Interferon gene expression in virus-induced human B-lymphoblastoid cells

Abstract

Virus infection of human cells induces the transient expression of interferon-α and interferon-β. This thesis presents the results of investigations into the expression of these interferons in the human B-lymphobastoid cell line, Namalwa, following induction by Sendai virus. Quantitative and qualitative changes in the synthesis of these interferon mRNAs and proteins were investigated in order to determine how interferon gene expression is controlled. Interferon mRNA was assayed both by translation in Xenonus oocytes and by hybridization with cloned interferon cDNA. Interferon was measured both by bioassay and by immunoradiometric assay using a monoclonal antibody to interferon-α. In addition the effects of various treatment which perturb the normal control of interferon production have been assessed. Sendai virus infection of Namalvra cells resulted in the coordinate induction and regulation of both interferon-α and interferon-β synthesis. Although significant amounts of interferon-β were present, the cells did not produce any functional interferon-β protein. It was concluded that the interferon-ß mRNA in these cells was inactive. Production of interferon was shown to be increased by incubating cells at reduced temperatures following induction. It was concluded that the normal inactivation and degradation of interferon mRNA which occurs during the shut-off of interferon production was inhibited at the lower temperature. This resulted in increased interferon production over a prolonged period. Treatment of cells with butyrate or 5'-bromodeoxyuridine before induction caused a dose-dependant increase in the rate of interferon mRNA and interferon synthesis. These treatments appear to coordinately affect the control of both interferon-α and interferon-β gene expression, since no differences could be detected in the characteristics of interferon or interferon mRNA produced by treated and untreated cells. The effect of these treatments was relatively specific, since polyacrylamide gel electrophoresis of proteins from butyrate- and 5'-bromodeoxyuridine-treated cells failed to detect any changes which were comprable to or could account for the effect on interferon synthesis