Isolation of influenzavirus A and B in PLC/PRF/5 cells

Virus isolation was attempted in PLC/PRF/5 cells, a continuous primary liver carcinoma line, and secondary rhesus monkey kidney (2 degrees RhMK) cells from 19 clinical samples from which influenza A (n = 4) and B (n = 15) had been isolated previously. Virus growth was determined by haemadsorption and immunofluorescence. Influenza A was recovered in both cell types from all four samples tested. Influenza B was re-isolated in both cell types from eight specimens, in PLC/PRF/5 only from two, and in 2 degrees RhMK only from one; no virus was recovered from the remaining four. Cultures of either virus were haemadsorption- and immunofluorescence-positive by six days post-inoculation. Cytopathic effect produced by the influenza A isolates in PLC/PRF/5 was minimal following initial inoculation of specimens, but increased on subsequent passage. Influenza B isolates produced a cytopathic effect in PLC/PRF/5 similar in extent and speed of development to that in 2 degrees RhMK. These results suggest that PLC/PRF/5 may be a suitable continuous cell line, and an alternative to monkey kidney cells, for the isolation and monitoring of antigenic variation of influenza viruses.