A refined guinea pig model for evaluating delayed-type hypersensitivity reactions caused by Q fever vaccines.

The previously established model for determining dermal granulomatous reactivity of Q fever vaccines uses footpad injections to sensitize Hartley guinea pigs. We describe a substantial refinement to that model by substituting an alternate injection route and replacing the model with the hairless Hartley guinea pig. The experimental design incorporates a matrix of various antigen and adjuvant combinations administered by subcutaneous (SC) and intradermal routes of administration. The two Coxiella burnetii antigens evaluated were phase-I whole-cell vaccine (WCV) and phase-I chloroform-methanol residue vaccine. The adjuvants used were complete Freund's (CFA), incomplete Freund's, and RIBI's De-Tox. Phase-I C. burnetii WCV in CFA administered SC provided the most efficacious regimen evaluated for sensitizing hairless guinea pigs. The establishment of this animal model allows evaluation of candidate Q fever vaccines in a more humane model than that previously available.