Inhibition of TRIG Agents by Virus-Induced Interferon. ∗

Abstract

The causative agents of trachoma and inclusion conjunctivitis (TRIC) have been called viruses in the past. However, TRIC agents possess several characteristics which clearly separate them from typical viruses. They possess a bacteria-like cell wall containing muramic acid; they contain both DNA and RNA; they elaborate enzymes involved in decarboxylation of carbohydrates and in folic acid synthesis; they are inhibited by antibacterial drugs; and at least some stages in the development of TRIC agents involve binary fission(l). Thus it appears that TRIC agents are more closely related to obligate intracellular bacteria or rickettsiae than to true viruses.

Up to the present time, interferons have been known to act only on true viruses. It was, therefore, of interest to determine whether virus-induced interferons would inhibit the replication of the more complex TRIC agents. Early in this work we were made aware of a publication by Mordhorst and Reinecke(2) in which it was claimed that interferon had no effect on TRIC agents, We wish to report here experiments which establish the inhibition of a TRIC agent by virus-induced mouse interferon in L cells.

Materials and methods. Interferon. Mouse interferon for these experiments was prepared by infecting strain L 929 cells, obtained from Dr. J. Youngner, with Newcastle disease virus (NDV) (E4 Herts strain) at a multiplicity of 1.5 pfu/cell (plaque forming units) as measured on chick embryo fibroblasts. The L cells were grown in one liter Blake bottles in a 5% CO₂ incubator at 37°C, using a growth medium of 10% calf serum in Eagle's Minimum Essential Medium (MEM) containing penicillin, streptomycin and myco-statin. Following infection, the cells were maintained on serum free MEM + antibiotics. Supernatants were collected 24 hours after infection.