Porcine conceptus proteins: antiviral activity and effect on 2',5'-oligoadenylate synthetase

Interferon-like proteins synthesized by conceptuses of domestic ruminants inhibit luteolysis during early pregnancy. Although pig conceptuses secrete trophoblast interferons during the period of CL maintenance, estrogen is involved with maintenance of the CL. The principal purposes of this work were to confirm production of trophoblast interferons by porcine conceptuses and to compare the effect of trophoblast interferons on endometrium of pigs and cattle. When measured using Madin-Darby bovine kidney (MDBK) cells challenged with vesicular stomatitis virus, antiviral activity in uterine flushings from cyclic gilts was not detectable throughout the estrous cycle; however, in pregnant gilts, antiviral activity increased from undetectable amounts to 4-11 x 10(3) U on Days 14, 16, and 18. Porcine embryos in culture produced 1,100 U/embryo/ml/24 h. Porcine conceptus secretory proteins induced 2',5'-oligo(A) synthetase in MDBK cells and in endometrial explants of cows but had no measurable effect on 2',5'-oligo(A) synthetase activity of endometrial explants of pigs. Similarly, endometrial 2',5'-oligo(A) synthetase of pregnant pigs was unaffected in vivo during the period of maximal synthesis of conceptus secretory proteins. Porcine conceptus secretory proteins produced no detectable increase in serum antiviral activity or 2',5'-oligo(A) synthetase activity of blood mononuclear leukocytes in utero-ovarian venous blood. These results suggest that conceptus interferons of pigs play different roles in the establishment of pregnancy compared to their roles in ruminants.