Antiviral Activity of 3-Methyleneoxindole

Abstract

3-Methyleneoxindole (MO), an oxidation product of the plant auxin indole-3-acetic acid, can selectively inhibit the repfication of herpes-, mengo-, polioviruses, and Sindbis virus. The antiviral action of MO, a sulfhydryl binding compound, is neutralized by 2-mercaptoethanol if the latter is added soon after exposure of infected cells to MO. If addition of 2-mercaptoethanol is delayed, the antiviral action of MO appears to be irreversible. Data Virus assays. The inhibitory effects of MO on virus replication were tested during a single cycle of multiplication. Monolayers of CEF and HeLa cells growing in 60-mm plastic petri dishes in a 5% CO.atmosphere were rinsed with 0.14 M NaCl and infected with the indicated viruses at a multiplicity of infection of 10. Generally, virus was allowed to adsorb to the cells for 1 h at 37 C, but the adsorption period of herpesvirus to HeLa cells was extended to 2 h. After adsorption, infected cells were rinsed three times with 0.14 M NaCl and incubated with 5 ml of growth medium containing the indicated concentration of MO. The growth of Sindbis virus and herpesvirus on CEF was estimated extracellularly by removing and pooling 1 ml of the growth medium from duplicate dishes at various times postinfection. Separate dishes were used for each time interval. The samples were stored at 70 C before measuring infectivity. To examine the effects of MO on the replication of poliovirus grown on HeLa cells, total virus was estimated by freezing the infected cells and medium at -70 C at the indicated times. The cells were frozen and thawed three times before measuring infectivity.

Mechanism of the Antiviral Action of 3-Methyleneoxindole

“…Duplicate plates were removed at the indicated hours, and after removal of the medium by suction, the monolayers were washed three times with 0.14 M NaCI and covered with 3 ml of 5% trichloroacetic acid. The cells were scraped and collected on glass fiber filters under suction and washed three times with 5- (20), actinomycin D does not neutralize the antiviral effect of MO.…”

“…Proc., p. 196, 1970) that MO can selectively inhibit the replication of cytocidal viruses belonging to six different groups. The antiviral effect of MO can be demonstrated in the presence of actinomycin D (20), an observation which rules out interferon as a mediator of the antiviral response. The accompanying report also demonstrates that MO is not virucidal; consequently, it was of interest to seek an explanation for the biochemical basis underlying the antiviral effect of MO.…”

“…In the accompanying paper (20), it is indicated that the antiviral activity of 3-methyleneoxindole (MO), a plant metabolite, is directed toward several deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) animal viruses. It has been reported (V. Tuli and I. Gordon, Bacteriol.…”

“…Methods used for the cultivation of HeLa cells and the propagation and assay of poliovirus are described in the accompanying paper (20).…”

“…After infection had proceeded for 3.5 or 6.5 h, the cells were scraped and concentrated in the growth medium to 4.6 x 106/ml and incubated with [5-'H Juridine (20 MCi/ml) for 30 min in a shaker bath maintained at 37 C. The preparation of cytoplasmic extracts is described above. [5-8H] (10).…”