Final Report Summary - REPLIXCEL (Highly efficient new generation synthetic RNA-replicon based vaccine) General aim: The project aimed to create novel, efficacious synthetic vaccines against influenza viruses; the vaccines have to be readily adaptable to meet whichever influenza virus sub-type threatens. The vaccines have also to prove the basis for a generic vaccine platform to treat in principle other, non-influenza viral infections. Approach: The basis of the synthetic vaccine are RNA-based constructs (RNA replicons); they are loaded in nanoparticle vehicles that modulate the delivery of the replicons to dendritic cells (DC), and compounded with innovative adjuvants to provide efficient antigen co-expression with ancillary ligands. With the aim to enhance targeting of DC, ligands for particular receptors have been added to the nanoparticle surfaces, whereas cationic groups in their bulk were used to to enhance the cytosolic release of the RNA within the cells.Consortium: The project hinges on the Transfer of Knowledge between academia and industry and therefore the consortium originally comprised two SMEs and two academic institutions, each having unique and complementary expertise: in nanoparticle technology (Medipol SA), in adjuvant and peptide chemistry (EMC), in replicon technology and DC biology (IVI) and surface/colloid chemistry (UMan). A concerted programme of recruitments and secondments between partners has allowed an extensive exchange of knowledge in these areas.One of the SMEs (Medipol SA) has retired from the project after almost two years of activity due to financial problems; a potential substitute (Nanohale AG) agreed to replace them but eventually could not join the project also due to financial problems. However, this has not led to significant modifications of the research programme of the project, but rather to a re-distribution of some tasks for both periods of the project. The demise of this industrial partner did not affect the impact and the possibilities of continuation of the project; indeed the success of Replixcel has laid the basis for a currently running FP7-funded consortium (UNIVAX) aiming at the pre-clinical development of the RNA- and nanoparticle-based vaccines developed in Replixcel.Science and Technology: The project has employed three major technologies(a) Replicon RNA (RepRNA). These are RNA-based constructs that in the cytoplasm of a cell can both produce target proteins and replicate their own structure; the latter, however, does not imply an infective behavior, since replicons cannot underdo long-term uncontrolled replication. RepRNA constructs were generated encoding influenza virus antigens, in addition to RepRNA encoding luciferase to facilitate the analysis of targeting to dendritic cells (DCs). If RepRNA constructs can be delivered to the cytosol, by generating multiple copies of itself they can increase the antigen load far beyond that possible with conventional inactivated vaccine delivery; this mimics more closely events in a virus infection promoting both the humoral and cell-mediated arms of immune defence. RNA-replicons therefore offer the potential for improved protection and dose-sparing, as well as single-shot efficacious vaccines. The Replixcel project has successfully achieved these goals for RepRNA encoding the HA (hemagglutinin, H5 subtype) and NP (nucleoprotein) of influenza virus.(b) Biodegradable nanoparticles. These carrier structures allow for the delivery of RepRNA, protecting them from degradation, allowing to escape unspecific uptake and targeting them to DC. Further, nanogels are designed to deliver RepRNAs into the cytoplasm, allowing the cargo to escape endosomal degradation and to localize in the cytosolic environment wherein they can translate and replicate. Therefore, in comparison to current vaccines, the Replixcel technology offers the combined advantage of targeting DCs and multiplication therein – DCs are the critical cells required for antigen delivery and presentation to the immune system, ensuring efficacious development of robust and long-lasting immunity. (c) Adjuvants. These compounds are based on a lipopeptide structure, which potentiate the presentation of antigens by activating the expression of the co-stimulatory molecules associated with maturation of DCs, and are therefore essential for promoting the development of an active immune defence. The delivery to DCs leading to translation and replication of the RepRNA was successfully achieved. Combining with (b) and (c) below, the RepRNA was successfully delivered in vivo inducing specific immune responses against the HA and NP.
