Inactivation of the human immunodeficiency virus by hypericin: evidence for photochemical alterations of p24 and a block in uncoating

Laser photosensitization of cells by hypericin

Administering a light dose of 90 J/cm2 at 599 nm during incubation with hypericin to a highly differentiated normal epithelial cell line (FRTL-5), derived from Fisher rat thyroid, and to a neoplastic cell line (MPTK-6), derived from the lung metastases of a thyroid carcinoma induced in Fisher rats, produces cell kill at drug doses 1000 times lower than those necessary to cause the same mortality in the dark. The photocytocidal activity of this polycyclic quinone drug on neoplastic cells is superior to that of antitumor anthraquinone drugs, such as daunomycin and mitoxanthrone, and to the photosensitized antiviral activity previously reported for hypericin.

Photoinactivation of influenza virus fusion and infectivity by rose bengal

Rose bengal inactivated influenza virus upon exposure to light. Infectivity and fusion were inactivated with the same dose dependence, supporting the suggestion that the virucidal activity of photodynamic agents against enveloped viruses may be generally due to inactivation of their fusion protein(s). Concentrations required for inactivation were found to depend upon the ratio of rose bengal to virus, rather than on the nominal aqueous concentration. Fusion-competent virosomes were inactivated similarly to intact virus particles. The HA2 portion of the influenza fusion protein HA underwent two different, apparently mutually exclusive modifications upon illumination with rose bengal: cross-linking, and conversion to a form that moved slightly more slowly on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Inactivation of viral fusion was inhibited by oxygen removal or addition of azide or beta-carotene, and was enhanced by D2O, consistent with partial involvement of singlet oxygen. The possibility of a second mechanism of viral photoinactivation, by direct interaction between the viral fusion protein and the photoactivated dye, is also discussed.