Fig. 4.

Sucrose gradient profiles of passaged A₂₄ Cruzeiro and O₁ Manisa. Identical numbers of BHK179 and BHK-2P cells, maintained in GMEM + 5% FCS or ACFM were infected with an MOI = 0.1 and virus was harvested after 20 hpi. The harvested virus was concentrated by ultracentrifugation and sedimented through a 15–45% sucrose density gradient. The peaks corresponding to 146S (fraction 9) and empty 75S particles (fraction 13) are indicated. FMDV protein content is shown as absorbance at 492 nm obtained with antibodies specific for O₁ (panel a, − 179: solid, grey line, -2P: dotted, black line) and A₂₄ (panel c, − 179: solid, grey line, -2P: dotted, black line for ACFM; dotted, grey line for serum-containing GMEM) in a standard FMDV antigen ELISA. RNA content corresponds to absorbance at 260 nm as measured with a spectrophotometer (panel b: O₁ isolates, panel d: A₂₄isolates, − 179: solid, grey line, -2P: dotted, black line for ACFM; dotted, grey line for serum-containing GMEM). For both assays, absorbances were normalized by subtracting the absorbance reading of fraction 2