Prime-boost regimen potency and efficacy with alphavirus replicons (SIV antigen) in non-human primates challenged with low-dose intra-rectal SIVsmE660

Background Self-amplifying RNAs (replicons) of positive-strand viruses such as alphaviruses are potentially safe and useful vectors for delivering vaccine antigens. Recombinant alphavirus replicon particles (VRP), carrying the self-amplifying RNA, protects rhesus macaques against SHIVSF162P4 challenge when used in a prime-boost regimen. Methods Novartis VRPs are being further tested using a current state-of-the art physiologically relevant low-dose SIV virus swarm challenge. To meet the need for the large numbers of VRP an alphavirus packaging cell line (PCL) was used for VRP production. We manufactured, characterized, stability and small animal potency tested VRPs expressing SIVmac239 envelope (env) and gag/pol fusion proteins (VRP Env, VRP Gag/pol, respectively) for a large macaque vaccine study. Macaques were co-immunized with both VRPs thrice followed by two boosts with an MF59-adjuvanted CHO cell-derived SIVmac239 trimeric env protein. Results