Genetic variability of the glycoprotein genes of current wild-type measles isolates.

The glycoprotein coding sequences from three wild-type measles viruses isolated in the United States during 1988-1989 were examined by mRNA templated sequencing to determine whether contemporary strains have undergone genetic changes relative to the vaccine strain, Moraten. These studies revealed variation in the hemagglutinin (HA) gene and, to a far lesser degree, the fusion (F) gene. The F protein coding region was highly conserved with only three predicted amino acid changes. Among the predicted amino acid changes identified in the HA was a new potential glycosylation site at residue 416, located toward the carboxy-terminal end of the HA peptide. Eighty percent of the predicted amino acid changes in the HA shared by the three wild-type isolates were clustered near the five previously identified potential glycosylation sites. A linear pattern of evolutionary change was observed after comparing the predicted amino acid HA changes from the 1988-1989 viruses to those predicted in the HA protein from U.S. wild types isolated in 1977 and 1983.