*2.3. FabF8:Stx2 Protects Cell Viability of Human Glomerular Endothelial Cells (HGEC) from Stx2 Effects*

Considering the deleterious effects of Stx2 on the HGEC viability, we evaluate the FabF8:Stx2 ability to neutralize Stx2 cytotoxicity on HGEC. In a dose-dependent manner, the FabF8:Stx2 significantly neutralized the cytotoxic effects caused by 0.5 ng/mL Stx2 in HGEC (*p* < 0.05, *n* = 3) in both tested treatment conditions (pre-incubation or co-incubation). After the Stx2 treatment, the HGEC viability percentage was 41.0 ± 1.2%. The highest protection of HGEC viability was observed with 10 μg/mL of FabF8:Stx2 and no significant differences were found between pre-incubation and co-incubation, since cell viability percentage with 10 μg/mL FabF8:Stx2 was 89.6 ± 5.0% and 81 ± 1.7% for each condition, respectively (Figure 3). To calculate the percentage of FabF8:Stx2 protection, we first calculate the maximum prevention possible to obtain in the HGEC viability by subtracting the percentage of viability after Stx2 treatment to the viability of controls. Then, we calculated the additional % of HGEC viability obtained with FabF8:Stx2 by subtracting the viability % of Stx2 treated cells to pre-incubation and co-incubation. Finally, with these results, the percentage of protection with FabF8:Stx2 at both experimental conditions was calculated with the following formula: [(% of cell viability Pre/Co treated with FabF8:Stx2—% of cell viability in Stx2 treated cells)/(% of control cell viability—% of cell viability in Stx2 treated cells)] × 100. The protection obtained with 10 μg/mL FabF8:Stx2 was 83.0 ± 5.1% at the pre-incubation condition, and 67.5 ± 1.7% at the co-incubation condition, without statistical differences (Table 2).

**Figure 3.** FabF8:Stx2 protects human renal endothelial cells (HGEC) against Stx2 cytotoxicity. HGEC were pre-treated with different concentrations of FabF8:Stx2 (1 h at 37 ◦C), and Stx2 (0.5 ng/mL) was then added, or cells were co-treated with FabF8:Stx2 (0.0001 μg/mL to 10 μg/mL) and Stx2 (0.5 ng/mL) simultaneously. Results are expressed as means ± SD of three experiments, pre/coincubation vs. Stx2, \* *p* < 0.05.

