QUORUM SENSING AGONISTS FOR CHOLERA THERAPY: SYNTHESIS, EVALUATION, AND STUDIES IN NANOPARTICLE DELIVERY

Abstract

The rapid spread of antibiotic resistance in Vibrio cholerae has created a need for antibiotic alternatives in cholera treatment. One promising therapeutic strategy involves modulation of quorum sensing, a system of bacterial communication that is used to regulate virulence in V. cholerae. Agonists of the membrane-bound receptor CqsS activate the quorum sensing pathway upon binding,resulting in inhibition of virulence factor production and biofilm formation. Although multiple known CqsS agonists are highly active in vitro, they also tend to be highly hydrophobic and often unstable, precluding delivery to the site of infection in vivo. In this work, we pursue two strategies toward the development of a cholera therapeutic that localizes at the site of infection in the small intestine. The first is the optimization of a structurally unique CqsS agonist based on leads identified in a high-throughput screen. This approach led to the identification of a molecule more active than CAI-1, the natural V. cholerae quorum sensing signal. The second strategy is the development of a nanoparticle carrier for the delivery of hydrophobic quorum sensing molecules to the small intestine. We report the encapsulation of CAI-1 in stable, water-dispersible nanoparticles designed for intestinal delivery using Flash NanoPrecipitation. These nanoparticles induce quorum sensing responses five orders of magnitude higher than identically administered CAI-1 saturated in aqueous solution, and release their cargo specifically in conditions present in the small intestine. They are also diffusive across in vivo delivery barriers such as intestinal mucus. Furthermore, preliminary experiments demonstrate that nanoparticles with many of these desirable properties can be fashioned from inexpensive, biocompatible materials. Overall, this work suggests that quorumsensing molecules employed in conjunction with nanoparticle technology are promising candidates as non-antibiotic cholera therapeutics.