Western blot analysis of M. catarrhalis strains. Proteins present in outer membrane vesicles prepared from the wild-type strain O35E (lane 1), the transposon mutant O35E.TN52 (lane 2), and the isogenic mutant O35E.CD1 (lane 3) were resolved by SDS-PAGE and analyzed by Western blotting with the UspA1- and UspA2-specific MAb 17C7 (A), the UspA1-specific MAb 24B5 (B), and the Hag-specific MAb 5D2 (C). Note that samples were heated at 100°C for 15 min prior to Western blot analysis. Under these conditions, UspA1 migrates as a 125-kDa protein and UspA2 migrates as a high-molecular-weight aggregate that is expressed in large amounts (bracket on the right side of panel A). Positions of molecular mass markers are shown to the left in kilodaltons. The arrowheads indicate selected antigens.