Elucidation of the HIV-1 virucidal mechanism of methylene blue photosensitization and the effect on primary isolates

The antiviral activity for primary isolates of human immunodeficiency virus (HIV) type 1 of a combination of methylene blue and light irradiation was investigated, in comparison with their virucidal effects on laboratory-adap ted HIV-1. The antiviral mechanism was evaluated in terms of reverse transc riptase activity and viral RNA in the same viral stock. Despite a marked re duction in RNA (>3.07 Log(10)) and infectivity (6.10 Log(10)) under conditi ons of 1 muM methylene blue and 5 J/cm(2) irradiation when HIV-1(HTLV-IIIB) as a representative HIV-1 was employed, relatively little degradation of t he viral envelope (0.20 Log(10)) and reverse transcriptase activity (1.52 L og(10)) was observed. Because no difference in the reduction of infectivity was found between primary isolates and laboratory-adapted HIV-1 (including HIV-2(ROD)), the antiviral mechanism of methylene blue photosensitization may be similar for all types of HIVs. Methylene blue photosensitization see ms to deprive HIVs of infectivity, mainly due to RNA damage, and weak struc tural and functional damage of viral proteins. J. Med. Virol. 62:421-425, 2 000. (C) 2000 Wiley-Liss, Inc.