Adaptation of human enteric coronavirus to growth in cell lines

Background: The existence of human enteric coronavirus (HEC) has been debat ed since its first description in stool by electron microscopy (EM) in 1975 . Needed to resolve the issue is its cultivation in readily available cell lines. Objectives: To grow HEC in cell lines. To describe its characteristics and to differentiate it from other human and animal coronaviruses. Study design: Originally grown in human fetal intestinal organ culture, HEC was passed in J774 cells (a mouse macrophage cell line) and C6/36 cells (a mosquito cell line). Its cytopathic effect (CPE) and pattern of immunofluo rescence were described. Its appearance was ascertained by negative stainin g and transmission EM. Its structural proteins were delineated by polyacryl amide gel electrophoresis (PAGE) and Western blotting (WB). The antigenic c haracter of the virus was determined by immunofluorescence and WE. Agglutin ation with mouse erythrocytes was performed. Results: In J774 cells, HEC induced the formation of giant cells and small syncytia. Immunofluorescence in both J774 and C6/36 cells was limited to th e cytoplasm. Studies with transmission EM revealed the virus to have the ty pical appearance of other coronaviruses, to be 80-120 nm in diameter, and t o bud into cysternae of the endoplasmic reticulum. By PAGE and WB, its majo r protein has an average molecular weight (MW) of 41 kilodaltons (kDa). Two other proteins had MWs of 190 and 24 kDa. By immunofluorescence and WE, HE C is antigenically distinct from human coronaviruses 0C43 and 229E and mous e hepatitis virus (A59 strain). Preparations of HEC did not agglutinate mou se erythrocytes. Conclusion: We conclude that HEC is a human coronavirus that is antigenical ly unrelated to 0C43 and 229E viruses. Growth of HEC in readily available c ell lines should aid in elucidating its role as a pathogen in human diarrhe al illnesses. (C) 1999 Elsevier Science B.V. All rights reserved.