Expression levels of chimeric ORFs. A) Map of RSV-F expression plasmids containing wild type, codon optimised, or chimeric ORFs. Numbers in boxes indicate mutated consensus poly(A) signals. B) Western blot analysis of RSV-F protein levels after transfection of the indicated expression plasmids. An expression plasmid for EGFP was cotransfected. Undiluted lysates had equal protein content and a similar amount of fluorescent activity revealing constant transfection efficiency. Numbers above the lanes indicate the dilution at which the cell lysates were loaded on the gel.