Modeling Alzheimer's in Germ-Free Mice

As a mouse model of Alzheimer’s disease we used heterozygous male 5xFAD transgenic mice and non-transgenic littermates (4 and 10 months of age) on a C57BL/6 J background co-expressing human APP^{K670N/M671L (Sw) + I716V (Fl) + V717I(Lo)} and PS1^{M146L + L286V} under the control of the neuron-specific Thy-1 promoter [38 (link)]. Mice were housed under specific pathogen-free (SPF) conditions under a 12-h light, 12-h dark cycle with food and water ad libitum at CEMT (Freiburg, Germany). GF 5xFAD mice were generated via embryo transfer by Kathleen McCoy. GF heterozygous 5xFAD and WT littermates were obtained from the Clean Mouse Facility (Bern, Switzerland). In order to deplete microbiota, mice were treated orally via drinking water with a mixture of antibiotics (ABX), containing 1 mg/ml vancomycin (Hexal), 1 mg/ml cefoxitin (Santa Cruz Biotechnology), 1 mg/ml gentamicin (Sigma-Aldrich) and 1 mg/ml metronidazol (Sigma-Aldrich) for 2 months as described previously [12 (link)]. All animal experiments were approved by the Ministry for Nature, Environment and Consumers` Protection of the state of Baden-Württemberg and were performed in accordance to the respective national, federal, and institutional regulations (G19–02 and X16-04A).