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.