FIG. 4.

Reactivity with polyclonal antisera to PspA and surface antigens. The data are the averages for at least three ELISA experiments in which plates were coated with whole cells and reacted with either PspA-specific antiserum (A) or antiserum reactive with noncapsular surface antigens (B). For MA1025, MA139, and JD803, the results for two independently obtained derivatives, which did not differ from each other, were combined. Binding was calculated relative to the binding of the capsule-negative strain JD611, which was defined as 100%. The results were compared by using Student's t test. P values for MA139 and JD803 are shown in parentheses for comparisons with D39. MA1025 and JD803 were not significantly different from WU2. The difference in antibody binding for D39 and WU2 was significant in both assays (P = 0.003 and P = 0.0009 for panels A and B, respectively).