T-cell stimulating protein A (TspA) of Neisseria meningitidis is required for optimal adhesion to human cells

T-cell stimulating protein A (TspA) is an immunogenic, T-cell and B-cell stimulating protein of Neisseria meningitidis. Sequence similarity between TspA and FimV, a Pseudomonas aeruginosa protein involved in twitching motility, suggested a link between TspA and type IV pili (Tfp). To determine the role of TspA an isogenic deletion mutant was created. Loss of TspA did not affect twitching motility or piliation indicating that there are functional differences between TspA and FimV. Mutation of tspA led to a significant reduction in adhesion of meningococci to meningothelial and HEp-2 cells, which was not due to a lack of transcription of adjacent genes or pilC1. Other Tfp-mediated phenotypes (i.e. auto-aggregation and transformation competence) were not altered. Our results indicate that the role of TspA in adhesion is unlikely to be directly linked to the function of Tfp. TspA was expressed by all N. meningitidis and Neisseria polysaccharea strains examined but not by Neisseria gonorrhoeae or Neisseria lactamica, although sequences with homology to tspA were present in their genomes. In summary, TspA is a highly conserved antigen that is required for optimal adhesion of meningococci to human cells.