Fig 2.

Antibody against the second extracellular domain of HbpD is increased in sera from homeless people. (A) Schematic structure of HbpD of B. quintana. Amino acid (aa) numbering is indicated at the top. The regions corresponding to the five HbpD deletion mutants are also indicated. The intracellular domain (gray bar), the extracellular domain (black bar), and the transmembrane domain (TM; open box) are shown. The transmembrane domains are located at residues 41 to 49, 85 to 93, 105 to 113, 187 to 195, 200 to 208, 242 to 250, 256 to 264, and 286 to 294 in HbpD. (B) Full-length forms and deletion mutants of HbpD were separated on a 15 to 25% SDS-PAGE gel and subjected to Western blotting with anti-Xpress antibody (top panel), sera from two homeless people (middle panels), and control serum (NC; bottom panel). Positions of molecular mass markers are indicated on the left. (C) Purified HbpD/101–200 was applied as a coating to ELISA plates, and antibody titers of sera from 65 homeless people were measured. The sera were separated into two groups based on the IFA IgG titer, as indicated at the bottom. Geometric means of the ≤1/128 and ≥1/256 groups were 0.042 and 0.127, respectively, as indicated by lines (P < 0.01).