COMPLEMENTATION BETWEEN TEMPERATURE-SENSITIVE MUTANTS ISOLATED FROM AEDES-ALBOPICTUS CELLS PERSISTENTLY INFECTED WITH WESTERN EQUINE ENCEPHALITIS-VIRUS

To obtain temperature-sensitive (ts) mutants, Aedes albopictus cells were persistently infected with wild-type Western equine encephalitis virus. Many leaky and a few stable ts mutants were found among small plaque-forming progeny virus from the cultures at the early stage (up to 30 days) after initial infection. At later times (80-170 days) the persistently infected cultures gave rise to small plaque variants with stable ts mutations. Twenty-four stable ts isolates from early and late passages were classified into three groups by RNA phenotype and complementation. They consisted of three RNA+ and one RNA- mutants with single-site mutation from the early cultures. The remaining 20 ts mutants isolated from the late cultures all had multiple-site mutations; 19 of these were double mutants and may be identical, and one was a triple mutant. We also demonstrated positive complementation between single and multiple mutants. All ts mutants isolated from persistently infected cells possess either the group III RNA- mutation or the group IV RNA+ lesion or the double mutation of group III/IV. The defect in the structural protein is likely to be in one of the envelope proteins, the E2 protein. It is possible that a control mechanism that favors the accumulation of such multiple mutants exists in persistently infected mosquito cells. © 1979.