Study On Virus Inactivation Of Plasma

In transfusion medicine, Careful donor selection and extensive laboratory testing have greatly improved the safety of the plasma supply. Despite of these highly successful measures, a small risk of viral transmission by transfusion still existed. Methylene blue photodynamic inactivation of fresh-frozen plasma units has been used as a routine procedure.Upon activation with visible light, methylene blue produce reactive oxygen species such as singlet oxygen and freedom radicel, which could damage viral nucleic acids, proteins, and lipids. Virus reduction with methylene blue damaged the most protein of plasma . In MB\light treated plasma of fibrinogen and other clotting factors ,such as factor VIII, were a substantially diminished, reaching 20~35% loss . The damage to proteins and lipids could be partially prevented with scavengers of reactive oxygen species such as histidine and tryptophan residues, but would also reduce viral reduction efficacy.The study showed there was an inverse correlation between the extent of coagulation factors damage during MB-potochemical treatment and the plasma vitamin C concentration. To determine whether vitamin C could influence the efficacy of inactivating virus by MB-photochemical method and protect partial protein of plasma against photooxidation.To determine whether vitamin C could influence the efficacy of inactivating the indicating viruses by MB-photochemical method. Cytopathic effect was used to test the effect of viruses inactivation. The results showed that addition of 240 u moI/L Vit C solution and 1 u mol/L MB to human single plasma unit followed by irradiating by fluorescence at an intensity of 40 000 lx for 60 min the titer of vasicular stomatitis virus could be decreased by more than 8 lgTICDso/mljWhich wasn't more than the routine procedure of MB/fluorescent light treatment . A segment of the nucleic acid encoding capsid protein of VSV was amplified with RT-PCR to study the effect of MB-photochemical method on VSV nucleic acid. The results showed that addition of Vit C 240 P mol/L to the plasma and the control plasma respectively followed by irradiation with fluorescence for 60 min caused destruction of the VSV RNA. The amplification of the target segment in a couple of plasma containing VSV was negative equally. The cell infection test was the same negative. The result indicated that the infectivity of VSV has parallel relation to detection of a fagment of the nucleic acid encoding capsid protein of VSV.To determine whether Vit C could protect plasma protein against photooxidation as a result of no affecting virus inactivation. To investigate the effect of this method on plasma components, analyes, such as the Clauss method, the one-stage method, biochemistry, microimmunoelectrophoresis, crossed immunoelectrophoresis and SDS-PAGE of the plasma treated with MB-photochemical method and the control plasma were carried out. The results showed that the recovery rates of fibrinogen and FVI:C were 83.55%. 81.67% respectively. MB-photodynamic method caused only significantdecrease in one kind of metabolites, ie, total bilirubin, in biochemical indices of the main components of plasma. No significant abnormality in molecular weight SDS-PAGE of plasma proteins was observed and no change in immunogenicity of components was seen in rnicroimmuno-electrophoresis and crossed immuno-electrophoresis. The essential indices of plasma components were improved to the extent under the condition of the addition of Vit C to plasma.In conclusion, the results of the present study indicated that not only plasma proteins were effectively protected by Vit C against oxidative damage but also virus inactivation was not prevented with Vit C scavenger. The addition of Vit C would be beneficial for improving the quality of plasma subjected to photodynamic treatment.