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Abstracts
Workgroup: Frontiers in Disease Research
Antimicrobial Peptides: Overlooked Mechanisms of Disease Resistance?
Principal Investigator(s):
Robert S. Anderson, Ph.D., University of Mayland Center for Environmental Science, Cheasapeake Bay Lab, anderson@cbl.umces.edu
Funding Period: 10/01/01-9/30/03
Oyster serum has been fractionated by various methods including ultrafiltration, HPLC, and column chromatography. Several molecules with antibacterial activity were isolated and characterized. One peptide likely to play a role in host defense (CVAP-1) was shown to have a mass of 4.3 kDa and to similar to defensin molecules found in other animals. It had activity against several bacterial species, as well as vs the oyster pathogen Perkinsus marinus. Attempts to sequence this peptide were as yet unsuccessful, probably due to insufficient sample size. Higher MW peptides with antimicrobial activity are currently under study, and several likely candidates in the >50 kDa class have been isolated. Of particular interest is a relatively large peak obtained using a QFF anion exchange column and a step-wise elution gradient. This molecule shows significant anti-Vibrio and anti-Perkinsus marinus activities; efforts are under way to measure specific activities vs a panel of microorganisms. This peptide has the advantages of relatively high concentration, broad range of activity, and technical ease of handling. In oysters many humoral defense molecules are produced and secreted by the hemocytes; therefore, we have produced sonicated hemocyte lysates, which are being fractionated on anion exchange columns. This has resulted in isolating two peptides with anti-Vibrio sp. which will be structurally and functionally analyzed.
IMPACTS and/or BENEFITS:
Antimicrobial peptides from C. virginica serum have been isolated using ultrafiltration, reverse-phase HPLC, and/or anion exchange column chromatography. The structure and function of these molecules are under study. To date, two <10 kDa and two >50 kDa peptides have been isolated with antibacterial and/or anti-P. marinus activities. An additional two antibacterial peptides have been isolated from C. virginica hemocyte lysates; these are being examined for anti- P. marinus activity as well. The major impact of this study will be a more complete understanding of C. virginica defenses against P. marinus, and other putative oyster pathogens.
PROJECT PUBLICATIONS:
Anderson, R. S. and A. E. Beaven. 2001. Antibacterial activities of oyster (Crassostrea
virginica) and mussel (Mytilus edulis and Geukensia demissa) plasma. Aquat. Living Resour. 14: 343-349.
Anderson, R. S. and A. E. Beaven. 2001. A comparative study of anti-Perkinsus marius activity in bivalve sera. J. Shellfish Res. 20: 1011-1017.
Mountz, A. and R. S. Anderson. 2002. Purification of a novel antimicrobial peptide from the Eastern oyster (Crassostrea virginica). J. Shellfish Res. 21: 405-406.
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