Antigen-specific T-cell responses in humans after intranasal immunization with a meningococcal serogroup B outer membrane vesicle vaccine

We have studied the ability of the Norwegian group B meningococcal outer me mbrane vesicle (OMV) vaccine, when administered intranasally without adjuva nt, to induce T-cell responses in humans. A group of 12 vaccinees was immun ized with four doses of OMVs (250 mu g of protein/dose) at weekly intervals , and a single booster dose was given 5 months later. In vitro T-cell proli feration in response to the OMV vaccine, purified PorA (class 1) protein, P orB (class 3) protein, and one unrelated control antigen (Mycobacterium bov is BCG) was measured by [H-3]thymidine incorporation into peripheral blood mononuclear cells obtained from the vaccinees before and after the immuniza tions. The nasal OMV immunizations induced antigen-specific T-cell response s in the majority of the vaccinees when tested against OMVs (7 of 12) and t he PorA antigen (11 of 12). None of the vaccinees showed a vaccine-induced T-cell response to the PorB antigen after the initial four doses. Although some individuals responded to all the vaccine antigens after the booster do se, this response was not significant when the vaccinees were analyzed as a group. We have also demonstrated that the PorA antigen-specific T-cell res ponses correlated with anti-OMV immunoglobulin A (IgA) levels in nasal secr etions, with anti-OMV IgG levels in serum, and with serum bactericidal acti vity. In conclusion, we have shown that it is possible to induce antigen-sp ecific T-cell responses in humans by intranasal administration of a meningo coccal OMV vaccine without adjuvant.