Effect of proline rich polypeptide from ovine colostrum on virus replication in human placenta and amniotic membrane at term; possible role of endogenous tumour necrosis factor alpha.

Freshly prepared organ cultures of human placentae and amniotic membranes at term show different sensitivity to vesicular stomatitis virus (VSV) infection. In six of 16 amniotic membranes and seven of 17 placentae VSV replicated to relatively high titres (10(3)-10(6)TCID(50)/ml). The others were partially or completely resistant to virus infection (<10(1)-10(2)TCID(50)/ml). Addition of the immunomodulating agent, proline-rich-polypeptide (PRP) from ovine colostrum to explants freshly obtained from the organs, influenced VSV replication in a manner dependent on the innate immune state of the organ culture. In cultures resistant to the virus, PRP at a concentration of 10 microg/ml increased 10-10 000 times the VSV titre. In contrast, treatment of highly sensitive cultures by PRP hardly influenced viral replication at all. The effect of virus stimulation by PRP was abolished by specific anti-TNF antibodies. The results indicate that endogenous TNF may be one of the mediators of virus stimulation by PRP. Antibodies against TNFalpha, added to VSV infected organ cultures sensitive to the virus reduced viral replication. The antibodies caused stimulation of virus replication in VSV-infected resistant organ cultures. The results indicate the double role of endogenous TNF in viral replication in placenta and the amniotic membrane.