Evaluation of a human colon adeno-carcinoma (Caco-2) cell line for isolation of respiratory viruses in nasopharyngeal aspirates frompatients with respiratory disease

Abstract

Background: Isolation of respiratory viruses routinely requires a panel of cell lines. Management of these cell lines is usually considered complex, cumbersome, long turnaround time and high cost. In order to improve the detection rate and cost, there is a need to evaluate any other cell line that could be as sensitive as the routine cell line for the detection of respiratory viruses. The human colon adeno-carcinoma (Caco-2) cell line has been shown to support the growth of enteroviruses, enteric viruses, and influenza A virus, and ability to grow coronavirus NL63 and SARS from culture isolates. In the present study, the isolation rate of respiratory viruses in Caco-2 from clinical specimens was studied and compared with the conventional panel of cell lines for the diagnosis of respiratory virus disease.

Material and methods: The study was performed in two stages. In the first stage, one hundred and eighty-nine nasopharyngeal aspirates confirmed positive by direct immunofluorescence were used to inoculate onto Caco-2, and HEp-2, A549, MDCK, LLC-MK2 cell lines at the same time. In the second stage, fifty-six nasopharyngeal aspirates were randomly selected and cultured on Caco-2, HEp-2, A549, MDCK and LLC-MK2. Infected cells were examined daily for cytopathic effect for up to 10 days. Virus was further identified by performing direct immunofluorescence test for detection of eight common respiratory viruses (respiratory syncytial virus, influenza A and B viruses, parainfluenza type 1, 2, 3, 4 viruses and adenovirus).

Results: Caco-2 (84%) was found to be the most efficient cell line to propagate the respiratory viruses from nasopharyngeal aspirate when compared with any positive by these conventional panel cells (78%) or individual cell line MDCK (38%), HEp-2 (21%), LLC-MK2 (27%) and A549 (37%). The latter differences were statistically significant (p = <0.000001). Furthermore, Caco-2 recovered 86% (36/42) viruses of conventional panel cells negative samples, while conventional panel cells recovered 80% (24/30) viruses of Caco-2 cells negative samples.

Conclusion: Caco-2 is sensitive to a wide range of virus and can greatly simplify routine cell culture service for isolation of respiratory viruses.