Self-replicating DNA expression system and immunogen

The present invention relates to a self-replicating DNA expression vector comprising an element from the beak and feather disease virus (BFDV) comprising a BFDV LIR element comprising a starting point of replication (Ori), a gene encoding a BFDV Rep protein and a heterologous polypeptide of interest under the control of a mammalian promoter wherein the Rep protein is capable of binding to Ori to initiate replication of the expression vector. Pharmaceutical compositions and cells comprising the self-replicating carrier are also provided. The self-replicating vector may be used in a method of inducing an immune response or expressing a polypeptide in a subject, or as an expression system. 本发明涉及包含来自喙羽病病毒(BFDV)的元件的自复制型DNA表达载体，其包括含有复制起点(Ori)的BFDV LIR元件，在哺乳动物启动子的控制下编码BFDV Rep蛋白和异源目的多肽的基因，其中，Rep蛋白能够结合Ori以启动表达载体的复制。还提供了包含自复制型载体的药物组合物和细胞。所述自复制型载体可用于在受试者中诱导免疫应答或表达多肽的方法中，或用作表达系统。