Abstract: The present invention provides for novel vector constructs comprising an origin of replication; a nucleotide sequence encoding an intein, the nucleotide sequence having a unique restriction enzyme site, critical amino acid residues located at the splice junctions of the intein, the intein inserted into a nucleotide sequence encoding a selectable marker; and a nucleotide sequence encoding suitable regulatory elements so as to effect expression of the vector construct in a suitable host cell. The vector constructs of the present invention may contain a DNA of interest cloned into a unique restriction site of the intein, and may be used as a vaccine alone or transformed into a vaccine vector. The vector constructs of this invention may further be used in methods of selecting translated open reading frames or genes, leading to the identification of potentially protective antigens of pathogenic organisms.