Genetic immunization was used to functionally test the genes of C. abortus as vaccines in a mouse challenge system. CP #7 (omlA) was significantly more protective than the genes encoding fewer than 50 amino acids (p-value of less than 0.05 when comparing lung weights). The chlamydial loads generally tracked with protection and the most protective genes were significantly lower than in unvaccinated controls (p < 0.05 in the Mann–Whitney U-test for genes CP #1, 2, 4–7, 9, 10) (Stemke-Hale et al., 2005).
