Early events in the interaction of adenoviruses with Hela cells: I. Penetration of type 5 and intracellular release of the DNA genome

Abstract

Combined biochemical and electron microscopic procedures were employed to follow the early interaction of adenovirus 5 with HeLa cells. Infection was started by first adsorbing the purified inoculum at low temperature, then initiating penetration by elevating the temperature. Within a few minutes attached particles were incorporated by viropexis, and became lodged in the vicinity of the nucleus. Initially the perinuclear particles possessing dense centers lay free in the cytoplasmic matrix, characteristically near nuclear pores. Later the dense perinuclear particles decreased in number and were replaced by capsid shells with lucent centers. This reconstructed morphological sequence was correlated with radiochemical data primarily on virus carrying 32P-label in the parental genomes. Analysis by cell fractionation and sucrose density gradients revealed that within 2 hours after warming most of the label had been transferred out of the cytoplasmic granule fraction and some became associated with nuclei. The labeled material could be extracted from purified nuclei and shown to possess the approximate density of adenovirus 5 DNA. Therefore, type 5 virus can penetrate rapidly and efficiently to the nuclear border where final uncoating and some transfer of the genome most probably commences in less than 1 hour.