Outer membrane vesicles from group B meningococci are strongly immunogenicwhen given intranasally to mice

Outer membrane vesicles (OMVs) from group B meningococci induced both serum and mucosal antibodies when given as a nasal and rectal vaccine to mice. C holera toxin (CT) enhanced the antibody responses in serum both after nasal and rectal immunizations, and the mucosal responses after rectal immunizat ions only. Nasal immunizations, however, were most effective, with mucosal responses which were not dependent on the use of CT. The serum bactericidal activity was similarly not enhanced by CT, indicating that the positive ef fect of CT on the serum IgG level was not including bactericidal activity. A small nasal booster dose induced antibody responses in serum as far as ei ght months after intranasal and subcutaneous immunizations, and in saliva a fter intranasal immunizations. Nasal vaccines may thus be favorably combine d with parenteral vaccines. (C) 1999 Elsevier Science Ltd. All rights reser ved.