FIG 1.

Vaccine antigen surface expression by isolates from the two outbreaks. Antigen expression was measured by flow cytometry using live bacteria and mouse MAbs or antisera to each of the individual antigens (see Materials and Methods). (A) Anti-capsular MAb. Dashed line, isolate CH819 from university A; solid black line, isolate CH840 from university B; dotted line, control strain NZ98/254. The data for the three strains are superimposed. Light gray shading, CH819 bacteria without added antibody (similar results without added antibody for the other two isolates are not shown). (B) Anti-FHbp MAb (JAR 41, which recognizes all FHbp sequence variants tested to date [14]). The line styles are the same as in panel A. (C) Mouse anti-NHba antiserum. The line styles are the same as in panel A, except the control strain is M4407, which is a naturally high expresser of NHba (10). (D) Mouse anti-NadA antiserum. The line styles are the same as in panel A, except the control strain is 5/99, which is a naturally high expresser of NadA (9, 11).