A Novel Outbred Mouse Model to Study Lung Memory Immunological Response Induced by Pertussis Vaccines

Lung tissue resident memory (T_RM) T cells can provide rapid and effective protective immunity against respiratory pathogens such as Bordetella pertussis We assessed an outbred CD1 mouse model and i.m. immunization to study vaccine-induced immune memory, using pertussis vaccines as an example. The phenotypes of cells from the lungs of CD1 mice that had been primed with either i.m. whole-cell B. pertussis (wP), acellular B. pertussis (aP) vaccines or buffer (unvaccinated) and challenged with B. pertussis were determined using flow cytometry and immunohistology. We observed a rapid and high increase of CD4⁺T cells expressing T_RM markers by flow cytometry, supported by immunohistology observations, in lungs from wP-immunized mice. Priming mice with wP vaccine induced a more potent CD4⁺ response in lungs following B. pertussis challenge than priming with aP vaccine, although both were less potent than that observed in primoinfected mice. We also observed for the first time, to our knowledge, that CD8⁺ and γδ⁺ T_RM-like T cell responses were induced in lungs of wP-primed mice postinfection. This novel outbred CD1 mouse model with i.m. immunization that enabled us to study vaccine-induced B. pertussis-specific memory T cells in lungs could be useful for evaluating candidate parenteral vaccines against B. pertussis or others pulmonary pathogens.