Evolution of attenuating mutations in dengue-2 strain S16803 PDK50 vaccine and comparison of growth kinetics with parent virus.

A live-attenuated dengue-2 virus strain S16803 vaccine candidate that is immunogenic and safe in humans was derived by 50 passages in primary dog kidney (PDK) cells. To identify mutations associated with attenuation of the dengue-2 PDK50 vaccine strain, we determined the nucleotide changes that arose during PDK passage of the dengue-2 virus. Thirteen mutations distinguished the PDK50 virus from low-passage parent resulting in amino acid substitutions in the premembrane (E89G), envelope (E202K, N203D), nonstructural proteins NS1 (A43T), NS2A (L181F), NS2B (I26V), and NS4B (I/T108T, L112F).

Identification of mutations in a candidate dengue 4 vaccine strain 341750 PDK20 and construction of a full-length cDNA clone of the PDK20 vaccine candidate.

Dengue 4 virus strain 341750 serially passaged 20 times in primary dog kidney (PDK) cells was shown to have reduced infectivity for rhesus monkeys but was immunogenic and protected the monkeys from challenge with low passage parent dengue 4 virus. The dengue 4 PDK20 virus was also shown to be attenuated for human volunteers. We compared the genomic nucleotide sequences of low passage parent and PDK20 attenuated vaccine strains and identified 11 nucleotide (nt) substitutions in the PDK20 genome.