HUMAN T-CELL RESPONSES AFTER VACCINATION WITH THE NORWEGIAN GROUP-B MENINGOCOCCAL OUTER-MEMBRANE VESICLE VACCINE

We have analyzed human T-cell responses in parallel with serum immunog lobulin G (IgG) antibody levels after systemic vaccination with the No rwegian group B Neisseria meningitidis outer membrane vesicle (OMV) va ccine. Ten adult volunteers, with no or very low levels of serum IgG a ntibodies against meningococci, received three doses intramuscularly o f the OMV vaccine (at weeks 0, 6, and 46). T-cell proliferation agains t the OMV vaccine, purified outer membrane proteins (PorA and PorB), a nd control antigens (Mycobacterium bovis BCG vaccine and tetanus toroi d) was measured by thymidine incorporation of peripheral blood mononuc lear cells before and after vaccination. The results showed that vacci nation with OMV elicits strong primary and booster T-cell responses sp ecific to OMV as well as the PorA (class 1) protein and significant, b ut markedly lower, responses against the PorB (class 3) protein. The m edian responses to OMV and PorA were 26 and 16 times the prevaccinatio n levels, respectively. Most of the vaccinees showed low T-cell respon ses against OMV and PorA before vaccination, and the maximum T-cell re sponses to all vaccine antigens were usually obtained after the second vaccine dose. We found a positive correlation between T-cell response s and anti-OMV IgG antibody levels (P = 0.50, P < 0.0001, for OMV and PorA). In addition, we observed a progressive increase in the percenta ge of CD45R0+ (memory) CD4-positive T cells (P = 0.002). In conclusion , we have shown that the Norwegian OMV vaccine against meningococcal B disease induced antigen-specific T-cell responses, kinetically accomp anied by serum IgG responses, and that vaccination increased the propo rtion of memory T-helper cells.