A phase 1 study of a group B meningococcal native outer membrane vesicle vaccine made from a strain with deleted lpxL2 and synX and stable expression of opcA.

This phase 1 clinical trial assessed the safety and immunogenicity of a native outer membrane vesicle (NOMV) vaccine prepared from a lpxL2(-) synX(-) mutant of strain 44/76 with opcA expression stabilized. Thirty-four volunteers were assigned to one of the three dose groups (25 mcg, 25 mcg with aluminum hydroxide adjuvant, and 50 mcg) to receive three intramuscular injections at 0, 6 and 24 weeks. Specific local and systemic adverse events (AEs) were solicited by diary and at visits on days 1, 2, 7 and 14 after each vaccination and at the end of the study at 30 weeks. Blood chemistries, complete blood count, and coagulation studies were measured on each vaccination day and again two days later. Blood for antibody measurements and bactericidal assays were drawn 0, 14, and 42 days after each vaccination. The proportion of volunteers who developed a fourfold or greater increase in serum bactericidal activity (SBA) to the wild-type parent of the vaccine strain with high opcA expression at 6 weeks after the third dose was 12/26 (0.46, 95% confidence interval 0.27-0.65). Antibody levels to OpcA were significantly higher in vaccine responders than in non-responders (p=0.008), and there was a trend for higher antibody levels to the lipooligosaccharide (LOS) (p=0.059). Bactericidal depletion assays on sera from volunteers with high-titer responses also indicate a major contribution of anti-OpcA and anti-LOS antibodies to the bactericidal response.These results suggest that genetically modified NOMV vaccines can induce protection against group B meningococcus.

Intranasal delivery of group B meningococcal native outer membrane vesicle vaccine induces local mucosal and serum bactericidal antibody responses in rabbits.

We have previously shown that intranasal immunization of mice with meningococcal native outer membrane vesicles (NOMV) induces both a good local mucosal antibody response and a good systemic bactericidal antibody response. However, in the intranasal mouse model, some of the NOMV entered the lung and caused an acute granulocytic response. We therefore developed an alternate animal model using the rabbit. This model reduces the probability of lung involvement and more closely mimics intranasal immunization of humans. Rabbits immunized intranasally with doses of 100 mug of NOMV in 0.5 ml of saline developed serum bactericidal antibody levels comparable to those of rabbits immunized intramuscularly with 25-mug doses, particularly when the primary intranasal immunization was given daily for 3 days. Intranasal immunization also induced a local mucosal response as evidenced by immunoglobulin A antibody in saliva, nasal washes, and lung lavage fluids. NOMV from a capsule-deficient mutant induced higher serum bactericidal antibody responses than NOMV from the encapsulated parent. Meningococcal NOMV could be administered intranasally at 400 mug with no pyrogenic activity, but as little as 0.03 mug/kg of body weight administered intravenously or 25 mug administered intramuscularly induced a pyrogenic response. These data indicate that the rabbit is a useful model for preclinical testing of intranasal meningococcal NOMV vaccines, and this immunization regimen produces a safe and substantial systemic and local mucosal antibody response.