Selection of Attenuated Dengue 4 Viruses by Serial Passage in Primary Kidney Cells

III. Reversion to Virulence by Passage of Cloned Virus in Fetal Rhesus Lung Cells

View More View Less
  • * Department of Tropical Medicine and Medical Microbiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96816
  • Department of Comparative Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96822

Two strains of primary dog kidney-passaged dengue (DEN) 4 (H-241) virus cloned by terminal dilution (PDK 24-TD3 and 35-TD3) were propagated in fetal rhesus lung (FRhL) cells to produce candidate vaccine virus seeds. Both serial passage and prolonged replication of PDK 24-TD3 in FRhL resulted in appearance of medium and large plaques in LLC-MK2 assays. When picked, these plaques proved to contain temperature-resistant, monkey-virulent revertants. Serial passage and prolonged replication of PDK 24-TD3 in LLC-MK2 cells did not result in reversion; but, prolonged replication in PDK cells did. Passage of PDK 35-TD3 in FRhL cells resulted in appearance of medium size plaques which, when picked, yielded temperature sensitive (ts) (38.5°C) viruses of low monkey-virulence. Because of its stability in monkeys and FRhL cells, reduced monkey virulence and ts property, PDK 35-TD3 is a promising candidate for trial in man.

Save