Immunogenicity and safety testing of a group B intranasal meningococcal native outer membrane vesicle vaccine

Abstract

The presently licensed meningococcal vaccine is a tetravalent capsular polysaccharide vaccine that induces immunity to serogroups A, C, Y, and W-135 but not to group B, which causes nearly half of the meningitis cases in the United States. The purpose of this study was to evaluate the safety and immunogenicity of an intranasal native outer membrane vesicle (NOMV) vaccine prepared from a capsule negative strain of group B of Neisseria meningitidis. In this study all volunteers received the same dose of vaccine, but we evaluated two different immunization schedules and the oropharyngeal and intranasal routes of vaccine delivery, assessed nasal cytology for cellular infiltration, and measured antibody-secreting cells (enzyme-linked immunospot assay [ELISPOT]) as an early marker for systemic immune response. Additionally, both intranasal and serum vaccine-specific antibodies were measured as well as serum bactericidal activity. Four groups with a total of 42 subjects were immunized on days 0, 28, and 56. Group 3 received an additional dose on day 7. Group 2 subjects were immunized both intranasally and oropharyngeally. Group 4 received a different lot of vaccine. All groups received approximately 1,200 microg of vaccine per subject. Patients were evaluated for side effects. The vaccine was well tolerated without evidence of inflammation on nasal cytology. The group receiving the extra vaccine dose showed the maximum increase in bactericidal activity. Thirty of 42 subjects demonstrated an increase in meningococcus-specific intranasal immunoglobulin A (IgA) titers, while 23 of 42 demonstrated an increase in specific IgG titers. The group receiving vaccine intranasally and oropharyngeally showed the highest rise in intranasal titers for both IgA and IgG. Groups 1, 3, and 4 showed a significant increase in antibody-secreting cells on ELISPOT. Eighteen of 42 volunteers demonstrated a fourfold or greater rise in bactericidal titers, with 81% showing an increase over baseline. We have demonstrated the immunogenicity and safety of a group B lipopolysaccharide-containing, intranasal, NOMV vaccine.

FIG. 1.

(a) Intranasal NOMV-specific IgG antibody titer normalized to the total IgG measured in the nasal secretion specimen. The asterisk indicates statistical significance; P < 0.05. (b) Intranasal NOMV-specific IgA antibody titer normalized to the total IgA measured in the nasal secretion specimen. The asterisk indicates statistical significance; P < 0.05. Interquartile ranges and maximum and minimum excluding outliers are shown.

FIG. 2.

Percentage of volunteers per group who mounted a ≥4-fold increase in bactericidal antibody titer from baseline when sera were assayed against bacterial strains 9162 and 8532. Group 3 showed statistical significance (P = 0.029) when the maximal increase in bactericidal titer over the baseline was compared between groups.