Cytotoxicity assay (LDH)
Lactate dehydrogenase (LDH) activity was used as an index of
cytotoxicity. At indicated time points 100µl supernatant of infected
cells (intracellular survival assay) were collected and stored at 4°C
until assay was performed. 1% Triton on cells were used as a positive
control. The Cytotoxicity Detection kit (Roche Diagnostics GmbH) was
used like manufacturer’s instructions and activity was determined with
an adsorption of 440 nm. Values of the measurement after 15 min were
used for calculation of the percentage of cytotoxicity with the 1%
TritonX-100 positive control as 100%.