Treponema pallidum attachment to surface and matrix proteins of cultured rabbit epithelial cells

Treponema pallidum strain Nichols adheres readily to rabbit epithelial cells (SF1Ep) in tissue culture. We examined a variety of sugars for their ability to inhibit attachment. Mannose, galactose, and N-acetylgalactosamine showed minor but reproducible inhibition of attachment at high concentrations, whereas sialic acid was highly inhibitory even at low concentrations. Whole-cell lysates of SF1Ep cells contained a large number of glycoproteins, which might be related to the sialic acid-inhibitable attachment. When the cells and extracellular matrix were fractionated, only a few proteins were found in the matrix fraction. They included a 220-kilodalton (kDa) protein, shown by immunoblotting to be fibronectin, and an approximately 90-kDa protein (both were isolated on SDS-PAGE gels). When nitrocellulose replicas of these SDS-PAGE gels were exposed to 125I-labeled T. pallidum, adherence was mainly to the 90-kDa protein.