Production of interferon by the conceptus in red deer Cervus elaphus

A type I interferon secreted by early sheep and cow conceptuses is responsi ble for the maternal recognition of pregnancy in these species. Interferon- tau (IFN tau) acts locally on the maternal endometrium to prevent luteolysi s and prolong progesterone secretion. The production of IFN tau was investi gated in early pregnancy in red deer, Cervus elaphus. The oestrous cycles o f 14 hinds were synchronized using intra-vaginal controlled internal proges terone-releasing devices. Hinds were run with a fertile stag, then slaughte red 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 I FN tau genes. The resulting PCR products were cloned and fully sequenced. S equence comparisons indicate that the transcript characterized is closely r elated to the IFN tau and interferon-omega genes of bovids and giraffe, sho wing > 85% nucleotide sequence homology and > 74% predicted amino acid simi larity with previously cloned genes. Northern blot analysis of total concep tus RNA using a homologous IFN tau probe confirmed the high expression of I FN tau which is encoded by a transcript of approximately 1 kilobase. Anti-v iral activity was measured in uterine flushes from pregnant hinds using a c ytopathic effect inhibition assay (4.3 x 10(3) +/- 0.78 x 10(3) iu ml(-1); n = 14), but was not detectable in flushes from nonpregnant hinds (n = 7), confirming that preimplantation red deer conceptuses release interferons. T his is the first demonstration of IFN tau expression in a cervid conceptus and provides evidence that IFN tau may be involved in the maternal recognit ion of pregnancy in red deer.