Target structures for HIV‐1 inactivation by methylene blue and light

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Abstract
In a photodynamic virus inactivation procedure for human fresh frozen plasma the plasma is exposed to visible light in the presence of 1 μM methylene blue. This procedure is known to inactivate HIV-1 by at least 106.32 TCID50/ml within 10 minutes. To elucidate the mechanism of photo-dynamic inactivation of HIV-1 by methylene blue/light treatment, reverse transcriptase (RT), the HIV-1 associated protein p24, and viral RNA were examined. In the dark, methylene blue up to 10 μM has no inhibitory effect on recombinant RT. In the presence of light, recombinant RT inactivation was dependent on illumination time and the concentration of methylene blue. After photoinactivation of the whole virus by methylene blue/light treatment, RT activity was also almost completely inhibited. Simultaneously, it was found by Western blotting that HIV-1 p24 and gp120 are altered in size, possibly due to protein cross-linking. In addition, it was shown by poly-merase chain reaction (PCR) inhibition assay that HIV-1 inactivation leads to destruction of its RNA. In summary, methylene blue/light treatment acts on HIV-1 at different target sites: the envelope and core proteins, and the inner core structures RNA and RT. © 1995 WiIey-Liss, Inc.