Abstract
Human coronaviruses, with two known serogroups named 229E and OC43, cause up to one third of common colds and may be associated with serious diseases such as nosocomial respiratory infections, enterocolitis, pericarditis and neurological disorders. Reliable methods of detection in clinical samples are needed for a better understanding of their role in pathology. As a first step in the design of such diagnostic procedures, the sensitivities and specificities of two viral diagnostic assays were compared in an experimental cell culture model: an indirect immuno-fluorescence assay using monoclonal antibodies and reverse transcriptase-polymerase chain reaction amplification of viral RNA from infected cells. Immunofluorescence detected human coronaviruses in cells infected at a MOI as low as 10(-2) (log TCID50/ml = 4.25 for HCV-229E and 2.0 for HCV-OC43; log PFU/ml = 4.83 for HCV-229E and 1.84 for HCV-OC43) versus 10(-3) (HCV-OC43) or 10(-4) (HCV-229E) for reverse transcriptase-polymerase chain reaction amplification (log TCID50/ml = 1.75 for HCV-229E and 1.5 for HCV-OC43; log PFU/ml = 2.3 for HCV-229E and 1.34 for HCV-OC43). There were no false positive signals with other human respiratory pathogens: influenza virus, respiratory syncytial virus and adenovirus. Moreover, each assay was coronavirus serogroup-specific. These results demonstrate the potential usefulness of immunofluorescence with monoclonal antibodies and reverse transcriptase-polymerase chain reaction RNA amplification for the rapid detection of human coronaviruses in infected cell cultures. Both methods could be applied to clinical specimens for the diagnosis of human infections.