Background: Previous studies explored the feasibility of using the photosensitizer methylene blue (MB) as a virucidal agent in red cell suspensions. Under treatment conditions (5 microM [5 mumol/L] MB, 3.4 x 10(4) J/m2) that resulted in more than 6 log10 inactivation of vesicular stomatitis virus (VSV) or of the enveloped bacteriophage phi 6, red cell membrane alterations were observed. Increased red cell ion permeability and the binding of plasma proteins to the red cell surface were the most sensitive indicators, which varied in a dose-dependent fashion.
Study design and methods: Inactivation of three additional extracellular viruses and intracellular human immunodeficiency virus type 1 (HIV-1) was assessed after MB phototreatment of red cell suspensions. Potassium leakage and IgG binding also were characterized in MB-treated red cell suspensions that were exposed to low-fluence light (6 x 10(3) J/m2).
Results: Different viruses exhibit a wide range of sensitivities to MB photoinactivation. For example, phototreatment conditions (5 microM [5 mumol/L] MB, 3.4 x 10(4) J/m2) that inactivated more than 6 log10 of VSV did not inactivate the nonenveloped picornavirus, encephalomyocarditis virus. In contrast, lower fluences (6 x 10(3) J/m2) inactivated approximately 5 log10 or more of Sindbis virus and approximately 4log10 of extracellular HIV-1. These less stringent phototreatment conditions (5 microM [5 mumol/L] 6 x 10(3) J/m2) caused lower rates of red cell potassium leakage (reduction by 6-fold) and little or no binding of plasma proteins to the red cell surface, compared to values observed previously with higher fluences. However, neither 6 x 10(3) nor 4.1 x 10(4) J per m2 fluences resulted in any inactivation of intracellular HIV as represented by changes in the amount of p24 antigen produced during co-culture of actively infected H9 cells.
Conclusion: MB-based protocols would require the use of high-efficiency (> 6log10) white cell-reduction filters or additional inactivation steps to deplete or inactivate intracellular virus.