How Neisseria gonorrhoeae, N. meningitidis and Bacillus anthracis cause disease.
Gonococci are chameleon-like bacteria – masters of disguise – that live at least two vastly different lifestyles! First, gonococci constantly change expression of many of their surface molecules, the ones that the host’s immune system tries to identify, and that help gonococci cause disease and evade or avoid the immune system. Gonococci wear fool-proof invisibility cloaks, enough to make even Harry Potter envious! Second, gonococci can live outside or inside cells of the urethra, the cervix, or the blood; and they wear quite different cloaks depending on where they reside. We have focused on studying two Neisseria virulence factors intimately involved in these interactions: Opa proteins and sialyltransferase. Opa proteins, a family of outer membrane proteins, are pluripotent virulence factors, allowing Ng and Nm to survive in the blood, and to adhere to, stimulate, invade and survive within human cells; talk about multitasking! Sialyltransferase (STase) is an enzyme on the surface of pathogenic Neisseria that transfers sialic acid (N-acetylneuraminic acid, Neu5Ac) from host CMP-Neu5Ac to terminal galactose residues of lipooligosaccharide (LOS), a complex glycolipid that is located in the Neisseria outer membrane alongside STase. Sialylated LOS renders Ng and Nm resistant to killing by human serum and human neutrophils, which is quite useful when they’re living outside cells, like in urethral or cervical pus or in the bloodstream. However, Ng and Nm occasionally like to hide inside epithelial cells, away from the hassles of antibacterial molecules and immune surveillance of everyday life. Sialylated (extracellular) gonococci, however, don’t bind to or invade epithelial cells well; thus – in order to enter host cells – they must down regulate expression of STase, shed their sialylated LOS, and quickly enter cells before they are killed by serum or phagocytic cells. So, the reversible sialylation of LOS is a pivotal event in Ng and Nm virulence.
We currently study regulation of expression of STase by environmental cues including contact with serum and association with human cells. Regulation of STase expression is remarkably complex, perhaps not surprising considering its significant role in virulence. In vitro, association of Ng with epithelial cells dramatically decreases STase expression. We study the molecular mechanisms of this phenomenon – from transcriptional to post-translational events.
For about 10 years we took a detour from our Neisseria path to study the interaction of B. anthracis with human macrophages and neutrophils, and focused on the virulence role of an exotoxin called Anthrolysin O (ALO), a member of the cholesterol-dependent cytolysin family. ALO has lethal and sublethal effects – depending on its concentration and on the presence of serum or cholesterol – on essentially all host cells, including human phagocytes. One of its unique properties is that it can signal through the classic "endotoxin receptor," i.e., Toll Like Receptor 4 (TLR4) – except, of course, it is not an endotoxin! ALO, and B. anthracis expressing ALO, have a plethora of ALO-dependent activities, including induction of pro-inflammatory cytokine release and associated intracellular signaling pathways, induction of neutrophil degranulation, priming for the oxidative burst, induction of cell death, and inhibition of phagocyte chemotaxis. We have found profound effects of antioxidants, like glutathione and N-acetylcysteine (NAC), on the interaction of ALO and anthrax spores with macrophages. NAC completely inhibits the sublethal effects of ALO on phagocytes, and dramatically increases the ability of macrophages to kill B. anthracis spores and vegetative cells.
In the News
"N-Acetylcysteine inhibits Bacillus anthracis spore germination by altering specific germination-pathway components"
Bernui ME, Smith M, and RF Rest
"Anthrolysin O, the Bacillus anthracis cholesterol dependent cytolysin, modulates human neutrophil and macrophage function"
Mosser EM, Pandya Y, Bernui M, and RF Rest
Infect. Immun., In revision, 2012.
"Soluble and liposome-encapsulated N-acetylcysteine (NAC) Increase the ability of human macrophages to kill Bacillus anthracis"
Bernui ME, Stone W, Smith M, and RF Rest
Infect. Immun., In revision, 2012.
"NLRP3 inflammasome is a target for development of broad-spectrum anti-infective drugs"
Thacker JD, Balin BJ, Appelt DM, Sassi-Gaha S, Purohit M, Rest RF, and CM Artlett.
Antimicrob. Agents Chemother., 56: 1921-30, 2012.
"Solvothermal Synthesis of Photocatalytic TiO2 Nanoparticles Capable of Killing Escherichia coli."
BY Lee, M Kurtoglu Y, Gogotsi M, Wynosky-Dolfi and Rest RF
Biodefence, NATO Science for Peace and Security Series A: Chemistry and Biology, Part 1, 3-10, DOI: 10.1007/978-94-007-0217-2_1. 2011.
"Rapid sporulation of Bacillus anthracis in high iron, glucose-free medium."
Purohit M, Sassi-Gaha S and Rest RF
Journal of Microbiological Methods 82: 282-287. 2010.
"Cold Plasma Inactivation of Bacillus cereus and Bacillus anthracis (Anthrax) Spores."
Dobrynin D, Fridman G, Mukhin Y, Wynosky-Dolfi M, Rieger J, Rest RF, Gutsol A and Fridman A
IEEE Transactions in Plasma Science. 38: 1878-1884. 2010.
"Array PZT/Glass Piezoelectric Microcantilevers for real-time detection of Bacillus anthracis with 10 spores/ml sensitivity and 1/1000 selectivity in bacterial mixtures."
McGovern JP, Shih WY, Mattiucci M, Rest RF, Purohit M, Pourrezaei K, Onaral B, and W-H Shih.
Review of Scientific Instruments. 80: 125104-1 – 125104-7, 2009. [also in December 15, 2009 issue of Virtual Journal of Biological Physics Research].
"1-Peptidyl-2-arachidonoyl-3-stearoyl-sn-glyceride: an immunologically active lipopeptide from goat serum (Capra hircus) is an endogenous damage-associated molecular pattern"
Thacker JD, Brown MA, Rest RF, Purohit M, Sassi-Gaha S, and CM Artlett
J. Nat. Prod., 72:1993-99, 2009.
"Cellular functions and X-ray structure of Anthrolysin O, a cholesterol-dependent cytolysin secreted by Bacillus anthracis."
Bourdeau RW, Malito E, Chenal A, Bishop BL, Musch MW, Villereal ML, Chang EB, Mosser EM, Rest RF, and Tang WJ.
Journal of Biological Chemistry 284: 14645-14656, 2009.
"Passive administration of monoclonal antibodies to Anthrolysin O prolong survival in mice lethally infected with Bacillus anthracis."
Nakouzi A, Rivera J, Rest RF, and Casadevall A.
BMC Microbiology 8: 159, 2008.
"Killing of human lymphocytes, monocytes, macrophages and neutrophils by the Bacillus anthracis cytotoxin Anthrolysin O."
Mosser EM and Rest RF.
BMC Microbiology, 6: 56, 2006.
Differential expression and transcriptional analysis of the α-2,3-sialyltransferase gene (lst) in pathogenic neisseria.
Packiam M, Shell D, Liu SV, Liu YB, McGee DJ, Srivastava R, Seal S, and Rest RF.
Infection and Immunity, 74: 2637-2650, 2006.
"Anthrolysin O and other gram-positive cytolysins are toll-like receptor 4 agonists."
Park J.M, Ng VH, Maeda S, Rest RF, and Kari M.
Journal of Experimental Medicine, 200: 1647-1655, 2004.