Preimmunization of SPF Mice With Capsid Virus-like Particle Has no Effect on CD8⁺ Immune Memory and Skin Inflammation...

Specific pathogen-free (SPF) laboratory mice have in recent years been criticized for their limited bench to bedside translational value, specifically within immunological and inflammatory research, due to their immature immune system caused by restricted pathogen exposure. Pathogenic reintroduction would result in the spread of infections, compromising staff safety and animal welfare and a risk of reducing reproducibility of in vivo studies. Previous studies have shown that preimmunizing SPF mice with inactivated murine pathogens efficiently induces increased levels of CD8⁺ effector memory T cells and higher inflammatory responses in a skin inflammation model. However, the method is laborious and carries infection risks if inactivation is improper. Therefore, a simpler and more standardized method is preferred to improve reproducibility and safety. We hypothesized that preimmunizing mice with an AP205 capsid virus-like particle (cVLP) would be a safe, easy, and effective method to stimulate memory T cells in SPF mice and increase the inflammatory response in an ovalbumin-induced (OVA) dermatitis model similar to the preimmunization with inactivated pathogens. The preimmunized mice seroconverted to the cVLP antigens, but the preimmunization did not induce higher levels of effector memory T cells compared to vehicle treated mice, nor did it affect the inflammatory response in the skin inflammation model. In conclusion, preimmunization with cVLP was not sufficient to induce a cellular immune response in the mice.