PROJECT SUMMARY/ ABSTRACT SUMMARY: Antibiotic resistance is increasingly a threat to human health resulting in difficult to treat infections, with some multidrug resistant pathogens being resistant to all or most all antibiotics. To combat this growing crisis, this U19 is taking an integrated approach to the generation and development of therapeutics against key virulence mechanism of bacteria. Specifically, this CORE will in an integrated approach with Projects 1 and 2, seek to develop monoclonal antibody (mAb) therapies against different bacterial adhesins that extensive studies have shown to be critical for the ability of pathogens to bind to and resist removal from host tissues and surfaces. Uropathogenic E. coli (UPEC) use CUP adhesive pili tipped with adhesin proteins to bind to a variety of human tissues including the uninflammed bladder, the inflamed bladder, the kidney, urinary catheters and the gastrointestinal tract (GIT). In addition, Klebsiella expresses a mannose binding FimH adhesin that is critical for the ability of Klebsiella to cause UTIs. Further, CUP adhesins in Acinetobacter baumanii, CupD and PrpD, as well as the EbpA adhesin at the tip of the sortase assembled pilus of the Gram-positive Enterococci, bind to fibrinogen on implanted catheters to promote biofilm formation and catheter-associated UTIs (CAUTIs). In collaboration with Project 1 this CORE will use state of the art high throughput cloning and selection methods to generate mAbs against all of these adhesins and evaluate their potential as antibiotic sparing therapeutics. These mAbs will also elucidate important epitopes for future anti-adhesin vaccine design. Further, all of the CUP adhesive pili are assembled by homologous systems involving a periplasmic chaperone and and outer membrane usher. The usher is a five domain assembly platform for CUP pilus polymerization and its transmembrane domain functions as a pore for extrusion of the assembled fiber. This pore is gated by a plug domain that only exits the pore when the usher is assembly a pilus fiber. Thus, usher proteins will be targeted for mAb generation and mAbs will be selected for both their ability to bind and inhibit usher mediated pilus assembly and/or for the ability to “open” the usher pore in the absence of a growing pilus fiber. Having an open pore without a pilus fiber will render the bacteria sensitive to antibiotics from our existing arsenal that are not generally able to cross the Gram-negative outer membrane and thus are not generally efficacious against Gram-negative pathogens. Targeting of adhesins and their assembly has the advantage that mutations in the binding pocket of targeted adhesins or in critical assembly sites in the usher to prevent binding of the therapeutic to its target would likely destroy adhesin function and thus render the pathogen non-virulent. The mAbs generated have the promise to be a viable alternative for the treatment of antibiotic-resistant infecitons. Therapeutic mAbs have not yet been fully harnessed for treating infectious diseases, perhaps due to the historic success of antibiotics. However, with antibiotic resistance on the rise, it is time to apply these potentially antibiotic-sparing tools to infectious disease.