A Serological Assay for Neutralizing Antitoxin Response in Patients with Clostridium difficile Infection

AbstractClostridium difficile is responsible for more thandeaths in the US each year and the infection represents an urgent threat to public health worldwideOf most concern is that the incidence of Cdifficile infectionCDIand disease severity is rapidly increasing in recent years due to the emergence of hypervirulent and antibiotic resistant strainsCDI is mainly caused by two major toxins TcdA and TcdBand toxinneutralizing antibodiesantitoxinsare responsible for effective immunityThereforeit is important to measure host antitoxin responses since such information will be crucial for assisting physicians to predict CDI progression and recurrenceas well as to guide the use of antibody based therapeuticsHowevercurrent assays to measure patient antitoxin responses are based on serum inhibition of toxinsbiological activities on cultured cellssuch assays are time consuminglaboriousand difficult to standardizeWe aim to develop a serological ELISA for predicting protective immunity against primary and recurrent CDI in patientsThis will help clinical management of CDI and also may be used as a companion diagnostic for passive and active immunotherapiesWe have identified a broadly neutralizing antibodybNAbNand established a Nbased competition ELISA in that CDI patient sera were assayed for inhibiting the binding of biotinylated Nto TcdBWe found that those sera with high neutralizing anti TcdB titers are also significantly more potent in inhibiting Nbinding to TcdB than sera with low neutralizing titersIn this projectwe will identify additional bNAbs from a panel of anti TcdB neutralizing antibodies we have developed and evaluate the bNAbs based ELISA inbanked serum samples from CDI patientsOur ultimate goal is to develop a simple serological ELISA screen for antitoxin protective immunityand thus help the clinical management of CDI and assist the future use of passive and active immunotherapies against this debilitating disease NarrativeClostridium difficile is responsible for more thandeaths in the US each year and host protective immunity against the infection is mediated via antitoxin antibodiesThe goal of this project is to establish a simple diagnostic for antitoxin responses in patients