FIG. 2.

Binding of MAbs to wild-type and mutant strains of M. catarrhalis. Colony paste of wild-type strain 035E, uspA1 mutant 035E.1, uspA2 mutant 035E.2, and uspA1 uspA2 double mutant 035E.12 spotted in duplicate on filter paper was probed with MAbs 11A6 and 17H4 in the colony blot radioimmunoassay (A) to prove the specificity of these MAbs for UspA1 and UspA2, respectively. These two MAbs were then tested for the ability to bind to whole cells of these same strains in the indirect antibody accessibility assay (B). Binding of the UspA1- and UspA2-specific MAbs to whole cells of these four strains is reflected by the amount (in counts per minute) of radioiodinated goat anti-mouse IgG bound to MAbs attached to the surface of the bacterial cells. MAb 3F12, a murine IgG MAb specific for the major outer membrane protein of H. ducreyi (34), was used as a negative control.