RESUMEN
A chlamydial vaccine efficacy trial with assessment of the clinical acceptability and serum antibody responses was performed in breeding sows. A BGM cell culture derived vaccine containing 10(8)/ml formalin-inactivated purified elementary bodies (Eb.) in sterile 0.15 M saline was prepared from Chlamydophila (Ch.) abortus strain OCHL03/99 which has been isolated in the herd from a sample of vaginal discharge. Vaccination was performed as a randomised trial with parallel treatment of a vaccinated group (25 sows) and non-vaccinated control group (20 sows). Sows received two 2.0-ml doses of vaccine intramuscularly at a three week interval. Control sows were dosed with sterile 0.15 M saline, accordingly. Serological response to vaccination was measured by ELISA with a total of 204 blood serum samples (114 from the vaccine group; 90 from the control group) using crude chlamydial LPS as the antigen. Compared to the control group, vaccinated sows showed a marked primary and secondary IgG serum antibody response following the two vaccinations. Antibody levels peaked between week 7 and 14 after priming vaccination, declined incrementally until week 27 but remained significantly higher than the corresponding sham-immune control levels and the prevaccination values of the vaccine group (p < 0.05). Western blot analysis of solubilized whole Eb. of Ch. abortus, Ch. pecorum, and Chlamydia (C.) suis with pre- and postvaccination sera confirmed that vaccination induced an antibody response preferentially against a range of 13 chlamydial antigens including the 40 kDa MOMP of Ch. abortus. Clinical side effects consisting of a transient mild local inflammatory reaction at the site of injection were observed in approx. 30% of vaccinated sows. These results provide the basis for further clinical evaluation of the Ch. abortus vaccine to protect sows from chlamydia-induced reproductive disorders.
