Dengue-2 vaccine: oral infection, transmission, and lack of evidence for reversion in the mosquito, Aedes aegypti.

The dengue-2 vaccine virus (S-1), and its parent virus (PR-159), were compared for their ability to infect orally, to replicate in, and subsequently to be transmitted by Aedes aegypti mosquitoes. The vaccine virus was markedly less efficient in its ability to infect mosquitoes orally. After ingesting infectious bloodmeals containing 3, 7 to 8.2 log10MID50/ml of the respective viruses, 56% (220/396) of the mosquitoes became orally infected with the parent virus contrasted with 16% (66/397) for the vaccine virus. None of the 16 infected mosquitoes transmitted the vaccine virus, while 14% (3/22) of the mosquitoes transmitted the parent virus. The vaccine virus remained temperature-sensitive (restrictive temperature 39 degrees C) after orally infecting and replicating in Ae. aegypti mosquitoes.