Mycoplasma Effects on SV40 Transformation of Human Amnion Cells

Abstract

The reproducible SV40 transformation of human epithelial amnion cells in vitro and the characteristics of the strains of transformed cells during subcultivation, have been reported previously (1-4). Since we have established that mycoplasma infection may affect spontaneously transformed amnion cells of the FL line, causing changes in morphology and growth ( 5 ) , in chromosome numbers and abnormalities (6-8), 2nd in tumor-producing capacity (9), it seemed pertinent to investigate possible effects of mycoplasma on SV40 transformation of amnion cells.The present data demonstrate that concurrent SV40 and mycoplasma infection modified the SV40 transformation. Effects were noticeable during the early events of transformation, and the characteristics of the transformed amnion strains were also affected. Materials and Methods. Virus. The SV40strain VA 45-54 GMK 4 used in the present experiments, has been previously described ( 3 ) . Details of methods for determining the infectious unit, IDSO/ml of culture fluid, using African green monkey kidney cells, have also been reported ( 3 ) . Since samples for virus titration contained mycoplasma which propagated to high titers in the test cultures, it was determined if the presence of mycoplasma had any effects on the virus titers. A series of SV40 and mycoplasma infected culture fluids were collected, and mycoplasma was eliminated from one aliquot of each by treatment with chlortetracycline HCI ( Aureomycin Lederle) , 1000 pg/ml for 5 hr at 37". These and the untreated aliquots were serially diluted for comparative end-1 This investigation was supported in part by point titrations in cultures of the monkey kidney cells. In the range of virus titers tested ( 104-5-107.5), the end points remained the same regartdless of the presence or absence of mycoplasma. However, the time of appearance of maxium cytopathic effect was delayed several days when. mycoplasma was present, and the morphological changes differed from those observed in the absence of mycoplasma. Thus, the vacuolization of the cells was less pronounced, and the cell sheet was held together by a stranded matrix. These differences were taken into consideration in the following experimental virus titrations.

Mycoplasmas and cell cultures.

“…Suppression of the formation of transformed foci was also noted, a finding confirmed by Ponten and MacPherson (138), who found complete inhibition of focus formation by RSV when the chick embryo fibroblasts had been previously infected with M. hominis. Presence of mycoplasmas has also been shown to be responsible for a prolonged time for the appearance of transformed foci of human amnion cells infected with SV40 (49).…”

Chromosome Changes in Cell Culture Induced by Mycoplasma Infection*

“…When infected in primary culture they maintained a relative resistance to mycoplasma during serial cultivation, as compared with transformed cells infected with mycoplasma after a number of subcultures. 28 The differences in cell destruction between primary and SV40transformed cells appeared to result from a cell change associated with the SV40 transformation;28 the relative resistance maintained after early mycoplasma infection has been interpreted as a mycoplasma-induced genetic change.8*28 Mycoplasma infection reduced the incidence of SV40 transformation, delayed the appearance of transformed foci, and caused reduction in the number of population…”