Neutralizing Antibodies to Typhoid Toxin

Project Summary / AbstractTyphoid fever is a major global health concern, with ongoing occurring outbreaks in some developing countries.The causative agent of typhoid fever is the gram-negative bacterium, Salmonella Typhi. It was recentlydiscovered that S. Typhi produces an unusual toxin known as typhoid toxin. The goal of this research programis to generate the first B cell epitope map of typhoid toxin, with a particular focus on identification of regionsassociated with the onset of toxin-neutralizing antibodies. In Specific Aim 1 we will generate a collection ofmurine monoclonal antibodies (MAbs) against all of the three components of typhoid toxin, CdtB, PltA and PltBand characterize them to identify potent MAbs by performing ELISA, cell-based toxin-neutralization assays,competition ELISA, pepscan analysis, mutagenesis, and surface plasmon resonance. In Specific Aim 2 a selectnumber of toxin-neutralizing MAbs generated in Aim 1 will be evaluated for the ability to passively protect miceagainst lethal dose typhoid toxin challenge. We will test whether the MAbs with the most potent toxin-neutralizingactivity in vitro are also protective in vivo. Additionally, we will begin to define the mechanism(s) by which themost potent MAbs neutralize typhoid toxin in vitro. The MAbs generated as part of this study will be powerfultools for more detailed mechanistic studies to better understand the biology of typhoid toxin and may even havepotential applications for therapeutics uses in humans.