Inhibition of VLY-mediated cytolysis of HeLa cells by anti-VLY scFvs. HeLa cells were exposed to VLY alone (3 μg/ml) or VLY (3 μg/ml) preincubated either with scFvs (500 μg/ml) or full-length MAbs (50 μg/ml). Cell viability was determined by colorimetric assay using MTS staining. Mean OD490 values (± 2SD) were calculated from triplicates. The neutralizing activity of each anti-VLY scFv variant is expressed in % of cytolysis. Complete cytolysis induced by VLY alone is set 100%.