Abstract

BackgroundHumanized mice featuring a functional human immune system are an important pre-clinical model for examining immune responses to human-specific pathogens. This model has been widely utilized to study human diseases that are otherwise impossible or difficult to investigate in humans or with other animal models. However, one limitation of using humanized mice is their native murine gut microbiome, which significantly differs from the one found in humans. These differences may be even greater for mice housed and bred in specific pathogen free conditions. Given the importance of the gut microbiome to human health and disease, these differences may profoundly impact the ability to translate the results from humanized mice studies to human disease. Further, there is a critical need for improved pre-clinical models to study the complex in vivo relationships of the gut microbiome, immune system, and human disease. We therefore created double humanized mice with both a functional human immune system and stable human-like gut microbiome.\n\nResultsSurgery was performed on NOD.Cg-PrkdcscidII2rgtm1Wjl/SzJ (NSG) mice to create bone-marrow, liver, thymus (BLT) humanized mice. After immune reconstitution, mice were treated with broad spectrum antibiotics to deplete murine gut bacteria and then transplanted with fecal material from healthy human donors. Characterization of 173 fecal samples obtained from 45 humanized mice revealed that double humanized mice had unique 16S rRNA gene profiles consistent with those of the individual human donor samples. Importantly, transplanted human-like gut microbiomes were stable in mice for the duration of the study, up to 14.5 weeks post-transplant. Microbiomes of double humanized mice also harbored predicted functional capacities that more closely resembled those of the human donors compared to humanized mice.\n\nConclusionsHere, we describe successful engraftment of a stable human microbiome in BLT humanized mice to further improve this preclinical humanized mouse model. These double humanized mice represent a unique and tractable new model to study the complex relationships between the human gut microbiome, human immune system, and human disease in vivo.