Immunization with Antigen-Pulsed Dendritic Cells Against Highly Virulent Cryptococcus gattii Infection: Analysis of...

Cryptococcosis caused by highly virulent Cryptococcus gattii (Hv-Cg) is an emerging infectious disease that affects immunocompetent individuals. The Hv-Cg outbreak began in 1999, but the mechanisms responsible for its hyper-virulence as well as protective immunity against Hv-Cg infection remain to be elucidated. To better understand the protective immunity against Hv-Cg infection, we developed a novel immunization method using antigen-pulsed dendritic cells (DCs). We constructed a capsule-deficient Cg strain (∆cap60) and used it as a vaccine antigen. Mouse bone marrow-derived DCs were pulsed with ∆cap60 and transferred into mice twice before pulmonary infection with Hv-Cg strain R265. This DC-based immunization strongly induced cell-mediated immunity, including Th1 cells, Th17 cells, and multinucleated giant cells enclosing fungal cells in lungs. This vaccination significantly ameliorated the fungal burden and the survival rate after pulmonary infection with R265. The efficacy of DC-based immunization was significantly but partially reduced in IFNγ-deficient mice, thereby suggesting that the Th1 and Th17 responses play roles in vaccine-induced protection against Hv-Cg infection. This approach might provide new insights into overcoming Hv-Cg infections in immunocompetent subjects. In this chapter, we describe the procedures for DC-vaccine preparation and the analysis of cytokine-producing CD4⁺ T cells.