Intracellular Localization of Type 4 Adenovirus

Abstract

Electron microscopic studies by several investigators (1-3) have shown virus-like particles in the nuclei of HeLa cells infected with adenoviruses. Morgan and his associates (3) showed disruption of the nuclear membrane in a few cells with release of virus-like particles into the cytoplasm, but did not note viral development in the cytoplasm. A tremendous number of particles have been observed by electron microscopic examination of thin sections of infected HeLa cells, a finding which seems to be out of proportion to the relatively low yield of infectious virus (2) thus suggesting that most of the particles seen are not infectious, or that the large number of intranuclear particles remain aggregated and therefore act as relatively few infectious units. Characteristic nuclear changes in HeLa cells infected with adenoviruses have also been described using light microscopy (4); these alterations have been correlated with formation of specific viral antigen and infectious virus (5). Cytoplasmic changes were also described, but were much less marked and not characteristic (4). Because microscopic observations cannot disclose the site of development of infectious virus, and because it seemed possible that a large proportion of the particles visualized were not infectious, studies were undertaken to determine the intracellular localization of infectious adenovirus. In the experiments described in this report, nuclear and cytoplasmic fractions of HeLa cells infected with adenoviruses were obtained by mechanical disruption and differential centrifugation, and infectious virus in these fractions was measured.The results obtained indicated that the majority of infectious type 4 adenovirus was isolated from the cytoplasm of the HeLa cell; experiments done with type 1 adenovirus, although not conclusive, yielded somewhat different results. The techniques used in these experiments have many limitations and *

Intracellular Localization of Type 4 Adenovirus

“…Possibilities which can not be excluded on the basis of available data include aggregation of virus so that one infectious unit represents many infectious particles, incomplete separation of infectious virus from cell components, inactivation of infectious virus coincidental with its release from the cell, and the inadequacy of the techniques employed to determine accurately the number of infectious particles. The data of the cellular fractionation studies (7) suggest that the first possibility, namely aggregation, is the most likely explanation for the discrepancy described.…”

“…Such a conclusion is of course justified only if the arrays of virus-like particles found in infected cells are actually aggregates of virus. As discussed in the preceding paper, the results of HeLa cell fractionation studies indicated that infectious type 4 adenovirus was associated with the "cytoplasmic" rather than the "nuclear" fraction, a finding which raised some question about the interpretation of the intranuclear changes (7). When the results of the fractionation studies were obtained, several possibilities concerning the nature of the intranuclear changes were considered.…”

Immunofluorescence studies on Coxsackie group a viruses

“…(Heceived December 13, 1964) The use of the fluorescent antibody method of Coons and Kaplan (1) in the past few years added much to our knowledge of the intracellular localization and replication of ~ number of viruses, such as adeno (2,3), reo (4,5), influenza (6), v~ccinia (7,8), psittacosis (9), measles (10) and others (11,12). Among enteroviruses, the most extensively investigated in this respect was poliovirus (13,14,15,16,17).…”