The effect of solvent/detergent-treated plasma on red cells stored in vitro

Characteristics of prion-filtered red cells suspended in pathogen-inactivated plasma (MB treated or solvent-detergent treated) for neonatal exchange transfusion

BACKGROUND AND OBJECTIVES

Neonates undergoing exchange transfusion require <5-day-old red cells suspended in plasma. This study assesses the effect of replacing the saline, adenine, glucose and mannitol (SAGM) of prion reduced (P-Capt) red cells with either methylene blue-treated plasma (MBTFFP) or OctaplasLG to reduce the risk of variant Creutzfelt-Jakob disease transmission.

MATERIALS AND METHODS

Twenty leucoreduced red cell units in SAGM were prion reduced on day 1. The SAGM was replaced by MBTFFP (n=10) or OctaplasLG (n=10). The units were irradiated and stored at 4°C for 24 h. A further 20 units were stored for 5 days before being processed as above. Haemolysis (%), potassium, ATP, 2,3-DPG and plasma proteins were measured.

RESULTS

Haemolysis remained low (≤0·16%). Following irradiation and storage, red cells in both types of plasma showed similar changes in potassium and ATP concentrations. The 2,3-DPG concentrations were well maintained although lower in red cells in OctaplasLG compared with those in MBTFFP (4·79 vs. 6·83 μmoles/g Hb on day 6). MBTFFP contained lower concentrations of fibrinogen, FV and FVIII. In OctaplasLG, alpha-2-antiplasmin was approximately 0·4 U/ml lower than in MBTFFP. After 24 h at 4°C, free protein S in OctaplasLG fell from 0·82 to 0·57 IU/ml. Other plasma proteins, in both types of plasma, were stable.

CONCLUSIONS

Red cells in both types of plasma demonstrated similar storage characteristics. The plasma proteins, except protein S in OctaplasLG, were stable over 24 h at 4°C in both types of plasma, and low FVIII concentrations were noted in the MBTFFP (group O) units used.

Reducing the risk of blood transfusion

There are continuing concerns over the safety of the nation's and the world's blood supply. The allogeneic blood supply is tested for antibodies to HIV1/2, HTLVI/II, hepatitis B, hepatitis C (HCV) and syphilis. Testing is also performed for donor ALT (SGOT) levels, for the presence of hepatitis B surface antigen, human immunodeficiency virus (HIV) p24 antigen and, using nucleic acid amplification testing (NAT), for HIV and HCV nucleic acids. Still, there are concerns regarding other pathogenic agents. Dr. Roger Dodd addresses a series of pathogens that are already known to be transmissible by transfusion. These include malaria, Chagas' disease, babesiosis, bacteria and some viral agents. The need for new donor screening assays to protect the integrity and purity of the blood supply must be balanced against the loss of potential donors and the cost of developing and implementing these new screening assays. This issue will be highlighted. Dr. Edward Snyder reviews the status of research into development of systems for pathogen inactivation (PI) of blood and its components. A proactive technology wherein PI reagents such as psoralen, riboflavin, dimethylmethylene blue or inactine are added to blood collection bags could assure multiple log reduction of a variety of pathogens including viruses, bacteria, protozoa and fungi without the need to initially pre-screen the blood for a specific pathogen. Such a program could also cover new pathogens as they enter the blood supply. As a key issue relates to the toxicology of these agents, Dr. Snyder provides data on a novel carcinogenicity assay that uses a heterozygous p53 knock-out mouse model. The criteria likely to be needed for PI technology to be adopted by the transfusion community are summarized.

Effects of methylene blue-treated plasma on red cells and stored platelet concentrates

BACKGROUND

Photochemical methods can effectively inactivate extracellular viruses and bacteria found in blood components. Treatment of plasma with methylene blue (MB), a phenothiazine dye, and visible light inactivates enveloped viruses including HIV-1. The effects of MB-treated plasma on cellular components stored in vitro have not been well characterized.

STUDY DESIGN AND METHODS

MB-treated plasma (83 microg MB/250 mL plasma) was added to single-donor platelets, stored AS-1 red cells (RBCs), irradiated RBCs, and frozen-deglycerolized RBCs. In vitro platelet assays performed after 1 and 5 days of storage in MB-treated plasma included pH, pO2, pCO2, HCO3, platelet number, lactate dehydrogenase, glucose, osmotic recovery, and CD62 expression. RBC components were examined at specific intervals for leakage of potassium, plasma hemoglobin level, and percentage of hemolysis. Direct antiglobulin tests, osmotic fragilities, and RBC antigen stability tests were also performed on RBCs stored in MB-treated plasma. Components stored with autologous plasma or nontreated allogeneic plasma served as controls.

RESULTS

Similar storage-induced changes in pH, glucose, and platelet numbers, as well as increases in lactate dehydrogenase, CD62 expression, and lactate were seen in single-donor platelets stored with MB-treated and control plasma. Platelet morphology scores and osmotic recoveries were not altered. Plasma hemoglobin and potassium and percentage of hemolysis increased equally in the various RBC components stored with MB-treated or nontreated plasma. Osmotic fragility and RBC antigen stability were not appreciably altered by MB-treated plasma.

CONCLUSION

Plasma treated by MB photoinactivation can be used for in vitro resuspension and storage of platelets or RBCs, because of the lack of influence of MB-treated plasma on a variety of in vitro platelet and RBC assays.

[Viral attenuation of labile blood products]

Viral inactivation is one of the possibilities to reduce the residual risk of blood products. It is now applied to all plasma derived products (PDP). Application of such techniques to labile blood products (LBP) is difficult for two main reasons: any method should inactivate cell-associated viruses and should avoid any injury of the cells constituting the active ingredient. Physical techniques may reduce the viral content of cellular BPL (leucodepletion, washing, gamma irradiation), but none of them is active enough to comply with the present requirements for efficacy. An important work has been dedicated to the development of virus photoinactivation techniques. They consist of the addition of a photoreagent followed by illumination at an appropriate wavelength which results in a photochemical reaction responsible for the viral inactivation. Treatment of platelet concentrates by psoralen derivatives and UV-A illumination significantly inactivate in vitro enveloped and naked viruses, free and cell-associated viruses and also sequences integrated in the viral genome. Recent progresses have led to these results without detectable functional alteration of platelets and mutagenicity. Viral inactivation of red blood cells yet did not reach the same level because hemoglobin does not allow the use of the photoreagent compounds applicable to platelet concentrates. Viral decontamination of fresh frozen plasma by solvent and detergent, active on enveloped viruses, has been used in France since 1992. Other techniques of comparable efficacy, have received an agreement in other countries. The research on viral inactivation of LBP could prove to be of great importance in the near future in bringing additional safety to patients not only for the residual viral risk but maybe also for the residual bacterial risk of LBP.