Comparison of (2′-5′) Oligo-adenylate Synthetase and Interferon Blood-Levels in Mice Early After Viral Infection

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Abstract
The level of the IFN-induced enzyme (2′-5′) oligo A synthetase in the peripheral blood mononuclear cells (PBMC) was determined in mice at different times following virus infection. There was a significant increase (4–7-fold) of the enzyme level within less than 12 h after i.p. injection of either VSV (107 pfu) or Sindbis virus (2.104 pfu). The elevated level was maintained for about a week and then the activity returned to normal. There was, however, a marked difference in the pattern of serum level of IFN during infection by the two viruses; while in the mice infected by VSV, serum IFN was very high on the first day and declined to an undetectable level by the fourth day, in the mice infected with Sindbis virus, serum IFN was barely detectable at the first day and then increased towards the fourth day of infection. Antiviral antibodies could be detected in the serum only about a week after infection. We conclude that viral infection can result in a rapid elevation of (2′-5′) oligo A synthetase in the PBMC, even when serum IFN remains low. Thus, quantitation of the enzyme level can be a useful diagnostic aid in viral infection particularly in the early stages and in cases in which antiviral antibodies and IFN can not be detected.