Comparison of predicted amino acid sequences of measles virus strains in the Edmonston vaccine lineage

Protein-encoding nucleotide sequences of the N, P, M, F, H, and L genes wer e determined for a low-passage isolate of the Edmonston wild-type (wt) meas les virus and five Edmonston-derived vaccine virus strains, including AIK-C , Moraten, Schwarz, Rubeovax, and Zagreb. Comparative analysis demonstrated a high degree of nucleotide sequence homology; vaccine viruses differed at most by 0.3% from the Edmonston,rt strain. Deduced amino acid sequences pr edicted substitutions in all viral polypeptides. Eight amino acid coding ch anges were common to all vaccine viruses; an additional two were conserved in all vaccine strains except Zagreb. Comparisons made between vaccine stra ins indicated that commercial vaccine lots of Moraten and Schwarz had ident ical coding regions and were closely related to Rubeovax, while AIK-C and Z agreb diverged from the Edmonston wt along slightly different paths. These comparisons also revealed amino acid coding substitutions in Moraten and Sc hwarz that were absent from the closely related reactogenic Rubeovax strain . All of the vaccine viruses contained amino acid coding changes in the cor e components of the virus-encoded transcription and replication apparatus. This observation, combined with identification of noncoding region nucleoti de changes in potential cis-acting sequences of the vaccine strains (C. L. Parks, R. A. Lerch, P. Walpita, H.-P. Wang, M. S. Sidhu, and S. A. Udem, J. Virol. 75:921-933, 2001), suggest that modulation of transcription and rep lication plays an important role in attenuation.