroblast growth factor 2 (FGF2) is a major regulator of developmental, pathological, and therapeutic angiogenesis. Its activity is partially mediated by binding to syndecan 4 (S4), a proteoglycan receptor. Angiogenesis requires polarized activation of the small guanosine triphosphatase Rac1, which involves localized dissociation from RhoGDI1 and association with the plasma membrane. Previous work has shown that genetic deletion of S4 or its adapter, synectin, leads to depolarized Rac activation, decreased endothelial migration, and other physiological defects. In this study, we show that Rac1 activation downstream of S4 is mediated by the RhoG activation pathway. RhoG is maintained in an inactive …

Chronic Exposure To Arsenic In The Drinking Water Alters The Expression Of Immune Response Genes In Mouse Lung, Courtney D. Kozul, Thomas H. Hampton, Jennifer C. Davey, Julie A. Gosse, Athena P. Nomikos, Phillip L. Eisenhauer, Daniel J. Weiss, Jessica E. Thorpe, Michael A. Ihnat, Joshua W. Hamilton

Dartmouth Scholarship

Background:

Chronic exposure to drinking water arsenic is a significant worldwide environmental health concern. Exposure to As is associated with an increased risk of lung disease, which may make it a unique toxicant, because lung toxicity is usually associated with inhalation rather than ingestion.

Objectives:

The goal of this study was to examine mRNA and protein expression changes in the lungs of mice exposed chronically to environmentally relevant concentrations of As in the food or drinking water, specifically examining the hypothesis that As may preferentially affect gene and protein expression related to immune function as part of its mechanism of …

Il-9 As A Mediator Of Th17-Driven Inflammatory Disease, Elizabeth C. Nowak, Casey T. Weaver, Henrietta Turner, Sakhina Begum-Haque, Burkhard Becher, Bettina Schreiner, Anthony J. Coyle, Lloyd H. Kasper, Randolph J. Noelle

Dartmouth Scholarship

We report that like other T cells cultured in the presence of transforming growth factor (TGF) beta, Th17 cells also produce interleukin (IL) 9. Th17 cells generated in vitro with IL-6 and TGF-beta as well as purified ex vivo Th17 cells both produced IL-9. To determine if IL-9 has functional consequences in Th17-mediated inflammatory disease, we evaluated the role of IL-9 in the development and progression of experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. The data show that IL-9 neutralization and IL-9 receptor deficiency attenuates disease, and this correlates with decreases in Th17 cells and IL-6-producing macrophages in …

Kinetics And Phenotype Of Vaccine-Induced Cd8+ T-Cell Responses To Toxoplasma Gondii, Kimberly A. Jordan, Emma H. Wilson, Elia D. Tait, Barbara A. Fox, David S. Roos, David J. Bzik

Dartmouth Scholarship

Multiple studies have established that the ability of CD8⁺ T cells to act as cytolytic effectors and produce gamma interferon is important in mediating resistance to the intracellular parasite Toxoplasma gondii. To better understand the generation of the antigen-specific CD8⁺ T-cell responses induced by T. gondii, mice were immunized with replication-deficient parasites that express the model antigen ovalbumin (OVA). Class I tetramers specific for SIINFEKL were used to track the OVA-specific endogenous CD8⁺ T cells. The peak CD8⁺ T-cell response was found at day 10 postimmunization, after which the frequency and numbers of antigen-specific cells …

A Truncation Mutation In Tbc1d4 In A Family With Acanthosis Nigricans And Postprandial Hyperinsulinemia, Satya Dash, Hiroyuki Sano, Justin J. Rochford, Robert K. Semple

Dartmouth Scholarship

Tre-2, BUB2, CDC16, 1 domain family member 4 (TBC1D4) (AS160) is a Rab-GTPase activating protein implicated in insulin-stimulated glucose transporter 4 (GLUT4) translocation in adipocytes and myotubes. To determine whether loss-of-function mutations in TBC1D4 might impair GLUT4 translocation and cause insulin resistance in humans, we screened the coding regions of this gene in 156 severely insulin-resistant patients. A female presenting at age 11 years with acanthosis nigricans and extreme postprandial hyperinsulinemia was heterozygous for a premature stop mutation (R363X) in TBC1D4. After demonstrating reduced expression of wild-type TBC1D4 protein and expression of the truncated protein in lymphocytes from the proband, …

Development And Validation Of An Index Of Musculoskeletal Functional Limitations, Jeffrey N. Katz, Elizabeth A. Wright, John A. Baron, Elena Losina

Dartmouth Scholarship

While musculoskeletal problems are leading sources of disability, there has been little research on measuring the number of functionally limiting musculoskeletal problems for use as predictor of outcome in studies of chronic disease. This paper reports on the development and preliminary validation of a self administered musculoskeletal functional limitations index.

Prion Protein Glycosylation Is Not Required For Strain-Specific Neurotropism, Justin R. Piro, Brent T. Harris, Koren Nishina, Claudio Soto, Rodrigo Morales, Judy R. Rees, Surachai Supattapone

Dartmouth Scholarship

In this study, we tested the hypothesis that the glycosylation of the pathogenic isoform of the prion protein (PrP^Sc) might encode the selective neurotropism of prion strains. We prepared unglycosylated cellular prion protein (PrP^C) substrate molecules from normal mouse brain by treatment with PNGase F and used reconstituted serial protein cyclic misfolding amplification reactions to produce RML and 301C mouse prions containing unglycosylated PrP^Sc molecules. Both RML- and 301C-derived prions containing unglycosylated PrP^Sc molecules were infectious to wild-type mice, and neuropathological analysis showed that mice inoculated with these samples maintained strain-specific patterns of PrP …

Cannabinoid Receptor Type 2 Activation Induces A Microglial Anti-Inflammatory Phenotype And Reduces Migration Via Mkp Induction And Erk Dephosphorylation, Edgar A. Romero-Sandoval, Ryan Horvath, Russell P. Landry, Joyce A. Deleo

Dartmouth Scholarship

Cannabinoid receptor type 2 (CBR2) inhibits microglial reactivity through a molecular mechanism yet to be elucidated. We hypothesized that CBR2 activation induces an anti-inflammatory phenotype in microglia by inhibiting extracellular signal-regulated kinase (ERK) pathway, via mitogen-activated protein kinase-phosphatase (MKP) induction. MKPs regulate mitogen activated protein kinases, but their role in the modulation of microglial phenotype is not fully understood.

Automated Identification Of Tumor Microscopic Morphology Based On Macroscopically Measured Scatter Signatures, Pilar Beatriz Garcia-Allende, Venkataramanan Krishnaswamy, P Jack Hoopes, Kimberley S. Samkoe, Olga M. Conde, Brian W. Pogue

Dartmouth Scholarship

An automated algorithm and methodology is presented to identify tumor-tissue morphologies based on broadband scatter data measured by raster scan imaging of the samples. A quasi-confocal reflectance imaging system was used to directly measure the tissue scatter reflectance in situ, and the spectrum was used to identify the scattering power, amplitude, and total wavelength-integrated intensity. Pancreatic tumor and normal samples were characterized using the instrument, and subtle changes in the scatter signal were encountered within regions of each sample. Discrimination between normal versus tumor tissue was readily performed using a K-nearest neighbor classifier algorithm. A similar approach worked …

Imaging Of Glioma Tumor With Endogenous Fluorescence Tomography, Dax S. Kepshire, Summer L. Gibbs-Strauss, Julia A. O'Hara, Michael Hutchins, Niculae Mincu, Frederic Leblond, Mario Khayat, Hamid Dehghani, Subhadra Srinivasan, Brian W. Pogue

Dartmouth Scholarship

Tomographic imaging of a glioma tumor with endogenous fluorescence is demonstrated using a noncontact single-photon counting fan-beam acquisition system interfaced with microCT imaging. The fluorescence from protoporphyrin IX (PpIX) was found to be detectable, and allowed imaging of the tumor from within the cranium, even though the tumor presence was not visible in the microCT image. The combination of single-photon counting detection and normalized fluorescence to transmission detection at each channel allowed robust imaging of the signal. This demonstrated use of endogenous fluorescence stimulation from aminolevulinic acid (ALA) and provides the first in vivo demonstration of deep tissue tomographic imaging …

U2os Cells Lacking Chk1 Undergo Aberrant Mitosis And Fail To Activate The Spindle Checkpoint, Laura Carrassa, Yolanda Sanchez, Eugenio Erba, Giovanna Damia

Dartmouth Scholarship

Chk1 is a conserved protein kinase originally identified in fission yeast, required to delay entry of cells with damaged or unreplicated DNA into mitosis. The requirement of Chk1 for both S and G2/M checkpoints has been elucidated while only few studies have connected Chk1 to the mitotic spindle checkpoint. We used a small interference RNA strategy to investigate the role of Chk1 in unstressed conditions. Chk1 depletion in U2OS human osteosarcoma cells inhibited cell proliferation and raised the percentage of cells with a 4N DNA content, which correlated with accumulation of giant polynucleated cells morphologically distinct from apoptotic cells, while …

The C. Elegans Snail Homolog Ces-1 Can Activate Gene Expression In Vivo And Share Targets With Bhlh Transcription Factors, John S. Reece-Hoyes, Bart Deplancke, M. Inmaculada Barrasa, Julia Hatzold, Ryan B. Smit, H Efsun Arda, Patricia A. Pope, Jeb Gaudet, Barbara Conradt, Albertga J.M. Walhout

Dartmouth Scholarship

Snail-type transcription factors (TFs) are found in numerous metazoan organisms and function in a plethora of cellular and developmental processes including mesoderm and neuronal development, apoptosis and cancer. So far, Snail-type TFs are exclusively known as transcriptional repressors. They repress gene expression by recruiting transcriptional co-repressors and/or by preventing DNA binding of activators from the basic helix-loop-helix (bHLH) family of TFs to CAGGTG E-box sequences. Here we report that the Caenorhabditis elegans Snail-type TF CES-1 can activate transcription in vivo. Moreover, we provide results that suggest that CES-1 can share its binding site with bHLH TFs, in different tissues, …

Vesicles In Poiseuille Flow, Gerrit Danker, Petia M. Vlahovska, Chaouqi Misbah

Dartmouth Scholarship

Blood microcirculation critically depends on the migration of red cells towards the flow centerline. We identify theoretically the ratio of the inner over the outer fluid viscosities λ as a key parameter. At low λ, the vesicle deforms into a tank-treading ellipsoid shape far away from the flow centerline. The migration is always towards the flow centerline, unlike drops. Above a critical λ, the vesicle tumbles or breaths and migration is suppressed. A surprising coexistence of two types of shapes at the centerline, a bulletlike and a parachutelike shape, is predicted.

Long-Distance Delivery Of Bacterial Virulence Factors By Pseudomonas Aeruginosa Outer Membrane Vesicles, Jennifer M. Bomberger, Daniel P. Maceachran, Bonita A. Coutermarsh, Siying Ye, George A. O'Toole, Bruce A. Stanton, Frederick M. Ausubel

Dartmouth Scholarship

Bacteria use a variety of secreted virulence factors to manipulate host cells, thereby causing significant morbidity and mortality. We report a mechanism for the long-distance delivery of multiple bacterial virulence factors, simultaneously and directly into the host cell cytoplasm, thus obviating the need for direct interaction of the pathogen with the host cell to cause cytotoxicity. We show that outer membrane–derived vesicles (OMV) secreted by the opportunistic human pathogen Pseudomonas aeruginosa deliver multiple virulence factors, including β-lactamase, alkaline phosphatase, hemolytic phospholipase C, and Cif, directly into the host cytoplasm via fusion of OMV with lipid rafts in the host plasma …