Infection Site Targeted Antitoxin Antibody (ISTAb) against Clostridium difficile

DESCRIPTION provided by applicant Exotoxins produced by a wide range of bacterial pathogens are known to play a key role in host pathogen interactions establishment of the infection and subversion of the immune responses Treatment and prophylactic strategies targeting bacterial toxins are validated by decades long history of multiple vaccines including tetanus diphtheria and pertussis Monoclonal antitoxin antibodies for treatment of bacterial infections represent a promising strategy and this premise is strengthened by the recent FDA approval of Raxibacumab anti PA GSK for treatment of inhalation anthrax In this Phase I SBIR project we intend to devise a novel technology that allows specific targeting of neutralizing antitoxin antibodies to the site of infection where the antibody is needed In this strategy we exploit cell wall binding domains CBD of various phage endolysins which bind with species specificity and high affinity to bacterial cell wall components Neutralizing antitoxi monoclonal antibodies will be fused to specific CBDs to generate Infection Site Targeted antitoxin Antibodies ISTAbs ISTAbs are expected to accumulate at the site of infection where they capture and sequester toxins thus immediately neutralizing pathogenic or immune suppressive effects of the toxins and prevent their release into circulation The antibody bacterium toxin complex is then expected to be cleared by phagocytes For creation of prototype ISTAbs we target C difficile a major public health threat in light of increased antibiotic usage and the emergence of resistant strains and a pathogen which relies heavily on toxin release to establish the infection Glucosyltransferases toxin A TcdA and B TcdB are produced by virulent strains of this organism and play a key role in pathogenesis of C difficile associated disease by targeting the Rho GTPase family of cellular proteins These toxins are validated as therapeutic targets in animal and human trials We have generated a set of highly neutralizing antibodies to both toxins and produced them in a plant expression system Thus this pathogen and the two toxins provide an excellent model for proof of concept studies for ISTAb technology The technology if successful will have far reaching applications to a wide range of bacterial pathogens where toxins play a key role in pathogenesis In Aim we will select the best CBD based on binding efficiency from a pool of different phage endolysins In Aim we will construct and characterize prototype ISTAbs using the best CBDs identified in Aim and our neutralizing anti TcdA and TcdB monoclonal antibodies Phase II projection Upon demonstration of proof of concept we envision a Phase II SBIR focused on detailed efficacy studies that include combination with antibiotics followed by process development and preclinical safety and pharmacokinetics PUBLIC HEALTH RELEVANCE Clostridium difficile is a bacterial pathogen and a major public health problem worldwide with over deaths and $ billion in healthcare expenses per annum in the U S alone C difficile associated diarrhea CDAD is the most common cause of antibiotic associated diarrhea and colitis in the U S In this proposal we devise a novel technology that allows antitoxin therapeutic antibodies against this pathogen to be specifically targeted to the site of infection where it is needed