Comparison of L proteins of vaccine and wild-type measles viruses.

The nucleotide sequences of the large (L) genes of ten measles virus (MV) strains were determined. These strains included the Moraten and Rubeovax vaccine strains and their Edmonston wild-type (wt) progenitor, two additional vaccine strains and five genotypically divergent wt isolates. The nucleotide and predicted amino acid sequences were compared with six previously sequenced L genes and the number and location of variable amino acid positions were characterized. The recent wt isolates demonstrated the greatest amount of variability found to date in the highly conserved L protein. Three full-length wt L proteins were expressed in mammalian cells and their ability to form a complex with the MV phosphoprotein was demonstrated. While no set of amino acid substitutions associated consistently with wt or vaccine strains was identified, these data will provide a basis for the analysis of the activity of L proteins from vaccine and wt viruses in a functional assay.