Bacillus thuringiensis-derived Cry5B Has Potent Anthelmintic Activity against Ascaris suum

Abstract

Ascaris suum and Ascaris lumbricoides are two closely related geo-helminth parasites that ubiquitously infect pigs and humans, respectively. Ascaris suum infection in pigs is considered a good model for A. lumbricoides infection in humans because of a similar biology and tissue migration to the intestines. Ascaris lumbricoides infections in children are associated with malnutrition, growth and cognitive stunting, immune defects, and, in extreme cases, life-threatening blockage of the digestive tract and aberrant migration into the bile duct and peritoneum. Similar effects can be seen with A. suum infections in pigs related to poor feed efficiency and performance. New strategies to control Ascaris infections are needed largely due to reduced treatment efficacies of current anthelmintics in the field, the threat of resistance development, and the general lack of new drug development for intestinal soil-transmitted helminths for humans and animals. Here we demonstrate for the first time that A. suum expresses the receptors for Bacillus thuringiensis crystal protein and novel anthelmintic Cry5B, which has been previously shown to intoxicate hookworms and which belongs to a class of proteins considered non-toxic to vertebrates. Cry5B is able to intoxicate A. suum larvae and adults and triggers the activation of the p38 mitogen-activated protein kinase pathway similar to that observed with other nematodes. Most importantly, two moderate doses of 20 mg/kg body weight (143 nM/kg) of Cry5B resulted in a near complete cure of intestinal A. suum infections in pigs. Taken together, these results demonstrate the excellent potential of Cry5B to treat Ascaris infections in pigs and in humans and for Cry5B to work effectively in the human gastrointestinal tract.

Entomotoxic and nematotoxic lectins and protease inhibitors from fungal fruiting bodies

“…A recent study reported a dose-dependent toxicity of CGL2, CCL2, AAL, and MOA toward larval and adult stages of the barbers pole worm, Haemonchus contortus in vitro, in which toxicity of the lectins correlated with their binding to the intestinal epithelium of this animal-parasite nematode (Heim et al 2015). Successful in vivo applications of nematotoxic, carbohydrate-binding protein toxins of microbial origin against parasitic nematodes were demonstrated for the Bacillus thuringiensis toxin Cry5B against the hookworm Ancylostoma ceylanicum in hamsters and against the large roundworm Ascaris suum in pigs (Cappello et al 2006;Hu et al 2012;Urban et al 2013). The nematotoxicity of all those carbohydrate-binding proteins proven to be effective against parasitic nematodes had previously been demonstrated in C. elegans, showing the power of this model organism for detection and characterization of nematotoxic proteins.…”

Protection and Delivery of Anthelmintic Protein Cry5B to Nematodes Using Mesoporous Silicon Particles

“…1,2 Current treatment revolves around mass drug administration (MDA) with benzimidazole anthelmintics (primarily albendazole), but widespread anthelmintic resistance in veterinary husbandry and reports of low efficacy of albendazole in human therapy suggest that new anthelmintics are urgently needed. 3,4 One of the more promising new anthelmintics in development for STHs is the crystal (Cry) protein Cry5B, derived from Bacillus thuringiensis , 5 which has been shown to be highly effective against in vivo infections of STHs such as Ascaris 6 and hookworm. 7 Cry5B is a member of the three-domain B. thuringiensis Cry proteins, which are pore-forming proteins that target the invertebrate (insect/nematode) intestine, in the case of Cry5B by binding to invertebrate-specific glycolipids present on the apical surface of the nematode intestine.…”

Microfluidic platform for electrophysiological recordings from host-stage hookworm and Ascaris suum larvae: A new tool for anthelmintic research

“…The preparation of infective A. suum eggs and inoculation of two pigs from the Beltsville Swine Herd were completed as described previously (Urban et al., 2013). Seven days after inoculation with 15,000 infective eggs, the lungs were removed and mixed with an equal volume of 37 °C normal saline in a Waring blender container with rotating cutting blades, and homogenized for approximately 20 s to produce a tissue suspension of fragments of ∼0.5 cm 3 .…”

“…Seven days after inoculation with 15,000 infective eggs, the lungs were removed and mixed with an equal volume of 37 °C normal saline in a Waring blender container with rotating cutting blades, and homogenized for approximately 20 s to produce a tissue suspension of fragments of ∼0.5 cm 3 . Host-stage L3s were isolated from the lung tissue using an agar-gel method (Urban et al., 2013), transferred to RPMI-c and kept in a 37 °C, 5% CO 2 , incubator until use. For EPG recordings, 10% (v/v) calf serum (CaS; Lonza BioWhittaker 14-401F, Walkersville, MD, USA) was added to RPMI-c.…”