TABLE 2.

Assay variables used in the analysis^e

Assay typea	Variable name	Target	Time points (mo)
ELISA	IgG	Anti-PA IgG protein	1, 2, 6, 7, last
	IL1Be	IL-1β proteinb	1, 2, 6, 7
	IL2e	IL-2 proteinb	1, 2, 7
	IL4e	IL-4 proteinb	1, 2, 7
	IL6e	IL-6 proteinb	1, 2, 6, 7
	IFNe	IFN-γ proteinb	1, 2, 7
	TNFe	TNF-α proteinb	1, 2, 6, 7
	R_IL4IFNe	Ratio of IL-4 protein to IFN-γ protein	1, 2, 7
RT-PCR	IL-1Bm	IL-1β mRNAb	1, 2, 6, 7
	IL-2m	IL-2 mRNAb	1, 2, 6, 7
	IL-4m	IL-4 mRNAb	1, 2, 6, 7
	IL-6m	IL-6 mRNAb	1, 2, 6, 7
	IFNm	IFN-γ mRNAb	1, 2, 6, 7
	TNFm	TNF-α mRNAb	1, 2, 6, 7
	R_IL4IFNm	Ratio of IL-4 mRNA to IFN-γ mRNA	1, 2, 6, 7
Toxin neutralization	TNA	Toxin neutralization activity ED50c	1, 2, 6, 7, last
Lymphocyte stimulation	SI	Lymphocyte stimulation indexb	1, 2, 6, 7, last
Avidity	AI	Anti-PA IgG avidity	1, 2, 7
ELISpotd	INFeLi	Frequency of IFN-γ-secreting cellsb	6, 7, last
	IL4eLi	Frequency of IL-4-secreting cellsb	1, 6, 7, last
	R_IL4IFNeLi	Ratio of frequency of IL-4-secreting cells to frequency of IFN-γ-secreting cells	6, 7, last

^aEighty assay variables were determined by 6 types of assays.

^bDetermined from in vitro PA-stimulated peripheral blood mononuclear cells (PBMC).

^cED₅₀, 50% effective dose.

^dELISpot, enzyme-linked immunosorbent spot assay.

^eThe study variables for vaccine dilution and time of challenge were also included in the model, for a total of 82 variables.