Human beta defensins (hBDs) are first-line defenders of the host's mucosa against microbial challenges. We were first to report them in Human Oral Epithelial Cells (HOECs) and demonstrated their antimicrobial and immunoregulatory properties as agents that alter inflammatory responses. We believe that harnessing these and other antimicrobial peptides (AMPs) correctly, i.e., promoting their expression in vulnerable sites, could impact the course of infection and wound repair. We have isolated and characterized a cell wall associated molecule from F. nucleatum ATCC 25586 that is principally responsible for hBD induction and refer to it as FAD-I for F. nucleatum Associated beta Defensin Inducer. We have identified that the molecule's activity resides in the cysteine-diacylglycerol complex at position 16, as alanine substitution abrogates activity, and that hBD2 induction is dependent upon interaction of FAD-I with TLRs 1 and 2 on the HOEC surface. Other AMPs are also induced by FAD-I, including Mip3? (CCL20) and LL37 which are elevated in epithelial cells following FAD-I challenge. Moreover, our preliminary data suggests that FAD-I's induction of hBD-2 happens with little simultaneous induction of pro- inflammatory cytokines. Functionally, HOECs challenged with FAD-I are protected from invasion by Porphyromonas gingivalis, a major etiologic agent in the initiation of periodontal destruction. Therefore, our overarching hypothesis is that commensal bacterial molecules, such as FAD-I, that promote the expression of beneficial innate response elements without inflammation, could be harnessed to protect tissues from microbial challenges and inflammatory damage. In order to develop FAD-I into a novel therapeutic agent, we will address several existing knowledge gaps including in vivo tests of FAD-I in various mouse mucosal tissues to determine its' ability to induce in situ AMP expression as well as develop a novel vehicle for delivery of FAD-I for intervention in disease modulation.
Our aims are intended to: (1) Determine key characteristics of FAD-I that result in stimulation of epithelial cell-derived AMPs in the absence of an inflammatory response; (2) Determine FAD-I's ability to induce mouse AMP orthologs and quantify pre-clinical FAD-I potency in vivo using the pre-clinical murine models of wound healing and inflammation; (3) Construct a FAD-I producing Lactobacillus for probiotic in vitro testing. Our overall intention is to prepare ourselves to use FAD-I for future translational studies in modulating dysbiosis and chronic inflammation in defined diseased mouse models, which may pave the way for interventional studies in humans.
Conventional antibiotics are losing the battle against infectious microbes and secondary infections from medical procedures. Through our research focusing on the body's own antibiotics; i.e., antimicrobial peptides (AMPs), we have identified an agent from a common bacterium found in the human mouth that promotes the release of these AMPs from cells that make up the linings of our body, resulting in protection from harmful microbes without promoting inflammation. We propose to study this agent in order to determine if it can be used to bolster the body's own defenses against bad microbes, resulting in fewer infections, reduced inflammation and improved healing.
| Miller, D P; Wang, Q; Weinberg, A et al. (2018) Transcriptome analysis of Porphyromonas gingivalis and Acinetobacter baumannii in polymicrobial communities. Mol Oral Microbiol 33:364-377 |
| Gupta, Sanhita; Ghosh, Santosh K; Scott, Mary E et al. (2010) Fusobacterium nucleatum-associated beta-defensin inducer (FAD-I): identification, isolation, and functional evaluation. J Biol Chem 285:36523-31 |
