NR ANWC
AU Seghatchian,J.
TI The Second International Forum on variant CJD and leucodepletion: UK
QU Transfusion Science 2000 Feb 1; 22(1-2): 45-46
VT
Introduction
The Second International Forum on variant CJD and leucodepletion: UK
In this forum we focused on the current position on prions in relation to variant CJD, to update participants on the potential utility of selective/universal leucodepletion and problems encountered during operational implementation of process validation and quality.
The morning session was chaired by Dr Sue Knowles. An excellent update on prions and transfusion was given by Dr John Barbara. How many of our potential donors are infected with vCJD remains unknown, though classical CJD appears in only 1 person per million per annum. Dr Chris Prowse addressed the relative distribution of prion protein in blood components. The major cellular compartment of normal prion protein is the platelet, with an approximately equal amount present in plasma. Red cells contain little if any normal prion protein, while most leucocytes contain levels of prion per cell similar to platelets, but leucocytes are present in lower numbers.
Dr Peter Foster spoke on removal of abnormal prion protein by plasma fractionation. Several steps (precipitation, depth filtration, chromatography procedures) could remove PrPsc , but whether they could completely remove vCJD infectivity from UK plasma-derived products remains to be validated.
Session 2 dealt with perspectives on universal/ selective leucodepletion with speakers from England, France, Germany, The Netherlands, Portugal, Northern Ireland and the United States. Dr Sue Knowles posed a set of questions: on plans for and the extent of national leucodepletion programs, the main 'driver' for leucodepletion, the specifications and methods to be used, the QA strategy, the major obstacles and benefits realised, the lessons learnt and what be done differently next time?
Dr Angela Robinson described what led the UK to decide on universal leucodepletion and to import plasma. Other speakers discussed selective leucodepletion strategies. In general everyone is trying to gain insight on new filters and apheresis devices. Filter manufacturers had been invited to present their products. All new developments have to be validated in routine, preferably in different centres, before making conclusions. Some implementation is not expected before 2000 unless unpredicted events occur. In Germany the process started with discussion on new methods and experiences at workshops, congresses etc. A special working subgroup has been created to prepare a statement summarising pro's and con's, and looking at pharmacovigilance. In most countries some leucodepletion filters perform slightly better than others.
The afternoon sessions, chaired by Dr Williamson and Dr Seghatchian, dealt with validation, clinical benefit and quality monitoring. Dr Williamson gave an update on the UK approach to and the clinical science of universal leucodepletion. Dr Murphy reported on the national validation of the Cobe Trima for multicomponent production. Dr Stein Holme reported on a new XL in-line filter for leucocyte depleted products using the Haemonetic plus, and the difficulty in measuring WBC subpopulations and cellular fragments. Martin Beard demonstrated the difficulty of leucodepleting blood from donors with sickle- cell trait and Larry Dumont spoke on the reduction of CMV load by leucoreduction. Dr Chris Prowse reported on relative retention/generation of prion and annexin V subsequent to filtration and storage. Measurement of cellular fragments by either flow cytometry or microscopically were also discussed by Dr Sensebe and Dr Sivakumaran. In the final Quality Monitoring session Dr Seghatchian highlighted the need for a real product 'NEQAS' for red cell and platelet concentrates, analogous to the stabilised low leucocyte blood component recently generated by NEQAS. The usefulness of the latter material was highlighted by Dr Barnett. While a good comparison was found between methods using this material however, discrepancies can be observed in unfixed red cell concentrates. This is substantiated by the national evaluation of IMAGN 2000 for quality monitoring of components which also demonstrated outliers when the flow method is compared to IMAGN and Nageotte systems. The cause of this remains to be elucidated but could be related to certain products, instruments, reagents or staff. Finally the role of statistical process control for leucodepleted products in France was highlighted by Maurice Masse's group and the outcome of NBS, SNBTS and Wales approaches were described by Beckman, Barclay and Gaham Rowe.
The feedback was highly encouraging. A selected number of papers from these proceeding are published in this journal to make them available to a broader audience.
13 December 1999
J. Seghatchian, National Blood Service, Colindale Ave, London NW9 5BG, UK
E-mail address: jerhard.seghatchian@nbs.nhs.uk
AD National Blood Service, North London, Colindale Avenue, London, UK
SP englisch