Lectin-Mediated Bacterial Modulation by the Intestinal Nematode Ascaris suum

Abstract

Ascariasis is a global health problem for humans and animals. Adult Ascaris nematodes are long-lived in the host intestine where they interact with host cells as well as members of the microbiota resulting in chronic infections. Nematode interactions with host cells and the microbial environment are prominently mediated by parasite-secreted proteins and peptides possessing immunomodulatory and antimicrobial activities. Previously, we discovered the C-type lectin protein AsCTL-42 in the secreted products of adult Ascaris worms. Here we tested recombinant AsCTL-42 for its ability to interact with bacterial and host cells. We found that AsCTL-42 lacks bactericidal activity but neutralized bacterial cells without killing them. Treatment of bacterial cells with AsCTL-42 reduced invasion of intestinal epithelial cells by Salmonella. Furthermore, AsCTL-42 interacted with host myeloid C-type lectin receptors. Thus, AsCTL-42 is a parasite protein involved in the triad relationship between Ascaris, host cells, and the microbiota.

Helminths and Bacterial Microbiota: The Interactions of Two of Humans’ “Old Friends”

“…Helminth products (including AMPs) could directly affect the diversity and composition of the microbiota. For example, A. suum ESPs contain several AMPs—such as lectins, cecropins, and members of the A. suum antibacterial factor family—which inhibit bacterial growth, impair biofilm formation, or neutralize bacteria by other mechanisms (e.g., agglutination) [ 111 , 112 ]. Helminth ESPs also include extracellular vesicles, which contain putative AMPs and are thought to be important mediators of the effects of helminths on the microbiota [ 113 , 114 ].…”