Antigenic granzyme A (GrA) as measured by enzyme-linked immunosorbent assay (ELISA) is in the mature conformation.

(A) Monoclonal antibody (mAb) GA 21 recognizes mature GrA and not the zymogen. Recombinant GrA zymogen (6 ng ) was incubated with cathepsin C (2 μg) as described previously19 and tested in the ELISA with mAb GA29 as a catching mAb and biotinylated GA 21 as the detecting mAb. Natural GrA (6 ng) was used as a control. (B) Correlation between levels of antigenic GrA and mature GrA in plasma of patients (n = 100) with Dengue fever (Spearman r = 0.884;P < .0001). Levels of soluble GrA and GrA in the mature conformation were detected by ELISAs, described in “Materials and Methods.”