Virus removal or inactivation in hemoglobin solutions by ultrafiltration or detergent/solvent treatment

Involvement of reactive oxygen species in hemoglobin oxidation and virus inactivation by 1,9-dimethylmethylene blue phototreatment

The participation of reactive oxygen species (ROS) in virus inactivation by 1,9-dimethylmethylene blue (DMMB) phototreatment in stroma-free hemoglobin (SFH) was investigated with the use of scavengers, quenchers and enhancer. Virus (R17 bacteriophage) photoinactivation by either activated monomer or dimer DMMB was suppressed by sodium azide (singlet oxygen quencher) and promoted by the substitution of H2O for deuterium oxide (D2O), which is known to prolong the lifespan of singlet oxygen. There was no or little effect of mannitol (hydroxyl radical scavenger) and superoxide dismutase (superoxide scavenger) on the photoinactivation. Similar experiments were conducted to investigate the mechanism of methemoglobin (Met-Hb) formation by the activated monomer of DMMB. There was little effect of the singlet oxygen quencher, histidine, or the enhancer, D2O, on Met-Hb formation. However, rutin, which inhibits not only singlet oxygen but also other ROS, and mannitol supressed the formation of Met-Hb by activated monomer. The addition of superoxide dismutase (SOD) did not inhibit the formation. In contrast to the activity of the DMMB monomer, that of the dimer was inhibited by histidine and enhanced by D2O. The addition of neither mannitol nor SOD affected Met-Hb formation by activated dimer. These results collectively suggest that virus photoinactivation by the activated monomer and dimer of DMMB as well as Met-Hb formation by the activated dimer proceed via a singlet oxygen mediated pathway. In contrast, singlet oxygen may play a less important role in Met-Hb formation by the activated monomer.

High Resolution Removal of Virus from Protein Solutions Using a Membrane of Unique Structure

We describe a new class of membrane that has the capability of removing particles such as viruses from solution with resolution and reproducibility superior to that of conventional membranes. This composite membrane is composed of a pre-formed microporous membrane plus a thin asymmetric, finely porous retentive layer that is quite different from conventional ultrafilters. The protein sieving characteristics of this membrane are nearly equivalent to, but slightly less than, that of conventional 100,000 Dalton cut-off ultrafiltration membranes. This membrane uniquely shows particle retention characteristics that increase monotonically from 3 to 8 logs as a function of particle diameter in the range of 28 to 93 nm. The performance of this membrane in both a single stage and a two stage system show that 4 to 6 log overall removal of virus particles in the size range 30 to 70 nm is possible with simultaneous high recovery of product protein. Clearance factors exceeding 6 logs are possible with viruses larger than 78 nm. In addition, the performance of process systems containing this membrane is predictable in accordance with the general membrane properties and equilibrium mass balance models. This membrane system is fully validatable and can be used in conjunction with other validated operations in a down-stream process to reliably achieve an over-all reduction of 12 logs of known or putative virus particles.