Balb/c mouse model and real-time quantitative polymerase chain reaction for evaluation of the immunoprotectivity against Q fever.

The Balb/c mice were infected with Coxiella burnetii and samples of blood and major organs from the infected mice were collected on days 1 to 14 after infection. The DNAs extracted from the samples were detected by a developed real-time quantitative PCR specific for C. burnetii and high loads of C. burnetii were found in spleens, livers, and lungs, particularly in spleens. The Balb/c mice were immunized with whole cell antigen (WCA) of C. burnetii and coxiella loads in spleens of mice were assessed by the real-time quantitative PCR on day 7 after challenge with C. burnetii. The analysis suggested that phase I whole cells were excellent immunogen that elicited complete protection against coxiella infection by two-booster but not one-booster immunization. The results suggest that the combination of Balb/c model and the real-time quantitative PCR assay is a reliable and sensitive way to evaluate the efficiency of vaccines against Q fever.