The long term objective of this proposal is determine the role of a cytolytic enterotoxin (Act) of A. hydrophila in the pathogenesis of disease. The investigators have isolated a 52 kDa polypeptide from a diarrheal isolate of A. hydrophila (SSU) that is associated with hemolytic, cytotoxic and enterotoxic activities and is lethal for mice. The toxin gene has been cloned, expressed and sequenced by the investigators. Site directed mutagenesis studies recently completed suggest different loci coding for the three biological activities associated with the toxin. The suggestion that Act plays a significant role in the infectious process is supported by the lack of virulence of an Act minus isolate of A. hydrophila and transposon mutants with reduced biological activity. More recent studies with an isogenic mutant of strain SSU that is without in vitro hemolytic and cytotoxic activity also supports the belief that this toxin is an important virulence factor. Characterization of the role of the toxin will proceed using the toxin negative mutant recently produced. Probing the antigenic and biologically active domains of the toxin will be accomplished following hyperexpression of the Act gene with a multi-host range vector. The functional domains of the toxin molecule will be mapped by generating anti-peptide antibodies and monoclonal antibodies. Site directed mutagenesis will be used to refine the role of amino acid residues in the biological activities of the toxin. The investigators also propose to study the regulation of the Act gene either by fusing it with a reporter gene or by mutagenesis of the chromosome of Aeromonas using a transposon which imparts antibiotic resistance to screen for toxin negative mutants. Finally, the investigators propose to study the mechanism of action of the toxin by probing the mechanism of cell damage and by examining the toxin receptor on the cell surface.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI041611-03
Application #
2887513
Study Section
Special Emphasis Panel (ZRG5-BM-2 (05))
Project Start
1997-07-01
Project End
2001-06-30
Budget Start
1999-07-01
Budget End
2000-06-30
Support Year
3
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
041367053
City
Galveston
State
TX
Country
United States
Zip Code
77555
Sha, Jian; Rosenzweig, Jason A; Kozlova, Elena V et al. (2013) Evaluation of the roles played by Hcp and VgrG type 6 secretion system effectors in Aeromonas hydrophila SSU pathogenesis. Microbiology 159:1120-35
Kozlova, Elena V; Khajanchi, Bijay K; Popov, Vsevolod L et al. (2012) Impact of QseBC system in c-di-GMP-dependent quorum sensing regulatory network in a clinical isolate SSU of Aeromonas hydrophila. Microb Pathog 53:115-24
Erova, Tatiana E; Kosykh, Valeri G; Sha, Jian et al. (2012) DNA adenine methyltransferase (Dam) controls the expression of the cytotoxic enterotoxin (act) gene of Aeromonas hydrophila via tRNA modifying enzyme-glucose-inhibited division protein (GidA). Gene 498:280-7
Khajanchi, Bijay K; Kozlova, Elena V; Sha, Jian et al. (2012) The two-component QseBC signalling system regulates in vitro and in vivo virulence of Aeromonas hydrophila. Microbiology 158:259-71
Suarez, Giovanni; Khajanchi, Bijay K; Sierra, Johanna C et al. (2012) Actin cross-linking domain of Aeromonas hydrophila repeat in toxin A (RtxA) induces host cell rounding and apoptosis. Gene 506:369-76
Khajanchi, Bijay K; Kirtley, Michelle L; Brackman, Sheri M et al. (2011) Immunomodulatory and protective roles of quorum-sensing signaling molecules N-acyl homoserine lactones during infection of mice with Aeromonas hydrophila. Infect Immun 79:2646-57
Kozlova, Elena V; Khajanchi, Bijay K; Sha, Jian et al. (2011) Quorum sensing and c-di-GMP-dependent alterations in gene transcripts and virulence-associated phenotypes in a clinical isolate of Aeromonas hydrophila. Microb Pathog 50:213-23
Sierra, Johanna C; Suarez, Giovanni; Sha, Jian et al. (2010) Unraveling the mechanism of action of a new type III secretion system effector AexU from Aeromonas hydrophila. Microb Pathog 49:122-34
Suarez, Giovanni; Sierra, Johanna C; Kirtley, Michelle L et al. (2010) Role of Hcp, a type 6 secretion system effector, of Aeromonas hydrophila in modulating activation of host immune cells. Microbiology 156:3678-88
Suarez, G; Sierra, J C; Erova, T E et al. (2010) A type VI secretion system effector protein, VgrG1, from Aeromonas hydrophila that induces host cell toxicity by ADP ribosylation of actin. J Bacteriol 192:155-68

Showing the most recent 10 out of 45 publications