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 of spotted fever group rickettsiae (rOmpA and rOmpB) were tested as DNA vaccines. Immunizations with each of three fragments (rompA(4999...6710), rompB(1550) (2738), and rompB(2459-4123)) conferred a degree of protection on vaccinated mice against virulent rickettsial challenge. Protection was achieved when DNA immunizations were followed by booster immunizations with the homologous recombinant protein. Proliferation and gamma- interferon secretion were detected after in vitro stimulation of lymphocytes from immunized animals with whole Rickettsia conorii antigen. The data validate particular segments of rOmpA and rOmpB as potent immunogens and hence as sources of immunostimulatory elements with specificity for T lymphocytes, which are the key effectors of protective immunity against rickettsial infections.