Peptide immunization of guinea pigs against Chlamydia psittaci (GPIC agent) infection induces good vaginal secretion antibody response, in vitro neutralization and partial protection against live challenge.

Immunization of female guinea pigs with a chimeric peptide consisting of variable domain IV (VDIV) and a region known as GP8 from the major outer membrane protein of Chlamydophila caviae, formerly Chlamydia psittaci guinea pig inclusion conjunctivitis strain, was performed to assess whether humoral immune responses could be elicited in the reproductive tracts of immunized animals. The C. caviae strain is able to cause a sexually transmitted infection in the guinea pig that closely parallels C. trachomatis infections in humans. The best anti-VDIV antibody response in vaginal secretions was achieved by intraperitoneal priming with subsequent intravaginal boosting (P < 0.001). Dot-blot analyses of vaginal secretions confirmed that these anti-VDIV antibodies, produced against a linear peptide, were able to recognize and bind to whole conformational C. caviae elementary bodies. Following live intravaginal challenge with C. caviae, a significant reduction in the intensity (P = 0.01) and an apparent reduction in the duration of the infection was evident between the guinea pigs immunized with VDIV-GP8 and non-immunized controls.