[Detection of the nucleic acids of hepatitis B and C viruses and human immunodeficiency virus for the biological screening of blood donations. Viral Hepatitis and Retrovirus Working Groups and Subgroup for Molecular Biology Applied to Transfusion Virol
Laboratoire de virologie transfusionnelle, Institut national de la transfusion sanguine, Paris, France.
Direct viral DNA or RNA detection by genomic amplification methods should contribute to the improvement of blood supply safety by reducing the pre-seroconversion window period. However, nucleic acid testing may not eliminate virus transmission from window period donations. Moreover, the virus subtype diversity has to be taken into account for the choice of nucleic amplification assays. Technology for nucleic acid testing has not been developed to be implemented in blood screening laboratories. The limitations of these procedures are mainly linked to the difficulties related to the automation of sample processing and to the possibilities of cross contamination of samples due to the high sensitivity of amplification methods. The extreme complexity of nucleic acid testing for single donation screening (development of an on-site automated high-throughput instrumentation, training, specialized facilities for sample processing, amplification and detection...) and its high cost mean that strategies using amplification testing of pooled samples should be developed.
[Update on hepatitis C virus: its variability and the implications]
Lunel F. Stuyver L. Brechot C. Maertens G.
Service de bacterio-virologie et d'hygiene hospitaliere, CHU d'Angers, France.
Hepatitis C virus (HCV) is the main etiologic factor of post-transfusional and sporadic hepatitis, called non-A non-B in the past. These infections are characterized by a very high number of chronic carriers always with a persistent viral increase, but often at a slow pace. The seriousness of liver disease differs from one individual to another, varying from an asymptomatic form with minor or no liver injuries, to cirrhosis and hepatocellular carcinoma. Physiopathological mechanisms involved in liver injuries are still poorly understood. The direct role of immune response and of possible genetic factors is still under study. This review aims at summing up the discovery of HCV, its structure, and its variability in the various genome regions in the same individual and from one individual to another. The different methods and techniques to analyze this variability are also reviewed, as well as the various suggested ways of classifying the different types. The geographical distribution and both clinical and biological consequences of this variability are also discussed.
[Hepatocytes in cell therapy]
Clement B. Desille M. Fremond B. Campion JP. Guguen-Guillouzo C. Bourel M. Guillouzo A.
Unite detoxication et reparation tissulaire, Inserm U456, Universite Rennes I, France.
Cell-based therapy could represent an alternative treatment to orthotopic liver transplantation in acute liver failures and for the correction of genetic defects of various enzymatic functions. Several recent studies indicate that hepatocytes injected either in the spleen or in portal vein can restore liver-specific function(s) in animal model systems. Alternatively, an extracorporal hybrid bioartificial liver might provide liver-specific functions, maintain the patient alive and allow spontaneous recovery of the patient's own liver, or act as a bridge toward liver transplantation in acute liver failures. Various drawbacks of devices such as flat culture substrates, hollow-fiber bioreactors or microcarriers led us to develop a reliable extracorporeal bioartificial liver based on alginate-entrapped hepatocytes. This system was used successfully for the correction of the Gunn rat genetic defect which results in the lack of bilirubin conjugation. The development of this system for clinical purposes requires large yields of functional hepatocytes. We isolated porcine hepatocytes by collagenase perfusion of the liver and cells were immobilized within alginate beads which were subsequently inoculated in a bioreactor. Porcine hepatocytes expressed liver-functions at high levels, particularly those involved in detoxification and biotransformation processes; they were immunoisolated from immunoglobins and could be cryopreserved. This system represents a promising tool for the design of an extracorporeal bioartificial liver in human beings.