A Humanized Gnotobiotic Piglet Model to Study Host-Microbiota Interactions

During the past decade, studies using culture-independent DNA sequencing-based approaches have found associations between the gut microbiota and several human disease conditions such as obesity, diabetes, allergies, etc. Many of these studies have used mouse models as surrogates for humans; however, there are marked differences between humans and mice in terms of anatomy, physiology, and immune system which may confound the translation of these findings to humans. The domestic pig (Sus scrofa) shares a high degree of anatomical, physiological, and immunological similarities with humans – thus, the pig is a valuable model for human gut microbiota studies. This study was conducted with the objective of establishing human gut-associated microbial communities in gnotobiotic piglets to develop a new model to investigate how microbial gene expression influences host metabolism by continuous sampling of the microbiome. Twenty germ-free piglets derived using cesarean section were ‘humanized’ by inoculation with human fecal matter obtained from ‘obese’ (BMI >30 kg/m²) and ‘lean’ (BMI <25 kg/m²) individuals, and were maintained in germ-free isolators. At 7-8 weeks of age, 5 of these piglets were cecum-cannulated within sterile surgery bubbles. Fecal samples were collected weekly from all piglets throughout the study while cecal samples were collected through the cannulae of the cannulated piglets at weekly time intervals during the final 3 weeks of the study. The study period was 8 weeks for the non-cannulated piglets, while the cannulated piglets were studied for 10 weeks. All fecal and cecal samples were subjected to 16S rRNA gene-based amplicon sequencing using the Illumina MiSeq^TM platform to characterize their bacterial community composition. Comparison of the fecal and cecal bacterial communities of the ‘humanized’ piglets with those of conventional pigs revealed that the ‘humanized’ piglet microbiota was more similar to a human microbiota than to a swine microbiota (p < 0.001). No adverse health effects were observed in the cannulated piglets as a result of the cannulation procedure. Currently, work is being carried out to investigate the influence of the microbiota on host gene expression using a transcriptome-based approach, evaluating the interaction between the cecal microbiota and the host gut epithelium.