Virus photoinactivation in stroma-free hemoglobin with methylene blue or 1,9-dimethylmethylene blue

Photoinactivation of vesicular stomatitis virus (VSV) in stroma-free hemoglobin (SFH) was carried out using methylene blue (MB) or 1,9-dimethylmethylene blue (DMMB). The VSV was more sensitive to inactivation by 660 nm light with 1 microM DMMB than with the same concentration of MB. Under conditions that inactivated 6 log10 of VSV, the methemoglobin content (Met-Hb[%]) and P50 of hemoglobin were changed by 1 microM MB phototreatment but were not changed by 1 microM DMMB phototreatment. The migration of hemoglobin during electrophoresis and the activity of superoxide dismutase were not changed by MB or DMMB phototreatment. In contrast to the results obtained with DMMB at 660 nm, 580 nm irradiation of SFH with DMMB resulted in a significant increase of Met-Hb(%) under conditions that only inactivated 1.19 log10 VSV. The 580 nm irradiation primarily activates the dimer and higher-order aggregates of the dyes, while 660 nm irradiation primarily activates the monomer. These results indicate that the monomer form of DMMB can effectively inactivate viruses without damage to SFH.