Mechanistic and Single-Dose <em>In Vivo</em> Therapeutic Studies of Cry5B Anthelmintic Action against Hookworms HuYan ZhanBin KeeganBrian Y. YiuYing M. MillerMelanie JonesKathryn AroianRaffi V. 2012 <div><h3>Background</h3><p>Hookworm infections are one of the most important parasitic infections of humans worldwide, considered by some second only to malaria in associated disease burden. Single-dose mass drug administration for soil-transmitted helminths, including hookworms, relies primarily on albendazole, which has variable efficacy. New and better hookworm therapies are urgently needed. <em>Bacillus thuringiensis</em> crystal protein Cry5B has potential as a novel anthelmintic and has been extensively studied in the roundworm <em>Caenorhabditis elegans</em>. Here, we ask whether single-dose Cry5B can provide therapy against a hookworm infection and whether <em>C. elegans</em> mechanism-of-action studies are relevant to hookworms.</p> <h3>Methodology/Principal Findings</h3><p>To test whether the <em>C. elegans</em> invertebrate-specific glycolipid receptor for Cry5B is relevant in hookworms, we fed <em>Ancylostoma ceylanicum</em> hookworm adults Cry5B with and without galactose, an inhibitor of Cry5B-<em>C. elegans</em> glycolipid interactions. As with <em>C. elegans</em>, galactose inhibits Cry5B toxicity in <em>A. ceylanicum</em>. Furthermore, p38 mitogen-activated protein kinase (MAPK), which controls one of the most important Cry5B signal transduction responses in <em>C. elegans</em>, is functionally operational in hookworms. <em>A. ceylanicum</em> hookworms treated with Cry5B up-regulate p38 MAPK and knock down of p38 MAPK activity in hookworms results in hypersensitivity of <em>A. ceylanicum</em> adults to Cry5B attack. Single-dose Cry5B is able to reduce by >90% <em>A. ceylanicum</em> hookworm burdens from infected hamsters, in the process eliminating hookworm egg shedding in feces and protecting infected hamsters from blood loss. Anthelmintic activity is increased about 3-fold, eliminating >97% of the parasites with a single 3 mg dose (∼30 mg/kg), by incorporating a simple formulation to help prevent digestion in the acidic stomach of the host mammal.</p> <h3>Conclusions/Significance</h3><p>These studies advance the development of Cry5B protein as a potent, safe single-dose anthelmintic for hookworm therapy and make available the information of how Cry5B functions in <em>C. elegans</em> in order to study and improve Cry5B function against hookworms.</p> </div>