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USU
Department of Microbiology
and Immunology |
Alison
D. O'Brien
Professor & Chair
Department of Microbiology and Immunology
Uniformed Services University of the Health Sciences
Ph.D., Ohio State University, 1976
aobrien@usuhs.mil
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Research:
Molecular Mechanisms of Bacterial Pathogenesis |
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The
objective of the major program in the laboratory is to define the
molecular mechanisms by which enterohemorrhagic Escherichia coli (EHEC)
cause hemorrhagic colitis and the hemolytic uremic syndrome. EHEC
are food-borne pathogens that cause outbreaks of disease
associated with ingestion of undercooked hamburgers or raw milk.
Such an outbreak occurred in 1993 in the Pacific Northwest. EHEC
are characterized by the production of Shiga toxins (Stxs) and the
capacity to adhere avidly to the large bowel epithelium. Our
studies on the virulence mechanisms of EHEC include: creation of
molecular tools (monoclonal antibodies and DNA probes) for
detecting toxin, investigation of the molecular genetics and
regulation of toxin synthesis, purification and characterization
of toxins, development of small animal models to further clarify
pathogenic traits of EHEC, and analysis of the molecular
mechanisms by which EHEC adhere to epithelial cells.
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On
the left is a fluorescent image of HEp-2 cells infected with EHEC
O157:H7. Polymerized
actin (red), Tir (blue), and nucleolin (green) appear to be
closely associated with the adherent bacteria.
On the right is a phase contrast image of the same cell.
(courtesy of Dr. James Sinclair). |
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Two
related projects are also on-going in the laboratory. These
include studies of: i.) the molecular mode of action of a newly
described Rho-modifying toxin (cytotoxic necrotizing factor type
1) of E. coli and its role in the pathogenesis of E.
coli-mediated urinary tract infections; ii.) immunoprotective
monoclonal antibodies (MAbs) against Bacillus anthracis
spores that confer protection against anthrax in animal models.
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Selected
Publications:
Melton-Celsa, A.R., J.F. Kokai-Kun, and
A.D. O'Brien. 2002. Activation of Shiga-toxin type 2d (Stx2d) by
elastase involves cleavage of C-terminal two amino acids of the Stx2d A2
peptide in the context of the appropriate B pentamer. Mol. Micro. 43:
207-215.
Woods, J.B., C.K. Schmitt, and A.D.
O'Brien. 2002. Ferrets as a model system for renal disease secondary to intestinal
infection with Escherichia coli O157:H7 and other Shiga-toxin producing Escherichia
coli. J. Infect. Dis. 185: 550-554.
Sinclair, J.F., and A.D. O'Brien. 2002.
Cell-surface localized nucleolin is a eucaryotic receptor for the adhesin
intimin-γ of Enterohemorrhagic Escherichia coli O157:H7. J. Biol. Chem. 277:
2876-2885.
Karpman, D., Z.D. Békássy, A. C Sjörgen,
M.S. Dubois, M.A. Karmali, M. Mascarenhas, K.G. Jarvis, L.J. Gansheroff, A.D.
O'Brien, G. S. Arbus, and J.B. Kaper. 2002. Antibodies to intimin and E.
coli secreted proteins A and B in patients with EHEC infections. Pediatric
Nephrology. 17: 201-211.
Dean-Nystrom, E.A., L.J. Gansheroff, M.
Mills, H.W. Moon, and A.D. O'Brien. 2002. Vaccination of pregnant dams with
intimin0157 protects suckling piglets from Escherichia coli
O157:H7 infection.
Infect. Immun. 70: 2704-2707.
Teel,
L.D., A.R. Melton-Celsa, C.K. Schmitt, and A.D. O'Brien. 2002. One
of the two copies of the gene for the activatable Shiga toxin type 2d (Stx2d) in Escherichia coli O91:H21 strain B2F1 is
associated with an inducible bacteriophage.
Infect. Immun. 70:4282-91.
Scott, M.E, A.R. Melton-Celsa, and A.D. O'Brien. 2003. Mutations in hns
reduce the adherence of Shiga-toxin producing E. coli O91:H21 strain
B2F1 to human colonic epithelial cells and increase the production of hemolysin.
Microb. Pathog. 34:155-159.
Jelacic, J.K., T. Damrow, G. S. Chen, S. Jelacic, M. Bielaszewska,
M.Ciol, A.R. Melton-Celsa, H. Carvalho, A.D. O'Brien, P. Tarr.
2003. Shiga toxin-producing Escherichia coli from Montana residents with diarrhea: analysis of bacterial
genotypes and clinical profiles of infected patients. J. Infect. Dis. 188:719-729.
Teel, L.D., B.R. Steinberg, N.E. Aronson, and A.D. O'Brien. Shiga toxin-producing
Escherichia coli-associated kidney failure in a 40-year-old and late diagnosis by novel bacteriologic and toxin detection methods. 2003.
J. Clin. Microbiol. 41:3438-3440.
Dean-Nystrom, E.A., A.R. Melton-Celsa, J.F.L. Pohlenz, H.W. Moon
and A.D. O'Brien. 2003. Comparative pathogenicity of Escherichia coli O157 and intimin-negative non-O157 Shiga toxin-producing
E. coli strains in neonatal pigs.
Infect. Immun. 71:6526-6533.
Judge,
N.A., H.S. Mason and A.D. O'Brien. 2004. Plant cell-based vaccine given
orally to mice primed with intimin reduces time of Escherichia coli O157:H7 shedding in feces.
Infect. Immun. 72: 168-175.
Fraser, M.E., M. Fujinaga, M.M. Cherney, A.R. Melton-Celsa, E. M.
Twiddy, A.D. O'Brien, and M.N.G. James. 2004. Structure of Shiga toxin
type 2 (Stx2) from Escherichia coli O157:H7. J Biol Chem. 279:27511-27517.
Sinclair J.F. and A.D. O'Brien. 2004 Intimin types alpha, beta, and
gamma bind to nucleolin with equivalent affinity but lower avidity than
to the translocated intimin receptor. J Biol Chem. 279:33751-33758.
Carvalho, H.M., L.D. Teel, J.F. Kokai-Kun, and A.D. O'Brien. 2005.
Antibody against the carboxyl-terminus of intimin-a
reduces Enteropathogenic Escherichia coli adherence to tissue culture cells and subsequent induction of actin polymerization.
Infect. Immun. 73: 2541-2546.
Dowling,
T.C., P.A Chavaillaz, D.G Young, A. Melton-Celsa, A. O'Brien, C.
Thuning-Roberson, R. Edelman, and C.O. Tacket. 2005. Phase 1
Safety and Pharmacokinetic study of a chimeric murine-human antibody c alpha Stx2 administered intravenously to healthy human adult volunteers.
Antimicrob. Agents Chemother. 49: 1808-1812.
Davis, J.M., S.B. Rasmussen, and A.D. O'Brien. 2005.
Cytotoxic Necrotizing Factor Type 1 Production by Uropathogenic Escherichia coli Modulates Polymorphonuclear Leukocyte Function.
Infect. Immun. 73: 5301-5310.
Carvalho, H.M., L.D. Teel, G. Goping, and A.D. O'Brien. 2005. A
three-dimensional organoid model for the study of intimin-attach and
efface lesion formation by enteropathogenic and enterohemorrhagic Escherichia coli.
Cell. Microbiol. 7: 1771-1781.
Wen, S.X., L.D. Teel, N.A. Judge and A.D. O'Brien. 2006. Genetic
toxoids of Shiga toxin types 1 and 2 protect mice against homologous
but not heterologous toxin challenge.
Vaccine. 24: 1142-1148.
Smith,
Y.C., K.K. Grande, S.B. Rasmussen, and A.D. O'Brien. 2006. A novel
three-dimensional organoid model for evaluation of the interaction of
uropathogenic Escherichia coli with terminally differentiated human urothelial cells
Infect. Immun.74: 750-757.
Sinclair, J.F., E.A. Dean-Nystrom
and A.D. O'Brien. 2006. The established intimin-receptor Tir and the
putative eucaryotic intimin-receptors nucleolin and beta 1 integrin
localize at or near the site of Enterohemorrhagic Escherichia coli O157:H7 adherence to enterocytes in vivo.
Infect. Immun. 74: 1255-1265.
Wen, S.X., L.D. Teel, N.A. Judge, and A.D. O'Brien. 2006. A plant-based
oral vaccine to protect against systemic Shiga toxin type 2
intoxication.
Proc. Natl. Acad. Sci. USA. 103: 7082-7087.
McNichol, B.A., S.B. Rasmussen,
K.C. Meysick, and A.D. O'Brien. 2006. A single amino acid substitution in the enzymatic domain of cytotoxic necrotizing
factor type 1 of Escherichia coli alters the tissue culture phenotype to that of the dermonecrotic toxin of Bordetella spp.
Mol. Microbiology. 60: 939-950.
Smith, M.J., L.D.
Teel, H.M. Carvalho, A.R.
Melton-Celsa, and A.D. O'Brien. 2006. Development of a hybrid Shiga
holotoxoid vaccine to elicit heterologous protection against Shiga
toxins type 1 and 2.
Vaccine. 24: 4122-4129.
Davis,
J.M, H.M. Carvalho, S.B. Rasmussen, A D. O'Brien. 2006. Cytotoxic
necrotizing factor type 1 (CNF1) delivered by outer membrane vesicles
of uropathogenic Escherichia coli attenuates polymorphonuclear leukocyte antimicrobial activity and chemotaxis.
Infect. Immun. 74:4401-4408.
Robinson, C., J. Sinclair, M. Smith, and A.D. O'Brien. 2006. Shiga toxin of Enterohemorrhagic Escherichia coli type O157:H7 promotes intestinal colonization.
Proc. Natl. Acad. Sci. USA. 103: 9667-9672.
Smith, M.J., H.M.
Carvalho, A.R. Melton-Celsa, and A.D. O'Brien. 2006. The 13C4
monoclonal antibody that neutralizes Shiga
toxin Type 1 (Stx1) recognizes three regions on the Stx1 B subunit and
prevents Stx1 from binding to its eukaryotic receptor
globotriaosylceramide.
Infect. Immun. 74:6992-6998.
Teel L.D., J.A. Daly, R.C. Jerris, D.
Maul, G. Svanas, A.D. O'Brien and C.H.
Park . 2007. Rapid
detection of Shiga toxin-producing Escherichia coli by Optical Immunoassay.
J Clin Microbiol. 45: 3377-3380.
McNichol, B.A., S.B. Rasmussen, K.C.
Meysick, and A.D. O'Brien. 2007. Two domains of Cytotoxic Necrotizing Factor
Type 1 bind the cellular receptor, Laminin Receptor Precursor Protein.
Infect. Immun. 75: 5095-5104.
Brahmbhatt, T.N., B.K. Janes, E.S. Stibitz, S.C. Darnell, P.
Sanz, S.B. Rasmussen, and A.D. O'Brien. 2007. Bacillus anthracis exosporium protein BclA
affects spore germination,
interaction with extracellular matrix proteins, and hydrophobicity.
Infect. Immun. 75:5233-5239.
Brahmbhatt, T.N., S.C. Darnell, H.M. Carvalho, P. Sanz, T.J. Kang,
R.L. Bull,S.B. Rasmussen A.S. Cross, and A.D. O'Brien. 2007. Recombinant exosporium protein BclA of Bacillus
anthracis effective as a booster for miceprimed with suboptimal amounts of protective antigen.
Infect. Immun. 75:5240-5247.
Sanz, P., L.D. Teel, F. Alem, H.M. Carvalho, S.C. Darnell, and A.D. O'Brien.
2008. Detection of Bacillus anthracis spore germination in vivo by bioluminescence imaging. Infect
Immun. 76:1036-1047.
Alcantara, C., R.V. Destura, J.E.
Sevilleja, L.F. Barroso, H.M. Carvalho, L.J. Barrett, A.D. O'Brien, and R.L.
Guerrant. 2008. Detection of epithelial cell injury and quantification of infection
in the HCT8 organoid model of Cryptosporidiosis. J. Inf. Dis. Manuscript in
press.
Smith, Y.C., S.B. Rasmussen,
K.K. Grande, R.M. Conran and A.D. O'Brien. 2008. Hemolysin of uropathogenic
Escherichia coli evokes extensive shedding
of the uroepithelium and hemorrhage in bladder tissue within the first 24 hours
after intraurethral inoculation of mice. Infect Immun. Manuscript in press.
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Bethesda, Maryland 20814 |
Tel. (301)295-3400
Fax (301)295-1545
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Last updated: 05/22/08
This web site is maintained by Reinaldo Fernández
E-mail any suggestions or comments to:
rfernandez@usuhs.mil
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