Molecular mimicry: a herpes virus glycoprotein antigenically related to a cell-surface glycoprotein expressed by macrophages, polymorphonuclear leucocytes, and platelets.

Bovine herpes virus type 1 (BHV-1) gIII is a major virion glycoprotein with homology to the immunoglobulin superfamily. We have investigated the possibility that gIII is related to host molecules and have identified a gIII-specific monoclonal antibody (mAb) that cross-reacts with normal bovine cells. The cross-reactive entity was expressed mainly on monocyte/macrophages (M phi), polymorphonuclear leucocytes (PMN) and platelets, and was identified as a 43,000-63,000 molecular weight (MW) cell-surface glycoprotein. For M phi, the glycoprotein appears to be a general lineage marker, rather than a maturation or activation marker, and may be a functional receptor, as evidenced by its endocytosis via coated pits and its involvement in proliferation of mononuclear cells in vitro. This novel leucocyte marker was also detected on subsets of human, ovine and canine M phi. Competitive binding assays with sera from cattle immunized with BHV-1 or gIII revealed apparent low responsiveness to the cross-reactive epitope. The results suggest that BHV-1 gIII is antigenically related to a novel host leucocyte receptor and that evasion and/or interference with leucocyte function may be a consequence of this molecular mimicry relationship.