[Truncated abstract] Around 50,000 hip and knee replacements are performed every year in Australia and this number has been increasing by around 13% annually since 1998 (Transplantation Society 2006). The incidence and number of revision surgery has increased by a similar proportion. Autogenous bone or allograft is still the gold standard grafting material and is currently used in a variety of reconstructive surgical procedures. The use of any allograft material carries with it the risk of transfer of disease from donor to recipient. These tissues can transmit the same viral and bacterial infections as blood, and the products of a single donation may be transplanted to several recipients. In contrast to blood, musculoskeletal tissues may come from surgical and cadaveric donation. Overall, the prevention of infection relies on the maintenance of rigid protocols for procurement, donor and allograft testing, secondary sterilisation, and the adherence to internal safety standards within the tissue banks. This thesis aims to determine the risk of viral infection among musculoskeletal tissue donors in Australia. We retrieved and analysed data retrospectively from three large tissue banks in Australia (Perth, Queensland, Victoria). This includes 12,415 musculoskeletal tissue donors, 10,937 of which are surgical donors and 1,478 of which are deceased donors, for the period of 1993 -2004. This data was analysed to determine the prevalence and incidence of viral infections such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV) and human T-lymphotropic virus (HTLV) in musculoskeletal allografts. The results indicate that the risk of viral infection from musculoskeletal tissue transplantation in Australia is low. ... The results indicate that the overall prevalence of screened transfusion-transmitted viral infections did not vary significantly for musculoskeletal donors over the study period, despite falling in the general population and first-time blood donors. In tissue donors, HIV incidence significantly decreased over time, and HBV decreased significantly during 1999-2001; however, there was an apparent increase in the estimated incidence of HCV in 2002-2004 compared with earlier years. Furthermore the residual risk estimate of HIV in the period 2002-2004 has declined 5-fold compared to estimates in the period 1993-1995. This is perhaps due to greater awareness of high risk behaviours among donors, improvement in donor recruitment and an overall decrease in infection levels in the general population. Musculoskeletal tissue is second only to blood as the most frequent transplanted human tissue. Viral infection is a potential complication of tissue transplantation. In this thesis the rates of HIV, HBV, HCV and HTV infection in musculoskeletal donors in Australia were identified and then compared with results in published data from Canada, Scotland and the United States. The study also compared that result with first-time blood donors because they have satisfied similar donor selection criteria (Galea et al. 2006). The results indicate that prevalence and incidence estimates for viral infection in Australian tissue donors are higher than those in blood donors. This was also reported in studies from other countries. Accordingly, it is crucial that viral prevalence and incidence be monitored to evaluate the safety of tissue supply and to improve donor selection processes.

Malgré l’existence d’un vaccin préventif efficace, l’infection chronique par le virus de l’hépatite B (HBV) demeure un problème majeur de santé publique. La persistance de l’infection par HBV étant clairement associée à des réponses immunitaires insuffisantes, l’immunothérapie par le vaccin à base d’ADN nu, visant à stimuler les réponses humorales et cellulaires, apparaît comme particulièrement pertinente pour la thérapie des hépatites B chroniques. Toutefois, l’efficacité thérapeutique d’une telle stratégie reste limitée chez l’homme, d’où la nécessité d’optimiser cette approche vaccinale pour une utilisation ultérieure en clinique. Ainsi, l’objectif général de ce travail de thèse était d’explorer, avec le modèle du DHBV (« Duck Hepatitis B Virus »), étroitement apparenté au HBV humain, si l’administration du vaccin à ADN par électroporation (EP) pouvait davantage améliorer son efficacité prophylactique et thérapeutique. Nous avons montré, dans un 1er temps chez des canards naïfs, que l’administration du vaccin à ADN par EP permet de potentialiser le pouvoir neutralisant et d’élargir le répertoire épitopique de la réponse humorale dirigée contre la protéine d’enveloppe du DHBV, même avec des doses d’ADN relativement faibles. Dans un 2ème temps, nous avons montré chez des animaux chroniquement infectés par le DHBV, que l’administration par EP du vaccin à ADN ciblant les protéines structurales du DHBV et le DuIFN-γ améliore considérablement l’efficacité thérapeutique du vaccin, notamment au regard de la séroconversion et de la clairance virale. Les résultats ainsi obtenus confirment l’intérêt majeur de cette approche vaccinale pour la thérapie des hépatites B chroniques / Despite the existence of an effective prophylactic vaccine, chronic hepatitis B virus (HBV) infection remains a major public health problem. Since persistence of HBV infection is mostly associated with insufficient immune responses, therefore DNA vaccination capable of activating both humoral and cellular immune responses appears as a pertinent strategy for chronic hepatitis B therapy. However, the efficacy of such therapeutic approach remains limited in humans. Improvement of DNA vaccine efficacy is therefore needed for future therapeutic applications in clinic. The main objective of this thesis was to investigate in the duck hepatitis B virus (DHBV) model, whether the protective and therapeutic efficacy of DNA vaccine can be enhanced using EP-based delivery system. Firstly, we showed in naïve ducks that EP-based delivery was able to improve the dose efficiency of DNA vaccine and to maintain a highly neutralizing, multi-specific B-cell response even with relatively low DNA doses, suggesting that it may be an effective approach for chronic hepatitis B therapy at clinically feasible DNA dose. Secondly, we showed in chronic DHBV-carriers that in vivo EP is able to dramatically enhance the therapeutic potency of DNA vaccine targeting hepadnaviral proteins. Indeed, this approach was able to consistently restore humoral immune response and to sustainably decrease and even clear viral infection. Thus, these data strongly support the use of this approach for chronic hepatitis B therapy in humans