A continuous line of epithelioid cells was established from explant skin tissues of the green sea turtle, Chelonia mydas. These cells, designated GTS, have been subcultured more than 60 times in commercially available mammalian cell culture medium supplemented with 5% bovine calf serum. Of those temperatures tested, optimal growth was achieved at 30 degrees C although replication occurred between 16 and 37 degrees C. These cells may be held as monolayers at 8 degrees C or stored frozen in growth medium containing 10% dimethyl-sulfoxide at -70 or -196 degrees C. The modal number of 55 chromosomes per cell is in agreement with the heterogametic female diploid number of this species. The GTS line represents the first established culture of normal epithelioid skin cells to be reported for a poikilothermic species.

The frequency of human cytomegalovirus (CMV) excretion during pregnancy denoting active infection has been demonstrated to increase as gestation advances and at term involves a significant percentage of women. This increase enhances the risk of congenital infection of the fetus. Thus it appears that some factor(s) unique to the condition of pregnancy favors susceptibility to maternal CMV infection. We designed our studies to investigate the possible association of the continuously rising levels of selected hormones and this increased susceptibility. Progesterone, 17 beta-estradiol, and cortisol were added to tissue culture media in final concentrations to match those occurring in term pregnancy serum. Two strains of human foreskin cells, one neonatal and the other fetal, were treated with either single or paired combinations of hormone-containing media. Lytic CMV replication in neonatal foreskin cells was enhanced by a maximum of 5.7-fold when these cells were treated with cortisol. Such enhancement did not occur in the fetal cells. No synergistic effects were seen when cortisol was used in combination with other hormones nor when neonatal foreskin cells were replicated for at least three generations in either single or paired combinations of hormones prior to use. Differential hormonal enhancement of CMV replication in vitro suggests a possible mechanism for the increased incidence of CMV infection observed during human pregnancy.

Since viral infection is in most cases contrary to the survival of the host cell, it is reasonable to assume that cells possess innate viral replication inhibitory mechanisms. Even between strains of permissive cells, degrees of permissiveness are observed. Restriction to human cytomegalovirus (CMV) replication in vitro is well known, especially in epithelioid cells or cells derived from certain organs. We have studied restriction in a fibroblastic strain of human embryonic kidney cells. By treatment of cell cultures with maximum physiologic concentration of the hormone cortisol (25 micrograms%) both pre and post virus inoculation, susceptibility to laboratory strain Ad169 CMV and low-passaged clinical isolate JSS CMV was enhanced by factors of 6.4 +/- 0.7 and 11.1 +/- 0.4, respectively; effectively converting these cells to a totally permissive state. A linear dose response, which peaks at 25 micrograms% and declines thereafter up to 300 micrograms%, is evident for both virus strains in this enhancement system. Breakdown of restriction increases in linear fashion with increasing time of cortisol pretreatment of cells. The characterization of cortisol effects converting restrictive human fetal cells in vitro to the permissive state further indicates that human hormones may play a significant role in CMV susceptibility in vivo.

No abstract