TABLE 2.

Median age of seroconversion to the indicated immunogen for patients with CF by Western blotting^aand ELISA^b

Antigen	Age (mo)	P value to PopB	P value to lysate
Western blotting
ETA	131	<0.001c	<0.001c
PcrV	60	0.11	<0.001c
ExoS	60	0.85	<0.001c
PopB	59		<0.001c
PA01 lysate	42	<0.001c
ELISA
ETA	78	<0.001c	<0.001c
ExoS	60	0.05c	0.003c
ExoS/PopB	40		0.33
PA01 lysate	27	0.33

^aWestern blotting was performed after the transfer of SDS-polyacrylamide gel electrophoresis-separated proteins to PVDF membranes. The membranes were probed with longitudinal sera (diluted 1/4,000; if negative, diluted to 1/1,000) from 48 patients with CF. The sera were analyzed in at least two independent experiments, and the averages are shown. Positive seroconversion was determined relative to an internal positive control that detected an immune reaction to PopB.

^bELISA was performed using 0.25 μg of purified proteins or 1 μg of PA01 cell lysate. Wells were probed with longitudinal sera (1/500 dilution) from 48 patients with CF. The sera were analyzed in at least two independent experiments with similar results; the results from one set of data are shown. Positive seroconversion was determined when the OD was 0.2 units above the negative controls (minus primary serum and minus secondary antibody).

^cStatistically significant (P ≤ 0.05) difference between the indicated samples.