Genetic variability among yellow fever virus 17D substrains.

The complete nucleotide sequence of the genome from two yellow fever (YF) virus strains, 17DD and 17D-213 was determined. Comparison of these sequences with those of other YF viruses, including the parental virulent Asibi strain, allowed the identification of 48 nucleotide sequence differences which are 17D strain-specific and potentially related to viral attenuation. Another 43 nucleotide sequence differences were not common to all 17D substrains and are therefore substrain specific. Of the 21 changes between 17DD and Asibi 15 only five led to amino acid substitutions whereas 13 substrain differences common to all 17D-204 substrains produced six amino acid substitutions. Since the exact passage histories of these viruses is known it was possible to calculate, for each strain, the number of accumulated changes per passage. Based on these data the 17DD strain was the most genetically stable virus.