Pre-immunization with inactivated pathogens recapitulates adult human immune memory in laboratory mice

Laboratory mice show poor translation to humans within a range of pre-clinical fields, which might be due to their specific pathogen free (SPF) status. SPF mice have CD8 + effector memory T cell levels more comparable to newborn than to adult humans or pet shop mice. However, reintroducing pathogens would re-introduce diseases, and, therefore, research facilities should look for safer alternatives. We inactivated mouse adenovirus type 1, minute virus of mice, mouse hepatitis virus, Sendai virus, Theiler’s encephalomyelitis virus (GD 7), and Mycoplasma pulmonis by ultraviolet irradiation, and mixed them with the adjuvant Addavax®. A subcutaneous injection twice with two weeks interval with 10 µg of each pathogen generated CD8 + effector memory T cell quantities significantly higher than untreated mice, and 82.3% of the pre-immunized mice were comparable with pet shop mice, while the overall quantities and percentages of T cells were un-affected. None of the pathogens were transferred from the pre-immunized mice to co-housed non-immunized mice. Pre-immunization with inactivated murine pathogens, therefore, may be used to safely create an immunological memory in mice.