Using microarray technology, we studied the early differential expression of 3,528 genes in human meningothelial cells in response to meningococcal challenge. Thirty-two genes were up-regulated, and four were down-regulated. Those up-regulated included the tumor necrosis factor alpha, interleukin-6 (IL-6), and IL-8 (but not IL-1␤) genes, suggesting that meningeal cells may be a local and early source of these cytokines. Also, a trend in up-regulation of anti-apoptotic genes and down-regulation of pro-apoptotic genes was observed. This is the first evidence that meningothelial cells may mount cytoprotective responses to pathogenic bacteria.

Proteins secreted by Neisseria meningitidis are thought to play important roles in the pathogenesis of meningococcal disease. These proteins include the iron-repressible repeat-in-toxin (RTX) exoprotein FrpC. Related proteins in other pathogens are secreted via a type I secretion system (TOSS), but such a system has not been demonstrated in N. meningitidis. An in silico search of the group B meningococcal genome suggested the presence of a uniquely organized TOSS. Genes encoding homologs of the Escherichia coli HlyB (ATPbinding), HlyD (membrane fusion), and TolC (outer membrane channel) proteins were identified. In contrast to the cistronic organization of the secretion genes in most other rtx operons, the hlyD and tolC genes were adjacent but unlinked to hlyB; neither locus was part of an operon containing genes encoding putative TOSS substrates. Both loci were flanked by genes normally associated with mobile genetic elements. The three genes were shown to be expressed independently. Mutation at either locus resulted in an inability to secrete FrpC and a related protein, here called FrpC2. Successful complementation of these mutations at an ectopic site confirmed the observed phenotypes were caused by loss of function of the putative TOSS genes. We show that genes scattered in the meningococcal genome encode a functional TOSS required for secretion of the meningococcal RTX proteins.During invasive meningococcal disease large amounts of lipooligosaccharide are released from the bacterial surface leading to massive inflammation and pathology (7). The contribution of secreted proteins to meningococcal pathogenesis, however, is not well understood. Exoproteins play a major role in the pathogenesis of many gram-negative pathogens and we have recently demonstrated that meningococcal secreted proteins (MSPs) play a central role in modulation of host cell genes with a role in inflammation and apoptosis (28). Proteins may be secreted by gram-negative bacteria by one of a number of known pathways, including those listed as types I to V (19). We and others have shown that meningococci secrete a number of proteins of a class called autotransporters, which are secreted via the type V pathway. These include the putative virulence factors immunoglobulin A (IgA) protease (22), the adhesin App (13, 30), AutA (1), and the serine protease AspA (NalP) (35,36). Meningococci also have genes with homology to fhaB and fhaC of Bordetella pertussis (21). In this pathogen the major virulence factor filamentous hemagglutinin (product of fhaB) is secreted via the two-partner secretion pathway (a variant of the type V pathway) with the help of the fhaC gene product (15). Meningococci are also known to secrete proteins with homology to the repeat-in-toxin (RTX) family of cytotoxins (33, 34). In other gram-negative pathogens such toxins are secreted via a type I secretion system (TOSS) (5), and the recombinant product of one of the meningococcal genes was shown to be secreted via the Escherichia coli hemolysin TOSS (32). The presence of a TOS...

Glyoxalase enzymes I and II are involved in a detoxi®cation process consisting of conversion of reactive dicarbonyl compounds (e.g., methylglyoxal) to less reactive hydroxy acids. The structural gene for meningococcal glyoxalase I ( gloA) was identi®ed by screening an expression library with a rabbit antiserum. The meningococcal gloA gene consisted of 138 deduced amino acids, with a calculated mol. wt of 15.7 kDa. The DNA and deduced protein sequence of gloA was compared to known sequences of glyoxalase I enzymes and showed high homology with gloA of several eukaryotic and prokaryotic species. Insertion of a gloA-containing plasmid in Escherichia coli increased the host organism's tolerance to methylglyoxal from <2 mM to >4 mM, thus demonstrating its functional identity. A databank search also revealed the presence of a putative gloB gene, encoding glyoxalase II (GlxII), in the recently released genomic sequences of Neisseria meningitidis and N. gonorrhoeae.

In recognition of the need for immunological memory-inducing components for future Neisseria meningitidis group B vaccines, we previously searched the proteome of N. meningitidis and identified T-cell-stimulating protein A (TspA). This study was designed to confirm the immunogencity of TspA and to examine the subset of T-helper cell responses to the protein in patients and nasopharyngeal carriers. The tspA gene was reconstructed, cloned, and expressed in Escherichia coli, and the recombinant TspA (rTspA) protein was affinity purified. T-cell proliferative responses to rTspA were detected in the peripheral blood mononuclear cells