Ultrastructural changes in KB cultures infected with adenovirus type 2

Abstract

Cultured human (KB) cells were examined in the electron microscope at various times after infection with adenovirus type 2. No ultrastructural changes were correlated with the early stages of infection, up to 7 hr post infection (p.i.). At 11 hr p.i., when viral DNA synthesis is known to be in progress, nuclei contain two distinct morphological types of inclusions. During the period of peak viral DNA, RNA, and protein synthesis (18–24 hr p.i.), 5 new types of intranuclear inclusions could be distinguished in addition to the two seen at 11 hr. At 18–24 hr p.i., cells also contained unusually electron dense mitochondria and distinctive spherical nucleoli composed of a homogeneous particulate component. By 36–48 hr p.i., after maximal accumulation of viral particles, the several types of intranuclear inclusions present did not exhibit the morphologies characteristic of the inclusions seen earlier, electron dense material accumulated in the cytoplasm, and the mitochondrial matrix was not as dense as at earlier times. KB cells infected with adenovirus type 2 at 42 ° were also examined. At this temperature, viral structural proteins are synthesized but no infectious virus or viral capsomeres are assembled. Intranuclear inclusions of infected cells maintained at 42 ° were all morphologically dissimilar to those observed when infection proceeded at 37 °. By 18 hr much dense material accumulated in the cytoplasm; mature virions were not observed. The dense cytoplasmic material was similar to that seen in infected cells maintained at 37 ° for longer and may represent viral structural protein.