Project description:BackgroundBiomphalaria glabrata is one of the main intermediate hosts of Schistosoma mansoni, the most widespread species of Schistosoma. Our previous studies proved that alternative oxidase (AOX), the terminal oxidase in the mitochondrial respiratory chain, widely exists in several species of intermediate host snails of Schistosoma. Meanwhile, inhibition of AOX activity in Oncomelania hupensis snails could dramatically enhance the molluscicidal effect of niclosamide. As a hermaphroditic aquatic mollusc, the high fecundity and population density of B. glabrata increase the difficulty of snail control, which is one of the critical strategies for schistosomiasis elimination. The present study aimed to investigate the possible role of AOX in the development and fecundity of B. glabrata snail, which could be manipulated more manageable than other species of intermediate host snails of Schistosoma.MethodsThe dynamic expression of the AOX gene was investigated in different developmental stages and tissues of B. glabrata, with morphological change and oviposition behaviour observed from juvenile to adult snails. Furtherly, dsRNA-mediated knockdown of BgAOX mRNA and the AOX protein activity inhibiting was performed to investigate the effect of AOX on the development and oviposition of snails.ResultsThe BgAOX gene expression profile is highly related to the development from late juveniles to adults, especially to the reproductive system of snails, with a positive correlation of 0.975 between egg production and BgAOX relative expression in ovotestis of snails. The inhibition of BgAOX at the transcriptional level and AOX activity could efficiently inhibit snail growth. However, the interference at the BgAOX protein activity level led to more severe tissue damage and more significant inhibition of oviposition than at the transcriptional level. This inhibition of growth and oviposition decreased gradually with the increase in the snail size.ConclusionsThe inhibition of AOX could efficiently disrupt the development and oviposition of B. glabrata snails, and the intervention targeting AOX at the juvenile stage is more effective for snails. This investigation explored the role of AOX in the growth and development of snails. It would benefit snail control in the future by providing a potential target while using molluscicides more efficiently.

Project description:Schistosomiasis is an infectious disease infecting mammals as the definitive host and fresh water snails as the intermediate host. Understanding the molecular and biochemical relationship between the causative schistosome parasite and its hosts will be key to understanding and ultimately treating and/or eradicating the disease. There is increasing evidence that pathogens that have co-evolved with their hosts can manipulate their hosts' behaviour at various levels to augment an infection. Bacteria, for example, can induce beneficial chromatin remodelling of the host genome. We have previously shown in vitro that Biomphalaria glabrata embryonic cells co-cultured with schistosome miracidia display genes changing their nuclear location and becoming up-regulated. This also happens in vivo in live intact snails, where early exposure to miracidia also elicits non-random repositioning of genes. We reveal differences in the nuclear repositioning between the response of parasite susceptible snails as compared to resistant snails and with normal or live, attenuated parasites. Interestingly, the stress response gene heat shock protein (Hsp) 70 is only repositioned and then up-regulated in susceptible snails with the normal parasite. This movement and change in gene expression seems to be controlled by the parasite. Other differences in the behaviour of genes support the view that some genes are responding to tissue damage, for example the ferritin genes move and are up-regulated whether the snails are either susceptible or resistant and upon exposure to either normal or attenuated parasite. This is the first time host genome reorganisation has been seen in a parasitic host and only the second time for any pathogen. We believe that the parasite elicits a spatio-epigenetic reorganisation of the host genome to induce favourable gene expression for itself and this might represent a fundamental mechanism present in the human host infected with schistosome cercariae as well as in other host-pathogen relationships.

Project description:Biomphalaria snails play a crucial role in the transmission of the human blood fluke Schistosoma mansoni. The gut microbiota of intermediate hosts is known to influence their physiological functions, but little is known about its composition and role in Biomphalaria snails. To gain insights into the biological characteristics of these freshwater intermediate hosts, we conducted metagenomic sequencing on Biomphalaria straminea and B. glabrata to investigate variations in their gut microbiota. This study revealed that the dominant members of the gut microbiota in B. glabrata belong to the phyla Bacteroidetes and Proteobacteria, which were also found to be the top two most abundant gut bacteria in B. straminea. We identified Firmicutes, Acidovorax and Bosea as distinctive gut microbes in B. straminea, while Aeromonas, Cloacibacterium and Chryseobacterium were found to be dependent features of the B. glabrata gut microbiota. We observed significant differences in the community structures and bacterial functions of the gut microbiota between the two host species. Notably, we found a distinctive richness of antibiotic resistance genes (ARGs) associated with various classes of antibiotics, including bacitracin, chloramphenicol, tetracycline, sulfonamide, penicillin, cephalosporin_ii and cephalosporin_i, fluoroquinolone, aminoglycoside, beta-lactam, multidrug and trimethoprim, in the digestive tracts of the snails. Furthermore, this study revealed the potential correlations between snail gut microbiota and the infection rate of S. mansoni using Spearman correlation analysis. Through metagenomic analysis, our study provided new insights into the gut microbiota of Biomphalaria snails and how it is influenced by host species, thereby enhancing our understanding of variant patterns of gut microbial communities in intermediate hosts. Our findings may contribute to future studies on gastropod-microbe interactions and may provide valuable knowledge for developing snail control strategies to combat schistosomiasis in the future.

Project description:BackgroundThe freshwater snails Biomphalaria alexandrina (Gastropoda: Planorbidae) has public health importance of being an intermediate host of Schistosoma mansoni, the parasite species that causes intestinal schistosomiasis in humans. Glutathione transferases (GSTs) play an important role in detoxification of a broad range of compounds including secondary metabolites and exogenous compounds. Studying GSTs in snails may clarify their role in detoxification of molluscicides.ResultsTwo glutathione transferases (BaGST2 and BaGST3) were purified and characterized from B. alexandrina snails. BaGST2 and BaGST3 were electrophoretically homogeneous preparations with subunit molecular weight of 23.6 kDa and molecular weight of 45 kDa. Isoelectric focusing of BaGST2 revealed the presence of two components at pI 4.47 and 4.67, while BaGST3 showed one band at pI 4.17. The specific activity of BaGST2 and BaGST3 toward 1-chloro-2,4-dinitrobenzene (CDNB) was 19.0 and 45.2 μmol/min/mg protein following 146- and 346-fold purification, respectively. The catalytic pH optima, km values, and the activation energies for BaGST2 and BaGST3 were determined. BaGST2 and BaGST3 were significantly inhibited by hematin and Cibacron Blue and to a less extent by bromosulfophthalein, S-butyl-GSH, S-hexyl-GSH, and S-P-bromobenzyl-GSH. BaGST2 and BaGST3 showed high activity against ethacrynic acid as substrate, and they also exhibited peroxidase activity on cumene hydroperoxide. The two enzymes showed identical patterns of lysine-C digestion after high-performance liquid chromatography. The amino acid sequences of three peptide fragments and peptide mass fingerprinting of fourteen peptides were used to predict the primary structure of BaGST2. A polypeptide of 206 amino acids (with 7 gaps, 3 of which could not identified) was predicted for BaGST2. The theoretical subunit molecular weight of BaGST2 is 22.6 kDa, with pI of 8.58. BaGST2 has 65% sequence identity and 78% positive with Biomphalaria glabrata GST7. The overall structure of BaGST2 at the N-terminal domain is identical to the canonical GST N-terminal domain, having the typical thioredoxin-like fold with a βαβ-α-ββα motif, whereas the C-terminal domain is made from 6 α-helices. A conservative GST-N-domain includes glutathione binding sites Y11, L17, Q53, M54, Q65, and S66, while a variable GST-C domain contains electrophilic substrate binding site H99, R102, A103, F106, K107, L161, and Y167. Phylogenetic tree showed that BaGST2 was clustered in the sigma group with GSTs sigma class from invertebrates and vertebrates.ConclusionsWe have purified and characterized two GSTs from B. alexandrina snails. Our study broadens the biochemical information on freshwater snail GSTs by demonstrating the role of BaGSTs in defense mechanisms against structurally different electrophilic compounds. BaGST2 and BaGST3 have Se-independent peroxidase activity, which indicates their role in cellular antioxidant defense by reducing organic hydroperoxides in B. alexandrina. A polypeptide chain of 206 amino acids was predicted. The primary structure of BaGST2 showed 65% sequence identity with Biomphalaria glabrata GST7. Sequence analysis indicates that BaGST2 is a GST-N-sigma-like with a thioredoxin-like superfamily. Phylogenetic tree confirms that BaGST2 belongs to the sigma class of GSTs superfamily.

Project description:BackgroundIntestinal schistosomiasis was confirmed endemic in Mangochi District, Malawi, in May of 2018 following an unexpected encounter with discreet populations of Biomphalaria spp. freshwater snails during routine malacological surveillance activities. Since then, only limited malacological surveillance of Biomphalaria has been carried out, and so the distribution of Biomphalaria populations in this area is currently unclear. Additionally, sites of active Schistosoma mansoni transmission in this area are also unknown. In the present study, through extensive malacological surveillance, we aimed to formally document the distribution of Biomphalaria in Mangochi District. We also aimed to identify active intestinal schistosomiasis transmission sites in this area through subjecting all collected Biomphalaria to a recently developed S. mansoni-specific molecular xenomonitoring PCR.MethodsThree malacological surveys were carried out along the southern shoreline of Lake Malawi, Mangochi District, Malawi, in November 2021, July 2022 and October/November 2022. All collected Biomphalaria were subjected to cercarial shedding analysis to identify active Schistosoma infections. Shed cercariae were then genotyped to species level using a standard multi-locus PCR and Sanger sequencing protocol. Following this, a subset of Biomphalaria from each collection site were also genotyped to species level using a standard PCR and Sanger sequencing protocol. All collected Biomphalaria were then subjected to a recently developed S. mansoni-specific molecular xenomonitoring PCR to identify infected, but non-shedding, Biomphalaria.ResultsA total of 589 Biomphalaria were collected across all three surveys. One single Biomphalaria (0.17%) specimen was found to be actively shedding Schistosoma cercariae, which were molecularly confirmed as S. mansoni. All genotyped Biomphalaria (n = 42) were molecularly identified as B. pfeifferi. A further 19 Biomphalaria specimens, collected from four different surveillance sites, were found to be infected with S. mansoni through molecular xenomonitoring. Intestinal schistosomiasis transmission was therefore identified at four different foci in Mangochi District.ConclusionsOur study highlights the importance of molecular approaches to investigate Biomphalaria populations and monitor Biomphalaria-associated intestinal schistosomiasis transmission in endemic areas. As such, the continued development and use of such approaches, in particular the development and use of molecular xenomonitoring assays that can be carried out in resource-poor schistosomiasis-endemic settings, is encouraged. The revision of ongoing schistosomiasis control programmes in Mangochi District, in line with WHO recommendations, is also encouraged.

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Establishment of Biomphalaria tenagophila snails in Europe.

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Establishment of Biomphalaria tenagophila snails in Europe.

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