Meningococcal outer membrane vesicle vaccine given intranasally can induce immunological memory and booster responses without evidence of tolerance

Abstract

We have studied the ability of outer membrane vesicle (OMV) vaccines from Neisseria meningitidis serogroup B to induce vaccine-specific antibody and spleen cell proliferative responses in mice after being administered intranasally (i.n.) and/or subcutaneously (s.c.). A series of four weekly i.n. doses (25 microg) without adjuvant or a single s.c. dose (2.5 microg) with aluminum hydroxide was followed 2 months later by secondary i.n. or s.c. immunizations. After i.n. priming, both immunoglobulin G (IgG) antibody responses in serum, measured by enzyme-linked immunosorbent assay, and IgA antibodies in saliva and extracts of feces were significantly boosted by later i.n. immunizations. The IgG antibody responses in serum were also significantly augmented by secondary s.c. immunization after i.n. as well as s.c. priming. Sera from mice immunized i.n. reached the same level of bactericidal activity as after s.c. immunizations. The s.c. immunizations alone, however, had no effect on mucosal IgA antibody responses, but could prime for booster antibody responses in secretions to later i.n. immunizations. The i.n. immunizations also led to marked OMV-specific spleen cell proliferation in vitro. Both serum antibody responses and spleen cell proliferation were higher after i.n. priming and later s.c. immunizations than after s.c. immunizations alone. There was thus no evidence that i.n. priming had induced immunological tolerance within the B- or T-cell system. Our results indicate that a nonproliferating meningococcal OMV vaccine given i.n. can induce immunological memory and that it may be favorably combined with similar vaccines for injections.

FIG. 1

IgG antibodies to meningococcal OMVs in serum from mice before (Pre) and after (Post) primary and secondary immunizations with four weekly i.n. doses or one s.c. OMV vaccine dose. The results, measured by ELISA, are given as individual values in arbitrary kilounits (kU) per milliliter.

FIG. 2

IgA antibodies to meningococcal OMVs in saliva from mice before (Pre) and after (Post) primary and secondary immunizations with four weekly i.n. doses or one s.c. OMV vaccine dose. The results, measured by ELISA, are given as individual values in arbitrary kilounits (kU) per milliliter.

FIG. 3

IgA antibodies to meningococcal OMVs in extracts of feces from mice before (Pre) and after (Post) primary and secondary immunizations with four weekly i.n. doses or one s.c. OMV vaccine dose. The results, measured by ELISA, are given as individual values in arbitrary kilounits (kU) per gram of dry feces.

FIG. 4

In vitro vaccine-specific spleen cell proliferation after primary i.n. and primary plus secondary s.c. immunizations of mice with meningococcal OMV vaccines. Four i.n. doses were given at weekly intervals, starting at week 0, and one primary and secondary s.c. dose each was given at weeks 1 and 13. A nonimmunized group of mice served as controls. Samples of spleen cells were collected at weeks 14, 15, and 16 and stimulated for 6 days in vitro with OMVs. The results are given as individual values and as medians (horizontal lines) in cpm after subtraction of background values obtained in the absence of OMVs (Δcpm).