Inactivation of acyclovir-sensitive and -resistant strains of herpes simplex virus type 1 in vitro by photodynamic antimicrobial chemotherapy

PURPOSE: To evaluate the efficacy of photodynamic antimicrobial chemotherapy (PACT) with the new porphyrin derivative TONS 504 and a light-emitting diode (LED) against acyclovir (ACV)-sensitive and -resistant herpes simplex virus type 1 (HSV-1). METHODS: Human FL cells infected with the viral strains were subjected to PACT with TONS 504 at various concentrations (0.01 to 10 mg/l) and irradiation at various light energies (10 to 30 J/cm(2)) and were then incubated for 24 h before analysis. RESULTS: Immunocytofluorescence analysis with antibodies to HSV-1 revealed that PACT eliminated HSV-1 and ACV-resistant HSV-1 in a manner dependent on the TONS 504 concentration and light energy. Complete eradication of both viruses was apparent at a TONS 504 concentration of 10 mg/l and light energy of 10 to 30 J/cm(2) as well as at a TONS 504 concentration of 1 mg/l and light energy of 20 or 30 J/cm(2). No antiviral effect was apparent with TONS 504 in the absence of irradiation or with irradiation in the absence of TONS 504. Staining of cell nuclei with 4′, 6-diamidino-2-phenylindole revealed no apparent cytotoxicity of the PACT system, a finding that was confirmed by the system’s failure to induce the release of lactate dehydrogenase from the host cells. CONCLUSIONS: We conclude that our PACT system based on TONS 504 and an LED is effective for eliminating HSV-1 and ACV-resistant HSV-1 without a harmful effect on host cells.