Fig 6. Specific antibodies determined by ELISA.

Sera samples were collected from mice immunized with rOmpB-4 combined with C. burnetii CMR (O+CMR-C), C. burnetii CMR alone (CMR-C), or rOmpB-4 alone (rOmpB-4) on days 7, 14, 21, and 28 days after first immunization, respectively. IgG (A), IgG1 (B), or IgG2a (C) to rOmpB-4 in sera was determined by ELISA and the ratio of IgG2a/IgG1 in each serum sample was also compared (D). The statistically significant differences of OD₄₅₀ on 28 days after first immunization among groups were analyzed using the Student’s t-test or Wilcoxon two-sample test according to their normality and homogeneity of variance. Results were expressed as mean ± SD (n = 3). P<0.05 was considered significantly different. ***, P<0.001.