Characterization of the antiviral activity constitutively produced by murine conceptuses: Absence of placental mrnas for interferon alpha and beta

Abstract

Antiviral activity has been found in conceptus and placental tissues in numerous species, including mice, pigs, sheep, cattle and humans. In sheep and cattle, the antiviral activity is due to an interferon alpha (IFN-α), but in other species the nature of the protein(s) responsible for placental activity is unknown. The objectives of this study were to determine if the constitutive antiviral activity associated with the mouse conceptus is produced as early as the peri-implantation period, and to determine if the activity is due to an IFN-α or -β. Conceptus and placental tissue explants released antiviral activity from Day 4 through at least Day 16 of gestation as measured in an agar overlay bioassay employing CHO cells challenged with vesicular stomatitis virus. This activity was neutralized by antiserum against MuIFN-α/β. The same antiserum failed, however, to immunoprecipitate radiolabeled proteins from medium collected from Day 4 blastocysts cultured in the presence of L-[³⁵S]-methionine. S1 nuclease analysis of placental RNA and screening of ectoplacental cone and extraembryonic ectoderm cDNA libraries with MuIFN-α and -β probes failed to detect IFN related mRNAs, even under relatively non-stringent conditions of hybridization. Thus, while antiviral activity is produced by peri-implantation conceptuses in several diverse mammalian species, it does not appear to be due to a conserved type of IFN in all these species.