Surface protein Adr2 of Rickettsia rickettsii induced protective immunity against Rocky Mountain spotted fever in C3H/HeN mice

Adr2 is a protective antigen of R. rickettsii. Protection offered by Adr2 is mainly dependent on antigen-specific cell-mediated immune responses, including efficient activity of CD4+ and CD8+ T cells to produce great amount of TNF-α and/or IFN-γ as well as rapid increase of specific IgG2a, which synergistically activate and opsonize host cells to killing intracellular rickettsiae.