Morphologic Observations of Green Monkey Kidney Cells After Single and Double Infection With Adenovirus 12 and Simian Virus 40

Abstract

Sequential morphologic changes in African green monkey kidney (GMK) cells after single infection with adenovirus 12 and double infection with adenovirus 12 plus simian virus 40 (SV40) were studied by light and electron microscopy. A pronounced nuclear stippling was the first significant change noted in both groups 16 hours after infection. This stippling resulted from an intranuclear accumulation and clumping of basophilic, electron-dense material. This characteristic nuclear alteration, never observed in the uninfected controls, progressively involved most cells and was ultimately associated with typical adenovirus cytopathic effects (CPE) in both the singly and doubly infected cultures. After 20 hours' incubation, adenovirus particles first appeared in those cultures infected with both viruses, and after 48 hours up to 80 percent of the cells examined contained intranuclear adenovirus particles. This was in contrast to the group infected with adenovirus 12 only, wherein virus particles were found in less than 5 percent of cells even after 72 hours' incubation. The dissociation between viral synthesis and the nuclear manifestations of viral CPE was further illustrated by the absence of any specific viral antigen detectable by fluorescent-antibody techniques in most cells of the singly infected group. Attempts to induce production of adenovirus particles in cells with altered nuclei, but without virus particles, by methods other than double infection with SV40 were not successful. Growth enhancement of adenovirus 12 by SV40 in GMK cells occurred only when the SV40 was added prior to, or simultaneously with, the adenovirus. If the inoculation sequence was reversed, the SV40-enhancing effect was inhibited, as evidenced by decreased adenovirus production. This inhibition was partial if the SV40 inoculation was delayed for as little as 30 minutes after the initial inoculation of adenovirus 12 and was complete when the interval extended to 6 hours.