Replication of human respiratory coronavirus strain 229E in human macrophages

Evidence for the replication of human coronavirus strain 229E (HCV 229E) in macrophages is presented. Virus antigen was detected in macrophages by an immunofluorescent technique 24 h after infection and virus particles were observed in the cisternae of the endoplasmic reticulum by electron microscopy. Giant cells were observed by light and scanning electron microscopy, and large multinucleate cells were seen by thin-section electron microscopy, suggesting that HCV 229E can induce syncytial formation in cultured human macrophages. Furthermore, the production of infectious virus by macrophages was demonstrated by an infectious centre assay.