Differentiation-dependent redistribution of heparan sulfate in epithelial intestinal Caco-2 cells leads to basolateral entry of cytomegalovirus

Human cytomegalovirus (HCMV) causes a broad spectrum of clinical manifestat ions in immunocompromised patients, including infection of the gastrointest inal tract. To investigate the role of epithelial cells in the gastrointest inal HCMV disease, we used the intestinal epithelial cell line Caco-2, whic h is permissive for HCMV replication. In differentiated Caco-2 cells, we sh owed previously that HCMV infection proceeds preferentially from the basola teral membrane, suggesting that receptors for HCMV may be contained predomi nantly in the basolateral membrane (A. Esclatine et al, 2000, J. ViroL 74, 513-517). Therefore, we examined expression and localization in Caco-2 cell s of heparan sulfate (HS) proteoglycan and annexin II, previously implicate d in initial events of HCMV infection, We observed that annexin II is expre ssed in Caco-2 cells, but is not essential for entry of HCMV We showed that , during the differentiation process, HS, initially present on the entire s urface of the membrane of undifferentiated cells, ultimately became sequest ered at the basolateral cell surface of fully differentiated cells. We esta blished by biochemical assays that membrane-associated HS proteoglycan medi ates both viral attachment to, and subsequent infection of, Caco-2 cells, r egardless of the cell differentiation state. Thus, the redistribution of HS is implicated in the basolateral entry of HCMV into differentiated Caco-2 cells. (C) 2001 Academic Press.