Characterization of MspA, an Immunogenic Autotransporter Protein That Mediates Adhesion to Epithelial and Endothelial Cells in Neisseria meningitidis

Abstract

A novel putative autotransporter protein (NMB1998) was identified in the available genomic sequence of meningococcal strain MC58 (ET-5; ST-32). The mspA gene is absent from the genomic sequences of meningococcal strain Z2491 (ET-IV; ST-4) and the gonococcal strain FA1090. An orthologue is present in the meningococcal strain FAM18 (ET-37; ST-11), but the sequence contains a premature stop codon, suggesting that the protein may not be expressed in this strain. MspA is predicted to be a 157-kDa protein with low cysteine content, and it exhibits 36 and 33% identity to the meningococcal autotransporter proteins immunoglobulin A1 (IgA1) protease and App, respectively. Search of the Pfam database predicts the presence of IgA1 protease and autotransporter ␤-barrel domains. MspA was cloned, and a recombinant protein of the expected size was expressed and after being affinity purified was used to raise rabbit polyclonal monospecific antiserum. Immunoblot studies showed that ca. 125-and 95-kDa fragments of MspA are secreted in meningococcal strain MC58, which are absent from the isogenic mutant. Secretion of MspA was shown to be modified in an AspA isogenic mutant. A strain survey showed that MspA is expressed by all ST-32 and ST-41/44 (lineage 3) strains, but none of the ST-8 (A4) strains examined. Sera from patients convalescing from meningococcal disease were shown to contain MspA-specific antibodies. In bactericidal assays, anti-MspA serum was shown to kill the homologous strain (MC58) and another ST-32 strain. Escherichia coli-expressing recombinant MspA was shown to adhere to both human bronchial epithelial cells and brain microvascular endothelial cells.

Modification of Lipooligosaccharide with Phosphoethanolamine by LptA in Neisseria meningitidis Enhances Meningococcal Adhesion to Human Endothelial and Epithelial Cells

“…6), which was consistent with a previous report by Unkmeir et al that meningococcal adhesion to HBMEC is not mediated by Opc and human fibronectin (43). Further, it is unlikely that meningococcal adhesion enhanced by LptA is mediated by recently reported new meningococcal adhesins such as NadA (4) and MspA (40), because NadA facilitates adherence to epithelial cells but not to endothelial cells (4) and both proteins are not expressed in all N. meningitidis strains (6,40). Enhancement of meningococcal adhesion by LptA appears to be mediated by unidentified adhesin molecules, which was also an implication of our previous study (36).…”

Phase Variation Mediates Reductions in Expression of Surface Proteins during Persistent Meningococcal Carriage

“…Since this gene encodes an adhesin (33,34), our results suggest that NadA is only required for initial colonization and is rapidly subject to selection for loss of expression as N. meningitidis persists in a host. Similar requirements during colonization may be ascribed to Opc and MspA, which encode known and putative adhesins (35,36) and were also found mainly in low expression states (52% for Opc and 78% for MspA; see Table SA6 in the supplemental material). The FetA OMP showed a significant trend toward lower expression states as a function of persistence (see Fig.…”

Meningococcal Internalization into Human Endothelial and Epithelial Cells Is Triggered by the Influx of Extracellular l -Glutamate via GltT l -Glutamate ABC Transporter in Neisseria meningitidis

“…Genome mining to investigate meningococcal autotransporters from whole-genome sequences identified several minor adhesion proteins: App (39), NhhA (36,40), MspA (52), and TspA (30). In addition, NadA has also been identified as an adhesion and invasion factor in human epithelial cells (5).…”