| 0474 Inhibition of Bacterial IgA1 Proteinases by a Chemically Modified Tetracycline | ||
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S.G. WALKER1, O.I. CARNU2, G. TÜTER3, M.E. RYAN1, and L.M. GOLUB2, 1 State University of New York SUNY Stony Brook, USA, 2 State University of New York - Stony Brook, USA, 3 Gazi Universitesi, Emek / Ankara, Turkey Objectives: This study was initiated to determine if the chemically modified non-antibacterial tetracycline 6-demethyl-6-deoxy-4-dedimethylaminotetracycline (COL-3 or CMT-3) inhibits the IgA1 proteinases produced by Streptococcus pneumoniae and Haemophilus influenzae. IgA1 proteinases are considered to be virulence factors for these two mucosal pathogens. CMT-3 does not inhibit bacterial ribosome function and does not appear to induce bacterial resistance but is a potent inhibitor of some mammalian and bacterial proteinases. Methods: Crude IgA1 proteinases preparations were produced and the enzyme activities adjusted such that 95% of the heavy chain of human IgA1 present in a standardized reaction was cleaved. Substrate cleavage was monitored by SDS-PAGE and quantified using Kodak 1D image analysis software. Titrating the drug over a range of 0.1 to 2.0 mM assessed the effect of CMT-3 on IgA1 cleavage in the standardized reaction. Results: As expected, the IgA1 proteinase preparations specifically cleaved the heavy chain of human IgA1. CMT-3 inhibited the IgA1 proteinases of S. pneumoniae and H. influenzae with IC50 values of 0.85 mM and 0.93 mM, respectively. Although both proteinases had similar IC50 values their inhibition curves differed. When percent inhibition is plotted against the concentration of CMT-3, a linear dose inhibition curve resulted for the H. influenzae proteinase whereas a sigmoidal dose inhibition curve was generated for the S. pneumonia proteinase. The difference between the curves most likely reflects the fact that S. pneumonia produces a metallo IgA1 proteinase whereas H. influenzae produces a serine IgA1 proteinase. The dose inhibition curves suggest that the mechanism of inhibition by CMT-3 likely differs between the two enzymes. Conclusion: In vitro, CMT-3 can inhibit the IgA1 proteinases produced by these mucosal pathogens. The drug may one day be used to target this important class of bacterial virulence factors to modulate the diseases caused by these pathogens. | ||
| Seq #45 - Microbiology/ Immunology and Infection Control 11:30 AM-1:00 PM, Saturday, 28 August 2004 Crowne Plaza Hotel AVSA II | ||
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