Blavignac, C. | Search bioRxiv

bioRxiv2024

Exploring the impact of digestive physicochemical parameters of adults and infants on the pathophysiology of Cryptosporidium parvum using the dynamic TIM-1 gastrointestinal model

BackgroundHuman cryptosporidiosis is distributed worldwide, and it is recognised as a leading cause of acute diarrhoea and death in infants in low- and middle-income countries. Besides immune status, the higher incidence and severity of this gastrointestinal disease in young children could also be attributed to the digestive environment. For instance, human gastrointestinal physiology undergoes significant changes with age, however the role this variability plays in Cryptosporidium parvum pathogenesis is not known. In this study, we analysed for the first time the impact of digestive physicochemical parameters on C. parvum infection in a human and age-dependent context using a dynamic in vitro gastrointestinal model. ResultsOur results showed that the parasite excystation, releasing sporozoites from oocysts, occurs in the duodenum compartment after one hour of digestion in both child (from 6 months to 2 years) and adult experimental conditions. In the child small intestine, slightly less sporozoites were released from excystation compared to adult, however they exhibited a higher luciferase activity, suggesting a better physiological state. Sporozoites collected from the child jejunum compartment also showed a higher ability to invade human intestinal epithelial cells compared to the adult condition. Global analysis of the parasite transcriptome through RNA-sequencing demonstrated a more pronounced modulation in ileal effluents compared to gastric ones, albeit showing less susceptibility to age-related digestive condition. Further analysis of gene expression and enriched pathways showed that oocysts are highly active in protein synthesis in the stomach compartment, whereas sporozoites released in the ileum showed downregulation of glycolysis as well as strong modulation of genes potentially related to gliding motility and secreted effectors. ConclusionsDigestion in a sophisticated in vitro gastrointestinal model revealed that invasive sporozoite stages are released in the small intestine, and are highly abundant and active in the ileum compartment, supporting reported C. parvum tissue tropism. Our comparative analysis suggests that physicochemical parameters encountered in the child digestive environment can influence the amount, physiological state and possibly invasiveness of sporozoites released in the small intestine, thus potentially contributing to the higher susceptibility of young individuals to cryptosporidiosis.

microbiology↗

bioRxiv2022

Spatial distribution and physicochemical properties of respirable volcanic ash from the 16-17 August 2006 Tungurahua eruption (Ecuador), and alveolar epithelium response in-vitro

BackgroundTungurahua volcano (Ecuador) intermittently emitted ash between 1999 and 2016, enduringly affecting the surrounding rural area and its population, but its health impact remains poorly documented. ObjectivesWe aim at assessing the respiratory health hazard posed by the 16-17 August 2006 most intense eruptive phase of Tungurahua. MethodsBased on detailed field surveys and grain size analyses, we mapped the spatial distribution of the health-relevant ash size fractions produced by the eruption in the area impacted by ash fallout. We used Scanning Electron Microscopy and Raman Spectroscopy to quantify the mineralogy, composition, surface texture and morphology of a respirable ash sample isolated by aerodynamic separation. The cytotoxicity and pro-inflammatory potential of this respirable ash towards lung tissues was assessed in-vitro using A549 alveolar epithelial cells, by Electron Microscopy and biochemical assays (LDH assay, RT-qPCR, multiplex immunoassays). ResultsThe eruption produced a high amount of inhalable and respirable ash (12.0-0.04 kg/m2 of sub-10 {micro}m and 5.3-0.02 kg/m2 of sub-4 {micro}m ash deposited). Their abundance and proportion vary greatly across the deposit within the first 20 km from the volcano. The respirable ash is characteristic of an andesitic magma and no crystalline silica is detected. Morphological features and surface textures are complex and highly variable, with few fibres observed. In-vitro experiments show that respirable volcanic ash are internalized by A549 cells and processed in the endosomal pathway, causing little cell damage, but some changes in cell morphology and membrane texture. The ash trigger a weak pro-inflammatory response. DiscussionThese data provide the first understanding of the respirable ash hazard near Tungurahua, and the extent to which it varies spatially in a fallout deposit. Given the long exposure duration of the surrounding population, the chronic effects of this inhalable, weakly bio-reactive ash on health could be further investigated.

ecology↗