Operating and Biocontainment Procedures of a Facility for Laboratory Mice with a Natural Microbiome: Immunophenotyping Procedure.

The use of laboratory mice with a natural microbiome, such as "Wildling mice", offers a promising research tool for both basic and applied science due to their close resemblance to the human superorganism. However, the breeding and maintenance of these mice, which harbor a diverse microbiome including bacteria, viruses, and parasites, pose significant challenges for animal husbandry facilities at research institutions. To address these challenges, a specialized facility concept was developed for housing "Wildling mice" at Charité - Universitätsmedizin Berlin. This approach involved designing a facility with specific structural features and operational protocols to effectively contain the natural microbiome, thereby protecting areas with higher hygiene standards. A methodology for blood sampling from both specified pathogen-free (SPF) and "Wildling mice" for immunophenotyping is demonstrated, highlighting the workflow and biocontainment measures implemented in the facility. Remarkable results reveal that "Wildling mice" exposed to a natural microbiome develop distinct immune cell populations, which are significantly reduced in mice bred and maintained under stringent hygiene conditions. The significance of this study lies in its potential to provide researchers with access to mice that possess a natural microbiome and a mature immune system similar to that of human adults. This approach could enhance the translatability of preclinical findings into clinical practice, thereby advancing the field of biomedical research.