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.