Figure 3.

(A) EDTA inhibition confirms complement contribution to viral lysis. ZIKV [1 x 10⁶ PFU/mL] was incubated with active or heat-inactivated human serum in the presence of increasing amounts of EDTA or Mg²⁺-EGTA. DMEM (not shown) and hiNHS were used as controls. (B) To prevent activation of the classical and lectin complement pathways, active or heat-inactivated human serum was pre-incubated with increasing amounts of C1 esterase inhibitor as indicated. (C) In the absence of C1q, most of the virus remained infectious whereas addition of purified C1q (70 μg/mL) restored the lytic effect on the virus. HiNHS was set to 100%. (D) Blocking of the lectin pathway by synthetic peptides (SFMI-1/2) did not rescue the virus. Combination of C1q-depleted serum and SFMI-1/2 served as additional control showing that the peptides had no effect on the infectivity of the virus. In all experiments, the viral titer was determined by plaque assays using Vero cells. Data were analyzed with one-way-ANOVA with Bonferroni post-hoc comparison (**p < 0.005). All virus lysis experiments were conducted in duplicates and repeated three times. The data represent mean values, and the error bars show standard deviations.