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Production of interferon by the conceptus in red deer Cervus elaphus

A type I interferon secreted by early sheep and cow conceptuses is responsible for the maternal recognition of pregnancy in these species. Interferon-tau (IFN) acts locally on the maternal endometrium to prevent luteolysis and prolong progesterone secretion. The production of IFN was investigated in early pregnancy in red deer, Cervus elaphus. The oestrous cycles of 14 hinds were synchronized using intra-vaginal controlled internal progesterone-releasing devices. Hinds were run with a fertile stag, then slaughtered on either day 20 (n = 10) or day 22 after withdrawal of progesterone (n = 11). Conceptuses were recovered after uterine excision and flushing with sterile saline. Conceptus RNA was reverse transcribed and amplified by PCR using primers designed from highly conserved regions of ovine and bovine IFN genes. The resulting PCR products were cloned and fully sequenced. Sequence comparisons indicate that the transcript characterized is closely related to the IFN and interferon-omega genes of bovids and giraffe, showing > 85% nucleotide sequence homology and > 74% predicted amino acid similarity with previously cloned genes. Northern blot analysis of total conceptus RNA using a homologous IFN probe confirmed the high expression of IFN which is encoded by a transcript of approximately 1 kilobase. Anti-viral activity was measured in uterine flushes from pregnant hinds using a cytopathic effect inhibition assay (4.3 x 10³ ± 0.78 x 10³ iu ml^–1; n = 14), but was not detectable in flushes from nonpregnant hinds (n = 7), confirming that preimplantation red deer conceptuses release interferons. This is the first demonstration of IFN expression in a cervid conceptus and provides evidence that IFN may be involved in the maternal recognition of pregnancy in red deer.