Yellow fever 17DD vaccine virus is temperature sensitive when grown in mosquito C6-36 cells

Twenty-three yellow fever (YF) vaccine viruses and three wild-type YF viruses were propagated independently in human adenocarcinoma (SW13) cells and mosquito Aedes albopictus C6-36 cells. The three YF 17DD vaccine viruses were found to be slightly temperature sensitive (ts) at 39.5°C versus 37.0°C (efficiency of plaquing 0.04 to 0.1) following propagation in C6-36 but not in SW13 cells. A plaque-purified preparation of the 17DD vaccine manufactured in Brazil was ts when grown in C6-36 cells and remained ts when passaged back into the SW13 cell line.