The effect of human cytomegalovirus (HCMV) on invasive capability of early pregnant extravillous cytotrophoblasts (EVTs) was investigated in vitro.Primary EVTs were obtained by complex phosphoesterasum digestion and gradient centrifugation from villous tissue aseptically taken from healthy pregnant women.Cytokeratin7 (CK7),vimentin (Vim) and c-erbB-2 were immunocytochemically detected to identify source of cells,and HCMVpp65 antigen was assayed to determine the infection state of primary EVTs by immunocytochemical staining.The EVTs were divided into two groups:control group and HCMV group,and the expression of c-erbB-2,matrix metalloproteinase-2 (MMP-2) and MMP-9 proteins was detected in two groups by immunocytochemistry and Western blotting.Enzymic activity changes of MMP-2 and MMP-9 were tested by gelatin zymography in primary EVTs infected with HCMV.The invasion of primary EVTs was detected by cell invasion assay in vitro after they were infected by HCMV.The cell source identification showed that the cells obtained were highly-pure primary EVTs,and primary EVTs could be infected by HCMV.Primary EVTs could express c-erbB-2,MMP-2 and MMP-9 proteins,and as compared with control group,the protein expression was decreased significantly in HCMV groups (P＜0.05).Primary EVTs could secrete active MMP-2 and MMP-9 in vitro,and the activity of two MMPs was decreased significantly in HCMV groups (P＜0.05).The in vitro cell invasion assay showed that the number of primary EVTs permeating Matrigel in HCMV group was decreased (P＜0.05).We are led to conclude that HCMV can infect primary EVTs and inhibit their invasion capability,suggesting that the impaired EVT's invasion capability might be related to the abnormal expression of c-erbB-2,MMP-2and MMP-9 proteins.