FIG. 3.

Humoral immune response to 1818^PE_PGRS and 1818^PE proteins following infection of mice with M. tuberculosis. Mice (C57BL/6) were challenged aerogenically with 500 CFU of the virulent Erdman strain of M. tuberculosis, and sera were collected at different time points from five mice. The humoral response to 1818^PE_PGRS (●) 1818^PE (○), the mycobacterial antigen Ag85B (■), and the control protein BSA (∗) was evaluated by ELISA. Plates were coated with purified histidine-tagged recombinant proteins, incubated with each sera at a dilution of 1:100, and detected using anti-mouse IgG whole-molecule alkaline phosphatase conjugate as previously described. Datum points are the averaged readings (with the indicated standard deviations) from the individual sera from five infected mice.