FIG. 4.

Immunization with the L. donovani BT1 null mutant and infectious challenge in BALB/c mice. Late-stationary-phase L. donovani promastigote cells (5 × 10⁷) expressing the LUC luciferase gene (34) were injected i.v. into the tail veins of either naive BALB/c animals (black box), mice previously immunized with the L. donovani BT1 null mutant (immunized L.d. BT1 KO) (hatched box), or mice previously infected with the wild-type parasites (immunized L.d. wt) (white box). Parasite loads in the liver were assessed by measuring luciferase activity as described previously (34). Results are averages for at least two independent experiments with five animals in each experiment.