Identification of protective components of two major outer membrane proteins of spotted fever group rickettsiae

Fragments representing the genes of the two major outer membrane proteins o f spotted fever group rickettsiae (rOmpA and rOmpB) were tested as DNA vacc ines. Immunizations with each of three fragments (rompA(4999...6710), rompB (1550) (2738), and rompB(2459-4123)) conferred a degree of protection on va ccinated mice against virulent rickettsial challenge. Protection was achiev ed when DNA immunizations were followed by booster immunizations with the h omologous recombinant protein. Proliferation and gamma- interferon secretio n were detected after in vitro stimulation of lymphocytes from immunized an imals with whole Rickettsia conorii antigen. The data validate particular s egments of rOmpA and rOmpB as potent immunogens and hence as sources of imm unostimulatory elements with specificity for T lymphocytes, which are the k ey effectors of protective immunity against rickettsial infections.