Fig 4. HBE-grown RSV virions are less infectious on HEp-2 cells when the comparison is based on genome numbers in the inoculum.

Images of HEp-2 and HBE 24 h after inoculation of 10⁷ genomes of RSV(HEp-2) (A and B) and RSV(HBE) (C and D). Infectivity was determined by ffu per 10⁶ genomes on HEp-2 (E) and HBE (D). Viruses were titrated on both cultures to quantify ffu and RNA was extracted from the unused inoculum and genomes quantified by RT-qPCR for the RSV N (nucleocapsid) gene. The mean of three independent experiments are plotted. (*** p < 0.001). Comparison of Ct value when using negative sense specific versus random primers for reverse transcription (G).