Comparative Studies on the Production and Assay of Interferon

Abstract

SIJMMARYInterferon was produced in chick embryo cell cultures orjn chick embryos by five viruses and in mouse embryo cell cultures or mouse lungs by two viruses. The slopes of the log dose response lines for the five chick interferons were compared by using vaccinia virus as the assay virus. Analysis of variance showed that they did not differ significantly. Partially purified interferon gave the same slope as the crude preparations. These findings allowed a comparison to be made of relative yields of interferon induced by different viruses in the same cell system. Viruses differed widely in their ability to induce interferon. Chikungunya virus induced about 70 times more interferon than did vaccinia or Newcastle disease virus and 2.6 times more interferon than Kumba virus. The slopes of the log dose response lines for two interferon preparations were compared by using Chikungunya virus as the assay virus. Analysis of variance showed that they were not significantly different. A comparison of the vaccinia and Chikungunya assays for interferon showed that the Chikungunya assay was approximately 2-9 times more sensitive when the amount of interferon depressing the plaque count by 50 yo (PDD 50 doses) were compared. An analysis of variance showed that the difference in slope between the two assays was small but approaching significance. Mouse interferon, induced by two viruses, yielded parallel dose response lines. However, the slope of the curves for mouse interferon was significantly different from that for chick interferon. Because of this difference in slope, interferon production by the same virus in the two cell types could not be validly compared.

Effect of proteolytic enzymes on vaccinia virus replication

“…Primary chick embryo cell cultures were prepared from 9-to 10-day-old embryos as previously described (4). At the time of use, usually 40 to 48 hours later, the cultures contained about 4 million cells on a glass surface area of 18 em 2.…”

Relative Effects of Interferon on Virus Plaque Formation.

“…Interferon preparations induced in chick embryo cell cultures by several viruses gave parallel dose response curves allowing estimates to be made of the relative potencies of each interferon preparation ( 1). When different viruses are employed to assay an interferon preparation the slope of the dose response lines may differ significantly ( 1).…”

“…Interferon was produced by inoculating chick embryo cell cultures with chikungunya virus ( 1 ) . The procedure was often modified in that the cultures were inoculated with virus immediately after dispensation of cells.…”

“…Serial dilutions of an interferon preparation were made in maintenance medium and 1.0 ml aliquots of each dilution were added to each of 4 bottles of chick embryo fibroblast cultures which were previously drained of growth medium. Immediately thereafter, approximately 200 PFU of vaccinia virus in1.0 ml of maintenance medium were added to each bottle. Control bottles received 1.0 ml of maintenance medium in lieu of interferon.…”

Interferon Production with Different Multiplicities of Semliki Forest Virus.

“…In a comparative study of the production of interferon by different viruses, G i f f d et aZ (2) showed that chikungunya viilus produced 2.6 times more interferon than did Semliki Forest virus when an input lmultiplicity of 0.06 PFU per cell was employed for the 2 viruses. Since it had not been established that this multiplicity of Semliki Forest v i m resulted in maximum production of interferon, the comparison 04 the efficiency of the 2 viruses may not be valid under all conditions.…”