Immunity to Chlamydia pneumoniae induced by vaccination with DNA vectors expressing a cytoplasmic protein (Hsp60) or outer membrane proteins (MOMP and Omp2)

Immune responses induced by intramuscular DNA immunization with Chlamydia p neumoniae genes coding for the major outer membrane protein (MOMP), cystein e-rich outer membrane protein 2 (Omp2) or the heat shock protein 60 (Hsp60) were studied. BALB/c mice were vaccinated intramuscularly three times at 3 -week intervals and challenged intranasally 2 weeks after the last injectio n. Immunization with pmomp or phsp60 showed 1.2-1.5 log reduction in the me an lung bacterial counts after the challenge. Specific antibodies were dete cted only in sera of the mice immunized with pomp2 and phsp60. although imm unization with pomp2 resulted in a strong serum antibody response against O mp2 protein, it failed to protect the mice. Immunization with any of the th ree vaccines did not reduce the severity of histologically assessed pneumon ia, but resulted in significantly higher lymphoid reaction in the lung indi cating immunological memory. (C) 2000 Elsevier Science Ltd. All rights rese rved.