Inhibition of an RTX Toxin Using Small Receptor-Based Peptides
Advisor: Angela Brown
With the current increase in antibiotic resistance and lack of new antibiotics, new methods for the treatment of bacterial illnesses are urgently needed. Our lab aims to develop anti-virulence strategies to diminish bacterial pathogenesis by inhibiting bacterial toxin activity. Aggregatibacter actinomycetemcomitans is a gram-negative bacterium responsible for the production and secretion of the leukotoxin known as LtxA. LtxA is a member of a large family of toxins, the repeats-in toxin (RTX) proteins. LtxA targets white blood cells through the recognition and binding of LtxA to the lymphocyte function-associated antigen-1 (LFA-1). In our study, we investigated the ability of synthetic peptides corresponding to reported LtxA binding domains of LFA-1 to inhibit LtxA toxicity against THP-1 cells. Previous studies have proposed that the LtxA binding domains lie within the range of amino acids 58-128 of the CD11a subunit of LFA-1, a region on the beta propeller (1). We synthesized five small peptides spanning this range. We ran individual cytotoxicity experiments, inoculating THP-1 cells with the specific peptide and LtxA to measure the ability of each peptide to inhibit LtxA-mediated cytotoxicity. Our results indicat that peptides W1S4, W2S1, W2S2, and W2S3 were effective in blocking LtxA activity, while W2S4 was not. Our results suggest that an initial binding of LtxA to these four beta propeller domains is integral to the toxin’s mechanism. Additionally, these findings demonstrate the possibility of using small peptides as a therapeutic to inhibit the activity of LtxA to reduce the pathogenesis of A. actinomycetemcomitans and other RTX toxins.
Acknowledgements: This research was supported by the NIH (R00DE022795) and the Lehigh University P.C. Rossin College of Engineering and Applied Science.
References: Kieba, Irene R., Karen P. Fong, Hsin-Yao Tang, Karl E. Hoffman, David W. Speicher, Lloyd B. Klickstein, and Edward T. Lally. "Aggregatibacter Actinomycetemcomitans Leukotoxin Requires B-sheets 1 and 2 of the Human CD11a B-propeller for Cytotoxicity." Cell Microbiol Cellular Microbiology 9.11 (2007): 2689- 699.
About Shannon Hayes:
Shannon Hayes is a senior at Lehigh University pursuing a B.S. in Bioengineering with a concentration in Biopharmaceuticals. Shannon has been working in Dr. Angela Brown’s lab since January 2016 and was selected to present her research at the annual Biomedical Engineering Society national conference this year. Outside of academics Shannon is involved in Society of Women Engineers, Lehigh Biomedical Engineering Society, and Pi Beta Phi.