Salmonella Type III Effector AvrA Stabilizes Cell Tight Junctions to Inhibit Inflammation in Intestinal Epithelial Cells

Salmonella Typhimurium is a major cause of human gastroenteritis. The Salmonella type III secretory system secretes virulence proteins, called effectors. Effectors are responsible for the alteration of tight junction (TJ) structure and function in intestinal epithelial cells. AvrA is a newly described bacterial effector found in Salmonella. We report here that AvrA expression stabilizes cell permeability and tight junctions in intestinal epithelial cells. Cells colonized with an AvrA-deficient bacterial strain (AvrA−) displayed decreased cell permeability, disruption of TJs, and an increased inflammatory response. Western blot data showed that TJ proteins, such as ZO-1, claudin-1, decreased after AvrA- colonization for only 1 hour. In contrast, cells colonized with AvrA-sufficient bacteria maintained cell permeability with stabilized TJ structure. This difference was confirmed in vivo. Fluorescent tracer studies showed increased fluorescence in the blood of mice infected with AvrA- compared to those infected with the AvrA-sufficient strains. AvrA- disrupted TJ structure and function and increased inflammation in vivo, compared to the AvrA- sufficient strain. Additionally, AvrA overexpression increased TJ protein expression when transfected into colonic epithelial cells. An intriguing aspect of this study is that AvrA stabilized TJs, even though the other TTSS proteins, SopB, SopE, and SopE2, are known to disrupt TJs. AvrA may play a role in stabilizing TJs and balancing the opposing action of other bacterial effectors. Our findings indicate an important role for the bacterial effector AvrA in regulation of intestinal epithelial cell TJs during inflammation. The role of AvrA represents a highly refined bacterial strategy that helps the bacteria survive in the host and dampen the inflammatory response

Security Implications of Making Computing Resources Available via Computational Grids

This report inrvestigates the issues of securing access to computin,g resources in computation. al grids. Grid en,viron,men.ts are built orb top of platforms that corrtrol access to resources within a sin,gle adenin.istrative domairr, at the g.r-an,ular.ityo f a use,r. In wide-area multi-domain. grid en.viron,men.ts, the overhead of mainiainin,g user accounts is prohibitive, a.rad secu7.in,g access to resources via user accountability is impractical. Typically, these issues are han,dled by inlplenlert,ting checks that guaran,tee the safety of applic~ations, so [hat they can rurt. in shared use^ accour1.t~. This work shows that safety checks - lan,guage-based, compile-time, link-time, load-lime - curren.tly implemen.ted in most grid en.virorrmen.ts are either in,adequute or limit allowed grid users and applicatiorrs. Techn.ique.s without such li7nitations are presen.ted. Shadow accoun,ts allow reu.se of user accounts without administrative overheads, and run-time solution~s - run-time 7non.itorirt.y and virtu.tr1 machines - allow arbilrary code to execute while erilforciny a given resource access policy

STUDY OF ANTIMICROBIAL PROTEIN FROM THE HEMOLYMPH OF FRESHWATER CRAB OZIOTELPHUSA SENEX SENEX AND ITS EFFICACY AGAINST THE HUMAN PATHOGENS

 Objective: The study was done to isolate the antimicrobial protein from the freshwater crab.Methods: Antimicrobial protein was purified by sequential step of ammonium sulfate precipitation, dialysis, ion exchange chromatography, and fast protein liquid chromatography. The apparent molecular mass was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS/MS). Primary structure analysis was done from MASCOT search engine. The antimicrobial activity of the protein was done using well diffusion method against Gram-positive and Gram-negative bacteria.Results: The molecular mass of antimicrobial protein was determined to be 33KDa by SDS-PAGE and MALDI-MS/MS. The antimicrobial protein contains eight peptides which were determined by MASCOT search engine. The protein exhibited antimicrobial activity both for Gram-positive and Gram-negative bacteria.Conclusion: The results could provide information for investigating the antimicrobial protein derived from the hemolymph of the freshwater crab Oziotelphusa senex senex

STUDY OF ANTIMICROBIAL PROTEIN FROM THE HEMOLYMPH OF FRESHWATER CRAB OZIOTELPHUSA SENEX SENEX AND ITS EFFICACY AGAINST THE HUMAN PATHOGENS

 Objective: The study was done to isolate the antimicrobial protein from the freshwater crab.Methods: Antimicrobial protein was purified by sequential step of ammonium sulfate precipitation, dialysis, ion exchange chromatography, and fast protein liquid chromatography. The apparent molecular mass was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS/MS). Primary structure analysis was done from MASCOT search engine. The antimicrobial activity of the protein was done using well diffusion method against Gram-positive and Gram-negative bacteria.Results: The molecular mass of antimicrobial protein was determined to be 33KDa by SDS-PAGE and MALDI-MS/MS. The antimicrobial protein contains eight peptides which were determined by MASCOT search engine. The protein exhibited antimicrobial activity both for Gram-positive and Gram-negative bacteria.Conclusion: The results could provide information for investigating the antimicrobial protein derived from the hemolymph of the freshwater crab Oziotelphusa senex senex