The present invention provides an isolated RNA molecule comprising: a) an
alphavirus 5' replication recognition sequence, wherein at least one
initiation codon has been removed from the 5' replication recognition
sequence; b) a nucleotide sequence encoding an alphavirus structural
protein; and c) an alphavirus 3' replication recognition sequence, with
the proviso that the RNA molecule does not contain a promoter that
directs transcription of the nucleotide sequence of (b), and wherein the
alphavirus 5' and 3' replication recognition sequences of (a) and (c)
direct replication of the RNA molecule in the presence of alphavirus
nonstructural proteins.