Project description:An aberrant Ascaris suum infection in a domestic dog in China in 2019 is described for the first time. This pathogen is a common roundworm of pigs with few reported cases in domestic animals. Our findings suggest a wider infection range with a possible transmission of A. suum to domestic animals that interact with humans.
Project description:BACKGROUND:Ascaris lumbricoides is one of the three major soil-transmitted gastrointestinal helminths (STHs) that infect more than 440 million people in the world, ranking this neglected tropical disease among the most common afflictions of people living in poverty. Children infected with this roundworm suffer from malnutrition, growth stunting as well as cognitive and intellectual deficits. An effective vaccine is urgently needed to complement anthelmintic deworming as a better approach to control helminth infections. As37 is an immunodominant antigen of Ascaris suum, a pig roundworm closely related to the human A. lumbricoides parasite, recognized by protective immune sera from A. suum infected mice. In this study, the immunogenicity and vaccine efficacy of recombinant As37 were evaluated in a mouse model. METHODOLOGY/PRINCIPAL FINDINGS:As37 was cloned and expressed as a soluble recombinant protein (rAs37) in Escherichia coli. The expressed rAs37 was highly recognized by protective immune sera from A. suum egg-infected mice. Balb/c mice immunized with 25 μg rAs37 formulated with AddaVax™ adjuvant showed significant larval worm reduction after challenge with A. suum infective eggs when compared with a PBS (49.7%) or adjuvant control (48.7%). Protection was associated with mixed Th1/2-type immune responses characterized by high titers of serological IgG1 and IgG2a and stimulation of the production of cytokines IL-4, IL-5, IL-10 and IL-13. In this experiment, the AddaVax™ adjuvant induced better protection than the Th1-type adjuvant MPLA (38.9%) and the Th2-type adjuvant Alhydrogel (40.7%). Sequence analysis revealed that As37 is a member of the immunoglobulin superfamily (IgSF) and highly conserved in other human STHs. Anti-As37 antibodies strongly recognized homologs in hookworms (Necator americanus, Ancylostoma ceylanicum, A. caninum) and in the whipworm Trichuris muris, but there was no cross-reaction with human spleen tissue extracts. These results suggest that the nematode-conserved As37 could serve as a pan-helminth vaccine antigen to prevent all STH infections without cross-reaction with human IgSF molecules. CONCLUSIONS/SIGNIFICANCE:As37 is an A. suum expressed immunodominant antigen that elicited significant protective immunity in mice when formulated with AddaVax™. As37 is highly conserved in other STHs, but not in humans, suggesting it could be further developed as a pan-helminth vaccine against STH co-infections.
Project description: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.
Project description:Cecropin P1 was first identified as a mammalian antimicrobial peptide isolated from the pig intestine. Much research aimed at characterizing this peptide has been reported. Recently, the workers who discovered the peptide corrected their original conclusion, and confirmed that this peptide originates in fact from the pig intestinal parasitic nematode, Ascaris suum. In the present study, we carried out a semi-exhaustive search for bacteria-inducible transcripts in A. suum by the cDNA subtraction method. The transcripts encoding cecropin P1 and novel Ascaris cecropins, designated cecropins P2, P3 and P4, were found to be positively induced factors. Chemically synthesized Ascaris cecropins were bactericidal against a wide range of microbes, i.e. Gram-positive (Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus) and Gram-negative (Pseudomonas aeruginosa, Salmonella typhimurium, Serratia marcescens and Esherichia coli) bacteria, and were weakly but detectably active against yeasts (Saccharomyces cerevisiae and Candida albicans). Cecropin P1-like sequences were also detected at least in two other species (Ascaris lumbricoides and Toxocara canis) of the Ascarididae. All Ascaris cecropin precursors contain an acidic pro-region connected by a tetra-basic cleavage site at the C-terminus. Such an acidic pro-region is also reported to be present in the tunicate cecropin-type antimicrobial peptide styelin. On the basis of the evolutionary position of nematodes and tunicates, the ancestral cecropin may have contained the acidic pro-region at the C-terminus.
Project description:Circular RNAs (circRNAs) are a recently identified RNA species with emerging functional roles as microRNA (miRNA) and protein sponges, regulators of gene transcription and translation, and modulators of fundamental biological processes including immunoregulation. Relevant to this study, circRNAs have recently been described in the parasitic nematode, Haemonchus contortus, suggesting they may have functionally important roles in parasites. Given their involvement in regulating biological processes, a better understanding of their role in parasites could be leveraged for future control efforts. Here, we report the use of next-generation sequencing to identify 1,997 distinct circRNAs expressed in adult female stages of the gastrointestinal parasitic nematode, Ascaris suum. We describe spatial expression in the ovary-enriched and body wall muscle, and also report circRNA presence in extracellular vesicles (EVs) secreted by the parasite into the external environment. Further, we used an in-silico approach to predict that a subset of Ascaris circRNAs bind both endogenous parasite miRNAs as well as human host miRNAs, suggesting they could be functional as both endogenous and exogenous miRNA sponges to alter gene expression. There was not a strong correlation between Ascaris circRNA length and endogenous miRNA interactions, indicating Ascaris circRNAs are enriched for Ascaris miRNA binding sites, but that human miRNAs were predicted form a more thermodynamically stable bond with Ascaris circRNAs. These results suggest that secreted circRNAs could be interacting with host miRNAs at the host-parasite interface and influencing host gene transcription. Lastly, although we have previously found that therapeutically relevant concentrations of the anthelmintic drug ivermectin inhibited EV release from parasitic nematodes, we did not observe a direct effect of ivermectin treatment on Ascaris circRNAs expression or secretion.
Project description:Recently, invertebrate models have been widely used for the study of innate immunity. Nematodes are novel potential candidates because of the experimental advantages of Caenorhabditis elegans. However, whether nematodes have active immune responses is still ambiguous. Previously, we reported ASABF (Ascaris suum antibacterial factor)-type antimicrobial peptides in the parasitic nematode Ascaris suum and the genetic model nematode C. elegans. Further screening of a cDNA library and an expressed-sequence-tag database search detected five novel members of ASABF (ASABF-beta, -gamma, -delta, - epsilon and -zeta) in A. suum. The transcripts for ASABF-alpha, -beta, -gamma, and -delta clearly increased in the body wall, and also in the intestine for ASABF-delta, 4 h after injection of heat-killed bacteria into the pseudocoelom (body cavity), suggesting that these peptides are inducible in the acute phase of immune response. These results also suggest that the nematodes can recognize bacteria in the pseudocoelomic fluid and evoke an active immune response.
Project description:Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was used to discover peptides in extracts of the large parasitic nematode Ascaris suum. This required the assembly of a new database of known and predicted peptides. In addition to those already sequenced, peptides were either previously predicted to be processed from precursor proteins identified in an A. suum library of expressed sequence tags (ESTs) or newly predicted from a library of A. suum genome survey sequences (GSSs). The predicted MS/MS fragmentation patterns of this collection of real and putative peptides were compared with the actual fragmentation patterns found in the MS/MS spectra of peptides fractionated by MS; this enabled individual peptides to be sequenced. Many previously identified peptides were found, and 21 novel peptides were discovered. Thus, this approach is very useful, despite the fact that the available GSS database is still preliminary, having only 1× coverage.