FIG 5 .

Disruption of ROP54 results in a dramatic decrease in virulence in vivo. (A) A plaque assay was used to verify viability of parasites injected into mice. More viable ∆rop54_II parasites were injected into the mice than into the controls. A total of 500 (A), 5,000 (B), or 50,000 (C) ROP54HA_II, ∆rop54_II, or ROP54c_II parasites were i.p. injected into C57BL/6 mice. An ~100-fold decrease in virulence was observed between ROP54HA_II (50% lethal dose [LD₅₀] of 500 parasites) and ∆rop54_II (LD₅₀ of 50,000 parasites). Virulence was mostly restored with complementation of ROP54.