Chronic infections produced in cultured cell strains by the virus of eastern equine encephalomyelitis

Abstract

The behavior of the virus of eastern equine encephalomyelitis in continuous roller tube tissue cultures of two rat tumor cell strains, four rat cell strains, derived from muscle, and two human tumor cell strains was studied. A temperature of 37° during incubation favored recovery from infection, while 31° favored a state of chronic infection. The presence of embryo extract stimulated cells to grow faster and so to recover. One of the cell strains derived from normal rat muscle consistently recovered and lost virus, but was consistently susceptible to three successive reinfections. The onset of gross destruction of a cell strain was accompanied by an increased yield of virus. The amount of virus which initiated an infection in the cell strains tested in tissue culture was about the same as the minimal amount which infected chick embryos. In some cases, however, tissue culture infections were not initiated by less than 100 chick embryo infectious doses. The human carcinoma strain HeLa developed a chronic infection after minimal inocula of virus, whereas a human fibrosarcoma strain (AFI) was promptly destroyed.