The membrane expression of Neisseria meningitidis adhesin A (NadA) increases the proimmune effects of MenB OMVs on human macrophages, compared with NadA- OMVs, without further stimulating their proinflammatory activity on circulating monocytes

Hypervirulent MenB causing fatal human infections frequently display the oligomeric-coiled coil adhesin NadA, a 45-kDa intrinsic outer membrane protein implicated in binding to and invasion of respiratory epithelial cells. A recombinant soluble mutant lacking the 10-kDa COOH terminal membrane domain (NadA(Delta 351-405)) also activates human monocytes/macrophages/DCs. As NadA is physiologically released during sepsis as part of OMVs, in this study, we tested the hypothesis that NadA(+) OMVs have an enhanced or modified proinflammatory/proimmune action compared with NadA(-) OMVs. To do this we investigated the activity of purified free NadA(Delta 351-405) and of OMVs from MenB and Escherichia coli strains, expressing or not full-length NadA. NadA(Delta 351-405) stimulated monocytes and macrophages to secrete cytokines (IL-1 beta, TNF-alpha, IL-6, IL-12p40, IL-12p70, IL-10) and chemokines (IL-8, MIP-1 alpha, MCP-1, RANTES), and full-length NadA improved MenB OMV activity, preferentially on macrophages, and only increased cytokine release. NadA(Delta 351-405) induced the lymphocyte costimulant CD80 in monocytes and macrophages, and NadA(+) OMVs induced a wider set of molecules supporting antigen presentation (CD80, CD86, HLA-DR, and ICAM-1) more efficiently than NadAOMVs only in macrophages. Moreover, membrane NadA effects, unlike NadA(Delta 351-405) ones, were much less IFN-gamma-sensitive. The activity of NadA-positive E. coli OMVs was similar to that of control OMVs. NadA in MenB OMVs acted at adhesin concentrations -10(6) times lower than those required to stimulate cells with free NadA(Delta 351-405). J. Leukoc. Biol. 86: 143-153; 2009.