Endothelial Cell Responses to Leptospira www.plosntds.org that a Treponema denticola leucine-rich repeat protein, LrrA, has been identified as an adhesion/tissue penetration factor [29, 30] . It is also possible that additional components of the surfaces of L. interrogans and L. biflexa might have different effects on host cells [31] [32] [33] . At this point, however, the determinants critical to the effects of L. interrogans-host cell interaction reported here remain to be identified, and neither bacterial adhesins nor host substrates can necessarily be predicted solely on the basis of the primary amino acid sequences.