Figure 2. Lack of cytotoxicity of TONS 504–PACT for host cells as evaluated with measurement of LDH release. A: Control conditions. Serum-free medium alone (vehicle only) or culture supernatants of uninfected FL cells that were either not subjected to TONS–504 photodynamic antimicrobial chemotherapy (PACT), not subjected to TONS 504–PACT but exposed to a cell lysis reagent, exposed to TONS 504 (10 mg/l) without irradiation, or subjected to irradiation (30 J/cm²) in the absence or TONS 504 were assayed for lactate dehydrogenase (LDH). B: Experimental conditions. FL cells infected with herpes simplex virus type 1 (HSV-1) or acyclovir (ACV)-resistant HSV-1 were subjected to TONS 504–PACT under the indicated conditions, after which culture supernatants were assayed for LDH. All data are presented as absorbance at 490 nm (A₄₉₀) minus A₅₉₅ and are means ± SD for three independent experiments.