A comparative analysis of gut microbiota disturbances in the Gottingen minipig and rhesus macaque models of acute radiation syndrome following bioequivalent radiation exposures.

In rodent studies, the gut microbiota has been implicated in facilitating both radioresistance, by protecting the epithelium from apoptotic responses and radiosensitivity, inducing endothelial apoptotic responses. Despite the observation that large animal models, such as the Chinese Rhesus macaque and the Gottingen Minipig, demonstrate similarity to human physiologic responses to radiation, little is known about radiation-induced changes of the gut microbiome in these models. To compare the two models, we used bioequivalent radiation doses which resulted in an LD50 for Gottingen Minipigs and Chinese Rhesus macaques, 1.9 Gy and 6.8 Gy, respectively. Fecal samples taken prior and 3 days post-radiation were used for 16S rRNA gene sequence amplicon high throughput sequencing (Illumina MiSeq). Baseline gut microbiota profiles were dissimilar between minipigs and rhesus macaques. Irradiation profoundly impacted gut microbiota profiles in both animals. Significant increases of intracellular symbionts were common to both models and to reported changes in rodents suggesting universality of these findings post-radiation. Remarkably, opposite dynamics were observed for the main phyla, with increase of Firmicutes and decrease of Bacteroidetes and Proteobacteria in minipigs but with enrichment of Bacteroidetes in rhesus macaques. Minipig changes in magnitude and in variety of species affected were more extensive than those observed in rhesus macaques. This pilot study provides an important first step in comparing the radiosensitive pig model to the comparatively more radioresistant macaque model, for the identification of microbial elements which may influence radiosensitivity.