First Metabolic Insights into Ex Vivo Cryptosporidium parvum-Infected Bovine Small Intestinal Explants Studied under Physioxic Conditions

SIMPLE SUMMARY: As the most relevant zoonotic cause of cryptosporidiosis, C. parvum infects cattle worldwide. In vitro studies on C. parvum are absent on the most important animal host under physiological oxygen conditions of the intestine. The aim of this study was to rectify this lack of knowledge, and to deliver a practical model to study C. parvum–host cell–intestinal microbiome interactions in the metabolic context. The present metabolic analyses of C. parvum-infected bovine small intestinal (BSI)-explants revealed a parasite-dependent reduction in important metabolic activities (e.g., glycolysis, glutaminolysis) at 3 hpi (hours post-infection) followed by striking increases in the same metabolic functions at 6 hpi, thus paralleling previously reported metabolic impacts of C. parvum on humans. In addition, PCA analysis confirmed physiological oxygen concentrations as a driving factor of metabolic responses in infected BSI explants. The present model allows the study of C. parvum-triggered metabolic modulation of intestinal cells. Moreover, this realistic platform offers the possibility to address pending questions regarding C. parvum–host cell–intestinal microbiome interactions. Thus, the present approach may deliver important insights into how to promote the innate immune system–intestinal microbiome alliances, which maintain the epithelial integrity of the gut thereby supporting human and animal health. ABSTRACT: The apicomplexan Cryptosporidium parvum causes thousands of human deaths yearly. Since bovines represent the most important reservoir of C. parvum, the analysis of infected bovine small intestinal (BSI) explants cultured under physioxia offers a realistic model to study C. parvum–host cell–microbiome interactions. Here, C. parvum-infected BSI explants and primary bovine small intestinal epithelial cells were analysed for parasite development and metabolic reactions. Metabolic conversion rates in supernatants of BSI explants were measured after infection, documenting an immediate parasite-driven metabolic interference. Given that oxygen concentrations affect cellular metabolism, measurements were performed at both 5% O(2) (physiological intestinal conditions) and 21% O(2) (commonly used, hyperoxic lab conditions). Overall, analyses of C. parvum-infected BSI explants revealed a downregulation of conversion rates of key metabolites—such as glucose, lactate, pyruvate, alanine, and aspartate—at 3 hpi, followed by a rapid increase in the same conversion rates at 6 hpi. Moreover, PCA revealed physioxia as a driving factor of metabolic responses in C. parvum-infected BSI explants. Overall, the ex vivo model described here may allow scientists to address pending questions as to how host cell–microbiome alliances influence intestinal epithelial integrity and support the development of protective intestinal immune reactions against C. parvum infections in a realistic scenario under physioxic conditions.