BACKGROUND: Primary rhesus monkey kidney cells (RhMK) can be used for the detection of respiratory viruses, including influenza and parainfluenza . The human colon adeno-carcinoma cell line, CACO-2, has been previously used for the growth of multiple influenza viruses, including seasonal, novel and avian lineages .
OBJECTIVE: We compared CACO-2, Madin-Darby Canine Kidney (MDCK), and RhMK cells for the isolation of viruses from patients presenting with influenza like-illness (ILI). STUDY
DESIGN: Nasopharyngeal specimens from patients with ILI in primary care settings were processed for conventional viral culture in MDCK, RhMK, and CACO-2 . Cells were examined microscopically for cytopathic effect (CPE) and confirmatory testing included immunofluorescent antigen (IFA) detection and real-time RT-PCR . Additionally , 16 specimens positive for respiratory syncytial virus (RSV) by PCR were inoculated on CACO-2 cells . Statistical analysis was done using Chi-square test with IBM Statistical Program .
RESULTS: Of 1031 respiratory specimens inoculated, viruses were isolated and confirmed from 331 (32.1 %) in MDCK cells , 304 (29.5 %) in RhMk cells, and 433 (42.0 %) in CACO-2 cells . These included influenza A/ (H1N1) pdm09, influenza A (H3N2), influenza B, parainfluenza virus (PIV) types 1 , 2, and 3, human coronavirus 229E (CoV-229E), human adenovirus (HAdV), herpes simplex virus 1 (HSV 1), and enterovirus (EV). Influenza A viruses grew best in the CACO-2 cell line . Time to observation of CPE was similar for all three cell types but unlike RhMK and MDCK cells, virus-specific morphological changes were indistinguishable in CACO-2 cells . None of the 16 specimens positive for RSV by PCR grew on CACO-2 cells .
CONCLUSIONS: The overall respiratory virus culture isolation rate in CACO-2 cells was significantly higher than that in RhMK or MDCK cells (p <0.05). CACO-2 cells also supported the growth of some viruses that did not grow in either RhMK or MDCK cells . Except for RSV, CACO-2 cells provide a worthwhile addition to culture algorithms for respiratory specimens.