Enhancement of sindbis virus self-replicating RNA vaccine potency by linkage of Mycobacterium tuberculosis heat shock protein 70 gene to an antigen gene

Recently, self-replicating RNA vaccines (RNA replicons) have emerged as an effective strategy for nucleic acid vaccine development. Unlike naked DNA v accines, RNA replicons eventually cause lysis of transfected cells and ther efore do not raise the concern of integration into the host genome. We eval uated the effect of linking human papillomavirus type 16 E7 as a model Ag t o Mycobacterium tuberculosis heat shock protein 70 (HSP70) on the potency o f Ag-specific immunity generated by a Sindbis virus self-replicating RNA ve ctor, SINrep5. Our results indicated that this RNA replicon vaccine contain ing an E7/HSP70 fusion gene generated significantly higher E7-specific T ce ll-mediated immune responses in vaccinated mice than did vaccines containin g the wild-type E7 gene. Furthermore, our in vitro studies demonstrated tha t E7 Ag from E7/HSP70 RNA replicon-transfected cells can be processed by bo ne marrow-derived dendritic cells and presented more efficiently through th e MHC class I pathway than can wild-type E7 RNA replicon-transfected cells. More importantly, the fusion of HSP70 to E7 converted a less effective vac cine into one with significant potency against E7-expressing tumors. This a ntitumor effect was dependent on NK cells and CD8(+) T cells. These results indicated that fusion of HSP70 to an Ag gene may greatly enhance the poten cy of self-replicating RNA vaccines.