Quantitative Studies on the Growth of Herpes Virus in HeLa Cells

SUMMARY: Less than a tenth of the pock-forming particles of the HFEM strain of herpes virus are able to initiate infection in HeLa cells, even after passage in these cells. The pock-forming virus attaches firmly to the cells but most of it remains susceptible to antiserum and presumably does not penetrate the cell. A small proportion of virus initiates infection in the HeLa cells, and, after exposure to more than one HeLa infectious particle/cell, new virus first appears in the cell fraction 12 hr. after infection, and 4 hr. later virus is released into the medium. Virus in the cell fraction can be detected either by disruption of the cells, or simply by removing the cells from the glass with ethylenediaminetetra-acetic acid (EDTA) or saline. This ‘EDTA fraction’ may contain virus released from the cell surface. An attempt was made to determine the number of virus-yielding cells, by inoculation of whole cells on to the chick chorioallantoic membrane. The proportion which yielded virus was lower than would be expected from the input of HeLa-infectious virus. After removal of superficially attached virus with antiserum, it was not possible to detect infective virus during the latent period in the majority of cells which ultimately released virus.

Herpes virus is well known as a cause of latent infection, and it is our interest in latency which has prompted further investigation of the growth of this virus. Previous work on herpes virus multiplication has been carried out in the chorioallantoic membrane cavity of fertile hens’ eggs (Scott, Coriell, Blank & Gray, 1953; Wildy, 1954; Yoshino & Taniguchi, 1956a, b) and in explants of rabbit cornea (Scott, Burgoon, Coriell & Blank, 1953). In recent years a more quantitative approach has been possible through the use of cell suspensions and monolayer cultures, and growth studies have been reported by Gostling & Bedson (1956) and Gostling (1956) in chick embryo cells, and more recently by Kaplan (1957) in rabbit kidney cells. We have studied the growth of herpes virus in HeLa cells because of the desirability of propagating cells indefinitely when studying latent infection. HeLa cells are also convenient because they are suitable for isolation of cell clones, and for study of virus release from isolated single cells.

This paper describes some aspects of virus growth in monolayer cultures of HeLa cells. Studies on plaque formation in HeLa cells (Farnham, 1958), cytological observations (Ross & Orlans, 1958), chemical changes (Newton & Stoker, 1958), electron microscope studies (Stoker, Smith & Ross, 1958) and single cell experiments (Wildy, P., Stoker, M. G. P. & Ross, R. W., unpublished) will be given in other communications.