Antibiotic-treated versus germ-free rodents for microbiota transplantation studies

We recently investigated the applicability of antibiotic-treated recipient mice for transfer of different gut microbiota profiles. With this addendum we elaborate on perspectives and limitations of using antibiotics as an alternative to germ-free (GF) technology in microbial transplantation studies, and we speculate on the housing effect. It is possible to transfer host phenotypes via fecal transplantation to antibiotic-treated animals, but problems with reproducibility, baseline values, and antibiotic resistance genes should be considered. GF animals maintained in isolators still seem to be the best controlled models for long-term microbial transplantation, but antibiotic-treated recipients are also commonly utilized. We identify a need for systematic experiments investigating the stability of microbial transplantations by addressing 1) the recipient status as either GF, antibiotic-treated or specific pathogen free and 2) different levels of protected housing systems. In addition, the developmental effect of microbes on host physiological functions should be evaluated in the different scenarios

Induction of CD8+ immune memory and enhanced inflammation in a skin inflammation model through pre‐immunization with inactivated pathogens

Abstract Laboratory mice live in specific pathogen‐free (SPF) conditions, resulting in an immature immune system comparable to that of newborns rather than adult humans or mice from pet shops. This condition may compromise their translational value. Reintroducing pathogens would lead to the uncontrolled spread of infections and associated diseases, so research facilities should seek safer alternatives. We immunized laboratory mice with a cocktail of pathogens, which were inactivated by ultraviolet irradiation and mixed with the adjuvant AddaVax. This immunization resulted in a higher percentage of CD8+ effector memory T cells compared to untreated mice, although the response was not as robust as in pet shop mice. In a model of skin inflammation, pre‐immunization led to an increased skin inflammatory response compared to non‐immunized mice. All immunized mice seroconverted to the pathogens in the mixture, while none of the non‐immunized mice housed together seroconverted to the pathogens applied to the pre‐immunized mice. In conclusion, pre‐immunization of mice impacts the immune system, which includes increasing the levels of CD8+ effector memory T cells