FIG. 5.

Solid-phase immunological analysis. Native Tf receptor proteins were affinity isolated with apo- or holo-hTf-Sepharose from M. catarrhalis 4223 (TbpA and TbpB, TbpA alone, or TbpB alone). Native Lf receptor proteins were affinity isolated with holo-hLf-Sepharose from strain N141 or from an N141 LbpB⁻ isogenic mutant (9). The Mbp receptor protein fusions were affinity isolated by using an amylose resin. Approximately 50 ng of isolated protein was spotted onto the nitrocellulose matrix and incubated with a 1:1,000 dilution of convalescent-phase sera from the patient infected with M. catarrhalis N141 (sera alone; columns 1 and 4), the same sera preincubated with approximately 1 mg of either Mbp::TbpB (column 2) or Mbp::LbpB (column 3) or with 100 μl of a crude extract from the N141 LbpA⁻ isogenic mutant (9) (column 5).