Production of a recombinant form of early pregnancy factor that can prolong allogeneic skin graft survival time in rats

Early pregnancy factor (EPF), an extracellular chaperonin 10 homologue, has immunosuppressive and growth factor properties. In order to carry out more extensive studies on the in vivo characteristics of EPF, a recombinant for m of the molecule has been prepared. Recombinant human EPF (rEPF) was expre ssed in Escherichia coli using the plasmid pGEX-2T expression system. Poten cy of rEPF in vitro in the rosette inhibition test, the bioassay for EPF, w as equivalent to that of native EPF (nEPF), purified from human platelets, and synthetic EPF (sEPF). However, the half-life of activity (50% decrease in the log value) in serum, following i.p. injection, was significantly dec reased (3.2 h, compared with nEPF 6.2 days, sEPF 5.8 days). This was though t to be due to modification of the N-terminus of the recombinant molecule i nhibiting binding to serum carrier proteins. Because EPF can modify Th1 res ponses, the ability of the recombinant molecule to suppress allogeneic graf t rejection was investigated. Following skin grafts from Lewis rats to DA r ats and vice versa, rEPF was delivered locally at the graft site and the ef fect on survival time of the allografts noted. Results demonstrated that rE PF treatment significantly prolonged skin graft survival time by as much as 55% in stringent models of transplantation across major histocompatibility barriers.